U.S. patent application number 12/075462 was filed with the patent office on 2008-09-04 for system for exchanging heat within an environment using a coaxial-flow heat exchanging structure with helically-finned tubing.
This patent application is currently assigned to Kelix Heat Transfer Systems, LLC.. Invention is credited to Michael L. Fraim, John E. Kidwell.
Application Number | 20080209933 12/075462 |
Document ID | / |
Family ID | 36954042 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080209933 |
Kind Code |
A1 |
Kidwell; John E. ; et
al. |
September 4, 2008 |
System for exchanging heat within an environment using a
coaxial-flow heat exchanging structure with helically-finned
tubing
Abstract
An coaxial-flow-flow heat exchanging structure having a proximal
end and a distal end for exchanging heat between a source of fluid
at a first temperature and the environment (e.g. ground, water,
slurry) at a second temperature. The coaxial-flow-flow heat
exchanging structure comprises a thermally-conductive flowguide
tube having a hollow conduit extending from said proximal end to
said distal end. A helically-finned tubing is disposed within the
hollow conduit of said thermally-conductive flowguide tube, and has
a central conduit for conducting a heat exchanging fluid, from said
proximal end, along the central conduit towards the distal end, and
returning back to the proximal end along a spiral annular flow
channel formed between the thermally-conductive flowguide tube and
the helically-finned tubing.
Inventors: |
Kidwell; John E.; (Tulsa,
OK) ; Fraim; Michael L.; (Corrales, NM) |
Correspondence
Address: |
Thomas J. Perkowski, Esq.
1266 East Main Street
Stamford
CT
06902
US
|
Assignee: |
Kelix Heat Transfer Systems,
LLC.
|
Family ID: |
36954042 |
Appl. No.: |
12/075462 |
Filed: |
March 11, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11076428 |
Mar 9, 2005 |
7347059 |
|
|
12075462 |
|
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Current U.S.
Class: |
62/260 ;
165/45 |
Current CPC
Class: |
F25B 30/06 20130101;
H01Q 1/02 20130101; Y02E 10/10 20130101; F28D 7/12 20130101; F24S
2080/05 20180501; F24F 3/001 20130101; F28F 1/36 20130101; F24T
10/17 20180501; F28D 7/106 20130101; C10L 3/10 20130101; F24T
2010/56 20180501; Y02E 10/125 20130101 |
Class at
Publication: |
62/260 ;
165/45 |
International
Class: |
F25D 23/12 20060101
F25D023/12; F24J 3/08 20060101 F24J003/08 |
Claims
1. An coaxial-flow heat exchanging structure having a proximal end
and a distal end for exchanging heat between a source of fluid at a
first temperature and the environment (e.g. ground, water, slurry)
at a second temperature, said coaxial-flow-flow heat exchanging
structure comprising: a thermally-conductive flowguide tube having
a hollow conduit extending from said proximal end to said distal
end; and spiral-finned tubing disposed within the hollow conduit of
said thermally-conductive flowguide tube, and having a central
conduit for conducting a heat exchanging fluid, from said proximal
end, along said central conduit towards the distal end, and
returning back to said proximal end along a spiral annular flow
channel formed between said thermally-conductive flowguide tube and
said helically-finned tubing.
2. The coaxial-flow-flow heat exchanging structure of claim 1,
which further comprises insulating center tubing disposed within
said central conduit, for conducting the heat exchanging fluid from
said proximal end, along said central conduct towards the distal
end with minimal thermal conduction through to said
helically-finned tubing, so that the heat exchanging fluid can
exchange (transfer) its heat to the environment via said
thermally-conductive flowguide tube as said heat exchanging fluid
flows back to said proximal end along said spiral annular flow
channel.
3. The coaxial-flow-flow heat exchanging structure of claim 1,
which further comprises a fluid manifold disposed on said proximal
end for injecting said heat exchanging fluid into said
coaxial-flow-flow heat exchanging structure at a third temperature,
and withdrawing said heat exchanging fluid out of said
coaxial-flow-flow heat exchanging structure at a fourth
temperature.
4. The coaxial-flow-flow heat exchanging structure of claim 1
installed in a deviated well bore.
5. The coaxial-flow-flow heat exchanging structure of claim 4,
wherein the deviated well bore is drilled nearly horizontal in an
aquifer zone to maximize heat transfer to the ground.
6. The coaxial-flow-flow heat exchanging structure of claim 4,
wherein the deviated well bore uses a short turning radius to
deviate from vertical to near horizontal and said
thermally-conductive flowguide tube is grouted to the surface to
prevent aquifer contamination.
7. The coaxial-flow-flow heat exchanging structure of claim 1,
wherein the spiral flow of fluid increases the heat transfer of the
fluid with said thermally-conductive flowguide tube by said
helically-finned tubing constantly rotating the fluid as it flows
through the channel formed between said thermally-conductive
flowguide tube and said helically-finned tubing.
8. The coaxial-flow-flow heat exchanging structure of claim 1,
wherein said fins have a flat edge parallel to said
thermally-conductive flowguide tube so as to divert the fluid into
the channel instead of around said fins.
9. The coaxial-flow-flow heat exchanging structure of claim 1,
wherein said helically-finned tubing has shoe-structure fused to
the bottom of said helically-finned tubing so as to prevent fin
damage during installation of said helically-finned tubing within
said thermally-conductive flowguide tube.
10. A natural gas dehydration system employing a heat pump system
provided with said coaxial-flow-flow heat exchanging structure of
claim 1.
11. A heat pump system having a ground or water loop, and
comprising: a heat pump, an aqueous based heat transfer fluid, and
a spiral flow heat exchanging structure including a
thermally-conductive flowguide tube and a helically-finned tube
disposed within said thermally-conductive flowguide tube.
12. The heat pump of claim 11, wherein the ground loop heat
exchanger is made from joints of tubing and thermally-conductive
flowguide tube.
13. The heat pump of claim 11, wherein said helically-finned tubing
includes an inner insulating tube providing thermal insulation
between fluid flowing through said inner insulating tube and said
helically-finned tube.
14. The heat pump of claim 11, wherein the well bores are over
sized to provide a thermal bank for small load peaks.
15. The heat pump of claim 11, wherein a large tank is used to
provide a thermal bank for large load peaks.
16. The heat pump of claim 11, wherein the ground loop core is used
to store heat from the cooling season to use during the heating
season.
17. The heat pump of claim 11, wherein absorbable gases are foamed
with the aqueous base fluid to improve heat transfer during the
cooling season.
18. The heat pump of claim 11, wherein a horizontal well is drilled
into an aquifer to improve heat transfer.
19. The heat pump of claim 11, wherein a concrete structure buried
in the ground is used to make the ground loop or thermal bank.
20. The heat pump of claim 11, wherein a concrete structure buried
in the ground is used to make a thermo-siphon to prevent ice
buildup on the road, sidewalk, or bridge surface.
21. The heat pump of claim 11, wherein an open-seawater-loop heat
pump is used to cool a submarine.
22. The heat pump of claim 11, wherein the load is a gas
dehydration unit or an oil de-waxing unit.
Description
RELATED CASES
[0001] This Application is a Continuation of the U.S. application
Ser. No. 11/076,428 filed Mar. 9, 2005; said Application being
assigned to and commonly owned by Kelix Heat Transfer Systems, LLC
of Tulsa, Okla.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to a novel method of and
apparatus for transferring heat using heat exchanging fluids that
are safely isolated from the environment above and below the
Earth's surface and circulated within a sealed heat exchanging
structure so as to improve the heat transfer performance of
aqueous-based fluid heat transfer systems, wherein the ground, a
lake, a river, or sea water is used as the primary or secondary
heat sink or heat source in the sealed heat exchanging
structure.
[0004] 2. Brief Description of the State of Knowledge in the
Art
[0005] The development of refrigeration processes, associated
equipment and two-phase chemical refrigerants evolved primarily
from the need of mankind to preserve food. Several different kinds
of heat transfer systems have been developed for dissipating heat
removed from the food to the exterior of the food storage
container.
[0006] One kind heat transfer system is a typical refrigeration
system which includes an evaporator for absorbing heat from one
location, a condenser for dissipating heat to another location, a
compressor for compressing the vaporous two-phase refrigerant
exiting the evaporator for delivery into the condenser where the
refrigerant is condensed back into a liquid, and a two-phase
throttling device connected to the evaporator inlet for receiving
the liquid refrigerant and refrigerant expansion, to complete a
refrigeration cycle.
[0007] Condensers can be constructed in various configurations,
namely: as a tube with air-cooled fins, or as a water-cooled tube
and shell configuration. In the water-cooled tube and shell
condenser, the rate of heat transfer between the
refrigeration-sealed system refrigerant and the water flowing
around the tube and shell condenser tube is much higher than the
rate of heat transfer between the refrigeration-sealed system
refrigerant and air flowing around the tubes of the air-cooled fin
and tube condenser.
[0008] A water-cooled tube and shell condenser is normally
connected with pipes to a cooling tower and a water pump. The heat
is absorbed by the water while circulated through the condenser.
The heat in the water entering the cooling tower is then dissipated
into the atmosphere from the water completing a closed- loop
water-cooled refrigeration process.
[0009] Environmental concerns have caused strict restrictions to be
placed on water-cooled tube and shell condenser systems utilizing a
water pump to gather water from other sources such as a lake, a
river, sea water, and other fluid systems to be circulated through
the water-cooled tube and shell condenser of heat transfer systems.
Environmental contaminations vary but are mostly related to
chemical concentrations and temperature variations being dispensed
into the water source.
[0010] A water-cooled tube and shell condenser can be connected
with pipes to a ground-source heat transfer well which is used to
dissipate heat into the Earth. In various manufacturing processes,
the required operating temperature and capacity or volume of heat
transfer fluid circulated through the ground source heat transfer
well, may not require adding refrigeration to the system.
[0011] Residential and commercial comfort air conditioning systems
using air-cooled condensers are well known in the art and are used
extensively world-wide on air conditioners including heat pumps.
Water-cooled tube and shell condensers are normally used in large
tonnage commercial and industrial applications such as high-rise
buildings, natural gas dehydration, and liquefied natural gas
gasification systems.
