U.S. patent number 3,863,710 [Application Number 05/313,934] was granted by the patent office on 1975-02-04 for heat exchange system.
Invention is credited to Richard M. Masters.
United States Patent |
3,863,710 |
Masters |
February 4, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
HEAT EXCHANGE SYSTEM
Abstract
A heat exchange system for heating a plurality of separate
locations or for dissipating heat from a heat source at a region
remote therefrom. A plurality of heat exchange devices in the form
of flexible containers or envelopes, are mounted in heat exchange,
or thermal, relationship with a conveying means which conveys a
heated fluid material from a heat source. The containers are
mounted so as to be maintained in a substantially extended
relationship with the conveying means so that the heat from the
heated fluid is effectively transferred via the heat exchange
device to the regions adjacent thereto, substantially primarily by
convection.
Inventors: |
Masters; Richard M. (Lexington,
MA) |
Family
ID: |
23217818 |
Appl.
No.: |
05/313,934 |
Filed: |
December 11, 1972 |
Current U.S.
Class: |
165/46; 47/2;
138/119; 138/149; 237/74; 126/59.5; 138/137; 237/59 |
Current CPC
Class: |
F28D
15/0266 (20130101); F28B 9/00 (20130101); F28D
15/00 (20130101); A01G 13/06 (20130101); F28D
15/02 (20130101); F28D 15/04 (20130101); F28F
21/06 (20130101) |
Current International
Class: |
A01G
13/06 (20060101); F28F 21/06 (20060101); F28F
21/00 (20060101); F28D 15/04 (20060101); F28D
15/02 (20060101); F28B 9/00 (20060101); F28D
15/00 (20060101); F28f 007/00 () |
Field of
Search: |
;237/67,74,59
;138/149,140,119,137 ;47/2 ;165/46 ;126/59.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Antonakas; Manuel A.
Assistant Examiner: O'Connor; Daniel J.
Attorney, Agent or Firm: Dike, Bronstein, Roberts, Cushman
& Pfund
Claims
What is claimed is:
1. A heat exchange system comprising
a heat source for heating a fluid material;
a plurality of independently operable heat exchange devices, each
of said devices being formed as a substantially flexible container
capable of dissipating heat;
means for conveying said heated fluid material to each of said heat
exchange devices in thermal relationship therewith so that heat
contained in said heated fluid material is transferred to said heat
exchange devices; and
means for mounting said heat exchange devices so that each of said
flexible containers slopes in a substantially uniform direction
from said conveying means independently of the pressure of the
heated fluid material in the system and the heat from said heated
fluid material is effectively transferred via said heat exchange
devices to the regions adjacent thereto.
2. A heat exchange system in accordance with claim 1 wherein said
flexible containers are arranged to be capable of dissipating heat
substantially by convection whereby said heat is effectively
transferred via said heat exchange devices primarily by
convection.
3. A heat exchange system in accordance with claim 1 wherein
said heated fluid material is a heated vapor; and
the interior of each of said heat exchange devices is directly
coupled to said conveying means whereby said heated vapor is
inserted into said heat exchange device.
4. A heat exchange system in accordance with claim 3 wherein
each said heat exchange device is mounted so that at least a
portion thereof is maintained at a level below said conveying
means; and further including
an opening in each said heat exchange device located in said
portion for permitting condensate resulting from the condensation
of said vapors to escape from said heat exchange device.
5. A heat exchange system in accordance with claim 4 and further
including one or more openings in each said heat exchange device
located in regions thereof where non-condensible gaseous substances
can collect for permitting said non-condensible gaseous substances
to escape from said heat exchange device.
6. A heat exchange system in accordance with claim 4 and further
including means for adding fluid material to said heat source to
make up for said escaped condensate.
7. A heat exchange system in accordance with claim 3 wherein said
heat exchange devices and said conveying means are mounted so as to
slope universally downward toward said heat source, said heat
exchange system being sealed whereby condensate resulting from the
condensation of said vapors is returned to said heat source.
8. A heat exchange system in accordance with claim 1 wherein
each said heat exchange device is formed as a separate sealed
flexible container the exterior surface of a first portion thereof
being mounted in thermal relationship with a portion of the surface
of said conveying means;
a working fluid material contained in said sealed container, the
portions of said container which are remote from said first portion
being effectively progressively more elevated above said conveying
means so that condensate resulting during operation from the
condensation of said working fluid material in a vapor state
collects in a liquid state in the region of said container which is
in thermal contact and in heat exchange relationship with said
conveying means.
