U.S. patent application number 13/571726 was filed with the patent office on 2013-08-08 for condenser for water heater.
The applicant listed for this patent is Samuel Vincent DUPLESSIS, Mark MOTYKA, Jonathan D. NELSON, Gregory M. THOMAS, Craig TSAI. Invention is credited to Samuel Vincent DUPLESSIS, Mark MOTYKA, Jonathan D. NELSON, Gregory M. THOMAS, Craig TSAI.
Application Number | 20130199460 13/571726 |
Document ID | / |
Family ID | 47711909 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130199460 |
Kind Code |
A1 |
DUPLESSIS; Samuel Vincent ;
et al. |
August 8, 2013 |
CONDENSER FOR WATER HEATER
Abstract
A water heater comprises a tank, a cylinder coil section and a
return-flow coil section. The cylinder coil section is in a heat
transfer relationship with the tank and encircles a first portion
of the tank. The return-flow coil section is in a heat transfer
relationship with the tank and encircles a second portion of the
tank. The cylinder coil section and the return-flow coil section
are continuous over at least the first and second portions of the
tank.
Inventors: |
DUPLESSIS; Samuel Vincent;
(Louisville, KY) ; MOTYKA; Mark; (LaGrange,
KY) ; NELSON; Jonathan D.; (Louisville, KY) ;
THOMAS; Gregory M.; (Louisville, KY) ; TSAI;
Craig; (Louisville, KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DUPLESSIS; Samuel Vincent
MOTYKA; Mark
NELSON; Jonathan D.
THOMAS; Gregory M.
TSAI; Craig |
Louisville
LaGrange
Louisville
Louisville
Louisville |
KY
KY
KY
KY
KY |
US
US
US
US
US |
|
|
Family ID: |
47711909 |
Appl. No.: |
13/571726 |
Filed: |
August 10, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61524418 |
Aug 17, 2011 |
|
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|
Current U.S.
Class: |
122/13.01 ;
165/177; 29/890.07 |
Current CPC
Class: |
F24H 4/04 20130101; F24H
9/165 20130101; F28D 15/00 20130101; F24H 9/124 20130101; Y10T
29/49396 20150115; Y10T 29/49895 20150115; B21D 53/02 20130101;
F24H 9/142 20130101; F24H 1/181 20130101; Y10T 29/49947 20150115;
F24H 1/182 20130101; F24H 9/02 20130101 |
Class at
Publication: |
122/13.01 ;
165/177; 29/890.07 |
International
Class: |
F28D 15/00 20060101
F28D015/00; B21D 53/02 20060101 B21D053/02 |
Claims
1. A water heater comprising: a tank; a cylinder coil section in a
heat transfer relationship with and encircling a first portion of
the tank; and a return-flow coil section in a heat transfer
relationship with the tank and encircling a second portion of the
tank; wherein the cylinder coil section and the return-flow coil
section are continuous over at least the first and second portions
of the tank.
2. The water heater of claim 1, wherein the second portion of the
tank is below the first portion of the tank.
3. The water heater of claim 1, wherein a thermal mastic compound
is applied to at least one of the cylinder coil section and the
return-flow coil section where the at least one of the cylinder
coil section and the return-flow coil section make metal-to-metal
contact with the tank.
4. The water heater of claim 1, wherein at least one of the
cylinder coil section and the return-flow coil section is subject
to a tension, wherein the tension is controlled as a function of
the coefficient of thermal expansion between a material of the tank
and a material of the at least one of the cylinder coil section and
the return-flow coil section.
5. The water heater of claim 1, further comprising one or more
clips which support a shape of a tube of at least one of the
cylinder coil section and the return-flow coil section.
6. The water heater of claim 5, wherein a given one of the one or
more clips has a length sufficient to distribute a contact stress
of a bracket connecting the tube and the tank.
7. The water heater of claim 1, further comprising at least one
spool placed at a point where a tube of at least one of the
cylinder coil section and the return-flow coil section changes
direction.
8. The water heater of claim 7, wherein the at least one spool has
a radius controlled as a function of a minimum radius for
preventing at least one of kinking and necking of the tube.
9. The water heater of claim 1, further comprising a foam layer
surrounding the tank and at least a given portion of the cylinder
coil section and the return-flow coil section.
10. The water heater of claim 9, wherein the cylinder coil section
and return-flow coil section are continuous over the given
portion.