[0012] A heat pump, originally called reverse refrigeration,
reverses the refrigeration process through the use of sealed system
valves and controls causing the evaporator to dissipate heat while
causing the condenser to absorb heat. In its cooling mode of
operation, a heat-pump air conditioning system will dissipate heat
into the Earth while, and absorb heat from the Earth in its heating
mode of operation.
[0013] Over the years, ground/water source heat pump has proven
very useful as a very efficient form of heating and cooling
technology. The use of ground/water source type heat pumps have
three distinct advantages over air source type heat pumps, namely:
during the peak cooling and heating seasons, the ground/water
source usually has a more favorable temperature difference than the
atmospheric air; the liquid-refrigerant exchanger on the heat pump
permits a closer temperature approach than an air-refrigerant
exchanger; and there is no concern with frost/snow/ice/dirt buildup
or removal on the heat exchanger.
[0014] In general, prior art heat pump installations have employed
undersized ground loops because refrigerant-based fluids can
provide a sufficient temperature difference between the fluid and
the ground so that enough heat is transferred to and from the
ground to match the heating/cooling load on the heat pump; however,
the use of undersized ground loops is also known to reduce the SEER
rating of the heat-pump system. Also, the design goals of prior art
heat pump systems have been to minimize the length of the metal
pipe used in the ground loop, while just passing the minimum
standards for efficiency.
[0015] When prior art heat pump systems experience peaks or spikes
in heating/cooling load during daily operation, thermal storage
solutions are oftentimes added to the system to average the load
over the time period of interest. Thermal storage solution also
help reduce the cost of the ground loop by allowing the loop to be
sized for the average base load over the day, week or season. In
fact, many large buildings and residences use thermal storage
solutions in order to reduce the cost of heating and cooling by (i)
using less expensive night-time electrical loads to heat/cool the
thermal mass, and then (ii) using the thermal mass to heat/cool the
building during the day. In order to reduce capital cost of the
heat pump system, prior art heat pump system installations often
use the metal rebar in the foundation or piling as a major part of
the thermal mass of the ground loop of the heat pump system.
[0016] Ground source or water source type heat pumps can use a
close or open loop as a heat exchanger. Open loops include water
circulated to cooling towers; water circulated between wells,
geothermal steam wells, water circulated in a body of water such as
a river or lake. Closed loops include aqueous based fluids and
refrigerant based fluids circulated in cooling/heating coils that
transfer heat to air, water, and ground. Most power plants use at
least one open loop to generate steam (the burner exhaust) and one
open loop (cooling towers or lake) to condense the steam back to
water. The de-ionized steam source water is preserved in a close
loop to prevent scale buildup in the heat exchanger. Most
conventional refrigerators, freezers and air conditioners use a
closed loop of refrigerant to cool the load and an open loop of
external air to condense the refrigerant.
[0017] The shortcomings and drawbacks of using air to transfer heat
from the condenser coil is that air requires a high temperature
differential and a large condenser coil surface area to get
reasonable heat transfer rates. The high temperature differentials
translate to a high-pressure differential which implies higher
energy costs to transfer a unit of heat. When a heat pump uses a
liquid, from a water or ground loop, to transfer heat from the
condenser coil, a smaller coil and a lower temperature and pressure
differential can be used to transfer the same unit of heat as the
air cool condenser coil which, in turn, improves efficiency and
reduces energy costs.
[0018] When closed loops are used in the ground or water source of
a heat pump system, there is a trade off between using (i) metal
tubing with a high heat transfer coefficient (i.e. which is subject
to corrosion and thermal expansion), and (ii) plastic tubing with a
low heat transfer coefficient (which is resistant to corrosion and
thermal expansion). For average soil conditions, plastic tubing
usually will require 3 times the heat transfer area of the metal
tubing to maintain an equivalent heat transfer rate. Metal tubing
is usually reserved for refrigerant based fluids due to the high
fill pressures and the reactivity of the refrigerant with plastic
tubing.
[0019] While protective coatings and grouting can reduce the
corrosion rates of metal tubing, pin holes in the coating or grout
can actually concentrate the anode corrosion rate in the pin-hole
area. Electrical measurements have shown that circulating aqueous
based fluids between the ground loop and heat pump can cause the
flow of a low level current between the building and the
ground.
[0020] In accordance with convention, a close-loop ground/water
source heat pump can use a refrigerant based fluid or an aqueous
based fluid. With refrigerant based fluids, the heat pump can use a
high differential temperature to transfer heat between the ground
and the fluid in the tubing, but extra energy load reduces the SEER
rating of the heat pump system. Metal tubing is used to contain the
pressurized refrigerant based fluid and minimize the volume of
refrigerant in the ground loop system due to the high heat transfer
coefficient of the metal. As discussed in U.S. Pat. No. 5,025,634
to Dressler, refrigerant based fluids have very high maintenance
cost when a small leak develops in the ground/water loop and a very
high environmental impact when there is a release of the
refrigerant. Also, over a long period of time, field experience has
shown that high pressure head loss can develop in the closed
ground/ water source loop when lubricating oil from the compressor
collects low spots in horizontal loop or at the bottom of the bore
hole in vertical loop. The inventors design goal was to use an
aqueous based fluid in the ground loop to overcome the
environmental risk and maintenance problems with refrigerant based
fluids.
[0021] With most aqueous-based fluid ground/water source loops, the
heat pump uses a small close-loop refrigerant heat exchanger to
transfer heat to or from the aqueous fluid. The small heat
exchanger reduces the capital cost of the heat pump and reduces the
chances of refrigerant releases to the environment. In areas with
ground movement, such as earthquakes zones, subsidence bowls, and
deep freeze/thaw zones, the borehole thermally-conductive flowguide
tube and transfer piping can develop leaks due to repeated damage
over time as discussed in U.S. Pat. No. 4,993,483 to Kurolwa. The
inventors design goal was to use a judicious choice of components
in the aqueous base fluid; so that, the environmental impact of a
large leak can be reduced to non-hazardous spill and the impact of
a small leak would be reduced to addition of make up fluid to the
loop.
[0022] Ground loop installations vary from trenched horizontal
loops to multiple bore holes. As disclosed in U.S. Pat. No.
4,644,750 to Lockett and Thurston and in U.S. Pat. No. 4,325,228 to
Wolf, a horizontal ground loop's performance is affected by
fluctuation in atmospheric surface temperature and soil moisture
content, whereas, the ground loop based on multiple bore holes has
a stable fluid temperature and heat transfer coefficient for both
heating and cooling thermal loads. For heat and cooling loads
located on small land surfaces or arid land, the ground loop heat
exchanger based on multiple bore holes can provide a heat pump with
a stable heat sink or source as described in U.S. Pat. No.
4,392,531 to Ippolito.
[0023] The first major improvements to ground loop fluid heat
transfer using metal tubing and refrigerant based fluids were
disclosed in U.S. Pat. No. 5,816,314 to Wiggs et. al, U.S. Pat. No.
5,623,986 to Wiggs, U.S. Pat. No. 5,461,876 to Dressler, U.S. Pat.
No. 4,867,229 to Mogensen, and U.S. Pat. No. 4,741,388 by Kurolwa
where metal tubing was bent into a helix shape to increase heat
transfer between the refrigerant and the ground. The five patents
show that the `vertical spiral heat exchanger` or the `bore-hole
spiral heat exchanger` provides the heat pump with a stable heat
sink or source for heating and cooling. The shortcoming of these
designs is the increased capital cost of spiral bending of the
tubing and the increased installation cost of trying to run spiral
bent tubing in a deviated well.
[0024] Another popular technique used in prior art heat pumps
involves insulating the metal, fluid-return tube from the bottom of
the bore hole so to prevent heat transfer from incoming fluid,
which significantly improves the heat exchanger performance. The
deficiency of prior art insulating methods has caused a significant
increase in installation costs and a significant increase in
capital cost associated with insulating materials. Notably, as the
return line was far enough away from the loop to not cause any
significant thermal interference, insulating the fluid return tube
was not required for earlier horizontal ground loop heat
exchangers.
[0025] U.S. Pat. No. 4,741,388 to Kurolwa discloses using a
spirally-corrugated outer tube to create the spiral flow shape for
increased heat transfer of the fluid, which is similar to the
spiral channeled tubes used in a steam boiler.
[0026] U.S. Pat. No. 5,623,986 to Wiggs discloses that external
spirally shape fins can be used to drill short vertical heat
exchangers into sand-loam soils or mud bottoms, but field
experience has shown that there is to much fin damage for hard
rock/ground surface.
U.S. Pat. No. 5,937,665 to Kiessel et al., discloses other
improvements to refrigerant based groundloops, wherein an air heat
exchanger is used to the system to reduce the load on the ground
loop.
[0027] U.S. Pat. No. 6,138,744 by Coffee discloses using a large
storage tank of water to a horizontal ground loop that is
continuously replenished by an external water source such as water
well. This technique involves combining an open water loop and a
lose ground loop.
[0028] U.S. Pat. No. 6,615,601 by Wiggs discloses combining a solar
heating loop and a water evaporative cooling loop to the ground
loop so as to supplement the heating and cooling load.
[0029] U.S. Pat. No. 6,212,896 to Genung discloses a ground loop
with large well bores to make room for a vertical thermal siphon to
enhance the heat transfer in the large well bore. The short coming
of this idea is that the heat is transfer to the
thermally-conductive flowguide tube wall with a laminar flow of
fluid.
[0030] U.S. Pat. No. 6,672,371 to Amerman et al. created a ground
loop by drilling multiple well bores from one pad and using plastic
U-tubes for the heat exchanger. By using many plastic U-tubes with
low heat transfer in series, an equivalent metal heat exchanger
performance can be achieved in the ground loop.
[0031] U.S. Pat. No. 6,789,608 to Wiggs discloses a technique for
extending the performance of the U-tube heat exchanger by
installing an insulating plate between the tubes to make two close
separate half wells with minimal thermal interference between each
well.
[0032] Thus, while various advances have been made in heat pump
system design and implementation, there is still a great need in
the art for an improved method of and apparatus for transferring
heat from above or below the Earth's surface using a sealed fluid
circulation system which may or may not incorporate the use of a
refrigeration system, while overcoming the shortcomings and
drawbacks of prior art methodologies and equipment.
