U.S. patent application number 11/158467 was filed with the patent office on 2008-06-05 for convective earrh coil.
Invention is credited to Steven Joseph Clark.
Application Number | 20080128108 11/158467 |
Document ID | / |
Family ID | 39474381 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080128108 |
Kind Code |
A1 |
Clark; Steven Joseph |
June 5, 2008 |
Convective earrh coil
Abstract
The present invention relates to a method of heat rejection and
extraction between a fluid and the earth, providing for a high
efficiency convective heat exchanger located in ground water, a
means for inducing flow of said ground water at its initial
temperature from ground water pool through said heat exchanger, a
means of inducing heat transfer from said ground water to said heat
transfer fluid or gas, a means of discharging said ground water at
a new temperature back into said ground water pool, and a piping
system suitable to transport said heat transfer fluid from a
thermal load at some remote location at a first temperature, though
the said convective heat exchanger and transporting the heat
transfer fluid at a new temperature to the location(s) where the
thermal energy is utilized.
Inventors: |
Clark; Steven Joseph;
(Aetna, CA) |
Correspondence
Address: |
Steven J. Clark
P.O. Box 250
Babb
MT
59411
US
|
Family ID: |
39474381 |
Appl. No.: |
11/158467 |
Filed: |
June 21, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60582573 |
Jun 24, 2004 |
|
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Current U.S.
Class: |
165/45 |
Current CPC
Class: |
Y02E 10/10 20130101;
F24T 10/10 20180501; F24T 10/40 20180501 |
Class at
Publication: |
165/45 |
International
Class: |
F24J 3/08 20060101
F24J003/08 |
Claims
1. A system for heat rejection and extraction between a heat
transfer fluid or gas and the earth, providing for a high
efficiency convective heat exchanger located in ground water, a
means for inducing flow of said ground water at its initial
temperature from said ground water through said heat exchanger, a
means of inducing heat transfer from said ground water to said heat
transfer fluid or gas, a means of discharging said ground water at
a new temperature back into said ground water, and a piping system
suitable to transport said heat transfer fluid from a thermal load
at some remote location at a first temperature, though the said
convective heat exchanger and transporting the heat transfer fluid
at a new temperature to the location(s) where the thermal energy is
utilized.
2. The heat rejection and extraction system in claim 1 wherein said
ground water can be below ground surface water in a well or cave,
or above ground surface water in a pond, lake, stream or ocean.
3. The heat rejection and extraction system in claim 1 wherein said
heat transfer fluid is a substance that would not harm or
deteriorate the quality of the said ground water if it were to leak
into the ground water, including water, water with non-toxic
additives, or other environmentally friendly fluid or gases.
4. The heat rejection and extraction system in claim 1 wherein said
convective heat exchanger utilizes the efficiencies of convective
heat transfer to thermally link the said ground water to the said
heat transfer fluid.
5. The heat rejection and extraction system in claim 1 wherein said
convective heat exchanger utilizes efficient heat exchanger design,
including tube-in-tube, spiral tubing, finned tubing, or a
rectangular or circular plate design.
6. The heat rejection and extraction system in claim 1 wherein said
convective heat exchanger utilizes thermally conductive materials
that are suitable for contact with the said ground water and said
heat transfer fluid, such as copper, cupronickel, stainless steel,
or plastic.
7. The heat rejection and extraction system in claim 1 wherein said
means for inducing flow of said ground water at its initial
temperature from said ground water pool through said heat exchanger
is an enclosed vertical chamber of sufficient length to generate
natural fluid flow forces due to the difference in temperature and
density of said ground water entering the said heat exchanger at
its initial temperature with the said ground water leaving the said
heat exchanger at its said new temperature.
8. The heat rejection and extraction system in claim 1 wherein said
means for inducing flow of said ground water through said heat
exchanger could be a mechanical pump.
9. The mechanical pump in claim 8 could be electrically driven or
could be driven by the flow of the heat transfer fluid acting upon
an impeller, which drives said pump, the said impeller could be
mechanically coupled via a sealed shaft, or could be magnetically
coupled.
10. The mechanical pump in claim 8 use centrifugal, displacement or
other known pumping strategies.