11. The water heater of claim 1, wherein the cylinder coil section
and return-flow coil section are formed of a non-copper
material.
12. The water heater of claim 11, wherein the non-copper material
is aluminum.
13. The water heater of claim 11, wherein the non-copper material
is steel.
14. The water heater of claim 13, wherein at least a part of at
least one of the cylinder coil section and the return-flow coil
section are coated with a zinc/aluminum/chromium type coating.
15. The water heater of claim 1, wherein the tank, the cylinder
coil section and the return-flow coil section are coated with a
sealant.
16. The water heater of claim 1, further comprising a transition
section extending between the cylinder coil section and the
return-flow coil section, wherein a strip of foam separates at
least a portion of the transition section and the cylinder coil
section.
17. A method for assembling a condenser of a heat pump water
heater, comprising: winding a first section of a coil around a
first portion of a tank of the heat pump water heater; and winding
a second section of the coil around a second portion of the tank of
the heat pump water heater, wherein the first section of the coil
comprises a cylinder coil section of the condenser and wherein the
second section of the coil comprises a return-flow coil section of
the condenser; wherein the first section and the second section are
continuous over at least the first and second portions of the
tank.
18. The method of claim 17, wherein the first section of the coil
is wound upwards around the tank and the second section is wound
downwards around the tank.
19. A condenser for a heat pump water heater, comprising: a
cylinder coil section configured to be in a heat transfer
relationship with and encircle a first portion of a tank of the
heat pump water heater; and a return-flow coil section configured
to be in a heat transfer relationship and encircle a second portion
of the tank of the water heater, wherein the cylinder coil section
and the return-flow coil section form a continuous coil structure
over at least the first and second portions of the tank.
20. A heat pump water heater comprising: a tank; and a condenser
comprising a cylinder coil section in a heat transfer relationship
with and encircling a first portion of the tank and a return-flow
coil section in a heat transfer relationship with the tank and
encircling a second portion of the tank, wherein the cylinder coil
section and the return-flow coil section are continuously formed.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority to the U.S.
Provisional Application identified as Ser. No. 61/524,418, filed on
Aug. 17, 2011, entitled "Condenser, Shroud, Foam Dam and Drip Plate
for Water Heater," the disclosure of which is incorporated by
reference herein.
BACKGROUND OF THE INVENTION
[0002] The subject matter disclosed herein relates to water
heaters, and more particularly to condensers in water heaters.
[0003] Water heaters such as heat pump water heaters (HPWHs)
typically utilize one of three categories of condenser designs: (1)
internal; (2) remote-located; and (3) external. In practice, almost
all condensers used in the HPWH industry are made of copper, due to
its excellent thermal transfer properties and workability.
[0004] Internal condensers are in contact with water, and are
typically located inside the tank of a HPWH. Internal condensers
that are placed in direct contact with the water have the advantage
of excellent heat transfer, but there is a risk of contamination if
a refrigerant/oil leak occurs. Thus, internal condensers must
generally have a double wall to abate this risk, thus increasing
the cost and resulting in a minor loss in heat transfer efficiency.
Internal condensers are also susceptible to the formation of hard
water scale in moderate-to-hard-water conditions, which reduces
heat transfer efficiency over time.
[0005] Remote-located heat exchanger condensers are located away
from the tank of a HPWH. Water is pumped from the tank at a first
temperature, through a heat exchanger, and returned to the tank at
a second temperature higher than the first temperature.
Remote-located heat exchanger type condensers require a costly pump
to circulate water from the tank to the heat exchanger. This
approach also results in a rapid change of outlet water temperature
from the water heater because the pump is quickly mixing the
incoming cold water throughout the tank as hot water is used.
Remote-located heat exchanger type heat condensers are also subject
to the risk of contamination of the water supply if a
refrigerant/oil leak occurs. Similar to internal condensers,
remote-located condensers are made with a double wall, resulting in
higher cost and a minor impact in heat transfer efficiency. Also
similar to internal condensers, remote-located condensers are
susceptible to the formation of scale in the heat exchanger in
moderate-to-hard water conditions, ultimately resulting in a
reduced circulation, and thus reduced heating.