SUMMARY AND OBJECTS OF THE PRESENT INVENTION
[0033] Accordingly, it is a primary object of the present invention
to provide a method of and apparatus for transferring heat from
above or below the Earths surface using a sealed fluid circulation
system employed a spiral-like heat transfer structure, while
overcoming the shortcomings and drawbacks of prior art
methodologies.
[0034] Another object of the present invention is to provide a
coaxial-flow heat exchanging structure having a proximal end and a
distal end for exchanging heat between a source of fluid at a first
temperature and the environment (e.g. ground, water, slurry) at a
second temperature.
[0035] Another object of the present invention is to provide such a
coaxial-flow heat exchanging structure which comprises an outer
thermally-conductive flowguide tube having a hollow conduit
extending from said proximal end and distal end, and
helically-finned tube disposed within the hollow conduit of the
outer thermally-conductive flowguide tube, and has a central
conduit for conducting a heat exchanging fluid, from the proximal
end, along the central conduct towards the distal end, and
returning back to the proximal end along a spiral annular flow
channel formed between the thermally-conductive flowguide tube and
the helically-finned tube.
[0036] Another object of the present invention is to provide such a
coaxial-flow heat exchanging structure which further comprises an
insulating center tube disposed within the central conduit, for
conducting the heat exchanging fluid from the proximal end, along
the central conduct towards the distal end, and returning back to
the proximal end along the spiral annular flow channel.
[0037] Another object of the present invention is to provide such a
coaxial-flow heat exchanging structure which further comprises a
cap installed on the proximal end and having fluid inlet and outlet
ports (e.g. a fluid manifold) for injecting the heat exchanging
fluid into the coaxial-flow heat exchanging structure at a third
temperature, and withdrawing the heat exchanging fluid out of the
coaxial-flow heat exchanging structure at a fourth temperature.
[0038] Another object of the present invention is to provide such a
coaxial-flow heat exchanging structure which can be used for
sinking heat into the ground during cooling operations, or sourcing
heat from the ground during heating operations.
[0039] Another object of the present invention is to provide a heat
pump system employing the coaxial-flow heat exchanging structure of
the present invention, wherein the heat transfer performance of
aqueous based fluid heat transfer is substantially improved, and
wherein the ground, a lake, a river, or sea water can be used as
the primary or secondary heat sink or heat source.
[0040] Another object of the present invention is to provide such a
heat pump system which may or may not incorporate the use of a
refrigeration subsystem.
[0041] Another object of the present invention is to provide such a
heat pump system, wherein the heat transfer performance of aqueous
based fluids is substantially improved by using heat-pump
heating/cooling heat exchangers where the ground is used as the
primary or secondary heat sink/source in a closed loop.
[0042] Another object of the present invention is to provide such a
heat pump system, wherein capital/installation cost of the total
heat pump system is substantially reduced.
[0043] Another object of the present invention is to provide a heat
pump system employing a coaxial-flow heat exchanging structure
which is installed into the earth, a lake, a river, sea water or
other heat sink or heat source to absorb heat or dissipate heat
into or from the heat transfer fluid by isolating the heat transfer
fluid entering the center insulating tube, from the helically
flowing fluid exiting the assembly. The interior surface of the
well thermally-conductive flowguide tube is the primary heat
transfer surface of the coaxial-flow flow heat exchanger
assembly.
[0044] Another object of the present invention is to provide a
coaxial-flow heat exchanging structure that cab be used in diverse
kinds of heat pump systems, wherein the coaxial-flow heat
exchanging structure can be manufactured as a primary system, a
system sub-component, or a sub-component kit.
[0045] Another object of the present invention is to provide a
coaxial-flow heat exchanging structure for ruse in a heat pump
system, wherein the heat exchanging surface area of the structure
is increased by fluting the plastic surface of the outer
thermally-conductive flowguide tube and by increasing the length of
the bore into the ground (bore length) as a result of drilling
deviated-type wells in aquifer zones of the Earth.
[0046] Another object of the present invention is to provide a
coaxial-flow heat exchanging structure for ruse in a heat pump
system, wherein as the heat transfer surface area and the contact
volume of the ground/water source loop increase, the circulating
fluid temperature will approach the average ground temperature
through out the full duration of the heating and cooling
seasons.
[0047] Another object of the present invention is to provide a heat
pump system, wherein a uniform bore hole is drilled into an aquifer
zone and a smooth metal pipe or a fluted plastic pipe is installed
within the bore hole so that the coaxial-flow heat exchanging
structure of the present invention can be installed in most
geologic ground types without major changes in installation
procedures.
[0048] Another object of the present invention is to provide a
method of and apparatus for enhancing the heat transfer in aqueous
based fluid ground/water source loop systems so that a low
differential temperature, high mass-rate heat pump can be used to
cool or heat a thermal load from a building or industrial
process.
[0049] Another object of the present invention is to provide a
ground/water source heat-pump system that has a SEER rating that
exceeds air-source heat pump systems and ground-source heat-pump
systems using a refrigerant based heat-transfer fluid.
[0050] Another object of the present invention is to provide an
improved heat pump system, wherein the aqueous based fluid contains
a biodegradable anti-freeze and dye to minimize the environmental
impact of leaks in the ground loop and improve leak detection in
the ground loop multi-well grid.
[0051] Another object of the present invention is to provide an
improved heat pump system, wherein for small leaks, make up fluid
is injected into the system to maintain system pressure and prevent
vapor locking the circulation pump, and for large leaks, the system
is systematically checked with a mass flow meter and an ultrasonic
leak detector to identify the location of the leak.
[0052] Another object of the present invention is to provide
apparatus for manufacturing the helically-finned tubing employed
within the coaxial-flow-flow heat transfer (exchanging) structure
of the present invention.
[0053] These and other objects of the present invention will become
apparent hereinafter and in the Claims to Invention.
BRIEF DESCRIPTION OF DRAWINGS
[0054] For a more complete understanding of how to practice the
Objects of the Present Invention, the following Detailed
Description of the Illustrative Embodiments can be read in
conjunction with the accompanying Drawings, briefly described
below, in which visual descriptions are provided showing the
installation of the present invention in the ground, water, or mud
line environments.
[0055] FIG. 1 shows the coaxial-flow heat exchanging structure of
the present invention shown installed in a deviated well bore with
smooth metal thermally-conductive flowguide tube, wherein the
deviated well bore is drilled nearly horizontal in the aquifer zone
to maximize heat transfer to the ground, wherein the deviated well
bore uses a short turning radius to deviate from vertical to near
horizontal and the metal thermally-conductive flowguide tube is
grouted to surface to prevent aquifer contamination.
[0056] FIG. 2 shows a natural gas dehydration system using a heat
pump system of the present invention shown in FIG. 1, with a
deviated well drilled in an aquifer for the ground loop, wherein
the natural gas and other liquids are produced from the well that
is completed in the gas zone.
[0057] FIGS. 3 and 4 show the front and back views of a section of
single spiral or helical finned tubing used to create an annular
spiral or helical flow channel within the coaxial-flow heat
exchanging structure of the present invention, for the aqueous
based heat exchanger fluid, and wherein this small-diameter, spiral
finned tubing can be delivered rolled on a large spool to install
in the thermally-conductive flowguide tube, the tubing is cut to
size and the well cap is fused on as shown in FIG. 48.
[0058] FIGS. 5 and 10 show the front and top views of a double
spiral/helical fin set used to create spiral or helical flow in
large bore thermally-conductive flowguide tube.
[0059] FIGS. 6 and 7 show the front and top views of a single
helically-finned tubing with the insulated inner tube installed in
the thermally-conductive flowguide tube shown in FIG. 1, wherein
the gas gap between the central insulated inner tube and the
helically-finned outer tube provides insulation, and the gap
distance between the walls remains uniform due to the 3 standoffs
on the inner insulation tube.
[0060] FIGS. 8 and 9 show the front and top views of the
single-helical finned tubing without the inner insulation tube
installed, and wherein the fins can be extruded with the tubing for
small diameters or extruded over a joint of larger diameter tubing,
and wherein for diameters exceeding 18 inches or 0.5 meters, the
fins can be rolled from flat stock and welded on the tubing
joint.
[0061] FIGS. 11 and 12 show the front and top view of the insulated
inner tubing, wherein the standoffs provide the gas gap needed for
insulation between the inner insulation tube and outer
helically-finned tube, wherein the fill gas can be argon, nitrogen,
or even ethane, however argon is a better insulation gas and is
readily available in the field.
[0062] FIGS. 13, 14 and 15 show the front, bottom and cross-section
views of insulated helically-finned tubing joint with collar for
large diameter helically-finned tubing that cannot be rolled on
spool.
[0063] FIGS. 16, 17, and 18 show the front, bottom and
cross-section views of the helically-finned tubing with collar
without the inner insulated tube installed.
[0064] FIGS. 19, 20, and 21 show the front, bottom and
cross-section views of the insulated inner sleeve that is fusion
welded on both ends inside the helically-finned tubing to provide
the gas gap, wherein high pressure argon or other gas can be used
to fill the gas gap before the fusion process, and wherein the
inner insulation tube can be made of high density, foamed plastic
to reduce heat transfer and friction pressure drop.
[0065] FIGS. 22 and 23 show the front views of tubing joints with a
single helical fin and a double pr helical fin.
[0066] FIGS. 24 and 25 show the front and top views of the
helically-finned tubing shoe that is fusion welded to the bottom of
the helically-finned tubing so as to protect the helical fins
during the installation process.
[0067] FIGS. 26, 27 and 28 show the front, bottom and cross-section
views of the smooth thermally-conductive flowguide tube that is
grouted in the earth, wherein the smooth thermally-conductive
flowguide tube is usually metal due to its high heat transfer
coefficient, wherein the threaded collars are used to attach the
joints together.
[0068] FIGS. 29, 30 and 31 show the front, bottom and cross-section
views of the fluted thermally-conductive flowguide tube that is
grouted in the earth, wherein the flutes on the plastic
thermally-conductive flowguide tube give it additional surface area
to counteract the low heat transfer coefficient of the plastic,
wherein the flutes also give the plastic thermally-conductive
flowguide tube additional strength.
[0069] FIGS. 32 and 33 show the forward and reverse flow patterns
in smooth thermally-conductive flowguide tube with helically-finned
tube, wherein during the cooling season, pumping down the annulus
gives the best approximation to a cross flow heat exchanger for
liquid-gas mixtures where the liquid adsorbs the gas phase when the
pressure increases as the mixture is pump down the
thermally-conductive flowguide tube annulus.