11. The heat rejection and extraction system in claim 1 wherein
said heat transfer fluid piping system utilizes materials that are
suitable for contact with the said ground water and said heat
transfer fluid, such as copper, cupronickel, stainless steel, or
plastic.
12. The heat rejection and extraction system in claim 1 wherein the
said means for inducing flow of said ground water may also promote
the natural stratification of the ground water into thermal layers,
allowing for storage of thermal energy.
13. The heat rejection and extraction system in claim 1 wherein
said system for heat rejection and extraction between a heat
transfer fluid or gas and the earth water cooling means is
connected to other heat sinks or heat sources, such as space
heating or cooling system, a potable water heating system, a
hydronic snowmelt system (a series of tubes buried in or beneath
sidewalks and driveways near the said building) or solar energy
panels, or waste heat collection system and controls are provided
to allow for the optimum storage and removal of thermal energy on a
daily and seasonal basis.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to a method of heat rejection
and extraction between a fluid and the earth.
BACKGROUND OF THE INVENTION
[0002] Traditionally, if the designer of a heating and/or cooling
system for building wanted to substantially improve the energy
efficiency of his building, he could invest in the installation of
a ground-source (or earth-coupled) heat-pump system. This would
require the installation of one or more water-source heat-pumps in
the building and installing a dedicated piping system from the
water-source heat-pumps to a ground coil. The ground coil heating
and cooling systems use the earth as an energy source and heat
sink. A series of pipes, commonly called a "loop," are used to
connect the heat pump system to the earth. In a few installations,
refrigerant from the heat pump is circulated through the ground in
a closed loop. However, the more common loops discussed here use
only water or a water and antifreeze mixture. While the value of
these systems in the savings of heating and cooling energy has been
profound, the real world-building owners generally have not been
able to justify the cost, complexity or size of the ground coil in
the competitive environment they face.
[0003] Traditionally, these ground coils have been done in one of
two ways. [0004] 1) Closed Loop Ground Coil Systems
[0005] Closed loop systems are becoming the most common. A fluid or
refrigerant is circulated through a continuous buried pipe. The
length of loop piping varies depending on ground temperature,
thermal conductivity of the ground, soil moisture, and system
design, or [0006] 2) Open Loop Ground Coil Systems
[0007] Used successfully for decades, ground water is drawn from an
aquifer through one well and is pumped to the surface, passes
through some fashion of heat exchanger, and is discharged sometimes
to the surface but usually to the same aquifer it was drawn from,
either through the same well or a second well at a distance from
the first. A special case of open loop systems is available when a
nearby pond or lake can be used as the water source instead of
drilling wells.
[0008] Closed Loop Ground Coil Systems general come in three
configurations: Horizontal, Vertical, and Pond.
[0009] Horizontal closed loop installations are generally most
cost-effective for small installations, particularly for new
construction where sufficient land area is available. These
installations involve burying pipe in trenches dug with back-hoes
or chain trenchers. Up to six pipes, usually in parallel
connections, are buried in each trench, with minimum separations of
one fourth of a meter between pipes and 3 to 5 meters between
trenches. Often slinky shaped coils --overlapping coils of
pipe--are used to increase the heat exchange per meter of trench,
but require more pipe per ton of capacity. Two-pipe systems may
require as much as 100 meters of trench per ton of nominal heat
exchange capacity.
[0010] Vertical closed loops are preferred in many situations. For
example, most large commercial buildings and schools use vertical
loops because the land area required for horizontal loops would be
prohibitive. Vertical loops are also used where the soil is too
shallow for trenching. Vertical loops also minimize the disturbance
to existing landscaping. For vertical closed loop systems, one or
more U-tubes are installed in a well drilled 30 to 150 meters deep.
Because conditions in the ground may vary greatly, loop lengths can
range from 40 to 100 meters per ton of heat exchange. Multiple
drill holes are required for most installations, where the pipes
are generally joined in parallel or series-parallel configurations.
Installation costs depend on geological conditions and local
drilling industry experience.
[0011] Both horizontal and vertical closed loop ground coil systems
can be relatively expensive compared with above ground air based
systems due to the extensive size requirements. This large area is
the result of the low thermal heat transfer rate of conduction from
the pipe to the ground and by poor conduction through the
ground.