[0006] External condensers, also referred to as externally applied
or wound condensers, usually employ a flow path from the top to the
bottom of a tank of a HPWH. External condensers are externally
wound or of a roll-bond type. The amount of the tank covered by the
condenser may vary based on the desired performance and cost
tradeoffs. This top-to-bottom flow path directs the hottest
refrigerant coming from the compressor to the top of the tank, and
the refrigerant loses its heat to the tank/water as it moves toward
the bottom of the tank. The result is a large (as much as .about.25
degrees) temperature gradient in the tank from top to bottom. The
larger the gradient, the more the consumer feels the water
temperature drop while using hot water. Also, the larger the
gradient, the less usable hot water can be delivered in the first
draw from the tank.
[0007] To reduce the gradient in the tank, a bottom-to-top
condenser flow path has been developed, such as that described in
U.S. Patent Application Publication No. 2010/0209084, entitled
"Residential Heat Pump Water Heater," which is assigned to General
Electric Company, the disclosure of which is incorporated by
reference herein. This bottom-to-top flow path directs the hottest
refrigerant toward the bottom of the tank, flowing up toward the
top of the tank, and has proven to deliver a small gradient in the
tank.
[0008] However, in some designs, if cold water is introduced into
the bottom of a hot tank of water (via the cold inlet dip tube),
the lowest portion of the condenser is exposed to the coldest
water. Refrigerant in the condenser migrates toward the coolest
point, thus tending to accumulate in the lower portion of the
condenser, where the refrigerant changes phase from gas to a
liquid. This liquid has a hard time making the gradual climb up the
spiral condenser path toward the restriction (thermal expansion
valve (TXV) or other), as gravity tends to pull it toward the
bottom of the tank. A mental image of this phenomenon can be
pictured as liquid refrigerant settling to the bottom of the tube,
slowly getting pulled back toward the bottom of the tank by
gravity, while refrigerant in vapor phase continues to make the
gradual climb, but is also condensing as it travels. Thus, the
refrigerant flow rate drops until the compressor has no refrigerant
to pump/move, and the system enters what has been called "vapor
lock," which can loosely be compared to a pump losing its prime. In
this condition, the heat pump is no longer able to do work, and the
heating process stalls.
[0009] The return-flow coil condenser described in the
above-referenced U.S. Patent Application Publication No.
2010/0209084 addresses the vapor lock issue by looping from the
bottom-to-top cylinder coil back to the bottom/underside of the
tank.
BRIEF DESCRIPTION OF THE INVENTION
[0010] As described herein, the exemplary embodiments of the
present invention overcome one or more disadvantages known in the
art.
[0011] In one embodiment, a water heater comprises a tank, a
cylinder coil section and a return-flow coil section. The cylinder
coil section is in a heat transfer relationship with the tank and
encircles a first portion of the tank. The return-flow coil section
is in a heat transfer relationship with the tank and encircles a
second portion of the tank. The cylinder coil section and the
return-flow coil section are continuous over at least the first and
second portions of the tank.
[0012] In another embodiment, a method for assembling a condenser
of a heat pump water heater comprises winding a first section of a
coil around a first portion of a tank of the water heater and
winding a second section of the coil around a second portion of the
tank of the water heater. The first section of the coil comprises a
cylinder coil section of the condenser and the second section of
the coil comprises a return-flow coil section of the condenser. The
first section and the second section are continuous over at least
the first and second portions of the tank.
[0013] In yet another embodiment, a condenser for a heat pump water
heater comprises a cylinder coil section and a return-flow coil
section. The cylinder coil section is configured to be in a heat
transfer relationship with and encircle a first portion of a tank
of the water heater. The return-flow coil section is configured to
be in a heat transfer relationship and encircle a second portion of
the tank of the water heater. The cylinder coil section and the
return-flow coil section form a continuous coil structure over at
least the first and second portions of the tank.
[0014] In a further embodiment, a heat pump water heater comprises
a tank and a condenser comprising a cylinder coil section in a heat
transfer relationship with and encircling a first portion of the
tank and a return-flow coil section in a heat transfer relationship
with the tank and encircling a second portion of the tank, wherein
the cylinder coil section and the return-flow coil section are
continuously formed.
[0015] Advantageously, embodiments of the invention reduce costs
associated with manufacturing and maintaining a water heater.
Embodiments also allow for improved water heater performance.
