U.S. patent application number 11/854602 was filed with the patent office on 2008-07-24 for heat transfer from a source to a fluid to be heated using a heat driven loop.
Invention is credited to Jack Lange.
Application Number | 20080173260 11/854602 |
Document ID | / |
Family ID | 39640053 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080173260 |
Kind Code |
A1 |
Lange; Jack |
July 24, 2008 |
HEAT TRANSFER FROM A SOURCE TO A FLUID TO BE HEATED USING A HEAT
DRIVEN LOOP
Abstract
Oil in a storage tank is heated by providing one or more
elongate conduits within the storage tank in the form of a loop
extending from an inlet manifold across the tank and returning to
an outlet manifold. The inlet manifold is connected to an
evaporator section at a heat source and the outlet manifold acts as
a return of the condensate. The conduit forms a loop and back flow
in the loop is prevented by providing a head in the liquid in the
conduit at a position adjacent to or at the evaporation section
caused by a standing column of the liquid with optionally a pump.
The flow around the loop at high speed sufficient to carry all
condensate forwardly is caused solely by application of energy to
the system by the heat source. Inert gases are collected
immediately upstream of the trap and can be purged therefrom.
Inventors: |
Lange; Jack; (Winnipeg,
CA) |
Correspondence
Address: |
ADE & COMPANY INC.
2157 Henderson Highway
WINNIPEG
MB
R2G1P9
omitted
|
Family ID: |
39640053 |
Appl. No.: |
11/854602 |
Filed: |
September 13, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10474774 |
Apr 15, 2004 |
7337828 |
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PCT/CA02/00490 |
Apr 11, 2002 |
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11854602 |
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60283150 |
Apr 12, 2001 |
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Current U.S.
Class: |
122/31.1 |
Current CPC
Class: |
F28D 15/06 20130101;
F28D 15/0266 20130101; F28D 15/0241 20130101 |
Class at
Publication: |
122/31.1 |
International
Class: |
F22B 1/02 20060101
F22B001/02 |
Claims
1. A method for transferring heat from a combustion heat source to
a fluid to be heated comprising: providing a combustion heat
source; providing a fluid to be heated at a position spaced from
the heat source; providing a closed system including at least one
conduit; providing an evaporation section of the closed system at
the heat source; providing a condensation section of the closed
system in the fluid to be heated; providing a heat transfer fluid
medium within the closed system having a temperature of boiling
from liquid to vapor such that heat from the heat source causes the
liquid to boil to form a vapor in the evaporation section and such
that release of heat from the condensation section to the fluid to
be heated causes the vapor to condense to liquid in the
condensation section; the at least one conduit forming a loop
extending from the evaporation section through the condensation
section and back to the evaporation section so as to conduct the
heat transfer fluid medium from the evaporation section to the
condensation section and back to the evaporation section; applying
heat energy to the heat transfer medium by the heat source at the
vaporizer section so that the thermal energy causes expansion of
volume due to a change of state; flow around the loop being biased
in one direction by the creation of a head.
2. The method according to claim 1 wherein the conduit and
condensation section have a resistance to flow of the vapor from
the vaporizer section to and through the condensation section and
wherein the head is arranged such that, subsequent to start-up and
during steady state flow of the heat transfer fluid medium in the
loop, the head defines a pressure in the liquid at least equal to a
pressure drop in the vapor caused by the resistance to flow of the
vapor in the conduit from the evaporation section to and through
the condensation section.
3. The method according to claim 1 wherein the head is generated by
a standing column of liquid without assistance from a pump.
4. The method according to claim 1 wherein the head is created by a
combination of pressure developed by a pump and a standing column
of the liquid.
5. The method according to claim 4 wherein the condenser is higher
than the pump and there is arranged to be a column of liquid at the
inlet to the pump.
6. The method according to claim 1 wherein there is provided a pump
and the condenser is lower than the pump and the pump is arranged
to generate a suction at the inlet acting to lift the liquid to the
pump.
7. The method according to claim 1 wherein the head is partly
generated by a pump and the operation of the process is controlled
by varying the flow rate of pump.
8. The method according to claim 8 wherein there is provided a
viewing port and the operation of the process is controlled by
varying the pump while viewing passage of vapor from the
evaporation section so as to ensure passage substantially wholly of
vapor with a minimal amount of liquid.
9. The method according to claim 7 wherein the pump is a positive
displacement pump so that the rate of flow is directly proportional
to a rotation rate of the pump.
10. The method according to claim 9 wherein the condensation
section is arranged at a height above the pump such that a column
of liquid generated thereby generates a pressure greater than a
required pressure for optimum operation and wherein the positive
displacement pump generates an outlet pressure below that of the
column.
11. The method according to claim 1 wherein the system contains a
total volume of liquid less than 43.5 litres or 1.5 cu. ft.
12. The method according to claim 1 wherein the system is evacuated
prior to start up.
13. The method according to claim 12 wherein the system is
evacuated prior to start up so that the operating pressure in the
vapor is less than 15 psi.
14. The method according to claim 12 wherein there is provided a
compressor having a storage tank and the system is evacuated prior
to start up by connecting the inlet of the compressor to the system
and wherein the system is purged after shut down by compressed air
from the storage tank.
15. The method according to claim 1 wherein the flow of vapor from
the evaporation section to the condensation section is at
sufficient velocity to carry all condensate forwardly to a position
where it can flow around the loop under gravity back to the
evaporation section.
16. The method according to claim 1 wherein substantially all the
vapor generated in the evaporation section is caused to condense in
the condensation section.
17. The method according to claim 1 wherein substantially no heat
transferred is transferred to the fluid to be heated by cooling of
the condensed liquid.
18. A method for transferring heat from a combustion heat source to
a fluid to be heated comprising: providing a combustion heat
source; providing a fluid to be heated at a position spaced from
the heat source; providing a closed system including at least one
conduit; providing an evaporation section of the closed system at
the heat source; providing a condensation section of the closed
system in the fluid to be heated; providing a heat transfer fluid
medium within the closed system having a temperature of boiling
from liquid to vapor such that heat from the heat source causes the
liquid to boil to form a vapor in the evaporation section and such
that release of heat from the condensation section to the fluid to
be heated causes the vapor to condense to liquid in the
condensation section; the at least one conduit forming a loop
extending from the evaporation section through the condensation
section and back to the evaporation section so as to conduct the
heat transfer fluid medium from the evaporation section to the
condensation section and back to the evaporation section; applying
heat energy to the heat transfer medium by the heat source at the
vaporizer section thermal energy causes expansion of volume due to
a change of state; and causing boiling of the liquid in the
evaporation section and flow of the vapor from the evaporation
section to carry non-vapor additives in the liquid in the
evaporation section into the conduit with the vapor.
19. The method according to claim 18 wherein the conduit is
arranged relative to the evaporation section such that boiling of
the liquid in the evaporation section does not cause liquid to
bridge the conduit so as to act as a bubble pump.
20. The method according to claim 18 wherein the conduit is
arranged relative to the evaporation section such that the velocity
of the vapor is greater than 500 ft/sec.
21. A method for transferring heat from a combustion heat source to
a fluid to be heated comprising: providing a combustion heat
source; providing a fluid to be heated at a position spaced from
the heat source; providing a closed system including at least one
conduit; providing an evaporation section of the closed system at
the heat source; providing a condensation section of the closed
system in the fluid to be heated; providing a heat transfer fluid
medium within the closed system having a temperature of boiling
from liquid to vapor such that heat from the heat source causes the
liquid to boil to form a vapor in the evaporation section and such
that release of heat from the condensation section to the fluid to
be heated causes the vapor to condense to liquid in the
condensation section; the at least one conduit forming a loop
extending from the evaporation section through the condensation
section and back to the evaporation section so as to conduct the
heat transfer fluid medium from the evaporation section to the
condensation section and back to the evaporation section; applying
heat energy to the heat transfer medium by the heat source at the
vaporizer section thermal energy causes expansion of volume due to
a change of state; wherein the system is at least partly evacuated
prior to start up such that during steady state operation the
pressure in the system is less than 15 psi above atmospheric
pressure.
22. A method for transferring heat from a combustion heat source to
a fluid to be heated comprising: providing a combustion heat
source; providing a fluid to be heated at a position spaced from
the heat source; providing a closed system including at least one
conduit; providing an evaporation section of the closed system at
the heat source; providing a condensation section of the closed
system in the fluid to be heated; providing a heat transfer fluid
medium within the closed system having a temperature of boiling
from liquid to vapor such that heat from the heat source causes the
liquid to boil to form a vapor in the evaporation section and such
that release of heat from the condensation section to the fluid to
be heated causes the vapor to condense to liquid in the
condensation section; the at least one conduit forming a loop
extending from the evaporation section through the condensation
section and back to the evaporation section so as to conduct the
heat transfer fluid medium from the evaporation section to the
condensation section and back to the evaporation section; applying
heat energy to the heat transfer medium by the heat source at the
vaporizer section thermal energy causes expansion of volume due to
a change of state; wherein the total volume of liquid in the system
is less than 43.5 litres or 1.5 cu ft.
23. A method for transferring heat from a combustion heat source to
a fluid to be heated comprising: providing a combustion heat
source; providing a fluid to be heated at a position spaced from
the heat source; providing a closed system including at least one
conduit; providing an evaporation section of the closed system at
the heat source; providing a condensation section of the closed
system in the fluid to be heated; providing a heat transfer fluid
medium within the closed system having a temperature of boiling
from liquid to vapor such that heat from the heat source causes the
liquid to boil to form a vapor in the evaporation section and such
that release of heat from the condensation section to the fluid to
be heated causes the vapor to condense to liquid in the
condensation section; the at least one conduit forming a loop
extending from the evaporation section through the condensation
section and back to the evaporation section so as to conduct the
heat transfer fluid medium from the evaporation section to the
condensation section and back to the evaporation section; applying
heat energy to the heat transfer medium by the heat source at the
vaporizer section thermal energy causes expansion of volume due to
a change of state; wherein flow around the loop is biased in one
direction by a head created in part by a pump; and wherein there is
provided a viewing port for viewing passage of vapor from the
evaporation section; and wherein the operation of the process is
controlled by varying the flow rate of the pump while viewing
passage of vapor from the evaporation section so as to ensure
passage substantially wholly of vapor with a minimal amount of
liquid.
24. A method for transferring heat from a combustion heat source to
a fluid to be heated comprising: providing a combustion heat
source; providing a fluid to be heated at a position spaced from
the heat source; providing a closed system including at least one
conduit; providing an evaporation section of the closed system at
the heat source; providing a condensation section of the closed
system in the fluid to be heated; providing a heat transfer fluid
medium within the closed system having a temperature of boiling
from liquid to vapor such that heat from the heat source causes the
liquid to boil to form a vapor in the evaporation section and such
that release of heat from the condensation section to the fluid to
be heated causes the vapor to condense to liquid in the
condensation section; the at least one conduit forming a loop
extending from the evaporation section through the condensation
section and back to the evaporation section so as to conduct the
heat transfer fluid medium from the evaporation section to the
condensation section and back to the evaporation section; applying
heat energy to the heat transfer medium by the heat source at the
vaporizer section thermal energy causes expansion of volume due to
a change of state; wherein flow around the loop is biased in one
direction by a head created in part by a pump; and wherein the pump
is a positive displacement pump so that the rate of flow is
directionally proportional to a rotation rate of the pump.
25. The method according to claim 24 wherein the condensation
section is arranged at a height above the pump such that a column
of liquid generated thereby generates a pressure greater than a
required pressure for optimum operation and wherein the positive
displacement pump generates an outlet pressure below that of the
column.
Description
[0001] This application is a Continuation-in-Part application of
application Ser. No. 10/474,774, filed Apr. 15, 2004 which is a
National Phase Entry of PCT/CA02/00490, filed Apr. 11, 2002.
[0002] This application claims the benefit under 35 U.S.C.119 of
the priority of Provisional Application Ser. No. 60/283,150, filed
Apr. 12, 2001.
[0003] This invention relates to a heating system transferring heat
from a heat source such as a combustion heating system to a fluid
to be heated which is particularly but not exclusively designed for
heating oil in storage tanks, oil emulsion treatment tanks and oil
upgrading and refining process vessels.
BACKGROUND OF THE INVENTION
[0004] Reference is made to U.S. Pat. No. 5,123,401 of the present
inventor issued Jun. 23, 1992 which discloses a combustion heating
device for use for example with oil processing equipment defines a
combustion chamber within which combustion wholly takes place. The
combustion chamber consists solely of a sleeve and end plate
defining a vertical cylinder and a layer of ceramic fiber
insulating material inside the sleeve defining the inner surface of
the combustion chamber. A burner is mounted in a bottom plate of
the device which can be pivoted to an open position exposing the
burner for service. Air channels are defined on the outside of the
sleeve so that incoming combustion air passes over the sleeve and
acts as a heat recovery for any heat escaping from the insulating
material. An outlet duct at an upper end of the combustion chamber
at right angles to the combustion chamber extracts the combustion
gases so that all heat exchange takes place outside of the
combustion chamber. The device improves heating efficiency and
reduces corrosion of heat transfer surfaces. In the arrangement
shown, a similar combustion chamber vertical configuration and
dimensioning with respect to the flame, together with the heat
recovery method from the outside walls of the combustion chamber,
which provided exceptionally high combustion efficiencies with a
naturally aspirated burner in the order of 80%+ in that device, are
employed.