[0070] FIG. 34 shows the forward flow pattern for a double
helically-finned tube, wherein the multiple helical fins are used
for large diameter thermally-conductive flowguide tube, wherein for
large diameters, the helically-finned tubing joints can be
pre-installed in the thermally-conductive flowguide tube joints for
shipment.
[0071] FIGS. 35 and 36 show front and top views of fluted
thermally-conductive flowguide tube with single spiral flow tubing
installed, wherein that the pitch of the helix and the fluted
thermally-conductive flowguide tube should be practically close for
maintaining the spiral flow pattern in the channel.
[0072] FIGS. 37 and 38 show the spiral flow pattern of fluid as it
is pumped down the annulus and up the annulus of the coaxial-flow
heat exchanging structure of the illustrative embodiment of the
present invention.
[0073] FIGS. 39, 40, 41 and 42 show cross-sectional views of the
tangential flow directions for the fluted control volume shape of
the coaxial-flow heat exchanging structure of the illustrative
embodiment of the present invention, wherein a square-like shape
control volume of the coaxial-flow heat exchanging structure
usually has one vortex for flow rates of interest, wherein a
rectangle-like shaped control volume of the coaxial-flow heat
exchanging structure with an aspect ratio near 2 to 1 usually has
two vortexes for flow rates of interest, and wherein for
rectangle-like shapes with an aspect ratio greater than 4 to 1,
there can be vortex near each fin with a laminar slot flow region
in the center of the control volume.
[0074] FIGS. 43, 44, 45 and 46 show cross-sectional views of the
tangential flow directions for a smooth rectangular control volume
shape of the coaxial-flow heat exchanging structure of the
illustrative embodiment of the present invention, wherein a
square-like shape control volume of the coaxial-flow heat
exchanging structure usually has one vortex for flow rates of
interest, wherein a rectangle-like shaped control volume with an
aspect ratio near 2 to 1 usually has two vortexes for flow rates of
interest, and wherein for rectangle-like shapes with an aspect
ratio greater than 4 to 1, there can be a vortex near each fin with
a laminar slot flow region in the center of the control volume.
[0075] FIG. 47 shows the helically-finned tubing in a corrugated
thermally-conductive flowguide tube of the coaxial-flow
coaxial-flow heat exchanging structure of the illustrative
embodiment of the present invention.
[0076] FIG. 48 shows a coaxial-flow heat exchanging structure of
the present invention installed with a well cap, wherein the well
cap holds the helically-finned tubing off the bottom of the
thermally-conductive flowguide tube so as to prevent buckling of
the plastic helically-finned tubing and seals the
thermally-conductive flowguide tube annulus from fluid leaks.
[0077] FIG. 49 shows fluid distribution around the helical annulus
of the coaxial-flow heat exchanging structure shown in FIG. 50, as
well as around its well cap, that is, for fluid being pumped down
the spiral annulus of the coaxial-flow heat exchanging
structure.
[0078] FIGS. 50 and 51 show the cross-section and top views of well
thermally-conductive flowguide tube and well cap installed in the
coaxial-flow heat exchanging structure of the present invention,
wherein the fluid return and injection manifold have been removed
for drawing clarity, and the well cap can have manifold of several
small holes for a low friction pressure drop or a single medium
size hole for a little higher friction pressure drop.
[0079] FIGS. 52, 53, and 54 show a compression ring well cap and
clamped well cap installed in the coaxial-flow heat exchanging
structure of the present invention, wherein either well cap has an
O-ring or U-ring seal around the well thermally-conductive
flowguide tube to prevent fluid leaks, wherein the clamps on the
thermally-conductive flowguide tube to prevent fluid pressure from
pumping well cap off the thermally-conductive flowguide tube for
shallow spiral tubing depths or high fluid pressures, and wherein
for permanent installations in cement structures, the well cap is
fusion welded, as shown in FIG. 52, so as to reduce the risk of
leaks.
[0080] FIGS. 55, 56, 57 and 58 show three different styles of
annulus fluid return for the helically-finned tubing employed
within the coaxial-flow heat exchanging structure of the present
invention, wherein the first style uses a connected manifold of
small holes or one medium size hole drilled in the well cap with
fluid exiting parallel or perpendicular to thermally-conductive
flowguide tube axis, wherein the second style uses tube fittings
welded/fused to the side of the thermally-conductive flowguide tube
for fluid injection and return (for use in concrete piling or pier
installations), wherein the third style uses a tube fitting welded
to the side of the thermally-conductive flowguide tube for annular
fluid return (for use in foundation installations when the tube
fittings are compression), and wherein all the designs have a low
friction pressure drop.
[0081] FIG. 59 shows a close up of the well cap and the insulated
helical flow tubing employed within the coaxial-flow heat
exchanging structure of the present invention, and wherein the
drawing shows the transition from internal insulation to external
insulation used in the horizontal run between wells or heat
pump.
[0082] FIG. 60 shows the coaxial-flow heat exchanging structure of
the present invention installed in a deviated well bore, wherein
the horizontal section of the structure is drilled into an aquifer
zone and the vertical section thereof connects the horizontal
section back to the surface.
[0083] FIG. 61 shows the coaxial-flow heat exchanging structure of
the present invention installed in a near horizontally bored well
in the side of a mountain, mesa, or hill, wherein the well bore
path is deviated to follow an aquifer zone if available at the
site, and wherein for buildings with a deep basement or built on
the side of a hill, the deviated well bores are drilled in the wall
of the basement.
[0084] FIG. 62 shows the coaxial-flow heat exchanging structure of
the present invention installed in a well bore that is cap below
the surface to prevent significant heat transfer to the
ground/water surface or atmosphere, and wherein for areas that have
significant ice or freeze/thaw movement, the distribution pipes
should be protected against damage and, if possible, the well
should be capped below the frost line.
[0085] FIGS. 63, 64, and 65 show the coaxial-flow heat exchanging
structure of the present invention installed vertically or
horizontally in foundations or pilings of a building, bridge, or
other structure.
[0086] FIGS. 66, 67 and 68 show the coaxial-flow heat exchanging
structure of the present invention suspended in an aqueous solution
or mud, wherein the vertical metal fins are used to increase the
heat transfer area of the thermally-conductive flowguide tube by
making an external thermo-siphon for aqueous solution
circulation.
[0087] FIG. 69 shows the coaxial-flow heat exchanging structure of
the present invention installed in a bridge component or piling,
wherein in earthquake areas, the pilings are wrapped in a metal
sheath to prevent structural damage in the earthquake, and the
sheath could be installed with spiral-like flow channels to provide
ground/water source heat to prevent icing of the road way or
sidewalks during the winter.
[0088] FIGS. 70 and 71 show the application of pad drilling of nine
deviated wells to minimize the ground surface impact while
maximizing the volume of ground contacted by the well bores,
wherein long term operation allows the ground loop to thermal bank
heat from the cooling season for use in the winter season, for
cooling loads only, a shallow horizontal loop can be added to the
ground-loop to remove heat from the thermal bank during the winter
season, in the limit of deviated well drilling, a horizontal well
as shown in FIG. 60 could replace the pad of nine deviated wells,
the pad drilling also has the advantage of reduced heat loss from
horizontal gathering piping and reduced risk of accidental damage
from contractor digging operations.
[0089] FIGS. 72 and 73 show the application of a single well heat
exchanger for a residential home and multiple pad drilled heat
exchangers for larger commercial heat and cooling loads, wherein an
optional thermal bank tank is provided for night time operation
when the electrical energy cost are cheaper or for day time
operation when solar cells can provide electrical energy.
[0090] FIGS. 74 and 75 show the installation of small and large
coaxial-flow heat exchanging structures of the present invention in
ground to prevent icing or snow accumulation on side walks, bridges
and heavily traveled intersections or steeply pitched roads.
[0091] FIGS. 76 and 77 show applications using sea water or ballast
water as the heat-pump heat sink for gas dehydration and oil
de-waxing, wherein coaxial-flow-flow heat exchanging structure of
the present invention installed in is used to extract heat from the
gas to cause the temperature to drop which then condenses water
vapor and/or light hydrocarbon vapors.
[0092] FIG. 78 shows the application of the coaxial-flow heat
exchanging structure of the present invention in a ground-loop heat
exchanging system used for pipeline quality gas dehydration on
shore for gas produced from remote offshore wells.
[0093] FIGS. 79, 80 and 81 show the coaxial-flow heat exchanging
structure of the present invention installed in a ground-loop heat
exchanger used for gas dehydration and condensate separation on
land for a single well or a gathering system, wherein as shown in
FIG. 80, the gas in the liquid separator is cooled to a temperature
near the aquifer temperature, and then gas is cooled with a heat
pump to a temperature near the gas hydrate temperature using a
rotating heat exchanger, wherein the glycol cycle or calcium
chloride salt cycle is used to remove moisture from the gas-hydrate
temperature to the -30 F dew point for pipeline sales, and wherein
the system reduces energy cost of gas dehydration and eliminates
the release of benzene, toluene and other carcinogenetic
hydrocarbon vapors to the atmosphere.
[0094] FIGS. 82 and 83 show the coaxial-flow heat exchanging
structure of the present invention installed in a seawater heat
exchanging system aboard a submarine for centralized and
decentralized air condition and equipment cooling, wherein the
purpose of the system is to reduce noise generation and increase
the safety in case of a hull breach.
[0095] FIGS. 84, 85 and 86 show both side and cross-section views
of the coaxial-flow heat exchangers of the present invention used
in a submarine application, wherein the outer tubes are made of
metal and they are finned to provide maximum heat transfer.
[0096] FIGS. 87, 88 and 89 show a side and cross-sectional views of
the coaxial-flow heat exchanging structure of the present invention
installed in an aqueous-based fluid to air heat exchanger.
[0097] FIG. 90 shows the application of a single well heat
exchanger for a residential home and multiple pad drilled heat
exchangers for larger commercial heat and cooling loads, and
wherein an optional thermal bank tank is provided for night time
operation when the electrical energy cost are cheaper or for day
time operation when solar cells can provide electrical energy.
[0098] FIG. 91 shows system of eleven deviated wells connected
together in a heat pumping network.