[0012] Pond closed loops are a special kind of closed loop system.
Where there is a pond or stream that is deep enough and with enough
flow, closed loop coils can be placed on the pond bottom. Fluid is
pumped just as for a conventional closed loop ground system where
conditions are suitable, the economics are very attractive, and no
aquatic system impacts have been shown. Unfortunately, over time,
the exposed pipe coils become fouled with dirt and microbiological
growth and lose their effectiveness.
[0013] Open loop systems are the simplest. Generally, two to three
gallons per minute per ton of capacity are necessary for effective
heat exchange. Since the temperature of ground water is nearly
constant throughout the year, open loops are a popular option in
areas where they are permitted. Open loop systems do have some
associated challenges: (1) Local ground water chemical conditions
can lead to fouling the heat pump's heat exchanger particularly if
oxygen, carbon dioxide and/or other gases are introduced or
disturbed in solution in the water. (2) Increasing environmental
concerns mean that local officials often require permitting to
assure compliance with regulations concerning water use and
acceptable water discharge methods. (3) As the water is returned to
the aquifer, challenges arise with re-injection flow rates,
oxygenating the water, creating a vacuum at the high point of the
loop, etc. (4) A open well system may not be practical where the
water table is very deep, because pumping requirements would become
prohibitive.
[0014] Open Loop Ground Coil Systems general come in three
configurations: Standing well, Multiple well and Pond.
Open Loops--Standing Wells
[0015] Standing wells, also called turbulent wells, may be as deep
as 500 meters, withdraw water from the bottom of the well,
circulate it through the heat pump's heat exchanger, and return it
to the top of the water column in the same well. Some systems
operate with less than 30 meters of well per ton of nominal
capacity. Short circuiting of return water to supply and
oxygenating the water are some of the concerns with this
approach.
Multiple wells
[0016] By providing distance between supply and discharge wells,
the short circuiting of return water to supply is usually avoided.
However additional wells and piping will be required and the
ability of the discharge well to accept the re-injection flow may
be limited. In addition, there may be permitting issues.
[0017] Pond or lake water can be drawn out, pumped through a heat
exchanger and returned to the pond. Debris, scaling and fouling of
the piping system and heat exchanger are concerns with this
approach.
[0018] While ground source systems provide energy savings, low
maintenance, and minimum noise, the relatively high cost of
constructing the ground coil reduces their popularity.
[0019] To avoid the high costs and problems associated with open
and closed loop ground coils; this novel invention demonstrates a
new means of thermally coupling heating and cooling systems with
the earth.
[0020] Prior art in ground coil systems focused on either using
vast array of pipes in the ground or pond as the heat exchanger
(closed loop system) or ground water was brought above grade to an
efficient heat exchanger using forced convection (open loop
system).
[0021] This innovative invention combines the advantages of open
systems (high heat transfer rates associated with convective heat
transfer) with the advantages of closed loop systems (no removal of
water from its location, with associated problems of permitting,
re-injecting and aerating). This novel approach, locates a high
efficiency, convection based, heat transfer coil in the aquifer or
pond. Ground or pond water is forced to flow through one side of
the heat exchanger either through the known principle of natural
convection, or with the assistance of a mechanical means, providing
forced convection. On the other side of the heat exchanger, a fluid
or refrigerant transfers the thermal energy to where it is needed
by a closed loop piping system. Since ground water is never removed
from its natural location, concerns of contamination, aeration,
permitting, and re-injection are avoided.
[0022] An additional unforeseen advantage of this unique invention
is that it promotes the natural thermal stratification of the
ground water. This means that cooler water settles below warmer
water. This allows the system designer to treat the ground water as
a huge thermal storage device. During times when heat is rejected
to the ground water, cool water is drawn from lower levels (either
by natural convection or a mechanical means), and heated and stored
in upper levels. The poor thermal characteristics of the earth
combined with the stratification effect prevent the thermal energy
from warming the cooler water below. Then when heat is need by the
building, the convection flow direction is reversed (either by
natural convection or a mechanical means), and warm water is cooled
and stored in the lower level of the ground water. Again, the poor
thermal characteristics of the earth combined with the
stratification effect prevent the thermal energy from cooling the
warmer water above. This thermal storage feature could allow
thermal energy stored during the day to be used for heat at night.