[0016] These and other aspects and advantages of the present
invention will become apparent from the following detailed
description considered in conjunction with the accompanying
drawings. It is to be understood, however, that the drawings are
designed solely for purposes of illustration and not as a
definition of the limits of the invention, for which reference
should be made to the appended claims. Moreover, the drawings are
not necessarily drawn to scale and, unless otherwise indicated,
they are merely intended to conceptually illustrate the structures
and procedures described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In the drawings:
[0018] FIG. 1 is a cross-sectional view of a conventional heat pump
water heater having a copper jointed conventional return-flow
condenser;
[0019] FIG. 2 is a side cross-sectional view of an improved heat
pump water heater having an aluminum or steel return-flow
condenser, according to one embodiment of the invention;
[0020] FIG. 3 is a cross-sectional plan view of the improved heat
pump water heater of FIG. 2;
[0021] FIGS. 4 and 5 are each side views of a bottom section of the
improved heat pump water heater 200 of FIG. 2;
[0022] FIG. 6 is a perspective view of a clip as shown in FIG.
4;
[0023] FIG. 7 is a cross-sectional view of the clip of FIG. 6 taken
along line A-A;
[0024] FIG. 8 is a perspective view of a spool as shown in FIG. 4;
and
[0025] FIG. 9 is a side view of the spool of FIG. 8.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE
INVENTION
[0026] One or more of the embodiments of the invention will be
described below in the context of an exemplary HPWH. However, it is
to be understood that the embodiments of the invention are not
intended to be limited solely to the HPWHs described herein.
Rather, embodiments of the invention may be applied to and deployed
in other suitable environments in which it would be desirable to
reduce the manufacturing costs and/or improve the performance of
water heaters.
[0027] Embodiments of a water heater described herein address at
least the vapor lock issue, described above, by providing a
jointless condenser coil in the form of a one-piece (unitary)
structure. The jointless design eliminates the need for the brazing
or other joining operation between the cylinder coil section and
the return-flow coil section, because the cylinder coil section and
return-flow coil section of the condenser coil are wound in a
single, continuous operation. While the cylinder coil section is
wound up the tank, the return-flow coil section is wound down to
the coolest part of the tank, near its bottom, to fully condense a
refrigerant that flows through the condenser. In some embodiments,
the return-flow coil section is wound around the bottom surface of
the tank. The return-flow coil section can be wound with a flow
path of outside to inside, starting from the outer edge of the
bottom surface of the tank and winding inside towards the center of
the bottom surface of the tank. In other embodiments, the
return-flow coil section is wound with a flow path of inside to
outside, starting at the center of the bottom surface of the tank
and winding towards an outer edge of the bottom surface of the
tank. The flow path of outside to inside or opposite is determined
at least in part by the tank bottom shape and desired performance
of the water heater. One skilled in the art would recognize that
various other winding patterns and condenser arrangements are
possible, such as winding the return-flow coil in an upward
direction. While illustrative embodiments may be described with the
particular winding patterns described above, the invention is not
limited solely to these winding patterns but is instead more
generally applicable to a variety of winding patterns and condenser
arrangements.
[0028] Benefits of this type of condenser include, but are not
limited to, lower manufacturing cost and improved heat exchange
performance. This approach also avoids the above-mentioned larger
issues associated with other types of condensers. Moreover,
embodiments of the improved condenser described herein
advantageously use features, such as, but not limited to, improved
attachment clips to tension the aluminum tubing and non-kink spools
to bend aluminum or steel tubing without kinking or crushing.
[0029] Where steel is used as the condenser tubing material,
embodiments of the invention help reduce/minimize condenser
corrosion due to moisture from external sources or condensation
forming on the tank, by using anti-corrosion coatings on the steel
condenser tubing and/or the tank. Additionally, embodiments of the
invention prevent water from accessing or contacting the condenser.
This also helps prevent general and/or galvanic types of corrosion.
The condensers described herein may be used in conjunction with
various water seepage abatement techniques, such as those disclosed
in the U.S. patent application identified by Attorney Docket No. GE
254601, entitled "Water Seepage Abatement in Water Heaters," and
the U.S. patent application identified by Attorney Docket No. GE
253942, entitled "Foam Dam for Appliance," which are filed
concurrently herewith and incorporated by reference herein.
[0030] FIG. 1 is a cross-sectional view of a prior art heat pump
water heater having a prior art copper jointed return-flow
condenser. In this arrangement, the condenser has a separate
cylindrical coil structure that is joined to a separate return-flow
coil structure. Since the two separate structures must be joined,
the joined structure does not form a one-piece, jointless structure
and is thus not considered continuous.