[0099] FIG. 92 is a front view of a rotating extrusion die used to
manufacture the helically-finned tubing within the coaxial-flow
heat exchanging structure of the present invention, wherein the die
is fabricated from a material compatible with the material being
extruded and with a melting point temperature above that of the
material being extruded.
[0100] FIG. 93 is a right side view of the rotatable extrusion die
showing how the center mold core is held in position by support
arms.
[0101] FIG. 94 is a front view of a rotatable extrusion die with
the opening to form the first flow guide and an additional flow
guide opening.
[0102] FIG. 95 is a right side view of the rotatable extrusion die
illustrating how the distance between the surface of the mold core
determines the desired wall thickness of the flow guide tube as it
is extruded through the rotatable extrusion die.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE PRESENT
INVENTION
[0103] Referring to FIGS. 1 through 91, the various illustrative
embodiments of the coaxial-flow heat exchanging structure of the
present invention will be now described in detail.
[0104] As shown in FIG. 1, a horizontal/deviated well is drilled
into an aquifer for installation of the ground loop heat exchanger
of the present invention, which is referred to herein as "a
coaxial-flow heat exchanging structure". As will be described in
greater detail hereinafter, the coaxial-flow heat exchanging
structure has a proximal end and a distal end for exchanging heat
between a source of fluid at a first temperature and the
environment (e.g. ground, water, slurry) at a second temperature.
The coaxial-flow heat exchanging structure comprises an outer
thermally-conductive flowguide tube having a hollow conduit
extending from the proximal end and distal end, and
helically-finned tube disposed within the hollow conduit of the
outer thermally-conductive flowguide tube, and has a central
conduit for conducting a heat exchanging fluid, from the proximal
end, along the central conduct towards the distal end, and
returning back to the proximal end along a spiral annular flow
channel formed between the thermally-conductive flowguide tube and
the helically-finned tube. The coaxial-flow heat exchanging
structure may also comprise an insulating center tube disposed
within the central conduit, for conducting the heat exchanging
fluid from the proximal end, along the central conduct towards the
distal end, and returning back to the proximal end along the spiral
annular flow channel.
[0105] A cap is installed on the proximal end and is provided with
fluid inlet and outlet ports to facilitate (i) the injection of the
heat exchanging fluid into the coaxial-flow heat exchanging
structure at a third temperature, and (ii) the withdrawal of the
heat exchanging fluid out of the coaxial-flow heat exchanging
structure at a fourth temperature. The coaxial-flow heat exchanging
structure of the present invention can be used a component within a
heat pump system to substantially improve the heat transfer
performance of aqueous based fluid heat transfer therein, wherein
the ground, a lake, a river, or sea water can be used as the
primary or secondary heat sink or heat source. Heat pump systems
employing the coaxial-flow coaxial-flow heat exchanging structure
of the present invention may or may not incorporate the use of a
refrigeration subsystem.
[0106] As shown in FIG. 1, the deviated well bore, with the
coaxial-flow heat exchanging structure installed therein, is used
as a heat exchanger with the aquifer in the ground. The well is
drilled with a short radius turn (less than 50 ft. radius) into the
middle of the aquifer zone. The metal thermally-conductive
flowguide tube (component of the coaxial-flow-flow heat exchanging
structure) is cemented with sanded grout to surface to prevent
aquifer contamination and increase the heat transfer coefficient to
the ground. After cementing operations, the thermally-conductive
flowguide tube is cleaned with a mild acid solution with surfactant
to remove mud, mill scale and grout tailings. The spiral pitch and
number of fins on the helically-finned tubing component are
selected to rotate the fluid at the desired heat-pump circulation
rate. Once these parameters have been determined, the
helically-finned (insulated) tubing is run to the bottom of the
flowguide tube shoe and sealed off at the thermally-conductive
flowguide tube cap with fusion welding. The array of wells can be
connected to the gathering lines (using insulated plastic surface
piping) for series or parallel operation with the heat-pump heat
exchanger formed by an arrangement of installed coaxial-flow heat
exchanging structures. Finally, the ground loop is filled with an
aqueous heat transfer fluid and the air is bled out of the high
spots in the system to achieve optimum performance. By using the
coaxial-flow heat exchanging structure of the present invention,
this deviated well design reduces installation cost and material
cost.
[0107] As shown in FIG. 1, the design goal for the ground/water
source loop of the heat pump system of the illustrative embodiment
of the present invention has been to provide enough heat-transfer
surface area and ground/water volume to insure the circulating
fluid temperature of the ground/water source loop does not go
above/below the average ground temperature by 7.degree. F. or
3.degree. C., under continuous load during peak of the
heating/cooling season. By maintaining a return fluid temperature
within 7.degree. F. or 3.degree. C. of the ground/water source
temperature, the SEER rating of the heat pump system will be
maximized for the whole heating/cooling season. A commercial
objective of the design has been to use a combination of metal and
plastic tubing to increase heat transfer to/from the ground while
reducing the life-time cost of the ground loop which includes the
capital, maintenance and operational cost averaged over the
life-time of the system.
[0108] If the time averaged thermal seasonal heat and cooling loads
are nearly equivalent, then the core volume of the ground loop can
be designed to store heat during the cooling season and,
subsequently, the heat can be extracted from the core volume during
the heating season. If the time averaged thermal load is mostly
heating or cooling, then ground loop is designed to transfer heat
without significant storage in the ground volume.
[0109] For small spikes over base load, larger well bore diameter
or the iron mass in the foundation can be used for thermal storage
to average out the operational temperature of the fluid. With a
helical fin design and the slot aspect ratio ranging from a 1 to 1
square to a 1 to 2.5 rectangle, tubing diameters can exceed 36
inches or 1 meter without significantly reducing heat transfer
coefficient to the ground/water source. For large spikes over base
load, a larger tank volume is added to the ground loop for
additional thermal storage.
[0110] For an estimated yearly thermal load, a thermal simulator
can be used to determine the number wells used in the ground loop
array, the amount of thermal storage needed to average out the
daily peak loads and the amount of core volume needed in the array
to store heat from the cooling season to use in the heating season.
For large thermal projects, the simulator can be used to optimize
capital cost of drilling (horizontal well bore length versus number
of wells in array), material cost of the thermally-conductive
flowguide tube (thermally-conductive flowguide tube diameter versus
metal or plastic), the approach temperature of the ground loop and
refrigerant used by the heat-pump system. However, the actual heat
transfer rate and time coefficient of the ground-loop array of
wells should be determined with a transient temperature test of the
ground loop and the actual heat storage of the ground loop should
be determined with a complete year of history of circulating fluid
temperature and load.
[0111] The well design parameters such as grout thickness,
thermally-conductive flowguide tube material, spiral pitch, number
of helical fins, insulated wall thickness of inner tube, and fluid
composition can be optimized using analytical equations for steady
state operation. Most of the well array design parameters such as
well depth, well length, well spacing should be optimized for the
given aquifer properties with a thermal simulator over a multi-year
load to account for the thermal storage of earth and the seasonal
transients. Most of thermal storage parameters for the insulated
volume of fluid in a tank or in the array of well bores, or the
insulated volume of concrete in the foundation can be empirically
fit with simple equations so that the peak loads can be averaged
over the daily operation of the heat pump. The design goal is to
install a ground loop with thermal storage so that it can transfer
the daily thermal load from the heat pump for the minimum capital
cost and operational cost.
[0112] FIG. 2 shows a natural gas dehydration system using a heat
pump system of the present invention as shown in FIG. 1, with a
deviated well drilled in an aquifer for the ground loop. In this
system, the natural gas and other liquids are produced from the
well that is completed in the gas zone. The natural gas moves
through the separator where brackish water and hydrocarbon liquids
are separated form the gas. The natural gas then moves through the
heat pump dehydrator where the temperature is reduced to condense
the water vapor and heavier hydrocarbon vapors from the natural
gas. Finally, the natural gas is then polished with a small glycol
unit to remove the last traces of water vapor for shipment in the
natural gas production supply lines. Notably, in the natural gas
dehydration system shown in FIG. 1, the deviated well provides
ground loop cooling to dehydrate natural gas in a natural gas
production environment. However, for other oil field cooling
applications, additional large surface thermally-conductive
flowguide tube holes can be drilled and cemented in the ground for
the external metal-pipe, ground-loop heat exchanger. For commercial
and residential heating and cooling applications, smaller plastic
pipe can be used to make the multi-well ground-loop heat exchanger.
Due to the actual drilling cost versus heat transfer area, it is
better to drill a slanted group of small diameter holes from a pad
than to drill one large diameter hole.
[0113] For cooling applications, the addition soluble gases to the
aqueous based fluid improve the heat transfer to ground/water
source. As the pressure increases with depth of fluid column, the
soluble gases are adsorbed by the aqueous fluid; the gases release
their stored heat to the fluid, and in turn raise the temperature
of the fluid which in turn increases the temperature differential
between the fluid and the ground/water source. Carbon dioxide (CO2)
and ammonia (NH3) gases foamed with surfactants create stable
aqueous based fluids used in this absorption process. The return
line requires insulation to prevent the absorption of heat as the
gases come out of solution as the fluid returns to the surface. The
absorption and desorption process acts like a low differential
temperature refrigerant cycle, but it can be quite effective in
increasing the heat transfer in the ground/water source loop.
[0114] For heating applications, the addition of solid particles
can increase the heat capacity of the aqueous based fluid. Micron
sized heavy metal or metal oxide particles can be mixed with the
aqueous based fluid and suspended with a shear thinning polymer
such as xanthan gum or borate cross-linked polymer. The fluid must
be kept in motion or the particles with eventually settle out and
plug the bottom of the well bore. Micron-sized glass spheres
containing a low melting point salt can also be used to increase
the heat capacity of the fluid while maintaining a particle
specific gravity close to 1. Particle specific gravities near to 1
will prevent settling of the particles in the aqueous fluid, thus
allowing a ground loop section to be shut down with out the danger
of plugging the well with settled particles. Field experience has
shown that the composition of the aqueous-based fluid should remain
simple to reduce capital cost and that increasing fluid flow rate
is a better solution to increase heat capacity of the system,
except where very high heat transfer rates are required.
[0115] Having given an overview of the coaxial-flow heat exchanging
structure of the present invention, shown used in a typical heat
pump system application, it is appropriate at this juncture to now
describe the individual components of the ground-loop heat pump
system in greater detail.