[0005] Reference is made to US Published Application 200710000453
published Jan. 4, 2007 of King which discloses a heat exchange
apparatus using a change of state of a liquid which is transported
from an evaporator to a condenser so that the liquid form the
condenser can return to be re-heated. In this application, the
purported claim to function as a "heat driven loop" is not
supported in that it is a "loop" only in the sense that the conduit
containing vapor forms a loop, whereas the fluid flow does not.
Both legs of the conduit exit the vaporization chamber above liquid
level, which makes it incapable of bias of flow in one rotational
direction. Neither is it "driven" because vapor simply travels up
towards the top of the joined tubes and condensate runs down to the
bottom of the joined tubes due to the effects of gravity only. It
is, in effect, two parallel thermo-siphons joined together at the
top and bottom ends and functions in accordance with the known
principle of such devices.
[0006] Reference is made to Canadian Patent 1,264,443 (Spehar)
issued Jan. 16, 1990 and U.S. Pat. No. 5,947,111 (Neulander et al)
issued Sep. 7, 1999 to Hudson Products Corp (which corresponds to
Canadian application 2,262,990) which describe prior art
arrangements and the disclosure of these prior patents is hereby
incorporated by reference to show the type of installation and use
to which the present device can to be put.
[0007] Reference is also made to the prior U.S. Pat. No. 4,393,663
(Grunes) which shows a heat loop arrangement for heating various
materials, primarily water, within a container. However this
arrangement has not been proposed for and is not suitable for the
heating of oil and particularly crude oil in a storage tank.
[0008] U.S. Pat. No. 4,216,903 Giuffre discloses a circuit using an
evaporation section and a condensation section connected by a
conduit with a trap located between the condensation section and
the evaporation section for the returning liquid feeding to a
receiver. The trap is discussed only in terms of blocking back flow
and is never discussed as being an active element in providing
drive for the fluid for useful purpose.
SUMMARY OF THE INVENTION
[0009] It is one object of the present invention to provide an
improved method of heat transfer from a heat source to a fluid to
be heated.
[0010] According to the present invention there is provided method
for transferring heat from a combustion heat source to a fluid to
be heated comprising:
[0011] providing a combustion heat source;
[0012] providing a fluid to be heated at a position spaced from the
heat source;
[0013] providing a closed system including at least one
conduit;
[0014] providing an evaporation section of the closed system at the
heat source;
[0015] providing a condensation section of the closed system in the
fluid to be heated;
[0016] providing a heat transfer fluid medium within the closed
system having a temperature of boiling from liquid to vapor such
that heat from the heat source causes the liquid to boil to form a
vapor in the evaporation section and such that release of heat from
the condensation section to the fluid to be heated causes the vapor
to condense to liquid in the condensation section;
[0017] the at least one conduit forming a loop extending from the
evaporation section through the condensation section and back to
the evaporation section so as to conduct the heat transfer fluid
medium from the evaporation section to the condensation section and
back to the evaporation section;
[0018] applying heat energy to the heat transfer medium by the heat
source at the vaporizer section so that the thermal energy causes
expansion of volume due to a change of state;
[0019] flow around the loop being biased in one direction by the
creation of a head.
[0020] Thus the system provides in its broadest terms, a `heat
driven` loop; with as opposed to induced systems such as those
gravity-drawn in both directions as in a thermo-siphon, or,
capillary-drawn in one of the two directions as in a heat pipe,
either in a looped tube configuration or in a single tube. Flow is
biased in one rotational direction by restriction in the other
rotational direction using a head but the specific means of
providing this head is secondary to the concept.
[0021] The head provides a mechanism for prevention back flow which
can be designed and arranged to not only prevent back flow, but
also to utilize the adjustability of the head to provide sufficient
back pressure and force of flow to maintain flow of vapor,
carry-over liquid from the vaporizer and condensate, substantially
in one direction, and drive this combination through resistance
imposed by restrictions and deployments, above and below the level
of the vaporizer, of the condenser.
[0022] The head also provides a block, for any residue of the inert
gases that are used for initial purging plus any inert gases that
are generated over a period of time by chemical interaction of the
fluid[s] and the materials from which the device is constructed and
the accumulation of which will progressively impair the
effectiveness of the system, against which these gases will
accumulate as swept along by the fluid flow while in operation and
unable to pass through the head, in a location that is accessible
from outside the vessel which enables these gases to be detected
and purged from the system utilizing the pressure of the system
while in operation. Thus the head is arranged so that it stops the
forward flow of the inert gases at the head and there is provided
an access opening which can be opened at the position immediately
upstream of the head so that the gases can be purged, with the
system under pressure so that the vapor drives out the inert gases
until escape of vapor is detected.
[0023] According to a second aspect of the invention there is
provided a method for transferring heat from a combustion heat
source to a fluid to be heated comprising:
[0024] providing a combustion heat source;
[0025] providing a fluid to be heated at a position spaced from the
heat source;
[0026] providing a closed system including at least one
conduit;
[0027] providing an evaporation section of the closed system at the
heat source;
[0028] providing a condensation section of the closed system in the
fluid to be heated;
[0029] providing a heat transfer fluid medium within the closed
system having a temperature of boiling from liquid to vapor such
that heat from the heat source causes the liquid to boil to form a
vapor in the evaporation section and such that release of heat from
the condensation section to the fluid to be heated causes the vapor
to condense to liquid in the condensation section;
[0030] the at least one conduit forming a loop extending from the
evaporation section through the condensation section and back to
the evaporation section so as to conduct the heat transfer fluid
medium from the evaporation section to the condensation section and
back to the evaporation section;
[0031] applying heat energy to the heat transfer medium by the heat
source at the vaporizer section thermal energy causes expansion of
volume due to a change of state;
[0032] and causing boiling of the liquid in the evaporation section
and flow of the vapor from the evaporation section to carry
non-vapor additives in the liquid in the evaporation section into
the conduit with the vapor.
[0033] According to a third aspect of the invention there is
provided a method for transferring heat from a combustion heat
source to a fluid to be heated comprising:
[0034] providing a combustion heat source;
[0035] providing a fluid to be heated at a position spaced from the
heat source;
[0036] providing a closed system including at least one
conduit;
[0037] providing an evaporation section of the closed system at the
heat source;
[0038] providing a condensation section of the closed system in the
fluid to be heated;
[0039] providing a heat transfer fluid medium within the closed
system having a temperature of boiling from liquid to vapor such
that heat from the heat source causes the liquid to boil to form a
vapor in the evaporation section and such that release of heat from
the condensation section to the fluid to be heated causes the vapor
to condense to liquid in the condensation section;
[0040] the at least one conduit forming a loop extending from the
evaporation section through the condensation section and back to
the evaporation section so as to conduct the heat transfer fluid
medium from the evaporation section to the condensation section and
back to the evaporation section;
[0041] applying heat energy to the heat transfer medium by the heat
source at the vaporizer section thermal energy causes expansion of
volume due to a change of state;
[0042] wherein the system is at least partly evacuated prior to
start up such that during steady state operation the pressure in
the system is less than 15 psi above atmospheric pressure.
[0043] According to a fourth aspect of the invention there is
provided a method for transferring heat from a combustion heat
source to a fluid to be heated comprising:
[0044] providing a combustion heat source;
[0045] providing a fluid to be heated at a position spaced from the
heat source;
[0046] providing a closed system including at least one
conduit;
[0047] providing an evaporation section of the closed system at the
heat source;
[0048] providing a condensation section of the closed system in the
fluid to be heated;
[0049] providing a heat transfer fluid medium within the closed
system having a temperature of boiling from liquid to vapor such
that heat from the heat source causes the liquid to boil to form a
vapor in the evaporation section and such that release of heat from
the condensation section to the fluid to be heated causes the vapor
to condense to liquid in the condensation section;
[0050] the at least one conduit forming a loop extending from the
evaporation section through the condensation section and back to
the evaporation section so as to conduct the heat transfer fluid
medium from the evaporation section to the condensation section and
back to the evaporation section;
[0051] applying heat energy to the heat transfer medium by the heat
source at the vaporizer section thermal energy causes expansion of
volume due to a change of state;
[0052] wherein the total volume of liquid in the system is less
than 43.5 litres or 1.5 cu. ft.
[0053] According to a fifth aspect of the invention there is
provided a method for transferring heat from a combustion heat
source to a fluid to be heated comprising:
[0054] providing a combustion heat source;
[0055] providing a fluid to be heated at a position spaced from the
heat source;
[0056] providing a closed system including at least one
conduit;
[0057] providing an evaporation section of the closed system at the
heat source;
[0058] providing a condensation section of the closed system in the
fluid to be heated;
[0059] providing a heat transfer fluid medium within the closed
system having a temperature of boiling from liquid to vapor such
that heat from the heat source causes the liquid to boil to form a
vapor in the evaporation section and such that release of heat from
the condensation section to the fluid to be heated causes the vapor
to condense to liquid in the condensation section;
[0060] the at least one conduit forming a loop extending from the
evaporation section through the condensation section and back to
the evaporation section so as to conduct the heat transfer fluid
medium from the evaporation section to the condensation section and
back to the evaporation section;
[0061] applying heat energy to the heat transfer medium by the heat
source at the vaporizer section thermal energy causes expansion of
volume due to a change of state;
[0062] wherein flow around the loop is biased in one direction by a
head created in part by a pump;
[0063] and wherein there is provided a viewing port for viewing
passage of vapor from the evaporation section;
[0064] and wherein the operation of the process is controlled by
varying the flow rate of the pump while viewing passage of vapor
from the evaporation section so as to ensure passage substantially
wholly of vapor with a minimal amount of liquid.
[0065] According to a sixth aspect of the invention there is
provided a method for transferring heat from a combustion heat
source to a fluid to be heated comprising:
[0066] providing a combustion heat source;
[0067] providing a fluid to be heated at a position spaced from the
heat source;
[0068] providing a closed system including at least one
conduit;
[0069] providing an evaporation section of the closed system at the
heat source;
[0070] providing a condensation section of the closed system in the
fluid to be heated;
[0071] providing a heat transfer fluid medium within the closed
system having a temperature of boiling from liquid to vapor such
that heat from the heat source causes the liquid to boil to form a
vapor in the evaporation section and such that release of heat from
the condensation section to the fluid to be heated causes the vapor
to condense to liquid in the condensation section;
[0072] the at least one conduit forming a loop extending from the
evaporation section through the condensation section and back to
the evaporation section so as to conduct the heat transfer fluid
medium from the evaporation section to the condensation section and
back to the evaporation section;
[0073] applying heat energy to the heat transfer medium by the heat
source at the vaporizer section thermal energy causes expansion of
volume due to a change of state;
[0074] wherein flow around the loop is biased in one direction by a
head created in part by a pump;
[0075] and wherein the pump is a positive displacement pump so that
the rate of flow is directionally proportional to a rotation rate
of the pump.
[0076] The system is primarily designed for use in heating crude
oil in a tank but can also be used for other heating systems
including heating air for forced air systems and space heating. The
system can also be used for heating oil in a duct of pipe as it
flows past the condensation section of the loop.
[0077] The system consists of a closed loop, sealed from atmosphere
and containing a fluid. The fluid is vaporized in the energy
absorbing section by the application of heat. The temperature and
pressure of the system vary in a fixed relationship according to
the vaporization characteristics of the fluid and the amount of
heat applied. The vapor is conducted to the energy emitting section
where it condenses giving off its latent heat. The condensate flows
back through the head to the energy absorbing section. Vapor is
driven in one rotational direction by the liquid differential
pressure of the condensate gathering head which self-adjusts to
overcome flow resistance through the energy emitting section of the
loop.
[0078] The system consists of a single conduit or a multiplicity of
such conduits connected by input and output manifolds to the
evaporation section at the heat source outside the storage tank or
fluid to be heated.
[0079] When the head is formed by a trap, the trap is not only self
adjusting but its range of adjustability can be increased or
decreased by increasing or decreasing the depth of the trap to
permit greater liquid level differentials to offset greater energy
emitting section resistance.
[0080] The configuration of the loop is such that the energy of the
system is sufficient to both overcome the resistance of the energy
emitting section but also to sustain a vapor flow velocity
sufficient to carry along with it substantially all the condensate
produced in the energy emitting section, plus a limited quantity of
liquid physically carried out of the energy absorbing section due
to boiling action. This is an important feature that should be
designed into the configuration in order to assure the conveyance
of additives, such as anti-corrosion agents and anti-freezing
agents, throughout the loop rather than have them confined to the
energy absorption section due to being precipitated due to
vaporization or isolated due to selective vaporization. However,
and this is important, the system should not carry over liquid from
the vaporizer so as to substantially form a conventional bubble
pump, such as in a percolator, so that the degree of bubble pump
action must be controlled by the design such that it occurs only to
the extent necessary to convey the additives and not to the extent
that it contributes significantly in the conveyance of heat.
[0081] Conveyance of heat substantially totally occurs due to
change of state at a fixed temperature rather then by loss of
sensible heat from this liquid by a decreasing temperature of the
liquid through the energy emitting section. In other words, the
bubble pump action must not significantly interfere with the
capability of the system to maintain a constant temperature across
the heating element when utilized for heating purposes.