9. A heat exchange system in accordance with claim 8 wherein
said conveying means is a heated pipe;
said first portion of said flexible container is wrapped around a
portion of said heated pipe; and further including
means for clamping said first portion to said pipe to maintain
thermal contact therewith.
10. A heat exchange system in accordance with claim 8 and further
including a wicking material positioned on at least a part of the
interior surface of said first portion of said flexible container
whereby said working fluid material in its liquid state is
effectively caused to be in good thermal relationship with
substantially all of said portion of the surface of said conveying
means.
11. A heat exchange system in accordance with claim 8 wherein said
working fluid material vaporizes in the existing ambient pressure
at a predetermined temperature whereby heat exchange operation
occurs above said predetermined temperature and no heat exchange
operation occurs below said temperature.
12. A heat exchange system in accordance with claim 8 wherein said
working fluid material vaporizes in the existing ambient pressure
at a temperature significantly lower than that of said heat source,
the pressure in said heat exchange device being limited by the
relationship of the area of said heat exchange device which is in
heat exchange relationship with said conveying means and the area
of said heat exchange device which is in heat exchange relationship
with said region adjacent thereto.
13. A heat exchange system in accordance with claim 1 wherein said
conveying means is in the form of a pipe comprising
a tubular core of thermal insulation material;
an outer layer on said core of a fluid and wear resistant material;
and
an inner layer on said core of a vapor impermeable material.
14. A heat exchange system in accordance with claim 13 wherein
said core material is a polyurethane foam;
said outer layer of material is nylon; and
said inner layer of material is polyurethane.
15. A heat exchange system in accordance with claim 1 wherein said
heat exchange devices are made of a plastic material.
16. A heat exchange system in accordance with claim 1 wherein said
heat exchange device is formed of a metal foil material.
17. A heat exchange system in accordance with claim 1 and further
including a plurality of separately located elements; and
wherein
said conveying means comprises at least one main conduit; and
a plurality of brand conduits connected to said main conduit;
at least one heat exchange device in thermal relationship with each
of said branch conduits, each of said heat exchange devices being
positioned adjacent one or more of said elements.
18. A heat exchange system in accordance with claim 17 wherein said
elements are agricultural plants.
19. A heat exchange system in accordance with claim 18 wherein said
agricultural plants are trees positioned in an orchard array and
each of said heat exchange devices are located adjacent one or more
of said trees below the branches thereof and substantially adjacent
the trunks thereof.
20. A heat exchange system in accordance with claim 17 wherein said
elements are campsites and said heat exchange devices are adapted
to be fixedly mounted in thermal relationship with one or more
units located at said campsites.
21. A heat exchange system in accordance with claim 20 and further
including means for permitting said branch conduits to be connected
and disconnected to said main conduit without significantly
disturbing the operation of the remainder of said system.
22. A heat exchange system in accordance with claim 1 for use in
dissipating heat from said heat source at a region remote therefrom
wherein
said conveying means comprises
main conduit means for conveying a heated fluid heated at said heat
source to said remote region and for returning cooled fluid to the
heat source region;
a plurality of branch conduits connected to said main conduit for
permitting the passage of said heated fluid there-through at said
remote region;
one or more of said heat exchange devices mounted in thermal
relationship to each of said branch conduits, all of said heat
exchange devices being located within said region to dissipate the
heat from said heated fluid to the atmosphere in said region;
and
a second conduit connected to said branch conduits for carrying
said cooled fluid away from said region.
23. A heat exchange system in accordance with claim 22 and further
including a cooling tower forming said region, said tower having an
open supporting structure at the base thereof and an opening at the
top thereof;
said heat exchange devices being mounted within said open
supporting structure thereby forming an array thereof within said
cooling tower
whereby heat dissipated by said heat exchange devices is
transferred to air which is drawn into said tower through said open
supporting structure, said heated air being exhausted at said top
opening of said tower.
24. A heat exchange system in accordance with claim 1 wherein
said conveying means comprises
at least one main conduit; and
a plurality of branch conduits connected to said main conduit;
at least one heat exchange device in thermal relationship with each
of said branch conduits.
25. A heat exchange system in accordance with claim 14, wherein
only the inner layer of said conveying means is capable of
substantially collapsing under conditions, wherein a minimum
pressure difference exists between the pressure external to said
pipe and the pressure within said inner layer.