[0031] The coil condenser 100 retains a bottom-to-top flow path,
which begins near the bottom of the cylindrical tank 102, as
originally intended, and forms a cylinder coil 104; but after
progressing toward the top 106 of the tank 102, it then returns
back to the bottom/underside 107 of the tank 102, and the tubing of
the condenser 100 forms a spiral coil 108 that is put in contact
with the bottom of the tank 102. The purpose of this configuration
is to bring the last path of the condenser comprising return-flow
coil 108 into thermal contact with the coldest part of the
tank/water. By this arrangement, the refrigerant has the greatest
opportunity to condense from gas to liquid before making the final
vertical path to the TXV/restrictor 112 and evaporator 110.
[0032] With copper tubing for the condenser 100, a two-piece
condenser design is typically used. This design requires a brazing
operation or other operation 114 to connect the cylinder coil 104
of the condenser 100 to the return-flow coil 108. The return-flow
coil 108 is a spiral shaped coil mounted on the bottom of tank 102.
The return-flow coil 108 passes refrigerant along the coolest part
of the tank to fully condense refrigerant. While FIG. 1 shows a
tank 102 with a bottom configuration that is concave, the tank
bottom may also be convex. Return-flow condensers concepts apply to
both concave and convex arrangements.
[0033] The type of material used to form a condenser and how the
condenser is wound are important. For example, material cost, as
well as the manufacturing cost to wind a condenser on the outside
of a tank is the largest disadvantage of an externally wound
condenser. Copper is the most common material used for almost all
heat pump water heater condensers types described above, but its
cost tends to be volatile and rising. Accordingly, it would be
advantageous to use other materials that are less costly. The
problem with doing so however is that many of such materials have
historically been deemed unsuitable for use in heat pump water
heater condensers, which get wet. For example, steel has been used
in refrigeration products. However, in that application, the
condenser does not get wet. Additionally, in the refrigeration
application, the condenser is post-painted to prevent corrosion due
to ambient humidity and incidental wetting. Accordingly, the
corrosion properties of steel are a significant obstacle to using
it as a heat pump condenser material.
[0034] Disclosed herein are embodiments of a condenser for a water
heater, which condenser may be formed of copper or of an
alternative material to copper, such as aluminum, steel,
cross-linked polyethylene, etc. If steel is used, it may be coated
with an anti-corrosion material.
[0035] A discussion of the obstacles to using alternative materials
such as aluminum and steel is provided below, along with
identification and discussion of solutions to such obstacles which
are utilized in various embodiments of the invention. Following
this discussion is a detailed description of specific embodiments,
with reference to FIGS. 2-9.
[0036] As briefly mentioned above, several obstacles have hitherto
prevented the successful application of aluminum or steel as a
condenser material. Embodiments of the invention overcome these
obstacles, thus allowing the use of aluminum or steel as a viable
material for heat pump condensers, regardless of the flow-path. In
one embodiment, either aluminum or coated steel is used to form an
externally wound condenser for a water heater.
[0037] There are several factors which should be taken into account
when choosing a material for a condenser in sealed systems for a
HPWH. These factors include, but are not limited to, cost,
coefficient of heat transfer, coefficient of thermal expansion
(CTE) versus an adjacent mating material, galvanic potential versus
an adjacent mating material, return-flow condenser considerations,
material strength, manufacturing processes to join components,
manufacturing processes to route tube on a tank, and manufacturing
methods to secure or attach the condenser tube to a tank.
[0038] Embodiments of the invention use aluminum as a condenser
material. The cost of aluminum is typically lower than copper, and
thus provides no obstacle for cost concerns. Similarly, the
coefficient of heat transfer of aluminum to steel conduction is
acceptable for most water heaters.
[0039] The CTE of aluminum is greater than the CTE of steel, which
is typically the adjacent material for tanks of water heaters.
Consequently, an aluminum tube will tend to separate from the tank
as temperature increases. In order to overcome this obstacle,
embodiments of the invention utilize higher tension when winding
the aluminum condenser on the tank as compared to the tension used
when winding a steel or copper condenser. Some embodiments will
also use thermal mastic which provides an expansion joint between
the coil and the tank wall to prevent voids during expansion.
Thermal mastic is a heat transfer compound applied to the
coils/tubing of the condenser at points where the coils/tubing make
metal-to-metal contact. Thermal mastic greatly increases the heat
transfer ability of the condenser.