[0116] As shown in FIGS. 3 and 4, single spiral or helical finned
insulated tubing is used to create an annular spiral or helical
flow channel within the coaxial-flow heat exchanging structure of
the present invention, for the aqueous based heat exchanger fluid.
As shown, this small-diameter, helically-finned tubing can be
delivered rolled on a large spool to install in the
thermally-conductive flowguide tube, and the tubing can be cut to
size and the well cap fused on as shown in FIG. 48.
[0117] In FIGS. 3 and 4, reference numeral 3B and 4A indicate to
the flow guide for a single helical or spiral fin. The flow guide
can be made out of plastic or metal depending on the static load on
the fin. Reference numerals 3A and 4B indicate the
thermally-conductive flow guide tube. The outer wall of the flow
guide tube can be made out of metal or plastic depending on the
buckling or tensile load of the tubing laying or hanging in the
well bore. FIG. 5 shows the front view of double helically-finned
insulated tubing. 5A points to the insulated flow guide tube.
Reference numeral 5B indicates the first flow guide while 5C points
to the second flow guide. The number of flow guides used in any
particular application is determined by the cross-sectional shape
of the flow channel and this topic is discussed in detail with
reference to FIGS. 39 through 46.
[0118] As shown in FIGS. 5 and 10, a double spiral/helical fin set
is shown used to create spiral or helical flow in large bore
thermally-conductive flowguide tube. In this design, the friction
pressure drop in the ground loop can be reduced, and the number of
fin sets can be increased to reduce the flow path length in the
well bore. Also, as the thermally-conductive flowguide tube size
increases, the number of helical fins can be increased to keep the
aspect ratio of the flow channel shape close to 2 to 1 as shown in
FIGS. 39 and 43.
[0119] As shown in FIGS. 6 and 7, a single helical-finned tubing
with the insulated inner tube is shown installed in the
thermally-conductive flowguide tube of FIG. 1. In this design, the
gas gap between the central insulated inner tube and the
helically-finned outer tube provides insulation, and the gap
distance between the walls remains uniform due to the 3 standoffs
on the inner insulation tube. Reference numerals 6A and 7C indicate
the wall thickness of the center tube in helically-finned insulated
tubing. The center tube wall thickness is calculated from the
material strength, from the buckling load of setting the tubing
down on the thermally-conductive flowguide tube shoe and from
tensile load of supporting the tubing from the thermally-conductive
flowguide tube cap. Reference numerals 6B and 7J indicate the
center tube flow channel. The channel diameter is determined from
the amount of thermal storage need in the ground loop or from the
friction pressure drop. Reference numeral 6C indicates the outer
flow guide tube wall thickness which must support the tensile load
of the tubing and flow guides hanging from the thermally-conductive
flowguide tube cap and it must support the shear stress of
installing the tubing in the thermally-conductive flowguide tube.
Reference numerals 6D and 7B indicate the top side surface of the
flow guide. The surface should be smooth to reduce the friction
pressure drop of the flowing fluid. 6E points out the bottom side
surface of the flow guide. Reference numerals 6F, 7E, 7F, and 7G
indicate the stand offs on the center tube used to create the
static or dead gas space between the center tube and the outer flow
guide tube. The standoffs can have a triangular shape for
installation at the factory, but field experience shows that the
standoffs should have a half cylinder shape for center tube
installation in the field. The number of standoffs used is
determined by the center tube diameter and center tube material.
Reference numerals 6G and 7D show the edge of the flow guide. For
small flow guide outside diameters, the edge can be flat, but for
large diameters the edge should be radius to prevent flow guide
damage by hanging up on an edge in thermally-conductive flowguide
tube collar. Reference numerals 6H and 7I indicate the static or
dead gas space used for insulation between the center tube and the
outer flow guide tube. The space could also be filled with a
ceramic fiber or ceramic paper. The gas space can be pressurized
with an inert, non-condensable gas such as argon, nitrogen,
refrigerant gases, methane, or ethane. The charge gas pressure
should be equivalent to half the hydrostatic pressure in the well
bore. Reference numeral 6I indicates the outer flow guide tube
exterior surface. The surface should be smooth to reduce friction
pressure lost and could be curved to promote tangential rotation of
the circulated fluid. Reference numeral 7A indicates the start of
the clock wise spiral turn of the flow guide. Reference numeral 7H
indicates shows the interior surface of the outer flow tube. To
reduce the heat transfer between the center tube and outer tube,
the surface could be coated with a reflective metal such as
aluminum, silver or gold or coated with a reflective ceramic powder
such as titanium dioxide.
[0120] In FIGS. 8 and 9, the single-helix finned tubing shown in
FIGS. 6 and 7 is shown without the inner/central insulation tube
installed. In this design, the fins can be extruded with the tubing
for small diameters or extruded over a joint of larger diameter
tubing. For diameters exceeding 18 inches or 0.5 meters, the fins
can be rolled from flat stock and welded on the tubing joint.
Reference numerals 8A and 9G indicate the inner diameter of the
flow guide tube where in the center tube will be assembled.
Reference numerals 8B and 8G indicate the beginning and the end of
the flow guide tube cut to the desired length to install in the
well bore. Reference numeral 8C indicates the exterior diameter of
the flow guide tube. Reference numerals 8D and 9B indicate the top
side of the flow guide. Not shown in these figures is the fact that
both the top and bottom surfaces of the flow guide can be curved to
promote tangential rotation of the fluid and to prevent slow
flowing areas in the corners of the spiral flow channel. Reference
8E and 9E show the interior surface of the flow guide tube. This
surface could be coated with a reflective metal such as aluminum,
silver or gold or coated with a reflective ceramic powder such as
titanium dioxide. Reference numerals 8F and 9F show the exterior
surface of the flow guide tube. This surface should be smooth to
reduce the friction pressure of the circulating fluid. The surface
could also be fluted to promote the tangential rotation of the
circulating fluid. Reference numeral 9A indicates the start of the
clock-wise rotation of the spiral flow guide. Reference numeral 9C
indicates the edge of the flow guide. For small flow guide outside
diameters, the edge should be flat to increase the friction
pressure drop of the slot flow so the circulating fluid follows the
flow guide instead of trying to bypass it. But for large diameters,
the edge should be radius with additional thickness to prevent flow
guide damage by hanging up on an edge in thermally-conductive
flowguide tube collar. Reference numeral 9D indicates the wall
thickness of the flow guide tube. The wall thickness is determined
by the material used and the compressive, tensile and shears loads
the tubing wall will be exposed to during installation and
operation.
[0121] As shown in FIGS. 11 and 12, the standoffs on the insulated
inner tubing provide the gas gap needed for insulation between the
inner/central insulation tube and outer helically-finned tube,
wherein the fill gas can be argon, nitrogen, or even ethane,
however argon is a better insulation gas and is readily available
in the field. In this design, a vacuum is established in the field
to check for leaks, then the gap is filled with gas to half of the
bottom hole pressure. Notably, the standoffs can have a
cross-sectional rounded shape instead of the triangular shape,
shown in FIG. 12, for easier installation in the field and to
prevent damage to the edge during installation in the field.
[0122] In FIGS. 13, 14 and 15, insulated helically-finned tubing is
joined with a collar for large diameter helically-finned tubing
that cannot be rolled on spool. In this application, the collar can
be fusion welded or threaded to the next joint in the field to make
a continuous piece of tubing for installation in the
thermally-conductive flowguide tube. Preferably, the inner tube is
fuse welded at the factory on both ends of the outer tube to
provide the seal for the gas gap.
[0123] In FIGS. 16, 17, and 18, the helically-finned tubing is
joined with collar without the inner insulated tube installed. In
this application, the collar is usually threaded for metal tubing,
slip for short lengths of plastic tubing or even twisted lock with
O-ring seal for long lengths of plastic tubing. Preferably, the
wire coil in the collar can be used to fusion weld plastic tubing
in the field during installation.
[0124] In FIGS. 19, 20, and 21, the insulated inner sleeve is
fusion welded on both ends inside the helically-finned tubing to
provide the gas gap. In this application, high pressure argon or
other gas can be used to fill the gas gap before the fusion
process. Also, the inner insulation tube can be made of high
density, foamed plastic to reduce heat transfer and friction
pressure drop.
[0125] In FIGS. 22 and 23, tubing joints are shown with a single
helix fin and a double helix fin. The number of helical/spiral fins
increases as the diameter of the thermally-conductive flowguide
tube increases to maintain the 1 to 1 or 2 to 1 aspect ratio of the
helical flow channel.
[0126] In FIGS. 24 and 25, a shoe structure is shown fusion welded
to the bottom (distal end) of the helically-finned tubing so as to
protect the spiral fins during the installation process. During
this process, the leading edge of the helically-finned tubing is
shown with a radius, however, it can be shaped like a truncated
cone. Also while there are four fins shown, notably however, the
number of fins can range from 3 to 6, depending on the number of
helical fins used on the tubing.
[0127] In FIGS. 26, 27 and 28, the smooth thermally-conductive
flowguide tube is shown from various views. During the installation
process, this tube structure in grouted in the Earth. Preferably,
the smooth thermally-conductive flowguide tube is usually metal due
to its high heat transfer coefficient. Threaded collars are used to
attach the joints together, and the thermally-conductive flowguide
tube shoe shown in FIG. 26 usually contains a cement valve and a
plug catcher. Small diameter tubing is used inside the
thermally-conductive flowguide tube to prevent grout contamination
therewithin and to flush the mud out of the flowguide tube after
grout placement. Such precautions should be taken because hardened
grout inside the flowguide tube can damage the plastic spiral edges
during insulation and reduce the heat transfer coefficient of the
metal wall. To ensure this, a small diameter coiled tubing is run
in the annulus of flowguide tube, and grout is pumped to fill the
annulus at substantially the same rate as the small diameter tubing
is pulled to the surface.