It is possible that even heat energy stored over the summer could
be used in the winter. Also with proper design of the distribution
system within the building, the heating and cooling energy could be
transferred to their needed uses by direct heat transfer, without
the need of a heat pump. For example, the energy removed to cool a
house in August, could be used to melt snow from a driveway in
January, with only the power consumption of a small pump.
[0023] Additional benefits of this novel invention accrue from the
substantially improved heat transfer rate of the heat exchanger
compared to conventional closed loop. This allows for a closure
approach between the temperature of the heat transfer fluid and the
ground fluid. This of course improves the efficiency of the whole
system and saves energy. This offers an addition advantage in cool
climates (ground temperatures below 10 to 15 degrees C.) when the
system is used to extract heat from the ground. Conventional ground
coils may have as much as a 15 degree total temperature difference
between the working fluid and the ground, meaning the fluid
temperature drops below freezing and requires antifreeze. This new
invention can provide an approach temperature of 5 degrees or less,
avoiding the need for antifreeze and its associated cost, energy
and pumping penalties, and ground water contamination concerns.
[0024] An additional unforeseen benefit of this novel invention is
that the depth of the aquifer is no longer a deterrent to using an
earth coil. Going down hundreds of meters to find an aquifer will
not adversely affect pumping energy, since with a closed loop the
return water going down pushes the supply water back up.
[0025] The present invention solves the problems, reduces the
initial cost and improves the performance of conventional earth
coil systems. The proper design and engineering, a single well
could provide heating and cooling for a large building. Moreover,
because the systems is simple and can require only one well, it is
readily fit for existing buildings. In addition, this single well
can serve multiple functions, such as housing a conventional well
pump providing water for domestic irrigation or fire fighting. It
can be appreciated that the cost of installing such an earth coil
system is relatively low, making it more enticing to the existing
building owner and building developers.
SUMMARY OF THE INVENTION
[0026] Thus and in accordance with a first aspect of the present
invention, there is provided a system for heat rejection and
extraction between a heat transfer fluid or gas and the earth,
providing for a high efficiency convective heat exchanger located
in ground water, a means for inducing flow of said ground water at
its initial temperature from ground water pool through said heat
exchanger, a means of inducing heat transfer from said ground water
to said heat transfer fluid or gas, a means of discharging said
ground water at a new temperature back into said ground water pool,
and a piping system suitable to transport said heat transfer fluid
from a thermal load at some remote location at a first temperature,
though the said convective heat exchanger and transporting the heat
transfer fluid at a new temperature to the location(s) where the
thermal energy is utilized.
[0027] Preferably said ground water can be below ground surface
water in a well or cave, or above ground surface water in a pond,
lake, stream or ocean.
[0028] Preferably said heat transfer fluid is a substance that
would not harm or deteriorate the quality of the said ground water
if it were to leak into the ground water, including potable water,
water with non-toxic additives, or other environmentally friendly
fluid or gases.
[0029] Preferably said convective heat exchanger utilizes the
efficiencies of convective heat transfer to thermally link the said
ground water to the said heat transfer fluid.
[0030] Preferably said convective heat exchanger utilizes efficient
heat exchanger design, including tube-in-tube, spiral tubing,
finned or enhanced tubing, or a rectangular or circular plate
design.
[0031] Preferably said convective heat exchanger utilizes thermally
conductive materials that are suitable for contact with the said
ground water and said heat transfer fluid, such as copper,
cupronickel, stainless steel, or plastic.
[0032] Preferably said means for inducing flow of said ground water
at its initial temperature from said ground water pool through said
heat exchanger is an enclosed vertical chamber of sufficient length
to generate natural fluid flow forces due to the difference in
temperature and density of said ground water entering the said heat
exchanger at its initial temperature with the said ground water
leaving the said heat exchanger at its said new temperature.
[0033] Advantageously said means for inducing flow of said ground
water through said heat exchanger could be a mechanical pump.
Preferably said mechanical pump could be electrically driven or
could be driven by the flow of the heat transfer fluid acting upon
an impeller, which drives said pump. The said impeller could be
mechanically coupled via a sealed shaft, or preferably, could be
magnetically coupled.