[0040] The galvanic potential of aluminum is not an obstacle to the
use of aluminum as a condenser material. There is a possible
galvanic coupling between an aluminum tube and a steel tank, but
the aluminum tube wall thickness is greater than that required to
service ten years of the corrosion rate of aluminum.
[0041] Return-flow condenser considerations present a problem for
the use of aluminum. Aluminum is difficult to join, and so a
brazing or other operation (114 as shown in FIG. 1) may become
prohibitively difficult and expensive for separate cylinder coil
and return-flow coil arrangements. To overcome this obstacle,
embodiments use a one-piece, jointless (hereinafter referred to as
"continuous" or "continuously formed") condenser comprising a
cylinder coil section and a return-flow coil section with a
transition section there between on the tank cylinder.
[0042] The material strength of aluminum provides an obstacle for
the use of aluminum as a condenser material. Material strength
considerations include characteristics of the material as a
pressure vessel such as the resistance to crush, collapse or kink
of tubing during handling. Aluminum tubes can easily collapse or
kink when secured to a tank for winding. Embodiments overcome this
obstacle through the use of clips which support the tube shape. The
clips maintain the shape of the aluminum tube while continuing to
hold the tube securely during the high-tension winding process
required to address the CTE obstacle discussed above. The clips
also avoid stress concentrations such as those caused by thermal
expansion by spreading contact load, and radii at bracket edges
that contact the tube. The inlet tube is clamped with a leader
length to allow winding, then the tube is formed to the inlet.
[0043] Manufacturing processes to route aluminum tubes on a tank
provide a further obstacle to the use of aluminum. Currently, there
is no method to wind a return-flow condenser without a joint.
Embodiments of the invention overcome this obstacle by winding
primary (cylindrical coil section) and return-flow (return-flow
coil section) condenser portions in a single pass, utilizing
non-kink spools at points were tubing direction changes. The spool
design provides a minimum radius for the tube bend to prevent
kinking of tube necking The spool design additionally cradles the
tube to prevent stress concentrations. The spool design can also
provide an insulator function between return line and heating coil
windings. For example, the spool may be designed such that it
forces the condenser tube to be positioned outboard of the original
coil.
[0044] Thus, embodiments of the invention provide techniques for
the use of an aluminum condenser on a water heater tank. No brazing
or other joining of the condenser tube under the foam in a tank
assembly is required by using a continuous operation to wind the
cylinder coil section and return-flow coil section of the aluminum
condenser. An improved clip attaches to the aluminum tube start and
stop points without crushing/kinking the aluminum tube. The
improved clip also allows the aluminum tubing to be wound with
higher tension than that used to wind copper to steel to minimize
gaps through the full heating range of the water heater. Spools are
provided at tube direction change points. The spools are non-kink
spools which permit the creation of an aluminum return-flow
condenser with no joints and not pinching or crushing of the
aluminum tube.
[0045] Steel presents a different set of obstacles to its use as a
condenser material. The cost of steel is presently lower than that
of copper, and thus cost is no obstacle to the use of steel as a
condenser material. The coefficient of heat transfer for
steel-to-steel conduction is acceptable, and thus similarly
presents no obstacle to the use of steel. The CTE of steel tubing
is the same as the CTE of steel tanks used for water heaters, and
as such presents no obstacle to the use of steel. The strength of
steel tubing is greater than the strength of copper tubing, and
thus there are no obstacles relating to material strength or
manufacturing methods to attach steel tubing to the tank of a water
heater.
[0046] There is a possible galvanic coupling between a coated steel
tube and a steel tank. This presents a significant obstacle to the
use of steel as a condenser material. Small defects in steel tube
coating can lead to a concentrated galvanic cell at the defect,
leading to a potential failure. Corrosion, however, must have a
source of water to progress. Also, general corrosion in a humid
environment may cause failure before the end of the useful life of
the product, which is about ten years. Embodiments of the invention
overcome this obstacle through the use of the continuous condenser
coil, which avoids water seepage or other leaks at a joint between
the cylinder coil section and the return-flow coil section of the
condenser coil. Embodiments may also use a tube coating capable of
preventing corrosion even if water accesses the condenser.
Zinc/aluminum/chromium type coatings such as are commercially
available under the GALVALUME.RTM. trademark, have been tested and
found acceptable. Embodiments may also remove any galvanic coupling
that negatively impacts the condenser, such as by placing a barrier
such as aluminum between the tank and the steel condenser. For
example, the entire condenser area may be wrapped with a thin
aluminum foil before the steel condenser is wound on the tank.