[0082] The only portions of the system where gravity is the
principal force determining condensate flow, or liquid position, is
the trap. Any transition from the energy emitting section to the
energy absorbing section where condensate flow to the trap may be
substantially directed by gravity, and, the portion of the energy
absorbing section where liquid is held in direct proximity to the
heat source by the configuration of that portion of the system.
[0083] Consequently, the heat energy emitting section of the loop
can be of any lateral or vertical deployment in relation to the
energy absorbing section, and can be of any sizing or other
physically restricting configuration and can accommodate whatever
other load demands requiring pressure differential that might be
placed upon the system provided all of that is within the
capability of the energy absorption section to absorb sufficient
heat energy and, the capability of the head to withstand sufficient
back pressure to overcome the resistance imposed by these.
[0084] A specific heat emission temperature can be selected by an
appropriate choice of a fluid having the desired
temperature/pressure relationship and a construction capable of
withstanding the pressure associated with that temperature, and can
be maintained while in operation by controlling the amount of heat
that is absorbed, by controlling fuel flow to the burner. The
controller can be actuated by sensing either temperature or
pressure of the vapor issuing from the vaporizer, which have a
fixed relationship.
[0085] In practice, the system is charged with water and additives,
purged with an inert gas such as argon, the internal pressure
reduced to close to a complete vacuum at normal ambient
temperature, the system sealed, and then operated at below a
maximum 15 psi. This pressure range is readily tolerated with
conventional construction and is below the pressure that would
warrant classification as a pressure vessel. In some applications,
the system would then remain permanently sealed and initial setting
of internal pressure in relation to temperature and the initial
charge of fluid would remain for the service life of the device. In
other applications, the system in its operational mode would be
sealed but provision would be made for the periodic servicing such
as; removal of buildup of inert gases due to chemical interactions
between fluid[s] and conduit material, replacement of the fluid due
to chemical degeneration, and re-establishment of vacuum at normal
ambient due to leakage.
[0086] However the system can also be operated at higher
temperatures and pressures and may use liquids different from water
which may have a higher boiling point although water is well known
to provide a very high latent heat of vaporization. The available
selection of heat transfer fluids is limited only by practicality,
and would include for example those shown in the attached Table,
the principle considerations and limitations being the vaporization
temperature/pressure relationship characteristics of the fluids and
the chemical interactivity between the heat transfer fluid and the
material utilized to construct the loop. A single or multiplicity
of heat transfer liquids can be employed in a given system. In one
arrangement, all of the transfer liquids may circulate throughout
the system in admixture by vaporization and condensing.
Alternatively, one or more of the liquids may act as a `boiling
bed` for others depending on the temperature and pressure range of
the system from shutdown to full operation and the vaporization
characteristics of the liquids. This is significant because
additives may be required for such purposes as inhibiting chemical
interaction and preventing freezing.
[0087] Because heat transfer is substantially wholly accomplished
by change of state, the temperature of the energy emitting section
is constant throughout its length and is selectable amongst fluids
having appropriate temperature/pressure characteristics and
chemical characteristics. Both of these characteristics are highly
desirable for processes that are enhanced by selectability and
controllability of temperature, such as the different processes
involved in petroleum processing, which would include:
[0088] [a] Water and particulate matter separation from raw
petroleum product which is facilitated by holding the raw product
at as uniform and high a temperature as can be sustained below the
boiling point of water in order to minimize viscosity which
promotes separation and to avoid boiling creating foam which
seriously disrupts the process due to interference with heat
transfer and other effects. It is an important aspect of this
system that not only does the uniform temperature of the heating
elements contribute to maintaining a higher average temperature of
the raw product just below the boiling point of water but, at no
point on the element is the raw product exposed to localized
temperatures above the boiling point of water causing localized
vaporization of water and occasioning precipitation and
accumulation of particulate matter on the surface of the heating
elements which reduces their effectiveness for heat transfer and
reduces their service life. This would be in contrast to direct
fired immersion tube heaters which feature a large temperature
differential over their length and
[0089] [b] Upgrading and refining of petroleum product, which are
essentially a matter of exposure of crude product to a variety of
temperatures which are selectable, controllable, and, as constant
as can be achieved over the heat transfer surface for the purpose
of producing by distillation various petroleum products which have
characteristic vaporization temperatures. The effectiveness of the
process, in terms of the purity of product, is enhanced by
maintaining the crude product within as narrow a temperature band
as possible.
[0090] Another important feature of this technology in that it is
highly adaptable to optimizing, or maximizing, heat transfer
capacity in relation to the internal volume of the system. This is
of significance in relation to the regulatory requirements for
pressure vessels. Pressure vessels are defined as containers in
which pressure is generated as a consequence of applying heat a
classic example being conventional steam boilers. There are two
further stipulations to the definition; that the pressure generated
be in excess of 15 psi, and that the volume of the vessel be in
excess of 65 liters. Anything of less volume, regardless of
pressure, is designated as a `fixture` and is not subject to the
requirements for operating a pressure vessel. These requirements
are onerous in that they include constant attendance by a certified
person and regular inspection. Such requirements may vary in
specifics from jurisdiction to jurisdiction but will substantially
involve maximum pressures and volumes.
[0091] Because the system described herein is capable of operating
at a great variety of temperatures and pressures compared to
conventional heat transfer systems involving steam or hot water due
to the variety of fluids that can be employed having different
temperature/pressure characteristics, much higher heating element
temperatures can be generated than is common for steam or hot water
systems and it is also possible to do so at lower pressures than
would be produced with water.
[0092] For example, propylene glycol could be utilized which has a
vaporization temperature of 605 Degrees F. at 16 psi gauge pressure
compared to a vaporization temperature for water of 250 Degrees F.
at 15 psi gauge pressure. Thus higher temperatures, and greater
heat exchange, can be achieved with propylene glycol than with
water at pressures below the limit specified for definition as
pressure vessel. Alternatively, at 40 psi gauge pressure, water
vaporization temperature increases to 287 Degrees F. while
propylene glycol vaporization temperatures rise to 1048 Degrees F.
Thus much higher temperatures and much greater heat exchange can be
achieved with vessel volumes below the limit specified for
classification as a pressure vessel and therefore classified as a
fixture regardless of pressure.
[0093] Hence this system provides two means of enhancing capacity
without encroaching upon the definition of a pressure vessel, by
the utilization of the higher temperatures associated with higher
pressures while maintaining volumes below the maximum for a
fixture, and the utilization of fluids that have a
temperature/pressure characteristic such that higher temperatures
can be maintained at pressures below the maximum for pressures for
pressure vessels and therefore unlimited in volume.
[0094] This aspect of this technology has particular significance
with respect to space and air replacement heating applications. In
such systems, self-contained, compact heater modules incorporating
higher temperature heat exchangers are an alternate to systems
consisting of conventional unit heaters, make-up air heaters, etc.,
incorporating larger, lower temperature heat exchangers, and
connected to a steam boiler via a steam and condensate circulating
system.
[0095] It is also significant in relation to the amount of material
employed in relation to capacity which, in turn, relates to cost of
manufacture.
[0096] The energy absorption section of the loop may be open to the
combustion action or may be encapsulated within an enclosed housing
which is filled with a liquid intermediate heating medium. The use
of an encapsulation and heating medium allows the heating system to
sustain an even, maximum tolerable temperature over the heat
absorption surface thus minimizing the amount of surface required
and contributing to the minimization of the volume of the system
pursuant. In practice, the intermediate heating medium is
preferably what is referred to as a thermal oil, capable of
maintaining stability at temperatures close to the crystallization
temperature of mild steel. The whole heat absorption surface is
then covered with that temperature. To the contrary, when directly
heated with combustion products, which normally would be of uneven
temperature, only the peak temperature could be at that level
otherwise the surface would be damaged and the average would be
considerably less. Encapsulation also enables more than one heater
module to be supplied with heat from one central fuel combustion
device by transferring the intermediate heating medium from that
device to any number of heater modules.
[0097] When used for heating a process liquid within a storage
tank, the heating system preferably includes an arrangement in
which one or more heating loops are heated externally of the tank
and extend into the tank so that heat is transferred from the
evaporation area at the heat source to the condensation area within
the tank. The evaporation area is located within a vessel, which
may contain high temperature heating oil in an encapsulating vessel
where the vessel is heated by a burner so that the oil transfers
heat to the condensation area of the single heat loop or of each
loop if there is more than one.
[0098] Also, a multiplicity of condensing sections can be heated
from one vaporizer such that more than one tank or more than one
space or make-up air heater can be supplied with vapor from one
vaporization source. The transition system from the vaporization
section to the condensation section[s] may be with rigid or
flexible conduit and may be such that the vaporizer can be located
at ground or floor level with conduit conveying vapor to
condenser[s] located at a higher level within the capability of the
system to maintain fluid flow substantially in one direction.
[0099] The burner is controlled by thermostats which may be located
within the tank so that the temperature of the oil within the tank
is maintained within required limits. Alternatively, the
temperature or pressure, as these are directly related, within the
heat loop may be detected for maintaining the required amount of
heat input to keep the temperature and pressure at the operating
value.
[0100] An over temperature shut off is provided for safety. This
may be provided within the loop itself preferably as a pressure
sensor. Preferably the shut off is of the resetting type so that
combustion is re-started after a predetermined cool down period
since this overcomes problems should the over pressure situation
causing the shut down to occur be temporary. This is particularly
possible where very viscous materials around the heat emission part
of the heat loop temporarily reduce or prevent convection currents
in the process liquid in the tank causing the emission part to
overheat since the viscous materials act as an insulator.
Alternatively the over temperature shut off may be located within
an encapsulating heating oil so that if the heating oil exceeds a
predetermined temperature the burner is shut off. Thus there is no
detection of temperature at the surface of the condensation area of
the heat loop within the tank.
[0101] It is an important feature of this system that it is capable
of cycling, fairly rapidly if need be, in response to an on/off
condensation section temperature or pressure control, or, be
capable of operating at reduced firing rates in response to a
modulating condenser temperature or pressure control, during the
start-up phase due to delays in establishing full heat exchange
capacity from the condenser s at full firing capacity because of
thermal and flow characteristics of the process fluid being heated.
Establishing generalized convection circulation in vessels filled
with raw petroleum products can be problematical during the heating
startup phase due to high viscosities, the effect of low
temperature exposure on viscosities variations in water content
particularly as that is trapped next to heating elements, and,
tendency of product to establish and accelerate flow along channels
of least resistance rather than establish overall convection
currents.
[0102] Reliable, stable operation during this initial startup
period when demand for product temperature is at its maximum but
tolerance of heat absorption is at its minimum is a major advantage
of the arrangement described herein over the Grunes et al
technology which requires stable operation above a minimum level of
heat input over a minimum period of time to establish and maintain
a liquid block at the `resistor` in order to operate with the flow
of vapor and liquid in one direction.
[0103] The heat loop is not a heat pipe of any form and does not
use surface tension to pump the liquid back to the heated area.
Instead the heat loop is a generally conduit with two generally
upwardly extending legs and two generally transverse arms forming a
loop. A trap is formed at the evaporation area at the bottom of one
leg so that vapor is prevented from flowing up the leg at the
evaporation area and thus the vapor is driven upwardly along the
leg at the evaporation area and transversely along the top arm from
the heat source outside the tank transversely into the body of the
tank.
[0104] In one arrangement there is provided a coil to coil
configuration because this is very cheap and effective. In this
arrangement the head is developed solely by a height of liquid in
the trap. In this arrangement the head in the trap is the height of
the condensate in the conduit flowing downward and parallel to the
vertical heat-in coil relative to the height of the vaporizing
liquid in the heat-in coil, and this will drive the flow, including
the condensate accumulation, through the horizontal heat-out coil.
However the head developed by the leg of liquid can be supplemented
by a pump. The condensate is thermally driven via expansion of the
liquid into vapor, at a 1700 to 1 ratio of change of volume, so
that condensate will always reservoir in the lowest part of the
loop. Even suction pumps must have a steady supply of liquid to
draw on to work in a recommended fashion. They will draw gases on
start-up if need be, but thereafter are intended to run with a
continuous supply of liquid. This reservoir, therefore, provides an
element of standing head.
[0105] In the arrangement of the present invention, the drive to
the material in the loop comes from the rapid expansion, due to the
addition of heat, of liquid into a vapor by a volume expansion,
with water, in the order of 1700 to 1. However, if totally
unrestricted, that expansion will be in both rotational directions
so that, by providing a restriction to flow in the undesired
rotational direction by the head, flow is established in the
desired rotational direction
[0106] Thus the system provides in its broadest terms, a `heat
driven` loop; with as opposed to induced systems such as those
gravity-drawn in both directions as in a thermo-siphon, or,
capillary-drawn in one of the two directions as in a heat pipe,
either in a looped tube configuration or in a single tube. Flow is
biased in one rotational direction by restriction in the other
rotational direction but the specific means of providing this bias
is secondary to the concept.