[0034] Preferably said means for inducing flow of said ground water
at its initial temperature from said ground water pool includes a
means of filtering out particles that would foul said convective
heat transfer means, and a means of eliminating or back flushing
said particles.
[0035] Preferably said heat transfer fluid piping system utilizes
materials that are suitable for contact with the said ground water
and said heat transfer fluid, such as copper, cupronickel,
stainless steel, or plastic.
[0036] Advantageously, the said means for inducing flow of said
ground water may also promote the natural stratification of the
ground water into thermal layers, allowing for storage of thermal
energy. Preferably said system for heat rejection and extraction
between a heat transfer fluid or gas and the earth water cooling
means is connected to other heat sinks or heat sources, such as a
hydronic snowmelt system (a series of tubes buried in or beneath
sidewalks and driveways near the said building) or solar energy
panels, or waste heat collection system and controls are provided
to allow for the optimum storage and removal of thermal energy on a
daily and seasonal basis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The foregoing aspects and many of the attendant advantage of
this invention will become more readily appreciated as the same
becomes better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawing, wherein:
[0038] FIG. 1 is a section view of the present invention for an
underground aquifer incorporating the present invention using
ground water directly as accessed through a deep well.
[0039] FIG. 2 is a section view of the present invention for a lake
incorporating the present invention using ground water and
incorporating a heat transfer driven pump to induce ground water
flow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0040] Referring to FIG. 1, a portion of an aquifer some depths
below the earth surface 1 is generally shown by reference numeral
2. A well 3 is drilled from the earth surface 1 until it reaches
the desired aquifer 2. Pipes 4 and 5 for supplying and returning
the heat transfer fluid from the thermal load 6 to the convective
earth coil 7 are run below the earth's surface 1 (preferably below
the frost line 8) to the well 3, and down the well 3 to the
convective earth coil 7. In FIG. 1, the convective earth coil 7 is
generally comprised of inlet 9, a vertical chamber 10, a convective
heat exchanger 11, and a discharge outlet 12. In FIG. 1 the
convective heat exchanger 11 is represented as a spiral tube within
a tube.
[0041] The convective earth coil can be used to inject heat into
the ground or extract heat energy from the ground. In the
illustrated embodiment, in operation in the heat injection mode,
warm heat transfer fluid flows from the thermal load 6 through pipe
4 into the top portion of the convective heat exchanger 11. Thermal
energy is transferred from the heat transfer fluid through the
convective heat exchanger 11 to the ground water 2. The thermal
energy increases the temperature of the ground water 2 that is in
contact with the convective heat exchanger 11. The increase in
temperature causes the warmer water to expand in volume,
proportionately decreasing its density. The warmer, lower density
water 13 will rise to the top of the aquifer 2 and cooler, denser
ground water 14 will be drawn in from below the ground coil to
replace it. This upward flow action within the convective earth
coil 7 will produce a flow of warm water 13 filling and stratifying
in the upper layers of the aquifer 2. The layers of warm water will
gradually work their way down to replace the cool water 14 being
drawn in at the base of the convective earth coil 7.
[0042] In the illustrated embodiment, in operation in the heat
extraction mode, cool heat transfer fluid flows from the thermal
load 6 through pipe 5 into the bottom portion of the convective
heat exchanger 11. Thermal energy is transferred from ground water
2 through the convective heat exchanger 11 to the cool heat
transfer fluid. The thermal energy loss decreases the temperature
of the ground water 2 that is in contact with the convective heat
exchanger 11. The decrease in temperature causes the cooler water
to contact in volume, proportionately increasing its density. The
cooler, higher density water 14 will drop to the bottom of the
aquifer 2 and warmer ground water 13 will be drawn in from above
the ground coil to replace it. This downward flow action within the
convective earth coil 7 will produce a flow of cool water 14
filling and stratifying in the lower layers of the aquifer 2. The
layers of cool water will gradually work their way up to replace
the warm water 14 being drawn in at the top of the convective earth
coil 7.