Description
DISCLOSURE OF THE INVENTION
Introduction
This invention relates generally to heat exchange systems and, more
particularly, to a system which uses a plurality of spatially
mounted flexible heat exchange devices adapted to transfer heat
primarily by convection from a heated fluid to the atmosphere in
which they are mounted.
BACKGROUND OF THE INVENTION
There are many applications in which it is desirable to utilize a
simple, inexpensive heat exchange system, either for heating a
plurality of separately located regions or for dissipating heat at
a region remote from a heat-generating source. For example, it may
be required to heat a plurality of elements, in some cases a
relatively large number thereof, spread out over a relatively large
area, such heating being required for unpredictable durations of
times. Such elements, for example, may be trees or other plants
which are placed within an orchard, such trees being subject to
frost damage thereto when temperatures of the orchard are
sufficiently low for short, unpredictable intervals. In other
applications, for example, one or more concrete forms which have
been poured and are in the process of being cured cannot be
permitted to freeze in cold weather. In still further applications
it may be desirable to heat separate locations in an area such as
at individual campsites of a camping area or individual vehicle
locations of an outdoor drive-in theater where the heating device
may be subject to damage or loss.
In situations requiring heat dissipation it may be desirable to
dissipate a relatively large amount of heat, such as from an
electrical generating plant. Such heat is often remotely dissipated
in extremely large cooling towers which may, in some instances, be
up to several hundred yards in diameter and height.
DISCUSSION OF THE PRIOR ART
In applications where heating is required in a region having
separately located elements, such heating is often performed by
using a plurality of independent heating units having oil or gas as
the fuel. Such heating units are usually arranged to be relatively
easily moved, started, stopped, fueled and stored. Such heaters may
produce open or confined flames or may provide glowing hot
surfaces, and often require a source of power for blowing air
across the heat exchanger portion thereof to distribute the warm
air for heating purposes. Usually such elements are placed at
strategic positions within the region, as within an orchard, for
example, where they are placed between two or more trees which are
to be heated. Such systems provide a rapidly rising column of warm
air with little lateral dispersion thereof until the column reaches
a level well above the heater unit. In many cases the level at
which appropriate dispersion takes place is also above the level of
the elements which are to be heated and, accordingly, much of the
heat's effectiveness is lost in the process.
Even if the air is confined in some way, such as in a large
building or under temperature inversion weather conditions, the
mass of air in the upper regions of the confined space must be
heated before that in the lower regions thereof and, therefore,
much of the heat does not effectively reach the elements to be
heated, which are generally placed in the lower regions, and is
thereby wasted. Moreover, the radiant heat transfer which occurs in
such systems is not effective in many applications because it heats
only the surface directly viewing the source thereof. Moreover, the
intensity thereof decreases rapidly and is, therefore, less
effective as the distance from the source increases. When a large
number of elements are required to be heated the costs may become
prohibitive when a relatively large number of such independent heat
sources is utilized. In order to avoid undesirably high costs, such
heaters have often been made as simple and inexpensive as possible,
the simplification thereof usually adversely affecting the safety,
reliability and durability of such units. Such cheaper heat sources
often provide poor combustion, a factor which further reduces the
overall efficiency of the system. Moreover, such heaters may
require additional maintenance and often produce excess smoke which
can soil the elements which are being heated and, further, may not
be permissible in some regions.
In those applications where a large amount of heat is to be
dissipated over a relatively large region, such as in cooling
towers, the prior art has utilized a complex array of metal pipes
having relatively large numbers of heat dissipating metal fins
effectively placed thereon. For such large cooling tower
applications the expense involved in providing the required heat
dissipative area in such finned structures is substantially large
and in some cases may be economically prohibitive.