[0128] In FIGS. 29, 30 and 31, a fluted thermally-conductive
flowguide tube is shown. In this design, the flutes on a plastic
thermally-conductive flowguide tube give it additional surface area
to counteract the low heat transfer coefficient of the plastic. The
flutes also give the plastic thermally-conductive flowguide tube
additional strength. The thermally-conductive flowguide tube shoe
in FIG. 29 usually has a cement valve and a plug catcher to
complete the grouting process. The thermally-conductive flowguide
tube shoe will also have metal forks to dig into the wall of the
hole to prevent the plastic thermally-conductive flowguide tube
from floating when the grout is pumped to surface. An option to
prevent the thermally-conductive flowguide tube from floating off
the bottom of the hole is to flash set a small volume of grout in
the bottom of the hole to hold the thermally-conductive flowguide
tube down while the rest of the grout is pumped to the surface with
a small diameter coiled tubing in the annulus of the hole. The
small diameter tubing is pulled to the surface at substantially the
same rate as the grout fills the annulus of the hole.
[0129] In FIGS. 32 and 33, the forward and reverse flow patterns
are shown in smooth thermally-conductive flowguide tube with single
helically-finned tube. During the cooling season, pumping down the
annulus gives the best approximation to a cross flow heat exchanger
for liquid-gas mixtures where the liquid adsorbs the gas phase when
the pressure increases as the mixture is pump down the
thermally-conductive flowguide tube annulus. As the gas phase is
absorbed, the fluid temperature increases with depth which in turn
increases the heat transfer to the ground or water. During heating
season or winter operation, pumping down the annulus with a cold
aqueous fluid gives the best approximation to a cross flow heat
exchanger due to the ground temperature increasing with depth. For
horizontal or deviated wells, it is better to pump down the inner
tube to maximize heat transfer at the end of the well.
[0130] FIG. 34 shows the forward flow pattern for a double
helically-finned tube. In this design, the multiple helical fins
are used for large diameter thermally-conductive flowguide tube.
For large diameters, the helically-finned tubing joints can be
pre-installed in the thermally-conductive flowguide tube joints for
shipment. O-ring seals are used in the spiral finned tube collars,
so when thermally-conductive flowguide tube joints are joined
together, the O-ring seals the spiral finned tubing also. This
helps reduce installation cost and shipping cost for large diameter
ground loops.
[0131] In FIGS. 35 and 36, a fluted thermally-conductive flowguide
tube is shown with single helix flow tubing installed. In this
design, the pitch of the spiral and the fluted thermally-conductive
flowguide tube should be practically close for maintaining the
helix flow pattern in the channel. The fluid will bypass the fins
around the space in the flutes. The whole assembly can be extruded
together as a tubing-thermally-conductive flowguide tube joint
combination, and the joint combination can be fusion welded in the
field with preinstalled wire coils in the collars.
[0132] FIGS. 37 and 38 show the helical flow pattern of fluid as it
is pumped down the annulus and up the annulus of the coaxial-flow
heat exchanging structure of the illustrative embodiment of the
present invention. Pumping down the annulus for near vertical well
bores gives the best approximation to a cross flow heat exchanger
for ground temperatures close the surface. For horizontal or
deviated wells in aquifers, it is better to pump down the inner
insulation tube to maximize the heat transfer at the end of the
well.
[0133] FIGS. 39, 40, 41 and 42 show cross-sectional views of the
tangential flow directions for an coaxial-flow heat exchanging
structure having a fluted control volume shape. An coaxial-flow
heat exchanging structure with a square-like shape control volume
usually has one vortex for flow rates of interest. An coaxial-flow
heat exchanging structure having a rectangle-like shaped control
volume with an aspect ratio near 2 to 1 usually has two vortexes
for flow rates of interest. For coaxial-flow heat exchanging
structures having rectangle-like shapes with an aspect ratio
greater than 4 to 1, there can be vortex near each fin with a
laminar slot flow region in the center of the control volume. The
laminar slot flow region of the coaxial-flow heat exchanging
structure reduces the heat transfer of the fluid with the
thermally-conductive flowguide tube wall and reduces the efficiency
of the helical flow ground flow loop of the coaxial-flow heat
exchanging structure of the illustrative embodiment of the present
invention.
[0134] FIGS. 43, 44, 45 and 46 show cross-sectional views of the
tangential flow directions for a coaxial-flow heat exchanging
structure having a smooth rectangular control volume shape. A
coaxial-flow heat exchanging structure having a square-like shape
control volume usually has one vortex for flow rates of interest. A
coaxial-flow heat exchanging structure having a rectangle-like
shaped control volume with an aspect ratio near 2 to 1 usually has
two vortexes for flow rates of interest. For a coaxial-flow heat
exchanging structure having a rectangle-like control volume shape
with an aspect ratio greater than 4 to 1, there can be a vortex
near each fin with a laminar slot flow region in the center of the
control volume. The laminar slot flow region reduces the heat
transfer of the fluid with the thermally-conductive flowguide tube
wall and reduces the efficiency of the helical flow ground flow
loop.
[0135] FIG. 47 shows a coaxial-flow heat exchanging structure
having a helically-finned tubing in a corrugated
thermally-conductive flowguide tube. In this design, the corrugated
flowguide tube wall increases the surface area and strength of the
thin walled thermally-conductive flowguide tube. The period of the
corrugation flutes is at least one quarter or less of the helical
fin to prevent significant fluid bypass around the fins. The
corrugations will increase the friction pressure drop in the
annulus of the coaxial-flow heat exchanging structure by a factor
of 10% and will increase the heat transfer rate and area thereof by
a factor of 40%.
[0136] FIG. 48 shows the helically-finned tubing in the
thermally-conductive flowguide tube of the coaxial-flow heat
exchanging structure installed with a well cap. The well cap holds
the helically-finned tubing off the bottom of the
thermally-conductive flowguide tube so as to prevent buckling of
the plastic helically-finned tubing and seals the
thermally-conductive flowguide tube annulus from fluid leaks. In
order to prevent buckling of the plastic spiral tubing, at least
2/3 of the helically-finned tubing should be hung in tension from
the well cap. Using the O-ring seal, well cap provides an easy way
to remove the spiral tubing in case thermally-conductive flowguide
tube fluid leak. The well cap can be attached to
thermally-conductive flowguide tube with threads, with compression
bolts or a compression ring.
[0137] FIG. 49 shows fluid distribution around the spiral annulus
of the coaxial-flow heat exchanging structure shown in FIG. 50, as
well as around its well cap, that is, for fluid being pumped down
the spiral annulus of the coaxial-flow heat exchanging
structure.
[0138] In FIGS. 50 and 51, an coaxial-flow-flow heat exchanging
structure of the present invention is shown as having a
thermally-conductive flowguide tube and a well cap. In this
application, the fluid return and injection manifold have been
removed for drawing clarity. The well cap can have a manifold of
several small holes for a low friction pressure drop or a single
medium size hole for a little higher friction pressure drop. The
single medium sized hole is usually threaded for a pipe connection,
and the small holes have an O-ring sealed quick-connect to prevent
fluid leaks and reduce the installation time of the pre-made
manifold.
[0139] In FIGS. 52, 53, and 54, coaxial-flow heat exchanging
structures of the present invention are shown having either a
compression ring well cap or a clamped well cap. In this design,
either type of well cap has an O-ring or U-ring seal around the
well thermally-conductive flowguide tube so as to prevent fluid
leaks. The clamps on the thermally-conductive flowguide tube are
provided to prevent fluid pressure from pumping well cap off the
thermally-conductive flowguide tube for shallow helical tubing
depths or high fluid pressures. For permanent installations in
cement structures, the well cap is fusion welded, as shown in FIG.
52, so as to reduce the risk of leaks.
[0140] FIGS. 55, 56, 57 and 58 show three different styles of
annulus fluid return for the helically-finned tubing employed
within the coaxial-flow heat exchanging structure of the present
invention. In the first style, the coaxial-flow heat exchanging
structure employs a connected manifold of small holes or one medium
size hole drilled in the well cap with fluid exiting parallel or
perpendicular to thermally-conductive flowguide tube axis. In the
second style, the coaxial-flow heat exchanging structure employs
tube fittings welded/fused to the side of the thermally-conductive
flowguide tube for fluid injection and return (for use in concrete
piling or pier installations). In the third style, the coaxial-flow
heat exchanging structure uses a tube fitting welded to the side of
the thermally-conductive flowguide tube for annular fluid return
(for use in foundation installations when the tube fittings are
compression). In all three designs, a low friction pressure drop is
achieved across the cap of the coaxial-flow heat exchanging
structure.
[0141] In FIG. 59, the well cap and the insulated helical flow
tubing employed within the coaxial-flow heat exchanging structure
of the present invention. This figures shows the transition from
internal insulation to external insulation used in the horizontal
run between wells or heat pump.
[0142] FIG. 60 shows the coaxial-flow heat exchanging structure of
the present invention installed in a deviated well bore. The
horizontal section of the structure is drilled into an aquifer zone
and the vertical section thereof connects the horizontal section
back to the surface. This design is used where there is a known
water saturated sand, sandstone, or limestone zone with high water
permeability or ground water movement to maximize heat transfer
rate of each well in the ground loop, the warn water will migrate
away from the well bore and create a very slow thermal siphon in
the porous formation. This design is used when the ground loop will
not be used to store heat from the cooling season to be extracted
in the heating season. Using this design, one or two wells can be
drilled for retro-fitting an office building or a city block of
residential houses with ground-loop heat pumps.
[0143] FIG. 61 shows the coaxial-flow heat exchanging structure of
the present invention installed in a near horizontally bored well
in the side of a mountain, mesa, or hill. In this application, the
well bore path is deviated to follow an aquifer zone if available
at the site. For buildings with a deep basement or built on the
side of a hill, the deviated well bores are drilled in the wall of
the basement.
[0144] FIG. 62 shows the coaxial-flow heat exchanging structure of
the present invention installed in a well bore that is cap below
the surface to prevent significant heat transfer to the
ground/water surface or atmosphere. For areas that have significant
ice or freeze/thaw movement, the distribution pipes should be
protected against damage and, if possible, the well should be
capped below the frost line.