Embodiments may also wind the steel condenser and coat the entire
tank/condenser assembly with paint or another sealant.
[0047] Return-flow condenser considerations with respect to the use
of steel present similar obstacles as in the case of the use of
aluminum. Steel-to-steel brazing is less robust than
copper-to-copper brazing. Thus, a continuous condenser is utilized,
as described above.
[0048] There are manufacturing processes to join steel to copper
components such as an evaporator or compressor. Current methods
include brazing. Embodiments may also utilize brazing, but perform
the brazing in a nitrogen (oxygen-free) environment, which requires
greater operator skill to ensure a proper joint. Embodiments of the
invention overcome this obstacle by utilizing a continuous
condenser on at least the tank cylinder, thus eliminating the need
to join steel in the foamed/tank assembly. As a result, only joints
which exist above the foam assembly are brazed and accessible for
service.
[0049] Manufacturing processes to route steel tubing on the tank
present similar obstacles as aluminum, as discussed above. Similar
techniques are used to overcome this obstacle for steel condensers.
In accordance with embodiments of the invention, the primary and
return-flow condenser sections are wound in a single pass,
utilizing non-kink spools at points where tubing direction changes.
The spool design provides a minimum radius for the tube bend to
prevent kinking or tube necking The spools also cradle the tubing
to prevent stress concentrations. The spool design can also provide
an insulator function between return line and heating coil
windings.
[0050] Thus, embodiments of the invention provide techniques for
the use of a steel condenser on a water heater tank. No brazing or
other joining of the condenser tube under the foam in a tank
assembly is required. Corrosion due to galvanic coupling between
the condenser tubing the tank and coating of the steel tubing is
reduced or minimized by preventing water or humidity from accessing
or contacting the condenser and using spools at tube direction
change points, which non-kink spools permit creation of a steel
return-flow condenser with no joints.
[0051] Copper, aluminum and steel tubing of the condenser for a
water heater should be tensioned to mate the condenser coils snugly
against the water heater tank so that the condenser coils are in a
heat transfer relationship with the tank. Aluminum tubing is placed
under greater tension than copper, which tension is also greater
than steel.
[0052] FIG. 2 is a cross-sectional view of an improved heat pump
water heater 200 having a continuous aluminum or steel condenser
202. FIG. 3 is a cross-sectional plan view of the improved heat
pump water heater 200 of FIG. 2. FIGS. 4 and 5 are each side views
of a bottom section of the improved heat pump water heater 200 of
FIG. 2.
[0053] As previously described, the heat pump water heater 200
includes a cylindrical tank 204, which may include a concave or a
convex bottom. The condenser 202 wraps around the exterior of the
tank 200 and includes a cylinder coil section 206, a return-flow
coil section 208, and a transition section 209 which extends
between cylinder coil section 206 and return-flow coil section 208.
Condenser 202 is a continuous coil which may be formed of any
suitable material. For example, depending on the embodiment, the
condenser 202 can be formed of cross-linked polyethylene (PEX),
copper, aluminum, steel, or other suitable material. A layer of
foam 203 surrounds the tank and condenser.
[0054] The condenser 202 may be attached to the tank 204 with one
or more clips 220 and/or spools 222, as shown in FIG. 4. The clips
220 are elongated and secure the tubing at the beginning and
endpoint of the condenser 202. Each clip 220 is configured to
cradle the condenser tubing to prevent its collapse (e.g.,
kinking), while creating sufficient grip to prevent slipping of the
tensioned winding. If aluminum tubing is used as the condenser
material, the tension applied to it will be greater than the
tension used to wind copper (or steel) tubing. Each clip 220 has a
channel 226 that cradles the condenser tubing against the tank 204
and prevents the condenser tubing from collapsing. FIG. 6 is a
perspective view of a clip 220. FIG. 7 is a side view of the clip
220 taken along the line A-A. The clip 220 has the channel 226
formed therein. The clip 220 also has a hole 227 formed therein,
which may be used to couple the clip 220 to the tank 204. While
FIG. 7 shows an unthreaded hole 227, the hole may be threaded in
other embodiments.