SUMMARY OF THE INVENTION
This invention, on the other hand, provides a relatively simple and
inexpensive system for transferring heat from one source and
distributing it to many independently operable heat exchange
devices which can all be located effectively in one large region
for maximum heat dissipation therein or can be remotely distributed
at separate sites located remotely one from another to heat a
plurality of independently positioned elements at the most
effective location and temperature for each such element. The heat
exchange devices are in the form of flexible containers, such as
plastic bags, which are relatively inexpensive to fabricate and
which are capable of dissipating sufficient heat for such purpose
substantially by convection. Such flexible containers can be placed
at the most effective locations and in the most effective numbers
for each particular application and a means for conveying a heated
fluid thereto is provided. The flexible containers are
appropriately mounted so that they are maintained in an extended
position with respect to the heated fluid conveying means and are
operatively connected to said conveying means so that heat from the
heated fluid material is effectively transferred via the containers
to the region in which the containers are located. Various
embodiments of the invention are described below with the
assistance of the accompanying drawings wherein
FIG. 1 shows in diagrammatic form a heating system in accordance
with the invention;
FIG. 2 shows a view in cross section of the pipe components
utilized in the system of FIG. 1;
FIGS. 2A and 2B show variations of the pipe components of FIG. 2 in
non-operating condition;
FIG. 3 shows a cut-away pictorial view of a branch fitting of the
piping components in the system of FIG. 1;
FIG. 4 shows a pictorial view of the flexible heat exchange devices
used in the system of FIG. 1;
FIG. 5 shows a view partially in section of another embodiment of
the heat exchange device of FIG. 4;
FIG. 6 shows a side view of still another embodiment of a heat
exchange device which can be utilized in the system of FIG. 1;
FIGS. 6A, 6B and 6C show the steps in the formation of the heat
exchange device as used in the system of FIG. 6;
FIG. 7 shows a view in cross section taken along the line 7--7 of
the heat exchange device in FIG. 6;
FIG. 8 shows a view in cross section of the heat exchange device of
FIG. 7 under different operating conditions of the system;
FIG. 9 shows the system of the invention as applied to the heating
of agricultural plants in an orchard;
FIG. 10 shows a more detailed view of a portion of the system shown
in FIG. 9;
FIG. 11 shows still another application of the invention as used
for the heating of campsites;
FIG. 12 shows an enlarged view of the installation of the heat
exchange devices in the system of FIG. 11;
FIG. 13 shows a diagrammatic view of the application of the system
of the invention to a cooling tower; and
FIG. 14 shows a view in more detail of the heat exchange devices as
used in the cooling tower system of FIG. 13.
As can be seen in FIG. 1, the system of the invention can be used
in an application wherein a plurality of elements 15 to be heated
are remotely positioned one from another. An appropriate fuel from
tank 1, as for example oil or gas, is fed to a combustion chamber 3
via an appropriate control valve 2 so as to provide a flame 4 which
is utilized to heat a fluid in a boiler 6, which fluid is supplied
thereto from a fluid tank 5 via pipe line 5A. The latter fluid, for
example, may be water so that when such water is heated in boiler 6
water vapor is generated therein which is then conveyed through
output conduit or pipe 7 past branch fittings 8. Each of the branch
fittings may be utilized to supply vapor to a remote location or,
as shown with respect to fitting 9, the branches can be temporarily
closed with appropriate self-closing plugs placed therein. The
system can be sealed at its furthest end by an appropriate cap 10
and may be further provided as needed with an air release valve 12.
Each of the branches which lead to the remote locations wherein
elements 15 are positioned comprises conduits or pipes 11 which are
attached to fittings 8 to supply vapor to heat exchange devices 13
which are in the form of flexible containers, such as plastic bags.
In the embodiment shown, each of the flexible containers is
connected by suitable connecting means to a branch pipe 11 and
further is appropriately mounted with one corner, for example,
fixedly attached, as at 14, to an appropriate fixed point in the
region adjacent the elements 15 which are to be heated so that each
of the containers are maintained in an extended position relative
to branch pipe 11.
The heated fluid, such as the vapor obtained from boiler 6, is
supplied to each independently operable heat exchange device 13 and
condenses within such heat exchange device, the heat which is given
up thereby being dissipated therefrom by convection to the
atmosphere surrounding the flexible plastic container. Air which
flows over the heat exchange device 13 is thereby heated, the
heated air then flowing to the element 15 to heat the latter
element as desired.
FIG. 2 shows in more detail a preferred embodiment of the pipes 7
and 11 of FIG. 1 wherein the pipe comprises a fluid and wear
resistant outer surface 17, a core of flexible insulation material
18 and a vapor impermeable inner surface 19. The outer surface
material may be nylon, for example, the core material may be a
flexible polyurethane foam material, and the inner surface may be
polyurethane, for example.