[0107] Thus the drive is created by the thrust of the 1700 to 1
expansion of the fluid, to the effect that this is the dominant
feature. Loops as disclosed herein will incorporate at least some
element of standing head, but such head could be quite minimal
because of restriction of available height for a standing column
such as where the condenser is deployed in a flat plain, such as in
ground thawing applications where hoses are spread over ground
surface. While the formation of a reservoir must occur because the
condensate will pool in the lower part of the system, the nature of
the configuration of that particular system does not provide much
of what we would consider a reservoir or a standing column of
water. Nonetheless, the liquid gets back to the inlet of the pump
because it is driven by the 1700 to 1 expansion of fluid that is
occurring behind it. in other words, while some element of standing
head is always present, it may be dimensionally inhibited as above,
in any event, thermal drive, not the specific nature of the
configuration or the backstopping, is the dominant factor in
keeping the loop going round, which, in the case of pumps, is by
such force delivering the liquid back either to a trapping
configuration which becomes a standing column at the inlet of the
pump, or directly to the inlet of the pump with that force, in
which manner such force of flow constitutes an `effective standing
head`.
[0108] The arrangement described herein can be used in many
possible areas of use two examples of which are portable and
temporary heating applications including space heating and ground
thawing and which is very compact, inexpensive and trouble-free for
that purpose, and, petroleum industry applications particularly
including both tank heating, the heating of liquids in a storage
vessel, and line heating, the heating of gaseous and liquid fluids
flowing through conduits. This particular configuration with or
without pump is simply the most inexpensive and effective way to do
these things.
[0109] Applications for this technology include, but are not
limited to;
[0110] permanent installation for space and air replacement
heating;
[0111] temporary and portable use for space heating, space heat
treatment, and ground thawing;
[0112] vessel and pipeline heating;
[0113] can be employed with alternate heat sources, such as waste
heat reclaim & recovery of geothermal heat;
[0114] The concept can be directed to any heating devices
embodying;
[0115] the driving of a heat transferring fluid around a loop
employing thermal energy;
[0116] via expansion of volume due to change of state
[0117] biased in one direction by the creation of a head with or
without the assistance of a pump;
[0118] and which can be operated at all pressures from total vacuum
through unlimited high pressure.
[0119] It is inherent to the principle, that practical designs
based on the concepts described herein can either demand or
permit:
[0120] minimal system volume in relation to capacity;
[0121] minimal material for heat exchange;
[0122] simplest of fabrication;
[0123] and the--simplest of componentry.
[0124] Therefore, units based on this principle:
[0125] achieve minimal unit cost in relation to capacity, compared
to competitive principles;
[0126] are very compact, and;
[0127] are very dependable.
[0128] With regard to application regulation requirements and
certifiable performance, the system:
[0129] can be operated at all capacities in the pressure range from
total vacuum to zero gauge; therefore is self evidently completely
benign with regard to pressure hazards;
[0130] the fluid employed can be water and food refrigerant so that
it therefore is completely benign with regard to environmental
concerns;
[0131] can also be operated at significant capacities in the higher
positive pressures range with commensurately higher fluid
temperatures and compactness, with a minimal volume containment
such that, by regulation, the system is considered safe for
unattended operation.
[0132] Also, the system:
[0133] readily achieves high efficiency [80%+] and very high
efficiency [90%+] fuel combustion,
is not subject to off-cycle losses,
[0134] and separately vents combustion products to atmosphere and
not into the space air;
[0135] it is flexible in application; vaporizer and heater sections
can be in a single unit or widely separated as separate units
horizontally and/or vertically;
[0136] can be operated indoors and in all outdoor ambient
temperatures;
[0137] separately vents and does not place combustion products in
the space air;
[0138] it is flexible in application; vaporizer and heater sections
can be in a single unit or widely separated horizontally and/or
vertically;
[0139] can be operated exposed to all ambient temperatures.
[0140] There is a great deal of consciousness, and sensitivity,
regarding hazard in utilizing steam, both on the part of the
general populace and regulatory authorities.
[0141] 1. When operated as a "no-pressure" system, i.e., at neutral
gauge pressure [0 psig] or less [in a vacuum], the system has no
potentially explosive potential. On rupture, the fluid contained
will simply go nowhere, or collapse in volume.
[0142] 2. It is also a "no contaminant" system in that the fluid it
contains is environmentally benign, a mixture of water, and
propylene glycol which is commonly used as a coolant for exposed
food products so that it is not considered to be a contaminant
unless food is soaked such as to affect eating quality.
[0143] The system, described as operating under the above
conditions, is not only safe, but is obviously safe.
[0144] Local regulations throughout North America having
jurisdiction over pressure containing devices such as the HDL, are
generally based on ASME codes but may contain some local
variations. Therefore the following references to ASME based codes
are to be considered as largely accurate generalizations. ASME
codes have not anticipated a device such as the system described
herein, and have envisioned `boilers` in terms of relatively
simple, voluminous vessels, always operated under positive pressure
[0 psig and above].
[0145] Consequently, ASME based regulations do not specify 0 psig
as a significant threshold which, when exceeded, would incur more
stringent operational requirements.
[0146] In fact, the first significant threshold specified is 15
psig maximum, at and below which a boiler is designated a
"low-pressure" system. At this level, the system is considered to
have some explosive potential, but such that operational
requirements imposed are only that the device must be inspected by
regulatory authorities once per year, and there is no requirement
that the boiler must have formally qualified persons [ticketed
stationery engineers] in attendance while operating.
[0147] Since inspection-only does not impose significant economic
hardship, the first significant pressure threshold officially
encountered with the HDL is therefore actually at 15 psig. The
advantage derived from this higher pressure, is that the boiling
point of water at 5 psig is 100 deg C. or 212 deg F., while at 15
psig it is 121 deg C. or 250 deg F., making the system more
effective at transferring heat in relation to the amount of
material used in its fabrication.
[0148] Also from a regulation standpoint, the next and last
significant threshold is over 15 psig, beyond which pressure a
boiler is designated a "high-pressure" system, and also beyond
which explosive potential is considered sufficiently greater that a
requirement is imposed that, in addition to regular inspection, the
boiler must have formally qualified persons [ticketed stationary
engineers] in attendance while operating. That would constitute an
economic hardship in a significant number of instances, and would,
for example, preclude the utilization of the system in many
potential applications envisioned, particularly; portable and
temporary heating applications of all kinds where such qualified
persons are not normally provided, and, smaller capacity
permanently installed applications such as vessel and conduit
heating where the additional cost of constant attendance would be
quite onerous. Typically, high-pressure systems would operate at
250 psig with the boiling point of water at 232 deg C. or 450 deg
F. Note the substantially higher operating temperature, again
reflected in a lesser amount of material used in the systems
fabrication. Such higher pressures and temperatures warrant greater
consideration from a safety standpoint, however, the system
qualifies for an exemption from all existing boiler regulations,
regardless of its operating pressure and temperature, up a limited
but comparatively quite large capacity compared to other
systems.
[0149] In addition to the two operating conditions described above,
there is a third operating condition that applies particularly
significantly to the system, which becomes relevant with respect to
regulatory jurisdiction. Explosive potential is a function, not
just of pressure, but also of volume of fluid contained,
particularly liquid that will flash into steam on pressure release.
Therefore, ASME code based regulations, in order to exclude
involvement what might be considered incidental usage of relatively
small volumes of high pressure steam such as; steam clothes
presses, coffee making machines, some steam washers, etc., exempt
from jurisdiction applications wherein the wetted volume, when at
rest, of the boiler is below a specified minimum at which the ASME
codes, and the regulations on which they are based, are simply
deemed not to have jurisdiction that is no inspection and no
attendance requirements are imposed. Such exemption is quite
common.
[0150] The significance of this with regard to the system herein,
emanates from the fact that it is a minimal volume system
throughout, including the vaporizer since small amounts of fluid
can be driven through the system at very high velocities. These may
theoretically reach velocities up to that of sound, at which point
fluid compressibility related stall will occur. Consequently,
heat-carrying capability tends to be quite large in relation to
internal volume. So the third operating condition that applies to
the present system that becomes pertinent in terms of practical
ramifications is that of creating a construction where vaporizer
wetted volumes are at or below the designated volume above which
ASME based regulations are deemed to apply and below which they are
not.
[0151] In practice the volume at which this regulation occurs is
43.5 litres or 1.5 cu. ft. The heating capacities which can be
realized by the present system are many multiples higher than other
devices qualifying for exemption under this regulatory provision
related to volume. Furthermore, capacities realized up to 400,000
btuh and more are well within the range of practical usage in the
applications envisioned. Hence a considerable further advantage can
be realized by making avail of this particularly the exemption from
qualified attendance that such exemption conveys.
[0152] ASME is a well informed and accepted authority with respect
to the setting an exemption volume, and therefore the present
system under this operating condition must be considered in fact
reasonably safe.
[0153] Also, for most effective heat transfer, that the flow rate
should be adjustable such that the flow as exiting from the
vaporizer is predominantly vapor with a trace of liquid carry-over
in order to assure that;
[0154] a) the fluid is substantially vapor and conveying latent
heat, and does not include a proportion of superheated vapor
conveying sensible heat, which is comparatively inefficient;
[0155] b) and that non-vaporizing liquid additives, such as
anti-freeze to prevent freezing in the system during off cycles at
low temperatures also passivating agents to inhibit corrosion, are
conveyed throughout the loop.
[0156] In order to control the process, therefore there is provided
a viewing port which allows the operator to view the vapor emerging
from the evaporator so that the operator can control the flow rate
by adjusting the head to achieve the above conditions.
[0157] Thus the system operates by providing a physical
configuration such that the actionary force creating flow in the
desired rotational direction, is offset by the reactionary force
causing an accumulation of liquid in a vertical column such as to
create by differential liquid levels, or head, a balance of forces
and blockage of flow in the undesired rotational direction.
[0158] This can be achieved by means of the insertion of a pump
into the loop at any point in the loop such as to create,
substantially all or in part, an equivalent head. The inlet of the
pump may be immersed in liquid from a column of the liquid or the
pump, if not immersed in liquid, will impel vapor and draw liquid
pocketed in the system to the inlet of the pump
[0159] The adjustment of the flow rate, for most effective heat
transfer as set forth above, can be obtained by use of a pump,
where the flow rate now also becomes adjustable by varying the
rotational speed of the pump impeller or by adding a flow
calibration valve or flow regulator to the system. With loops that
are inherently tuned to optimum effectiveness by the specifics of
their physical design and have a fixed overall configuration, and
are not exposed to variable temperatures, a flow calibration valve
or regulator may not be required to achieve optimum
effectiveness.
[0160] It is to be noted that with all forms of pumps, flow rate is
affected by standing columns of liquid in the system, and depending
on their orientation with respect to flow direction, some will
exert a positive effect on flow and some will exert a negative
effect. Also, the extent of effect on flow rate of such standing
columns will vary from one type of pump to another. For example,
with centrifugal pumps, which do not in themselves constitute
complete physical intervention with regard to flow in that there is
continuous open passage through the rotor, the effects of standing
columns tends to be most pronounced, while with positive
displacement pumps which do provide physical intervention such
effects are diminished. Hence, smaller variations tend to be
handled satisfactorily, at least closely enough to permit
fine-tuning, by the less expensive centrifugal pumps, while more
extreme variations tend to require the more expensive positive
displacement pumps which are commonly of the reciprocating type.
Rotational pumps that exercise a substantial degree of positive
displacement, such as gear and vane pumps, are intermediate both in
producing satisfactory results and with respect to costs.
[0161] In some applications the relative locations of the vaporizer
and condenser are not fixed. This may occur for example in
applications where portable and temporary heat is required and the
equipment is moved from site to site. Therefore the horizontal and
vertical displacement of the vaporizer and condenser may vary as
the equipment is moved on the site or from one site to another.
This may occur particularly where the vertical displacement may be
significant such as in instances where the vaporizer is at ground
level and the condenser is placed at some level in a high rise
building. In this case, the system is therefore capable of
accumulating substantial liquid level differential heads. In this
case it may be desirable to minimize the effects of such pressure
exerted from the column through the pump by the utilization of a
positive displacement pump. In such pumps, the adjustment of the
flow rate to obtain most effective heat transfer can be achieved
simply by varying the rotational speed of the pump. Alternatively a
flow calibration valve or flow regulator can be added to the system
to detect flow rate and to vary the pump to obtain a desired flow
rate. In locating the pump, general good practice is to place the
pump such that it constitutes the lowest point in the system, and
that suction pumps, being more costly than lift pumps and prone to
cavitation with the hot liquids employed, should not be utilized
unless other factors proscribe the locating of the pump at the
lowest point in the system. Where the vaporizer is at ground level
and the condenser is located in the basement or a lower level, for
example in a parkade, and, due to the extremity of the downward
vertical displacement of the condenser from the vaporizer, and the
system is therefore not capable of accumulating significant liquid
level differential head, or delivering sufficient effective
standing head, it may be necessary to maximize the effect of the
pump by employing a pump of sufficient lift to raise the condensate
from the condenser level and with proper adjustment deliver it with
adequate head to achieve flow rate for most effective heat
transfer. Most effective heat transfer is obtained where the heat
transfer takes place as a result of change of state rather than by
cooling, and this can be obtained by controlling the head generated
by the standing column and where provided the pump so as to
establish a mode where minimal liquid is transferred while
providing the entrainment of a trace of liquids carrying over
non-vaporizing additives such as anti-freeze and passivating agents
into and throughout the system
BRIEF DESCRIPTION OF THE DRAWINGS
[0162] Embodiments of the invention are described herein in
conduction with the attached drawings as follows:
[0163] FIG. 1 is a schematic cross sectional view of a first
configuration of heating system according to the present invention
for the heating of oil in tanks primarily for separation of
water/oil emulsion.