[0055] As best seen in FIG. 5, the spools 222 are positioned at
points where the condenser flow path changes direction. In some
embodiments, the condenser flow path changes direction at the
transition section 209 between the cylinder coil section 206 and
the return-flow coil section 208. The transition section 209 is a
portion of the coil that extends between the end of the cylindrical
coil section and the beginning of the return-flow coil section. As
shown in FIGS. 4 and 5, spools 222 are placed at ends of the
transition section 209. The spools 222 are dimensioned to ensure
that a minimum bend radius of the condenser tubing is not exceeded.
Each spool 222 also includes a channel 228 that cradles the
condenser tubing to prevent the tubing from collapsing. FIG. 8 is a
perspective view of a spool 222. FIG. 9 is a side view of the spool
222. FIGS. 8 and 9 show the channel 228 formed in the spool which
is used to cradle the condenser tubing and prevent the tubing from
collapsing. While FIGS. 8 and 9 show a semi-circular spool 222, the
spool may be a full circle, ellipse, or other shape with an
appropriate channel 228 which is desired for a given condenser
arrangement.
[0056] The clips 220 and spools 222 may be metal, or molded of a
suitable polymer or plastic material. One or more fasteners and/or
adhesives are used to attach the clips 220 and the spools 222 to
the tank 204. In one embodiment, the fasteners are weld studs that
secure the clips 220 and/or spools 222 to the tank 204.
[0057] As shown in FIG. 5, a strip of foam 224 may be used to
insulate the return coil transition from contacting the cylinder
coils 206 between spools 222 shown in FIGS. 4 and 5. The foam strip
224 provides insulation between the cylinder coils and the return
coil, as any thermal communication between the cylinder coils and
the return coil reduces efficiency of the water heater. In FIG. 5,
strips of foam 224 are placed at both ends of the transition
section 209 around the spools 222. It is important to note that
while FIG. 5 shows strips of foam 224 along the length of the
spools 222, in other embodiments, foam strips may extend over the
entire transition section 209. In addition, in some embodiments,
the coil may not change direction at the transition section, such
that strips of foam are not placed over the length of a spool.
[0058] In use, a controller 218 as shown in FIG. 3, coupled with
one or more sensors, such as a thermostat, determines when water in
the tank 204 has dropped below a predetermined temperature. The
controller 218 then activates the compressor 212 to move
refrigerant through the condenser 202 and activates the fan 216 to
draw air through the evaporator 210. Heat from the ambient air is
transferred to the refrigerant, which vaporizes and travels through
the cylinder coil section 206. The compressor 212 adds heat by
pressurizing the refrigerant. As the refrigerant travels through
the cylinder coil section 206, heat is transferred to the water in
the tank 204, and some of the refrigerant begins to cool (and
change state into a liquid). After passing through the cylinder
coil section 206, the refrigerant enters the return-flow coil
section 208 and imparts heat to the cool water entering the tank
204 at the bottom. Thereafter, the refrigerant passes through the
TXV/restrictor 214, where it is depressurized (and thus cooled)
before again entering the evaporator 210.
[0059] Thus, in one or more embodiments, a heat pump water heater
has a tank and includes a condenser coil comprising a continuously
formed cylinder coil section and return-flow coil section with a
transition section extending there between. The cylinder coil
section is in a heat transfer relationship with the tank and
encircles (or is positioned around) an upper portion of the tank.
The return-flow coil section encircles (or is positioned around) a
lower portion of the tank and is in a heat transfer relationship
therewith. As mentioned above, the condenser coil may be formed of
any suitable material. However, in one embodiment, the condenser
coil is formed of a metal that is not copper (e.g., aluminum or
steel).
[0060] As used herein, an element or function recited in the
singular and proceeded with the word "a" or "an" should be
understood as not excluding plural said elements or functions,
unless such exclusion is explicitly recited. Furthermore,
references to "one embodiment" of the claimed invention should not
be interpreted as excluding the existence of additional embodiments
that also incorporate the recited features.
[0061] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to make and use the invention. The patentable
scope of the invention is defined by the claims, and may include
other examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if they
have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal languages
of the claims.
[0062] Although specific features of the invention are shown in
some drawings and not in others, this is for convenience only as
each feature may be combined with any or all of the other features
in accordance with the invention. The words "including",
"comprising", "having", and "with" as used herein are to be
interpreted broadly and comprehensively and are not limited to any
physical interconnection. Moreover, any embodiments disclosed in
the subject application are not to be taken as the only possible
embodiments. Other embodiments will occur to those skilled in the
art and are within the scope of the following claims.
* * * * *