As can be seen in FIG. 2A the structure of FIG. 2 as made from the
materials specified above, or their equivalents, can be laid flat
under equal internal and external pressure conditions so as to
minimize the non-condensible gas in the system when the system is
not operating. Alternatively, as shown in FIG. 2B, it may be only
the fluid conducting inner portion 19 which collapses, a plurality
of openings 50 along the structure allowing the ambient pressure to
reach inner tube 19.
FIG. 3 shows the construction of a branch fitting 8 wherein there
is a main conduit portion 20 having a main through passage 20A
having an opening 20B therein for coupling the main passage to a
branch conduit portion 21 having a branch passage 21A. A
constriction element 22 may be positioned in branch path 21A and
may be arranged to have either a fixed or variable opening 23
therein which can be utilized to balance the vapor in the various
heat exchange devices with their required loads. The opening 23 may
be located so as to facilitate flow of liquid condensate back into
passage 20A where required.
FIG. 4 shows in more detail the flexible container which operates
as the heat exchange device 13 of the system when it is coupled to
a branch pipe 11 at the end remote from branch fitting 8. As seen
therein, such device comprises a membrane envelope such as a
plastic bag which is appropriately sealed over the opening of
branch pipe 11 with a clamp 24. Vapor 25 which is introduced into
the envelope condenses therein and thereby gives up heat which is
conducted through the membrane into the surrounding environment by
convection.
In the embodiment depicted in FIG. 4, the flexible container is
fixedly mounted adjacent an element to be heated in such a manner
that a corner 13A thereof is fixedly mounted at 14 so that the end
of the container which is remote from branch pipe 11 is at a lower
level than the latter. Accordingly, as the vapor condenses, the
fluid condensate 26 is collected in the lower part of container 13
by flowing down the sides of the envelope to the lowest point in
the vicinity of the corner 13B thereof. An appropriate opening 27
may be placed in the envelope to permit the condensate to flow out
as shown. An additional hole 28 may also be placed at the upper
portion 13A of the envelope, if desired, in order to allow all air
or other non-condensible gasses to escape from the container so
that the vapor which is supplied through branch pipe 11 is
permitted essentially to completely fill the entire envelope.
When the heating system of FIG. 1 is used with heat exchange
devices mounted as shown in FIG. 4, all the pipes and passageways
through which the vapor passes are arranged to slope downwardly
from boiler 6 as the vapor flows therefrom toward the exit holes
27. Such an arrangement prevents the liquid condensate from flowing
back in a direction toward the boiler which back flow might tend to
hinder the flow of vapor within the various passageways. In such a
system, fluid from tank 5 is continually added to make up for that
which is lost through the flowing of condensate out the holes 27 of
flexible containers 13. Such an embodiment may be advantageous in
that the non-condensible gasses can be automatically exhausted from
the flexible containers and there is less concern that leaks in the
system will reduce its effectiveness. Hole 27 can be at any
location in the envelope so long as it is essentially at the lowest
point.
FIG. 5 shows another embodiment of the invention utilizing the
components depicted in FIG. 4 wherein the flexible envelope is
sealed at one end and one corner thereof is tied at an elevation at
which the sealed end is at a higher level than the input end which
is clamped at pipe 11. In this particular embodiment since the
envelope is in a sealed form, the holes 27 and 28 present in the
embodiment of FIG. 4 are not used. In accordance therewith the
liquid condensate 26 flows from the sealed end toward and into the
branch pipe 11 and back to the boiler. Accordingly, such an
embodiment as utilized in an overall system of FIG. 1 requires that
the heat exchange devices 13 and all means for conveying the liquid
condensate slope downwardly toward the boiler source of vapor so
that the condensate is returned for reheating. While condensate is
present in pipes 7 and 11 and branch fittings 8 during operation
thereof it need not be present in some applications in sufficient
quantities to block passage of the vapor. Such a configuration
requires no continual addition of make-up liquid from tank 5 but
the overall system must be kept substantially sealed so as to be
free from leaks and other sources of non-condensible gasses which
may exclude the vapor from entering the desired heat exchange
regions of the overall system.