[0164] FIG. 1A is a cross sectional view along the lines A-A of
FIG. 1.
[0165] FIG. 2 is a schematic cross sectional view of a second
configuration according to the present invention.
[0166] FIG. 3 is a schematic cross sectional view of a third
configuration of heating system according to the present
invention.
[0167] FIG. 4 is a top plan view of the condensation section of the
heating system of FIG. 2 which is within the tank.
[0168] FIG. 5 is a schematic cross sectional view of a
configuration of the condensation section of the conduit for use in
heating fluid within a duct.
[0169] FIG. 6 is a top plan view of the evaporation section of the
heating system of FIG. 3 which is arranged for connection to the
section shown in FIG. 4.
[0170] FIG. 7 is a front elevational view of the evaporation
section of FIG. 6 of the heating system of FIG. 3.
[0171] FIG. 8 is a side elevational view of the evaporation section
of FIG. 6 of the heating system of FIG. 3.
[0172] FIG. 9 is a schematic illustration of a modified
configuration of heating system according to the invention for use
for example in ground thawing
[0173] FIG. 10 is a schematic illustration of a further modified
configuration of heating system according to the invention for use
for example as a portable air heater.
[0174] FIG. 11 is a side elevational view of the portable air
heater of FIG. 10 showing a typical layout.
[0175] Table A attached hereto shows a list of possible fluids for
use in the system as heat transfer medium.
DETAILED DESCRIPTION
[0176] FIGS. 1 and 1A show a first configuration which is shown for
heating a fluid within a container 4.
[0177] It will be appreciated that each of the different
configurations shown and described herein can be used in different
locations for heating different materials including water, oil or
petroleum products and air. Thus in FIG. 2 the configuration is
shown for use in heating air within a duct for example in a space
heating system for generating heated air for heating a building or
for example in heating make up air for applying heat to air taken
from the exterior of the building for applying heated air into the
building to make up air drawn from the building in ventilation.
[0178] The configuration shown in FIG. 3 is again shown for heating
or other fluid within a tank. The configuration shown in FIG. 5 is
shown for heating liquid within a pipe or duct.
[0179] However it will be appreciated that the configuration of the
evaporation section as described hereinafter can vary and be
selected from any one of the configurations shown herein for use
with the different fluids to be heated. Yet further additional
configurations can be provided for the evaporation section which
are not shown herein.
[0180] Advantage can be obtained by encapsulation of the
evaporation section within a heat communication medium such as a
heating oil but this is not essential to any of the configurations
shown.
[0181] Advantage can be obtained by providing a manifold which
connects the evaporation section to the condensation section so
that one or more conduit portions from the evaporation section can
connect to a different number of conduit portions in the
condensation section. However the use for the manifold is not
essential and the system can comprise a single complete conduit
which communicates with both the evaporation section and
condensation section or can comprise a multiple number of separate
conduits each independently connected to the evaporation section
and to the condensation section.
[0182] Turning firstly to FIG. 1 there is shown a first
configuration in which the fluid 4A within a tank 4 is heated by a
heat loop 10 according to the present invention including a
condensation section 11 and an evaporation section 12. The heat
loop is formed by a pipe of rectangular cross section including an
upper leg 13 and a lower leg 14 which are parallel and spaced by an
open section 15 therebetween. The legs 13 and 14 are horizontal and
extend from the evaporation section outside the container into the
container to the condensation section 11. The heat loops pass
through a bulk head 16 of the tank at one wall of the tank.
[0183] The horizontal legs 13 and 14 are connected by vertical leg
portions 17 and 18 which are short in comparison with the length of
the legs 13 and 14.
[0184] The evaporation section 12 is located within an
encapsulating container 19 which has a cylindrical peripheral wall
as best shown in FIG. 1A which fully encompasses the legs 13 and 14
and the leg portion 17. It will be noted from FIG. 1A that there
are provided two heat loops side by side and it will be appreciated
that the system may include only one such heat loop or a series of
such heat loops side by side and spaced within the encapsulation
container 19 and extending therefrom into the tank 4. The
evaporation section is contained within a housing 20 including a
burner 21 which burns a suitable fuel for heating the outside
surface of the encapsulation container 19. The ends of the
encapsulation container are closed by the bulkhead 16 and by an end
plate 22 so as to be fully closed around the evaporation section 12
and to enclose therebetween a heating oil 23 which is heated by the
combustion from the burner 21 so as to transfer heat from the
outside surface of the encapsulation container 19 to the
evaporation section of the heat loops. The housing 20 includes a
flue 24 for escape of the combustion products from the burner 21
exiting from the housing 20 outside the container 4.
[0185] The heat loop 10 contains a heat transfer medium 25 which is
in liquid form at the bottom of the heat loop and in vapor form in
the top of the heat loop. The amount of the heat transfer medium is
arranged so that the surface 26 is within the leg 14 and is
confined by a bulkhead trap member 27 at the junction between the
leg 14 and the leg portion 18. Thus the bulkhead trap 27 extends
downwardly at the leg portion 18 into the liquid below the surface
26 so as to provide a trap which prevents vapor from entering the
leg portion 18 from below thus causing vapor to flow only in the
clockwise direction and around the loop and preventing backflow of
vapor.
[0186] In the evaporation section 12, the liquid is heated so as to
generate a vigorous boiling action sufficient to generate vapor
rapidly in the evaporation section. The vapor is prevented from
running along the leg 14 by the trap 27 and thus must rise along
the leg portion 17 and run along the leg 13 to generate a flow
around the loop in the clockwise direction. The dimensions of the
loop relative to the amount of heat applied through the
intermediate heating oil 23 to the evaporation section is arranged
so that the vapor moves at high velocity greater than 500 feet per
minute and more preferably of the order of the speed of sound so as
to generate rapid flow of significant volume of the vapor so as to
transfer the latent heat of evaporation of all of that volume of
vapor from the evaporation section to the condensation section
where all that vapor condenses. The maximum efficiency can be
obtained when all of the vapor is condensed and when little or no
heat is transferred from the liquid to the fluid for A by cooling
the liquid.
[0187] It will be noted that in the leg portion 18, there is a
volume of liquid up to a surface 26A which generates a head of
liquid at a height H which is responsive to a pressure differential
across the trap 27. This pressure differential is equal to the drop
in pressure caused by the resistance to flow of the vapor within
the loop from the evaporation section to the condensation
section.
[0188] In FIG. 1 is shown a control system 70 for controlling the
supply of fuel to the burner. This includes a first temperature
sensor 71 in the process liquid, generally oil, within the tank.
The sensor may be located adjacent the leg 13 and is used in
conjunction with the control system as a thermostat. The control
system in response to the measured temperature acts to control the
supply of fuel to maintain a required energy supply to maintain a
required temperature within the process liquid. A second
overpressure or over temperature sensor 72 detects an upper limit
pressure or temperature within the system which exceeds a
predetermined operating condition. This is normally used to shut
down the system in the event that the pressure or temperature
exceeds this maximum allowable condition. When heating crude oil or
similar materials, the process fluid at start up is often resistant
to absorbing heat and thus acts in effect as an insulator
surrounding the condensation section. The control system of the
present device is arranged therefore at start up to operate in
response to the upper limit sensor either to modulate the fuel
supply to a rate commensurate with the rate of energy which the
process liquid can absorb or to cycle the fuel supply on and off.
Thus with the modulation system, the control unit 70 is arranged to
detect an over temperature condition and to reduce the fuel supply
until that over temperature condition is cancelled. The fuel supply
is then gradually increased until the over temperature condition is
again reached. The system then operates to find a balance at which
the fuel supply is equated to the maximum heat which can be
absorbed by the process liquid. As the process liquid increases in
temperature its resistance to absorbing heat reduces until it
exceeds the maximum energy input, in which case the maximum fuel
supply is maintained until the thermostat operates when the
required operating temperature is reached. The on-off cycling of
the fuel supply can be used in the same manner but is less
efficient to increase the temperature of the process liquid at the
maximum rate since the fuel supply rate is not optimized. Thus the
temperature sensor acts with the control unit as a thermostat at a
predetermined set temperature of the oil and the safety over limit
detector, which is responsive to an over pressure or over
temperature in the conduit, is arranged to modulate or cycle the
energy supplied to the evaporation section during a start up phase
below the set temperature to maintain heating of the oil while the
oil is resistant to absorbing heat.
[0189] Turning now to FIG. 2, there is shown an alternative
arrangement which operates on the same principle but has a number
of modifications. The evaporation section is modified so as to
provide an improved heat transfer efficiency. Thus the evaporation
section comprises a coil 30 of the loop which is shaped into a
helix extending from the bottom leg 14 to the top leg 13. The
helical coil is mounted within a cylindrical encapsulation chamber
19A with a cylindrical heat receiving surface 19B facing inwardly
toward the axis of the cylinder. The burner 21A is located on the
axis and comprise a simple single burner nozzle which burns a
suitable fuel primarily natural gas which thus can form an
unobstructed flame within the combustion zone defined by the inside
surface 19B. Between the inside surface 19B and an outside surface
of the cylindrical encapsulation chamber 19A is provided a heat
transfer oil as previously described.
[0190] The coil is spaced from the inner and outer walls of the
cylindrical container leaving space for the oil to generate
convection currents to transfer heat efficiently and constant
temperature from the inside surface to the whole of the coil housed
within the cylindrical container.
[0191] In this embodiment the trap within the bottom leg 14 is
replaced by a U bend form of trap indicated at 27A. Thus there is
formed two legs 27B and 27C of sufficient length to contain the
head H of the liquid within the leg 27C to match the pressure drop
through the loop caused by resistance to flow. It will be
appreciated that the resistance to flow within the more complex
loop shown in FIG. 2 is higher than that in the simple loop shown
in FIG. 1 so that there is a requirement for an increased height of
the head H. The head is self adjusting provided the length of the
trap is sufficient so that the liquid does not pass the bottom of
the trap allowing vapor to bubble over and move in the opposite or
counter clockwise direction. This length can be adjusted in order
to ensure that the head H has sufficient length by increasing the
length of the U-bend. On method by which this can be achieved is by
forming the section of the conduit at the U-bend from a flexible
pipe material. The U-bend can then be formed by draping the
flexible material over suitable supports arranged to provide the
required leg length. The trap shown in FIG. 2 is outside the
evaporation section separate therefrom allowing such adjustment to
be readily effected depending upon actual conditions in an
installed location of the system. The vaporizer section thus may be
connected to the condenser section with flexible hose which would
permit the vaporizer to be located at lower level than the
condenser within the capability of the system to maintain desired
fluid flow characteristics. So that the vaporizer sits on the
ground and condenser tubes are at a higher level.
[0192] In FIG. 2 the upper leg includes a manifold 13A and the
lower leg includes a manifold 13B allowing the manifolds to be
connected to a plurality of the loops within the condensation
section. Thus a single coil may be connected to a plurality of
condensation loops or a plurality of coils may be connected to a
single condensation loop or a plurality of coils may be connected
to a plurality of condensation loops.
[0193] In FIG. 2, the fluid to be heated is air 4B within a duct 4C
driven by a fan 4D. The loop 11 in the condensation section may be
a complex multi pass loop including fins 4E so as to provide a
large surface for engaging the air within the duct.
[0194] In FIG. 3 is provided an arrangement including the manifold
13A and 13B. On the condensation side of the manifold is shown a
single loop in the condensation section indicated at 11 of a simple
nature. Again the loop may be more complex including a plurality of
such loops in parallel or in series. The loop in the condensation
section 11 maybe arranged so that the legs are horizontal as
indicated in dash line 13A or the legs may be inclined upwardly as
indicated in solid line 13B. It will be appreciated that the
inclined arrangement shown at 13B provides additional gravitational
forces for carrying the condensate back to the return manifold 13B.
However the flow necessary to carry the medium to the top of the
loop provides an additional resistance to flow which thus may
require an increased height H of the head of the liquid within the
trap. The velocity of the flow is arranged so that the condensate
within the first leg is carried by the vapor so that none returns
to the evaporator section along the vapor leg but all is carried
around at the end of the loop into the condensate leg to return to
the evaporator section through the condensate leg and through the
trap.
[0195] In the embodiment of FIG. 3 the evaporation section is
defined by a pair of spaced tanks 40 and 41 which are connected by
transverse heat transfer tubes 42. The arrangement of the heat
transfer tubes is shown in more detail in the figures described
hereinafter. The vapor leg 13 is connected to the top of the tank
40 and receives vapor therefrom. The leg 14 extends to the bottom
of the tank 41 to form a trap 27C. The burner 21 is located between
the two tanks to apply heat to finned heat transfer tubes 42. The
liquid within the tanks communicates through the tubes 32 and boils
within the tubes 42 so as to generate vapor in the upper part of
the tanks and the upper tubes and to generate sufficient vigorous
boiling action so that the liquid also enters the upper tubes and
keeps the upper tubes wetted. The vigorous boiling action generates
high velocity vapor which enters the leg 13 and is prevented from
entering the leg 14 by the trap 27C.