[0145] FIGS. 63, 64, and 65 show the coaxial-flow heat exchanging
structure of the present invention installed vertically or
horizontally in foundations or pilings of a building, bridge, or
other structure, wherein the heat exchanger can take advantage of
the metal rebar used in the concrete to increase the effective
surface area of the outer tube. By installing the ground-loop heat
exchanger in the ground or water below the structure, the
cement/concrete sheath can perform two functions: structural
support and heat transfer to the water or ground. If the heating
load is small enough and the temperature difference large enough,
then heat exchanger can be used in the thermo-siphon mode using the
density difference between cold and warm aqueous solution,
otherwise a heat-pump is used to increase the heat transfer rate,
and as the piling spacing is very close in building foundations,
the whole volume of ground contained between the pilings can be
converted to a thermal bank for peak loads or even to store heat
from the cooling season to be used in the heating season. Also, if
the top of basement foundation is isolated with insulation, then
cement structure and some surrounding ground can be converted into
a thermal bank for peak load averaging during winter heating and
summer cooling.
[0146] FIGS. 66, 67 and 68 show the coaxial-flow heat exchanging
structure of the present invention suspended in an aqueous solution
or mud. In these applications, the vertical metal fins are used to
increase the heat transfer area of the thermally-conductive
flowguide tube by making an external thermo-siphon for aqueous
solution circulation. The fin width to thickness aspect ratio
should be less than 10 to 1 to optimize the use of metal and heat
transfer to the aqueous solution or mud. For installations in
bodies of water, the fins are coated for anode operation to prevent
bio-film growth and scaling, which reduces the heat transfer to the
aqueous solution.
[0147] FIG. 69 shows the coaxial-flow heat exchanging structure of
the present invention installed in a bridge component or piling. In
earthquake areas, the pilings are wrapped in a metal sheath to
prevent structural damage in the earthquake, and the sheath could
be installed with spiral-like flow channels to provide ground/water
source heat to prevent icing of the road way or sidewalks during
the winter.
[0148] FIGS. 70 and 71 show the application of pad drilling of nine
deviated wells to minimize the ground surface impact while
maximizing the volume of ground contacted by the well bore. In such
applications, long term operation allows the ground loop to thermal
bank heat from the cooling season for use in the winter season. For
cooling loads only, a shallow horizontal loop can be added to the
ground-loop to remove heat from the thermal bank during the winter
season, in the limit of deviated well drilling, a horizontal well
as shown in FIG. 60 could replace the pad of nine deviated wells.
The pad drilling also has the advantage of reduced heat loss from
horizontal gathering piping and reduced risk of accidental damage
from contractor digging operations.
[0149] FIGS. 72 and 73 show the application of a single well heat
exchanger for a residential home and multiple pad drilled heat
exchangers for larger commercial heat and cooling loads. In this
application, an optional thermal bank tank is provided for
nighttime operation when the electrical energy cost are cheaper or
for day time operation when solar cells can provide electrical
energy. For remote cooling operations, e.g. for equipment used in
cell phone towers, the ground loop can provide a uniform
operational temperature, wherein for rest area restrooms, solar
cells with battery back up can power the heat pump to prevent
freezing of the plumbing and provide guest comfort. Also, a long
horizontal well drilled in an aquifer can replace a pad of deviated
wells.
[0150] FIGS. 74 and 75 show the installation of small and large
coaxial-flow heat exchanging structures of the present invention in
ground to prevent icing or snow accumulation on side walks, bridges
and heavily traveled intersections or steeply pitched roads. In
such applications, the ground heat can keep the road surface from
icing up and increase the evaporation rate of moisture on the road.
Spring and summer operations can thermally bank (i.e. store) heat
for intermittent winter surface de-icing, and to reduce energy
cost, the highway department can remote operate the heat pump hours
before the bad weather conditions move in the area and prevent the
road conditions from becoming bad.
[0151] FIGS. 76 and 77 show applications using seawater or ballast
water as the heat-pump heat sink for gas dehydration and oil
de-waxing. In such applications, the coaxial-flow heat exchanging
structure of the present invention can be used to extract heat from
the gas to cause the temperature to drop which then condenses water
vapor and/or light hydrocarbon vapors. The coaxial-flow heat
exchanging structure can also be used to extract heat from oil with
a cold finger to cause the wax to build up on the cold finger
instead of on the pipeline wall transporting the oil to shore or
the heat pump can be used to heat the oil to prevent or clean the
wax buildup on the pipeline wall. The helical flow tubing can be
submerged in the open seawater or submerged in the ballast water in
the structure, wherein for open sea water, the exterior of the
helical flow tubing is coated for anode operation to prevent
bio-film growth on the heat exchanger. Using a closed loop heat
exchanger with the seawater in locations teaming with sea life,
greatly reduces the maintenance cost of the other heat exchangers
especially, the heat exchanger used on the power plant.
[0152] FIG. 78 shows the application of the coaxial-flow heat
exchanging structure of the present invention in a ground-loop heat
exchanging system used for pipeline quality gas dehydration on
shore for gas produced from remote off shore wells.
[0153] FIGS. 79, 80 and 81 show the coaxial-flow heat exchanging
structure of the present invention installed in a ground-loop heat
exchanger used for gas dehydration and condensate separation on
land for a single well or a gathering system. As shown in FIG. 80,
the gas in the liquid separator is cooled to a temperature near the
aquifer temperature, and then gas is cooled with a heat pump to a
temperature near the gas hydrate temperature using a rotating heat
exchanger. The glycol cycle or calcium chloride salt cycle is used
to remove moisture from the gas-hydrate temperature to the -30 F
dew point for pipeline sales. The system can reduce energy cost of
gas dehydration and eliminate the release of benzene, toluene and
other carcinogenetic hydrocarbon vapors to the atmosphere.
[0154] FIGS. 82 and 83 show the coaxial-flow heat exchanging
structure of the present invention installed in a seawater heat
exchanging system aboard a submarine, for centralized and
decentralized air condition and equipment cooling. The purpose of
the system is to reduce noise generation and increase the safety in
case of a hull breach.
[0155] FIGS. 84, 85 and 86 show both side and cross-section views
of an array of coaxial-flow heat exchangers of the present
invention used in a submarine application. In this application, the
outer tubes are made of metal and they are finned to provide
maximum heat transfer. The fin width to thickness ratio is less
than 10 to 1 to optimize the weight to heat transfer ratio. Also,
mixed oxidant is injected into the seawater or a saltwater
chlorinator to treat the seawater and prevent bio-film buildup on
the fins. The heated seawater can be pre-diluted with fresh
seawater to prevent showing a thermal plume around the
submarine.
[0156] FIGS. 87, 88 and 89 show a side and cross-sectional views of
the coaxial-flow heat exchanging structure of the present invention
installed in an aqueous-based fluid to air heat exchanger. In this
application, the heat exchanger is shown in an `A` frame style.
However, it can be used in the conventional block style. In this
application, dirt particles are removed from the air with a filter
or electrostatic precipitator, to prevent fouling the heat
exchanger and reduce bio-film growth in the condensate line. Also,
an optional ultraviolet light (not shown) can be used to sterilize
the air and the surface of heat exchanger, to prevent mold and
mildew from growing on the heat exchanger and in the duct work.
[0157] FIG. 90 shows the application of a single well heat
exchanger for a residential home and multiple pad drilled heat
exchangers for larger commercial heat and cooling loads. In this
application, an optional thermal bank tank is provided for night
time operation when the electrical energy cost are cheaper or for
day time operation when solar cells can provide electrical energy
for remote cooling operations. For equipment used in cell phone
towers, the ground loop can provide a uniform operational
temperature. For rest area restrooms, solar cells with battery back
up can power the heat pump to prevent freezing of the plumbing and
provide guest comfort. Also, a long horizontal well drilled in an
aquifer can replace a pad of deviated wells.
[0158] FIG. 91 shows a system of eleven deviated wells connected
together in a heat pumping network. This schematic illustrates how
the coaxial-flow-flow heat exchanging structure of the present
invention can be combined in various ways to realize improved heat
pumps systems capable of handling diverse thermal loads.
[0159] Referring to FIGS. 92 through 94, apparatus will be
described for manufacturing the helically-finned tubing used within
the coaxial-flow-flow heat exchanging structure of the present
invention.
[0160] In FIG. 92, a rotating extrusion die is shown for
manufacturing the helically-finned tubing within the coaxial-flow
heat exchanging structure of the present invention. Preferably, the
die is fabricated from a material compatible with the material
being extruded and with a melting point temperature above that of
the material being extruded. The die can be attached to a rotating
fixture on the extrusion machinery using bolt holes 92H, 92I, 92J,
and 92K. The rotatable extrusion die can also be welded to a
rotating fixture.
[0161] As the liquid material is forced through the extrusion
machinery outlet, the rotatable extrusion die 92A can rotate
coaxial-flowly in the clockwise or counter-clockwise direction to
form the flow guide through opening 92B. The coaxial-flow flow heat
exchanger flow guide tube and helical shaped flow guide is formed
by material passing through opening 92L. The desired thickness of
the flow guide and height of the flow guide from the external
surface of the flowguide tube are determined by the dimensions of
opening 92B. The inside surface of the flow guide tube is formed by
surface 92N. The external surface of the flow guide tube is formed
by surface 92M. The center mold core 92C is supported and connected
to the rotatable die by support arms 92D, 92E, 92F, and 92G. The
center mold core can extend beyond the front surface of 92A to
support the extruded material as it exits the rotatable die which
is determined by the material being extruded.
[0162] FIG. 93 shows how the center mold core 93C and 93E are held
in position by support arms 93G, 93H, and 931. The bolt holes 93J,
93K, and 93L can be drilled through or threaded. The flowguide tube
external surface mold 93B and 93F shown can be perpendicular to the
front surface of FIG. 92, 92A and can be angular. FIG. 94 shows how
a rotatable extrusion die with the opening 94B is used to form the
first flow guide and an additional flow guide opening 94C.
Additional flowguide form openings can be cut or machined into the
rotatable extrusion die 94A to form a number of flow guides desired
during the extrusion process. FIG. 95 illustrates how the distance
between the surface 95C of the mold core 95B determines the desired
wall thickness of the flow guide tube as it is extruded through the
rotatable extrusion die.
[0163] While various illustrative embodiments of the present
invention have been disclosed in great detail herein above, is
understood that the coaxial-flow heat-transfer technology employed
in heat pump systems of the illustrative embodiments may be
modified in a variety of ways which will become readily apparent to
those skilled in the art of having the benefit of the novel
teachings disclosed herein. All such modifications and variations
of the illustrative embodiments thereof shall be deemed to be
within the scope and spirit of the present invention as defined by
the Claims to Invention appended hereto.
* * * * *