FIGS. 6, 7 and 8 show another embodiment of a heat exchange device
13 which can be utilized in the system of the invention wherein the
heat exchanger device 13 is a self-contained and completely sealed
unit, the interior of which is not directly coupled in any way to
the interior of pipe 11 or to the heated vapors or liquid which is
passing therethrough. The flexible envelope can be first evacuated,
charged with an appropriate amount of working fluid 29 and then
sealed. A portion of the envelope is then wrapped in thermal
relationship about the exterior of a portion of the pipe 11, which
is preferably not insulated in this area, which pipe carries heated
vapors or a heated liquid, and appropriately secured such as with a
suitable clamp 30, or by the use of a suitable adhesive for bonding
the envelope to the exterior surface of the pipe. The envelope is
supported at one corner, as at 14, to a convenient fixedly mounted
structure so that the envelope extends at an angle away from pipe
11. As shown in FIG. 7 a portion of the interior surface of the
envelope can be covered with a porous wicking material 31. When the
system is not in operation the heat exchange device is in an
essentially collapsed state as shown in FIG. 8 wherein the
temperature of pipe 11 is below the boiling point of the working
fluid 29 contained therein. Accordingly, the fluid 29 is in a
liquid state and the envelope is collapsed substantially tightly
except for the region which contains the working fluid 29. The
collapsed exterior surface of the heat exchange device 13 thereby
provides no effective heat exchange function with respect to pipe
11 or the surrounding atmosphere. During operation the pipe member
11 is heated in any appropriate way such as by passing a heated
fluid, either in a liquid or vapor state, therethrough or by any
other appropriate means, the heat thereof being conducted from pipe
11 through the portion of envelope 13 which enclosed pipe 11 to the
working fluid 29. When the temperature of the working fluid is
thereby raised to a point where it exceeds its boiling point at
whatever pressure exists through the envelope 13, the working fluid
boils and produces a vapor 25 which causes an expansion of the
volume inside the envelope 13. The vapor, accordingly, condenses on
and gives up its heat through the envelope and primarily by
convection therefrom to the external atmosphere, the condensate 26
thereby forming on the interior wall of the envelope as shown. When
the heating rate is at a maximum the envelope is substantially
filled with vapor and the fluid level of the working fluid 29 drops
to a minimum. If the wicking material is not used, enough working
fluid for efficient operation is required so that the fluid level
during operation remains substantially at or above the pipe 11. It
has been found that under such circumstances the boiling process
tends to produce audible noise at levels which may not be tolerable
in some applications. However, the addition of wick 31 as shown in
FIGS. 7 and 8 permits the use of less working fluid 29, the wick
thereby drawing the fluid upwardly by capillary action so as to wet
the entire heated surface of the envelope which encircles pipe 11.
It is found that when such wicking material (and, consequently,
less working liquid) is utilized, the noise level is much less
audible. Further, the temperature drop through a thin wetted wick
can be less than that through a large bulk of boiling liquid, which
factor may be of interest in some more critical applications. In
either case the supporting structure 14 maintains the envelope at a
level higher than the pipe 11 so that the fluid reservoir is always
in communication with the heated portion of the envelope at pipe
11, the condensate thereby running downwardly toward the clamped
portion thereat. When the heating rate is less than at its maximum
value, the vapor only partially fills the envelope and, thus, the
heated area is a fraction of the total area of the envelope.
An advantage of the embodiment shown in FIGS. 6-8 is that the heat
exchange device can be installed or removed from the system without
interruption to the operation of the overall system during such
activity. The overall heat which is dissipated can be varied simply
by adding or removing heat exchange devices 13. Moreover, in such
an embodiment the failure of one or a few of the heat exchange
devices, e.g., the rupture thereof, does not interfere with the
integrity of pipe member 11 or with the operation of any of the
other heat exchange units other than to reduce the contribution to
the overall heat transfer by the loss of whatever is contributed by
the particular unit which has failed. The working fluid 29 can be
selected so that its boiling point is useful for particular
applications. For example, it may be desirable that the heat
exchanger not operate until a particular temperature level is
reached at pipe member 11 (e.g., at the pipe's dangerous overheat
temperature point). Accordingly, a working liquid having a boiling
point at the expected ambient pressure substantially at such
overheat temperature is selected so as to cause the heat exchange
device to begin its operation at that point so as to maintain the
temperature of pipe 11 at or below such predetermined temperature
point.
The device can be made to function at a temperature significantly
below that of the heat source 11 with a suitable fluid, if the area
in heat exchange relationship with said heat source 11 is small
enough with respect to the effective heat exchange area of the
envelope relative to the surrounding region to limit the heat input
to a value which can be dissipated by the device without producing
excessive pressure at the temperature of the vapor in the
device.