[0196] In FIG. 4 is shown the manifolds 13A and 13B on the exterior
of the tank 4. The manifolds are connected to a plurality of the
loops, each including an upper leg and a lower leg 14 extending
from the manifold 13A to the manifold 13B. It will be noted that in
FIG. 4 the bottom leg 14 is offset to one side of the top leg 13 so
that the leg 13 does not lie directly vertically above the leg 14
but instead both are exposed in plan view. This arrangement maybe
provided in order to allow increased communication of heat by
convection in the vertical direction from the upper surfaces of the
legs 13 and 14.
[0197] Turning now to FIGS. 6, 7 and 8, there is shown more detail
of the configuration of evaporator section shown in FIG. 3. Thus
the tanks 40 and 41 shown in plan view in FIG. 6 are connected to
the pipes 13 and 14 which extend to a connector plate 43 and 44
respectively for connection to an additional duct portion extending
from the connector plate to the respective manifold 13A, 13B. The
tubes interconnecting the tanks 40 and 41 are arranged in two rows
42A and 42B with the row 42A arranged between the tubes of the row
42B so as to allow heat and combustion products passing between the
tubes of the row 42B to impact upon the underside of the tubes of
the row 42A. This configuration improves the communication of heat
from the burners 21 underneath the tubes to the tubes and to the
liquid boiling within the tubes. A flue vent is communicated with
the chamber 45 surrounding the tubes on the combustion zone and
extends from the top of the combustion zone rearwardly and then
upwardly to a top connection plate 47 of the flue 46. The legs 13
and 14 include horizontal portions extending rearwardly together
with vertical portions which extend downwardly into the top of the
respective tank at a position midway across the width of the tank.
The combustion chamber is mounted on a stand 50 which is located
under suitable frame members 51 of the structure which support the
combustion chamber.
[0198] In FIG. 5 is shown a concentric arrangement which is
provided as a condensation section from the leg 13 to the leg 14
where the condensation section is formed as a hollow cylinder
within a duct 60. Fluid flowing within the duct thus enters a wider
section of the duct as indicated at 60A within which is located the
hollow cylinder 61 forming the condensation section. Thus the fluid
within the wider section 60A can pass around the outside of the
hollow cylinder and also through an interior 62 of the hollow
cylinder to provide an increased contact surface between the
condensation section and the fluid to provide an improved heat
transfer therebetween as the medium condenses within the
condensation section.
[0199] The condenser heat exchanger which is a hollow section metal
may have a single vaporizing section or may lead to one or a
multiplicity of condensing sections.
[0200] The vaporizer water legs are fabricated metal containers
forming manifolds for the condenser heat exchanger sections.
[0201] The vaporizer heat exchanger is a hollow section metal which
may be finned and can be increased or decreased in number and
length in order to increase or decrease efficiency of heat exchange
from heating source.
[0202] The heating medium may be any liquid or liquid mix,
typically water or water/glycol, generally including a metal
passivating agent.
[0203] The heat source may be a direct flame from an introduced
flame, or could also be heated via a secondary heating medium such
as hot oil delivered to an encasement around the vaporizer heat
exchanger tubes. A common source of hot oil can heat either a
single or a multiplicity of Heat Driven Loops.
[0204] The pressure differential trap may be a condenser return leg
extended down into the condensate tank.
[0205] The liquid level differential and pressure creates pressure
that impels vapor into outlet leg of condenser and prevents
back-flow of vapor into return leg.
[0206] Vapor flow, that is the velocity of vapor, as dictated by
the cross sectional area of the outlet leg, the resistance to flow
of the condenser, and the pressure differential across the outlet
and return legs of the condenser created by the liquid level
differential in the trap, carries all condensate in the direction
of vapor flow.
[0207] Condensate flow, that is the condensate driven back to the
vaporizer is effected by vapor flow but there may be some gravity
assistance if condenser operating angle is above horizontal.
[0208] This allows a range of condenser operating angles from
horizontal. The above principle is expected to be effective in
moving the major flow of condensate in the same direction as the
vapor at angles of at least 10 degrees from horizontal. `Effective`
can be defined as substantially achieving the enhancement of heat
exchange associated with unidirectional flow of vapor and
condensate as opposed to counter-directional flow. Theoretically,
by increasing the trap differential pressure and regulating the
size of the outlet leg of the condenser, the angle from horizontal
could be extended to 90 deg.
[0209] There is a region of turbulent boiling in the sealed system
and the starting pressure can be regulated to anything that can be
achieved above a complete vacuum. Having established the starting
pressure, the void space is generally purged with an inert gas,
such as argon. Especially under vacuum conditions, boiling will be
turbulent with large bubbles of steam carrying globs of liquid
along with it, but without the liquid bridging the conduit to avoid
the formation of a bubble pump. These globules of water will splash
into the upper vaporizer heat exchanger tubes keeping them wet,
and, to some extent, be carried into and possibly through the
condenser.
[0210] It is the adjustability of the differential pressure between
the supply and return legs of the condenser plus the ability to
achieve higher pressures sufficient to overcome resistance imposed
by more complex configurations, even involving the entraining and
lifting of condensate, that distinguishes the arrangement of FIG. 3
from the arrangement of FIG. 1 of the technology. The arrangement
of FIG. 1 has its particular merits in that it has a very simple
layout that does not rigidly confine the heating medium in any part
of it. Therefore the medium can be water only, which can freeze
without the accompanying expansion damaging the device, and that
the device can be fired without harmful effects from a frozen
condition. Utilizing water only can present an advantage in that
exposure to heat can cause breakdown of chemically more complex
substances [such as glycol]. In the oil industry, these devices
will commonly be used outdoors, so these qualities could be of
significance.
[0211] Other load demands could consist of mechanical utilization
of energy. This would include, for example, the driving of a
turbine for any number of purposes including the generation of
electricity, the direct driving of a pump, fan, etc.
[0212] It may be possible to utilize mechanical back-flow resisting
devices such as ball-check, swing-check, or, spring-loaded valves
such as to increase resistance to back pressure. However in
practice, mechanical methods of blocking back pressure may be
impractical in that they eventually will require maintenance.
Conventional steam traps, for example, are susceptible to
occasional problems. Compared to conventional steam systems the
present invention may use different liquids, higher temperatures,
higher vapor and condensate velocities etc, plus a need for rugged
reliability. It is one of the distinguishing features of the
present arrangement that it is entirely `thermodynamic`, i.e., heat
driven, without any moving parts.
[0213] One problem which can arise is the accumulation of inert
gases which is a commonly encountered phenomenon with this type of
technology. A gradual build-up of inert gases occurs in these
systems, depending on materials utilized and chemical action
between them, which displaces vapor and decreases effectiveness,
which, with single tube technology, sometimes determines service
life because its effects are not readily monitored or remedied. It
is inherent to the present principal of operation that this major
concern becomes much more manageable and is therefore an important
feature of the invention.
[0214] A loop with significant force of flow such as the present
arrangement, has the advantage that any inert gases in the system
will be driven into what is referred to as an accumulation sector,
which is the sector of the loop just before the trap and will be
confined there while the system is in operation due to the forward
flow of the vapor and the locking or trap effect of the liquid in
the trap. Thus an access opening 75 is located immediately in
advance of the trap for sampling of the presence of inert gases and
for purging of those gases. It will be appreciated that in the
presence of such gases, the opening of the access opening by
service personnel will cause the vapor pressure and flow to
discharge the inert gases through the opening until the presence of
vapor in the discharge indicates that all gases have been purged.
Such inert gases may be introduced for purging and subsequently not
fully evacuated, such as argon which is commonly used for this
purpose, and/or produced as a result of chemical activity such as
hydrogen as from reaction between water and iron, the predominant
element in mild steels and present to some degree in stainless
steels, and which occurs even in the absence of free oxygen, hence
the need for passivating agents. With the arrangement as described
herein, that sector would normally be out of or at least extending
partly out of the immersed portion of the heating element, the
significance being that it is accessible in that it will not be
completely immersed. The build up of inert gases can be detected by
a decrease in temperature in an area of the conduit immediately
upstream of the trap which is caused by the inert gases preventing
the vapor from condensing in that area and thus properly heating
the conduit. Thus the temperature at this area can be monitored on
an ongoing or periodic basis to detect an unacceptable build up of
the inert gases. Alternatively, the inert gases when they build up
will reduce the vacuum in the system when shut down and again their
presence can be detected by service personnel carrying out a
pressure test at shut down and detecting the presence or reduction
of the initial preset vacuum level.
[0215] With single tube technologies whether tubes are employed
singly or in a plurality, such as conventional heat pipes and
thermo-siphons, as in the prior art of Spehar and Neulander
mentioned above, and which are commonly employed sloped upwards
into the vessel, the inert gases accumulate and remain, whether the
system is in or out of operation, in what is referred to as a
`block` in the high end of the tube, which is the sector furthest
immersed in the process fluid and most inaccessible.
[0216] In a sector where there is such accumulation of inert gases,
heat exchange is significantly impaired because the inert gases
block out vapor and preclude the change of state which is the
substantial means of conveying heat. Only sensible heat from
liquids that may flow through the sector would be transmitted from
the accumulation sector.
[0217] With loops, the decline is such that effective heat exchange
is significantly impaired but not altogether eliminated because
there is at least some sensible heat available from condensate and
throw-over liquid flowing through that sector. At the boundary
between the sector of the heating element that is performing
normally and maintaining a substantially constant temperature, and
the sector where there is accumulation of inert gases, heating
element temperatures start to decline in an observable,
significant, and regular fashion.
[0218] However, with single tubes, there is no such flow of liquid
and heating element temperatures will decline much more drastically
and that sector is effectively `blocked`, or idled, for heat
exchange purposes. Moreover, with loops, when in full operation and
the system under positive pressure, the accumulation is moved to a
sector that is normally accessible for measurement of temperature,
the difference between the entry temperature of vapor to the
heating element and the temperature in the accumulation sector
being an indication of the degree of accumulation of inert gases,
and purging of the inert gases, utilizing the operating pressure of
the system itself, usually from the highest point in the system
just prior to the trap.
[0219] There is no practically convenient means of either
measuring, or even detecting, such accumulation with single tubes,
which occurs at its greatest extension into the process fluid, and
similarly, no practically convenient means of purging such
accumulation if it could be detected. With single tubes, such
measurement and purging devices would have to extend back through
the tubes themselves or through the vessel. These are very
difficult environments warranting correspondingly expensive
solutions compared to the simple access provided by the present
system.
[0220] This a significant improvement presented by the present
system over all single tube technologies also over the prior art of
the Grunes et al technology when operating below that critical
level where it flips from unidirectional flow, which causes such
accumulation to occur in a sector next to the trap as above, to
counter-directional flow which, with its particular configuration,
would likely cause dispersion of the inert gases throughout the
system while in operation which would generally impair
effectiveness, and, accumulation at a highest point when not in
operation.
[0221] The heating of water and petroleum products, especially
crude petroleum products that are towards the "heavy", that is
comparatively viscous end of the scale, present differing problems.
Water is comparatively easy to heat. Resistance to heat transfer is
at its minimum at commencement when temperature differential is at
its greatest and increases as temperature rises. Convection
currents are readily established and the whole process is quite
dependable and predictable. For heating purposes, water properties
are `constant`, on both a case to case basis, and with respect to
any individual case. With petroleum, on the other hand, heating
properties are much more variable and complex in that:
[0222] [a] Petroleum has `non-Newtonian` flow characteristics. This
has to do with viscosity varying not only with temperature but with
also flow velocity and boundary effects between currents in
different directions in the same vessel. In other words, flow,
particularly convection flow, tends to be affected in rather
unpredictable ways by specific configurations of vessels and
heating elements. This effect tends to be more pronounced with
heavier, more viscous, petroleum products.
[0223] [b] Crude petroleum product varies greatly in content and
characteristics; viscosity of liquid petroleum product, proportion
of liquid petroleum product, amount of entrained gaseous petroleum
product, proportion of water, salinity of water, amount of
entrained particulate matter, sand, usually and associated more
with heavier product, these would be the main variables.
[0224] [c] Boundary effects between the heating elements and
petroleum products are much more problematic, with crude petroleum
especially, in that; resistance to heat transfer will always be
higher than with water and will be variable depending on the
effects of all of the forgoing, and, the flashing of petroleum
products and/or entrained water into gases causes foam to collect
in the immediate vicinity of heating elements which further resists
heat transfer.
[0225] [d] Also, petroleum products, particular heavier crude
products, have a tendency to `channel`, at least initially, when
being heated, i.e., set up localized convection currents which get
hotter, less viscous, and therefore more active, while bypassing
volumes of un-circulating and unheated liquid. Eventually, enough
heat is transmitted to these un-circulating volumes that they
become entrained in an overall convection flow pattern.
[0226] [e] The foregoing are `non-constant`, as well as variable,
in the sense that same configurations do not always set up same
flow patterns and rates of heat transfer, as is the case with
water, because the summation of the effects of the foregoing always
produce some net differences with respect to flow and heat transfer
characteristics and these differences are often not of an
observable nature and scale.