[0043] Referring to FIG. 2, a lake is generally shown by reference
numeral 2. Pipes 4 and 5 for supplying and returning the heat
transfer fluid from the thermal load (not shown) to the convective
earth coil 7 are run below the earth's surface 1 (preferably below
the frost line 8) to the lake 2, and to the convective earth coil
7. In FIG. 2, the convective earth coil 7 is generally comprised of
inlet 9, a vertical chamber 10, a convective heat exchanger 11, a
discharge outlet 12, and a means of anchoring and support the
assembly 3.
[0044] In FIG. 2 the convective heat exchanger 10 is represented as
a plate type heat exchanger. The illustrated embodiment includes
screens at the inlet 9 and discharge 12 to keep debris and fish out
of the heat exchanger. The illustrated embodiment includes an
impeller 15 in the heat transfer stream that is magnetically
coupled to a pump 16 in the lake water stream 14.
[0045] The convective earth coil can be used to inject heat into
the lake or extract heat energy from the lake. In the illustrated
embodiment, in operation in the heat injection mode, warm heat
transfer fluid flows from the thermal load through pipe 4 into the
top portion of the convective heat exchanger 12. Thermal energy is
transferred from the heat transfer fluid through the convective
heat exchanger 12 to the lake water 2. The thermal energy increases
the temperature of the lake water 2 that is in contact with the
convective heat exchanger 12. The increase in temperature causes
the warmer water to expand in volume, proportionately decreasing
its density. The warmer, lower density water 13 will rise to the
top of the lake 2 and cooler, denser lake water 14 will be drawn in
from below the convective earth coil 7 through the filter screen 9
to replace it. This upward flow action within the convective earth
coil 7 will produce a flow of warm water 13 filling and stratifying
in the upper layers of the lake 2. The layers of warm water will
gradually work their way down to replace the cool water 14 being
drawn in at the base of the convective earth coil 7. The heat
transfer fluid leaving the heat exchanger acts on impeller 15,
which is magnetically coupled to pump 16. Pump 16 assists the
natural convective flow, and increase the flow of lake water 2.
[0046] In the illustrated embodiment, in operation in the heat
extraction mode, cool heat transfer fluid flows from the thermal
load through pipe 5 into the bottom portion of the convective heat
exchanger 12. Thermal energy is transferred from the heat transfer
fluid through the convective heat exchanger 12 to the lake water 2.
The thermal energy decreases the temperature of the lake water 2
that is in contact with the convective heat exchanger 12. The
decrease in temperature causes the cooler water to contact in
volume, proportionately increasing its density. The cooler, higher
density water 13 will sink to the bottom of the lake 2 and cooler,
denser lake water 14 will be drawn in from above the convective
earth coil 7 through the filter screen 12 to replace it. This
downward flow action within the convective earth coil 7 will
produce a flow of cool water 13 filling and stratifying in the
lower layers of the lake 2. The layers of cool water will gradually
work their way up to replace the warm water 14 being drawn in at
the top of the convective earth coil 7. The heat transfer fluid
entering the heat exchanger acts on impeller 15, which is
magnetically coupled to pump 16. Pump 16 assists the natural
convective flow, and increase the flow of lake water 2.
[0047] Although described above are types of convective earth
coils, it can be appreciated by those skilled in the art that other
methods of heat exchange may be utilised.
[0048] Additional options include: 1) Transferring the heat energy
via a heat exchanger to a series of tubes buried in or beneath
sidewalks and driveways, thereby providing both building heat
rejection and a snow melt system, 2) Storing thermal energy from a
solar collector during the day and transfer the energy to domestic
hot water the following morning.
[0049] As can be seen in the description above, earth heat
extraction, injection and storage may be accomplished by utilizing
convective heat exchange devices within the ground water. Moreover,
in contrast to the prior art, the convective heat coil 7 is
relatively simple in manufacture as compared with closed loop earth
coils. As can be appreciated by those skilled in the art, the
improved heat transfer characteristics of the convective earth coil
may provide cool enough cold water temperatures, or warm enough hot
water temperatures that eliminate the need for a complex heat
exchanger including an evaporator and compressor in order to
generate cooling or heating from a more moderate temperature
fluid.
[0050] Additionally, the compressor type heat exchangers require
large amounts of power and are relatively noisy. In contrast, the
circulating pumps require only a small amount of power.
[0051] It is, of course, to be understood that the invention is not
intended to be restricted to the details of the above embodiments
which are described by way of example only.
* * * * *