In utilizing the configuration of FIG. 6, the heat exchange
envelope can be most efficiently formed in order to be conveniently
wrapped around the branch pipe 11, as shown in a preferred
formation thereof depicted in FIGS. 6A, 6B and 6C. As shown therein
the formation thereof begins with a simple collapsed tubular
plastic envelope structure 13 which lays flat, as shown in FIG. 6A.
In the flat state the envelope structure has the reference points
A, B and C, and corner points D, E, F and G, and midpoints H and J,
shown therein, which points are useful in describing the folding
process. First of all, points A, B and C are selected so that A and
B form a line AB corresponding to the longitudinal axis Y--Y of the
envelope on its upper layer, and B and C form a line BC parallel
thereto on its lower layer. The selection of A, B and C is such
that the distance AB + BC = DE/SIN .theta., B being the midpoint of
DE, and .theta. being the angle formed between the envelope 13 and
pipe 11 where the former is wrapped around the latter as shown in
FIG. 6C. The ratio of the lengths AB and BC thereby essentially
determine such angle .theta.. If a wick is included in the interior
surface of the envelope it is secured thereto and centered along
the line formed by ABC (in FIG. 6B) in one or more pieces, leaving
material for the seam. The tube is sealed by forming a leak tight
seam along DBE.
The exchanger device is formed by pulling points A and C in
opposite directions so that the points A, B and C lie in a
substantially straight line and by flattening out the triangles ACE
and ACD. The entire folded exchanger device can then be further
flattened to remove ambient gas and charged with working fluid as
required and appropriately sealed in a leak-tight seam, such as
along the line HJ, for example. To install the exchanger the
triangular portions, ACE and ACD, are placed on a heat source as by
wrapping around a pipe 11, for example, with the line ABC being
aligned with the axis of the pipe. The exchanger can then be bonded
to the heat source with an application of a suitable adhesive, or
double sided tape or, in the case of a pipe, it can, when wrapped
around the cylindrical surface of the pipe, be secured with a clamp
as shown in FIGS. 6 and 6C.
In FIGS. 4, 5 and 6 the flexible envelope can be of a suitable
material, preferably a plastic film material such as polyester,
nylon, polyimide or paper or cloth or even of very thin sheet metal
or rubber material. Further, the material may be a plastic film
which has been metallized with a very thin coating of a metal to
reduce the problem of gas permeability.
FIG. 9 shows in simple diagrammatic form one particular application
for the system of the invention wherein it is utilized for heating
agricultural units, such as trees or other plants which may be, for
example, planted in an orchard array and during certain seasons be
subjected for short intervals of time to an undesirable low
temperature environment. The trees are separately positioned at
various independent locations throughout the orchard, usually in a
uniform manner as shown, and the heat generating source 32 of the
system is placed at a convenient location with respect thereto, the
location being shown in the embodiment of FIG. 9, as substantially
central to the overall array. Appropriate pipe members 7 carry
heated vapors, as described above, to each of the independently
operating heat exchange devices which are tied thereto through
branch lines 11. While any one of the embodiments shown in FIGS. 4,
5 and 6 may be utilized for the combination of branch lines and
heat exchange devices, as the array of elements which are to be
heated becomes relatively large in size and number and the
temporary nature of the installation becomes more evident, the
particular embodiment shown in FIG. 4 may be more desirable in some
applications since it is less subject to difficulties due to leaks
and due to the presence of non-condensible gasses in the system. In
such installations water is a reasonable fluid, so that the need
for make-up fluid is not a disadvantage and the deposit of fluid
from the system at the trees should not prove harmful. Clearly,
however, the other embodiments shown in FIGS. 5 and 6 and/or other
fluids may also be used in such an application.
FIG. 10 shows in somewhat more detail how the heat exchange devices
could be applied to the individual trees 33. For example, a heat
exchange envelope 13 may be suspended from appropriate branches of
a single tree by suitable wires, or cords 34 or the like, so as to
be suspended under the branches and substantially adjacent the
trunk of the tree. Alternatively, a larger heat exchange envelope
may be used and suspended from the branches of more than one tree
to extend thereunder as shown. The column of heated air in the
vicinity of the heat exchange devices moves upwardly through the
branches and provides for efficient heating thereof.