[0227] With water, the heat loop system may have a heat transfer
rate of 10,000 btuh/sq ft. of heat exchange surface at commencement
of heating at somewhere just above freezing which will decrease in
a regular fashion to perhaps 8,000 btuh/sq ft when the water
reaches a control temperature of somewhere just below boiling. With
a vessel of a given size and configuration, filled to a given
level, and heated with a heater of a given size, configuration and
capacity, this type of result will not vary from instance to
instance.
[0228] With petroleum product, at commencement of heating with
cold, stiff and highly adulterated product, the initial heat
transfer might be very low, say in the order of 200 btuh/sq ft. of
heat exchange surface. This may rise to 1000 btuh/sq ft as
convection circulation is established and then decrease to 800
btuh/sq ft as control temperature is reached. As previously
indicated, this may vary from instance to instance, even in a given
application.
[0229] The differences between the heat transfer characteristics of
wafer and petroleum products tends to be amplified with; cruder, as
opposed to more refined, and, heavier, as opposed to lighter,
petroleum products.
[0230] In other words, the technology must cope not only with great
variation in demand, but great variation in heat transfer
characteristics as load is imposed. It is inherent to the present
design that it will self-adjust to all of his--there will be
unidirectional flow from start up to shutdown, and at all levels,
of operation.
[0231] That is not the case with the Grunes et al technology.
Heating portable water is an application that lends itself readily
to full on/full off operation. It is inherent to the Grunes et al
technology that it will tend to flip back and forth between two
modes of operation at intermediate levels of operation. It must get
up to some minimum level of operation to either; flip over through
boiling action, or create through condensation, enough liquid to
maintain a level in the accumulator, which is critical to
establishing and maintaining unidirectional flow. At below that
level of operation, the restriction and the accumulator associated
with it, which has a largely fixed, at least a minimum, draining
rate, will remain clear of liquid. Vapor and condensate will flow
in opposite directions in both legs of the device in the manner of
a conventional, single tube thermo-siphon. It could actually be
considered to be two single tube thermo-siphons abutting each other
at both ends.
[0232] The arrangement of the present invention has an improved
operation because:
[0233] [a] the amount of material employed in relation to the
amount of heat transferred. Because transfer is being accomplished
by change of state, the amount of energy that can be transferred by
a given amount of fluid is proportionate to the rate at which the
fluid is circulated each cycle representing the transfer of the
total latent heat capacity of the amount of fluid in the system. By
maximizing flow rate and therefore heat transfer rate both the
amount of fluid required and the amount of material required to
create the necessary volume to contain it will be minimized. That
would be within the physical capability of the system to transfer
heat in and out, of course, but that too can be enhanced in
relation to volume enclosed by the addition of suitable fins to
facilitate heat transfer, encapsulation to maximize average contact
temperature, etc. Maintaining flow rate of vapor and condensate in
one direction, as compared to vapor in one direction and condensate
in the other and resisting each other, at all levels of operation,
will maximize effectiveness. The capability of accomplishing and
maintaining that at all levels of operation in this particular
application represents a considerable improvement.
[0234] [b] the ability of the device to sustain a driving force
through the system at all levels of operation. This extends beyond
[a] above in that there are potential applications where the
ability to create pressure differentials and overcome resistance is
a critical to the devices operation. This would include any
application where the system is utilized to perform a mechanical
function. With the Grunes et al technology, at below some critical
level of operation, such a device would cease to operate.
[0235] Points [a] and [b] in particular are general advantages that
the present technology presents over the Grunes et al technology.
The capability of maintaining stable operation under varying and
unpredictable loading, a common condition in some aspects of
petroleum processing, particularly with cruder and heavier
products, is a specific advantage in that application but presents
potential advantages in other applications as well. Point [b] above
is not directly associated with the heating or processing of any
particular substance it is simply an advantage to have a device
that provides a force to operate something to be capable of doing
so throughout a full range of operating levels as opposed to just
an upper portion of that range.
[0236] There are a number of different types of traps which are
possible for use with this construction;
[0237] 1. A submerged bulkhead which is shown in FIG. 1. With this
configuration, the liquid must flow under a bulkhead to pass into
the vaporizing area. The down-leg of the trap is made distinct from
the vaporizing area by this panel but the up-leg of the trap and
the vaporizing area are one and the same.
[0238] 2. The "U" Trap shown in FIG. 2. The legs of the trap are
separated by being placed in separate vertical conduits joined at
the bottom with the up-leg of the trap leading into the bottom of,
and is distinct from, the vaporizing area.
[0239] 3. The Down-leg Trap shown in FIG. 3. In this configuration,
the up-leg of the trap and the vaporizing area are one and the
same.
[0240] All these work according to the same principle--back
pressure in the vaporization area opposed and balanced by liquid
level differential pressure in the trap. The range of back pressure
that can be tolerated can be adjusted in all three cases by
increasing the depth of the trap.
[0241] The "U" Trap configuration presents the advantages;
[0242] It is a simple and straightforward matter involving minimal
additional material to increase its pressure range by making the
"U" deeper, whereas increasing the range of the other
configurations would involve deepening the whole vaporization area,
which would involve considerably more bulk, and, it is inherent to
the "U" Tube approach that violent boiling action will not
penetrate through to the up-leg because the up-leg will always be
in its entirety below the boiling area, which is not necessarily
the case with the other two configurations. It could be claimed
that these configurations are more susceptible to violent boiling
action reaching the up-leg of the trap which would then nullify or
substantially impair the desired effect of driving flow in one
direction.
[0243] However, having said all that, it is a simple matter to
adjust the other configurations to these disadvantages simply by
having the bulkhead and the open-ended conduit descend into a well
provided for that purpose in the bottom of the vaporization
area.
[0244] The submerged bulkhead and the Down-leg traps have an
advantage over the "U" Trap in that extra material is not required
for the up-leg.
[0245] The down leg trap shown in FIG. 2 has the advantage that the
condensate is collected in the heating source and hence remains
heated without losing any heat by sitting in a separate or exposed
trap. This could be overcome by providing suitable insulation.
[0246] Turning now to FIG. 9, there is shown a system similar to
that described above which includes the following major elements;
vaporizer A; condenser in the form of ground thawing hoses B; the
main loop C; liquid feed pump D; liquid storage container[s] E; air
compressor with storage tank F and generator G.
[0247] The system further includes the heat transfer medium 101A as
liquid; 50% water/50% propylene glycol, and 101B as vapor; liquid
storage container[s] 102; solenoid valves 103 A and B; compressor
with air cylinder and circuits 104 A and B; flow regulating pump
105; heat source 106; vaporizer 107; heat transfer pump 108;
multiple port manifolds 111 A and return B; flow viewing ports
supply 112 A and return 112 B; pressure control or relief 113 A and
temperature control 113 B; sector where condensation is completed
114; flow calibration valve 115; loop vent valve 116 and generator
117.
[0248] At rest, after assembly on site all liquid heat transfer
medium as liquid 101 is in the container 102, and the loop itself
is void of liquid and at zero gauge pressure [0 psig]. The solenoid
valves 103B are open and 103A are closed The liquid is in the
liquid storage container 102 isolated from the Loop mode at
initiation of the start-up procedure.
[0249] In preparation, the compressor 104 with circuits 104A open
and 104B closed, is turned on, and air in the Loop pumped out to
create a pre-selected partial vacuum, such as is attainable with
equipment available for practical use in the field which may be in
the order of 6 in Hg. Then the compressor 104 is automatically shut
off in response to an internal control set at that proportion of
vacuum.
[0250] In start-up, the solenoid valves are switched into the
container 102 open to the Loop mode with the solenoids 103A and
103B open. Simultaneously, the flow regulating pump 105 and the
heat source 106 are turned on. A charge of heat transfer medium as
liquid 101 is drawn from the container 102 into the Loop, and
thence through the pump 105 into the vaporizer 107. The transfer
pump 108 may be utilized to assist in charging the Loop, depending
on the vertical positioning of the container 102 relative to the
Loop. The liquid 101 is heated in the vaporizer 107 by the heat
source 106, and is increased in temperature until it changes state
into a vapor, also occasioning an increase of pressure and a rapid
and substantial increase in volume in the order of 1700 to 1 as
that occurs. This rapid increase in volume tends to force the fluid
in both directions, but flow is biased in one direction around the
Loop by the reactive force of the head 109 at the pump inlet such
as is trapped in the configuration of the Loop, which, with or
without combination with a head created by a pump 105, depending on
the adequacy of a reactive force created by the liquid column
atone, to create such bias.
[0251] The Loop is maintained in the start-up mode until the fluid
charge is sufficient in amount to complete a flow of liquid around
the loop, as indicated by the fluid, subsequent to heat release and
condensation in the ground thawing flexible hose 110, appearing
predominantly or entirely as a liquid passing through the return
viewing port 112B and thence providing an accumulation as the head
at inlet of pump 109.
[0252] The pressure in the Loop will progressively rise during
start-up in response to the continued operation of the heat source
106, until limited by a heat source pressure control 113A located
at the outlet of the vaporizer 107 and set at 0 psig maximum, or
alternatively, a temperature control 113B set at 212 degF., the
temperature commensurate with vaporization at 0 psig. In practice,
a combination of both a temperature control and pressure limiting
control or relief device may be used to supervise temperature and
limit pressure respectively, with the one acting in redundancy to
the other.
[0253] During Continuous Operation; when operation shows stability
as above, the solenoid valves are switched into the operating mode
with 103B open and 103A closed, and the container 102 is isolated
from the Loop.
[0254] At 0 psig, the vapor 101B has a temperature of 212 deg F. at
the point of control where emitted from the vaporizer 107, which is
the same as the boiling point of water when exposed to atmospheric
pressure. However, downstream from that point in the Loop, and up
to the pump 105, there will actually be a slight, progressive
reduction of absolute pressure/increase of vacuum, and commensurate
temperature, due to the draw of the pump 102. As well, in the
section where heat loss and condensation are occurring, in the
ground thawing flexible hosing 110, the initial temperature of the
condensate will also be at 212 degF., and there will be a loss of
sensible heat and temperature from the condensate as that
progresses through the hosing 110, but this will be small in
relation to the latent heat loss which is without decrease in
temperature. Moreover, the collective temperature reductions of the
two foregoing effects are minor such that for practical purposes
and discussion, the temperature throughout the Loop whether it
contains vapor or vapor/condensate mix, the temperature may be
regarded as being at a constant 212 degF. and the pressure at a
constant 0 psig. In any event, a hose 110 temperature which might
stand at a full 212 degF. does not occasion any significant boiling
of ground water from thaw because there would be instant surface
cooling as cold ground water comes into contact with and absorbed
heat from the hose.
[0255] It should be noted that, where it is practical and
permissible, the system can be operated at higher and lower
pressures than 0 psig, and at commensurately higher and lower
temperatures that 212 degF., should that be desired. For example,
operating at 15 psig might be considered in some instances because
that has a commensurate temperature of 250 degF., and is officially
considered "low pressure", which is regarded as not presenting a
particular hazard when operated without constant attendance.
[0256] Maintaining a head at pump inlet can be critical to
continuous operation because the combination of a partial vacuum
and elevated temperature may result in the pump being prone to
internal cavitation, i.e., the liquid likely to flash into a vapor
at the point where it enters the impellor where a further localized
pressure drop occurs. Therefore, the amount of the fluid charge,
and the configuration of the Loop, should be such that a liquid
pressure will be continuously exerted on the inlet of the pump
while in operation. Hence, the head at pump inlet, in combination
with the thrust of the rapid expansion of fluid, serves three
purposes; supplementing the impulsion of the pump in driving the
fluid around the loop, contributing to prevention of pump
cavitation, and, as an arrangement enabling accumulation of a
protective surplus for the fluid charge required by the Loop for
continuous operation.
[0257] With the system, a relatively steep downward temperature
gradient in the Loop, typical of conventional hot-liquid systems,
will commence only at the sector in the loop where condensation of
fluid is completed 114. In an optimized system, as properly scaled
and adjusted, that point is just before entry to the return
manifold 111B.
[0258] The system is further optimized in terms of heat transfer
capacity in relation to fluid mass flow and material employed, by;
configuring the Loop, providing a fluid charge such that a small
carryover of liquid from the vaporizer 107 can take place, and
making the system adjustable, such that by viewing fluid flow
through the supply viewing port 112A and adjusting the heat supply
and the fluid flow rate, usually by setting the heat source 106
capacity to a maximum, and adjusting either the rotational speed of
the flow regulating pump 105 or, with a fixed speed pump, adjusting
the flow calibration valve 114, such that observation at the supply
flow viewing port 112A indicates a trace of liquid passing through,
otherwise entirely vapor. This assures that the fluid is virtually
all being vaporized and is substantially conveying latent heat
only, and is not being superheated and partly carrying sensible
heat as well which by comparison with the former is inefficient. It
is a function of the flow regulating pump to keep that mix of
substantially vapor, minimally liquid at the point of entry into
the condenser 110.
[0259] Also, that small amount of liquid carryover serves another
useful purpose in that it assures that additives for other purposes
such as the antifreeze to prevent freezing of the fluid in any part
of the system, should there be shutdown in cold weather, and
passivating agents to reduce corrosion, are conveyed throughout the
Loop.
[0260] The use of a generator 117 to supply electrical power to the
pumps and compressor in order to make the system entirely self
sustaining and fully portables as opposed to connection to a fixed
electrical outlet, is optional.