FIG. 11 shows the system of the invention as applied to a group of
campsites, or other temporary housing units. Vapor from boiler 6
flows through piping system 7 which can be temporarily or
permanently placed above the ground or permanently installed below
the ground. The vapor flows to branch fittings 8 which can be
located at the prepared sites. When a unit is to be occupied, a
rigid or flexible pipe 11 can be plugged into the branch fitting
and a valve opened to allow heated vapor into a heat exchanger
device 13 which can be deployed in a tent 35 or in various trailer
units 36, or other housing units as desired. A detailed description
of a heat exchanger 13 as tied to an appropriate point within a
tent 35 is shown in FIG. 12. In the campsite application it is
clear that any one of the heat exchange device configurations of
FIGS. 4, 5 and 6 can be used. In a preferred embodiment it might be
more desirable to utilize a high temperature vapor such as steam,
to more efficiently transfer the heat over greater distances via
the piping system, while using separably mounted heat exchanger
devices as in FIG. 6 which contain a working fluid therein of a
lower boiling point (e.g., Freon 113) so that the heat exchange
operation at the individual campsites will operate at the lower
boiling point of the working fluid (e.g., at approximately
117.degree. F.) which structure would reduce the possibility of
danger to the occupants of the campsite as from accidental contact
with the higher temperature. Alternatively, a higher temperature
vapor, such as steam, could be used in a heat exchange envelope
which has sufficient thermal insulation properties so that the
exterior surface thereof is maintained at a lower temperature than
the interior surface thereof, or other suitable safeguards may also
be used.
FIG. 13 shows the system of FIG. 1 as applied to a dry cooling
tower such as utilized for dissipating heat generated from an
electric power plant. As shown therein the power plant 37 rejects
heat in a heated fluid flowing through a pipe 38 which extends into
a cooling tower 39 to an array 43 of heat exchange devices therein
(a portion of which is seen in more detail in FIG. 14) where it
transfers its heat to the air which is drawn in through the open
supporting structure 40 at the base of the tower, over such array,
and eventually upwardly through the tower where the heated air is
exhaused to the atmosphere via opening 41 at the top thereof. The
cooled fluid then returns to the power plant through pipe 42.
Though it is possible to use any of the configurations of heat
exchange devices shown in FIGS. 4, 5 and 6, in this application it
may be more suitable to utilize those of FIG. 6 inasmuch as the
heated fluid from the generating plant is most likely to be water
at a temperature of about 120.degree. F., considerably below the
boiling point thereof, so that a working fluid within the heat
exchange devices which boils at a temperature below such water
temperature (e.g., Freon 113 which boils at 117.degree. F.) can be
used.
FIG. 14 shows one manner in which the heat exchange devices can be
placed in an array 43, a portion thereof being shown therein. Other
physical configurations for a heater exchange array which may be
well suited to various applications may be devised by those in the
art. In the particular configuration shown therein a heated fluid
from the power plant generating source flows into the heat
exchanger network through pipe 38 from which small amounts are
extracted through branch pipes 44. A plurality of heat exchange
devices 13 are secured to the branches in a manner such as shown in
FIG. 6, for example, and are supported at one corner, as required,
at points 14 on supporting posts 45. Cooled fluid is then returned
to the system through pipe 42.
As can be seen, the total number of heat exchange devices and the
array in which they are arranged can be selected for the particular
heat dissipation requirements involved. Several hundreds or several
thousands of such devices may be utilized at the base of a cooling
tower which tower may be several hundred feet or several hundred
yards in diameter and in height. Because of the simplicity of the
piping and the low cost of the heat exchange devices, which are in
the form of the flexible envelope containers discussed above, the
cost per unit area of heat exchange can be much lower than that of
presently known systems which utilize an elaborate array of metal
pipes having metal cooling fins. Moreover, in the system of the
invention the heat exchange operation does not occur when the
working fluid temperature falls below its boiling point so that the
system is automatically protected from damage due to freezing, as
when the heated input fluid flow stops for one reason or another in
cold weather. The latter situation has been a problem in the use of
current dry cooling tower designs.
While in the particular embodiments discussed above the heat
exchange which occurs is primarily by convection, the heat exchange
devices may also be arranged to provide for heat exchange by other
processes such as by radiation or conduction, or by appropriate
combinations thereof. Further, those in the art may devise other
embodiments and applications for the system of the invention as
described above, which embodiments are well within the scope of the
invention. Accordingly, it is desired that the invention not be
limited by the details of the embodiments described above except as
defined by the appended claims.
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