[0261] During shut-down, the heat source 106 and the pump 105 are
shut off, and the Loop allowed to cool to facilitate handling.
Liquid will remain in the pump 106, vaporizer 107 and head or
liquid column portion of the Loop, and some condensate may remain
in the flexible tubes 110 of the thawing section. The solenoid
valves are switched into the liquid evacuation mode with 103A and
103B open. It is advisable at shutdown to then open the Loop vent
116 to atmosphere to neutralize the vacuum that will occur and
increase as the Loop cools. The air compressor 104 is turned on and
when the air storage cylinder is charged with pressurized air
circuit 104B is opened. Compressed air is then released into the
Loop, which drives the remaining liquid 101B out of the Loop and
back into the storage container 102. Completion of this can be
observed through the return viewing port 112B. Generally, the
resistance of the pump 105 to reverse flow assures that this air
pressure is exercised sufficiently in one direction to complete
evacuation of liquid. To further assure this, a check valve 117 may
be added to the Loop. Hence the fluid charge is evacuated from the
Loop and returned to the storage container 102.
[0262] The system may now be unassembled and removed from the
site.
[0263] Conventional hot-liquid-only ground thawing devices
typically operate at a liquid charge temperature of 170 degF. at
the supply manifold, which is reduced to 130 degF. at the return
manifold, a reducing but average temperature of 150 degF., due to a
sensible heat transfer to ground thawing of 40 btu for each lb of
fluid circulated. Attempting to operate at higher temperatures is
inhibited by localized flashing in the vaporizer of the water
portion of the liquid charge in the system into steam, which
creates appreciable loss of fluid through the venting to
atmosphere.
[0264] By comparison, the present system holds a constant
temperature of 212 degF. throughout, due to the fluid charge
leaving the supply manifold as a vapor at 0 psig with a
commensurate change of state temperature of 212 degF., and entering
the return manifold as a liquid, with condensation completed in
between at that change of state temperature, with a latent heat
transfer to thawing ground of not less than 1000 btu for each lb of
vapor/liquid circulated. Furthermore, the present system is sealed
when operating, so there are neither boiling nor evaporative losses
to atmosphere of the fluid charge.
[0265] Because thawing with the present system is at a
significantly higher and constant temperature of 212 degF., as high
as possible without causing `drying`, i.e., boiling away of ground
water which can be detrimental to thawing, as compared to a
declining but average temperature of 150 degF. with conventional
thawing devices, the present system creates an appreciably faster
rate of thaw.
[0266] Also, because with the present system mass flow circulation
to carry a given capacity is significantly less, and, other than a
small liquid feed pump to the vaporizer, the fluid is driven around
the loop by thermal energy causing expansion, as compared to a much
higher mass flow of liquid circulated wholly by an electrically
driven pump, the electrical power requirement for the present
system is comparatively quite small. This is readily supplied by a
compact and relatively inexpensive portable generator making
complete self containment and full portability more economical.
[0267] Also the system heat transfer medium, a mixture of propylene
glycol which is a food refrigerant, and water, is officially rated
as environmentally benign, and the fluid charge is retained in the
system at a maximum pressure of 0 psig, which presents no
pressure-related hazard. Furthermore, at significant capacities of
400,000 btuh and more, the volume of fluid contained is so small,
that it is below the amount at which ASME based regulations apply.
In other words, the present system is not only actually safe, but
is readily appreciated by prospective users as self-evidentially
safe, as well as being formally defined as safe under prevalent
regulations.
[0268] Furthermore, the present system is compact and, in terms of;
components, materials required, and manufacturing processes
employed, is relatively simple and inexpensive to build.
[0269] It should also be noted that the particular system
arrangement illustrated, enables charging the system with fluid
from original containers--such as the barrels in which premixed
liquids are received from liquid suppliers--and returning the
charge to those same containers. This particular system arrangement
produces considerable advantage in that liquid handling is
minimized and storage simplified--as well as provides a simple
means of measuring liquid loss by field users during as operating
period simply by checking levels going out and back in.
[0270] Turning now to FIGS. 10 and 11 there is shown an arrangement
for portable air heating where the condenser section 200 is mounted
at a variable position significantly higher or lower than the
evaporator section 201 so that a variable height column of liquid
is generated at the inlet to the pump 202. In this case the pump is
a positive displacement pump so that the rate of flow is positively
controlled by the rate of rotation of the pump regardless of
changes in the height of the column.
[0271] As shown in FIG. 11, the condenser section 200 is mounted in
a portable unit 204 with a radiator 205 and a fan 206 directing air
through the radiator for injection into an area to be heated.
[0272] The evaporator section 201 is similarly mounted in a
separate portable unit 207 and includes a combustion chamber 208
and a combustion burner 210 and an evaporation coil 211. The fluid
is communicated between the evaporation coil 211 and the radiator
205 by tubing 209.
[0273] For permanent, and portable and temporary space heating,
this arrangement has considerable flexibility in application. The
vaporizer section and the condenser section, coupled together, may
be deployed as a unit, located as desired and permitted in the
space[s] to be heated. In such deployment, with some limitation at
the lower end of capacities, the unit so formed, is competitive
with, and superior in performance to, any other type of indirect
fired heater.
[0274] However, the vaporizer and condenser sections may also be
deployed as separate modules and be displaced from each other
significant distances both horizontally and vertically.
[0275] This flexibility presents significant advantage in such
applications as portable and temporary heating in urban high-rise
buildings.
[0276] Currently, there are only two large scale distribution grid
modes for the delivery of energy convertible to heat, the most
familiar expressions of each being; the conduction of electricity
though cables, and the conveyance of natural gas through pipelines;
both modes being suitable for long range and localized distribution
grids. The conversion to heat, for such requirement, at points of
employment takes place through conductivity resistance in the one
instance and combustion in the other. Practical characteristics of
such grids are that they are flexible, relatively inexpensive, and
that energy costs/losses in transmission are acceptably low in
relation to energy delivered.
[0277] Other sources of heat energy would principally be liquid
fuels delivered in bulk lots in containers--such as propane in
which instance delivery is in pressurized containers and therefore
storage is of particular concern and consequently heavily
proscribed or even prohibited by regulation most notably in urban
high-rise contexts.
[0278] However, this arrangement represents a third and new grid
mode; it conveys energy from the heat source to the spot or points
of heat application in the form of the latent heat constituent in
vapor--and in a manner uniquely suited to smaller and portable
grids.
[0279] What specifically is meant by in this instance by way of
unique suitability and smaller scale grid distribution, are; a
practical means of heat creating energy transmission, readily
deployable and knocked down, of sufficient range such as to enable
spot heating or multiple point space heating, throughout the
interior of the type of high-rise buildings generally encountered
in densely populated urban centers, both upwards into the
commercial or living spaces and downwards into basement and parkade
spaces--well beyond the practical range of electrical cabling from
main panels--and inside and around which the storage of liquid fuel
is heavily proscribed or prohibited.
[0280] In such applications, this arrangement presents options for
the locating of the fuel consuming portion of the device, the
vaporizer, and the space heat generating portion, the condenser or
`heater`, not available with other types of systems, and that are
economically acceptable.
[0281] With electricity, for example, the vaporizer, which is quite
compact, can be located next to the electrical panel with energy
for heat generation supplied with an acceptable size and length of
cable from the panel. With propane, for example, the vaporizer can
be located adjacent to its storage area if and as permitted, with
fuel energy supplied in a standard manner with hose lengths that
give proper clearances. The condenser[s], or heater[s], can be
located as desired and are movable.
[0282] With this arrangement, the vapor can be driven at
sufficiently high velocities through a grid of such type that
energy cost/loss in relation to energy delivered, can be acceptably
limited. Delivery of vapor and return of condensate are through
acceptably small hoses that can be strung up and down through
high-rises in numbers of ways; through openings generally available
during construction, or stairwells and elevator shafts, or, on the
exterior of buildings.
[0283] In applications where potential hazard from vapor and
condensate hoses are a particular concern due to human habitation,
it is proposed that this arrangement be operated at 0 gage pressure
or less [no pressure] which presents no pressure-related hazard,
also that fluid contained is a mixture of water and a commonly used
food refrigerant, propylene glycol, which is rated benign with
respect to human contact and environment.
[0284] It should also be noted with respect to such flexibility in
application, particularly regarding vertical displacement of the
vaporizer and condenser upwards and downwards, and with regard to
the system being operated at optimum effectiveness, which may be
defined as a combination of; [a] transmitting heat substantially as
latent heat only, with the fluid exiting the vaporizer
substantially as an unsuperheated vapor, and [b] while entraining a
trace of liquid carryover including non-vaporizing liquid additives
such as anti-freeze and passivating agents for corrosion prevention
such that these will be carried throughout the system, with respect
to which certain effects of variable vertical displacement must be
considered.
[0285] In all applications for which this arrangement is proposed,
there will be a combination of some standing head, water in a
column, being exerted positively on flow, and some resistance to
flow to be overcome, as well as in some instances standing heads
being exerted negatively on flow that also have to be overcome. In
applications where the condenser configuration is such that gravity
would cause it to drain or stand in the lower portion of the
condenser such as to create a standing head exerting positive
effect on flow, there may be an absence of standing heads being
exerted negatively on flow.
[0286] Additionally, in any configurations that tend to restrict
the height of such standing columns, the thrust imparted to the
flow of condensate by the 1700 to 1 expansion of fluid from a
liquid to a vapor that is occurring behind the sector of the Loop
where condensate is progressively accumulating will tend to drive
the condensate into any available trapping configuration as well as
into such trapping configuration as may be specifically provided at
the inlet of the pump, and/or, directly into the inlet of a pump in
which latter case, due to force of flow, it provides a head, which
may be only a standing column of the liquid or it may be
supplemented by the effects of a pump.
[0287] The foregoing will be the case both where flow is solely
thermally driven, and where a pump or equivalent device supplements
such flow. In other words there will always be some element of
standing column and effective head in all forms of this
arrangement.
[0288] It also follows that in applications where that standing
column may be variable, such as in portable and temporary heating
and ground thawing, where the vertical displacement of the
vaporizer and condenser will vary from site to site and even on a
given site, this will tend to cause flow rate to deviate from
optimum effectiveness as that is described in the foregoing.
Variable temperature exposure may also tend to cause flow to
deviate from optimum effectiveness.
[0289] When the flow rate is too high in relation to heat
absorption, the fluid will only partially vaporize and will
alternate between surges of vapor and liquid, in the manner of a
bubble pump, such that a significant portion of heat may be
transmitted as sensible heat in the liquid which is less efficient
in terms of material employed to achieve a given capacity. When the
flow rate is too low in relation to heat absorption, the fluid will
not only completely vaporize but will also superheat such that a
significant portion of heat may be transmitted as sensible heat in
the vapor which is also less efficient in terms of material
employed to achieve a given capacity of heat transfer. In both
these non-optimum instances, flow tends to be unstable in that in
the first the heat exchanger material tends cool down and then
regain temperature alternately, and in the second tends to overheat
and then loose temperature alternately, with stability gained as
optimum effectiveness is approached.
[0290] In such circumstances, the addition of a pump to the Loop
will contribute to achieving optimum effectiveness in that a solely
thermally driven Loop which depends only on a standing column to
drive flow will be more profoundly affected by such variability and
instability, than a Loop with a pump which tends to significantly
dampen such effects. In fact, the addition of a pump plus a flow
calibration valve or flow regulator to fine-tune flow rate, becomes
a preferred means of assuring optimum effectiveness in all
applications because of ease and the relative steadiness created in
operation over a wide range of variable conditions. However, it
should also be noted that in fixed configurations where relative
locations of components do not vary and that are not exposed to
variable temperatures, without or with a pump, it may be inherent
to the physical nature of the design that flow is fixed at optimum
effectiveness without the requirement of a calibration valve or
flow regulator.
[0291] In variable configurations, as vertical displacement becomes
more extreme, different types of pumps will be more effective than
others in dampening variation of flow. Smaller variations tend to
be handled to a satisfactory extent, in that fine-tuning can be
provided by a flow calibration valve or flow regulator, by the less
expensive centrifugal pumps, while more extreme variations tend to
require the more expensive reciprocating positive displacement
pumps. Rotational pumps that exercise a degree of positive
displacement, such as gear and vane pumps, are intermediate in both
producing satisfactory results and with respect to costs.
[0292] It should also be noted, that full utilization of the head
created by the thermally created liquid level differential to the
point of using it exclusively in applications where variability and
instability are not a concern, will minimize or eliminate the
electrical or other energy requirement to drive a pump, as well as
the overall energy requirement of the loop when both a standing
column and a pump are utilized, because thermal energy can be
utilized directly from a fossil fuel source and at a very high
efficiency level in this Heat Driven Loop.
[0293] In an arrangement where there is a considerable distance
between the vaporizer and the condenser so that the hoses
transporting the fluids therebetween are long, it may be desirable
to apply electrical heat from a resistance heating wire in or on
the hoses to compensate for excessive heat loss. In this way the
vapor is maintained in the required vapor phase from the outlet of
the vaporizer to the inlet to the condenser without the necessity
to superheat the vapor. This technique will provide an improved
efficiency of heat transfer which will overcome the extra heat
energy required to heat the hoses electically.
* * * * *