U.S. patent application number 12/316715 was filed with the patent office on 2009-06-25 for heat exchanger, heat exchanger tube and methods of making and using same.
Invention is credited to Floyd J. Lewis, JR., Timothy E. Mimitz, SR., Sunil Raina, Fred C. Scheideman.
Application Number | 20090159248 12/316715 |
Document ID | / |
Family ID | 40787208 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090159248 |
Kind Code |
A1 |
Mimitz, SR.; Timothy E. ; et
al. |
June 25, 2009 |
Heat exchanger, heat exchanger tube and methods of making and using
same
Abstract
A heat exchanger tube is disclosed herein comprising a first
portion, a twisted portion, and a transition portion between the
first portion and the twisted portion. The transition portion
includes a reinforcing sleeve. A heat exchanger formed from the
tube and a method of forming a heat exchanger tube also are
disclosed. The tube is useful in making a heat exchanger configured
to operate at high pressures without mechanical failure.
Inventors: |
Mimitz, SR.; Timothy E.;
(Williamsburg, MA) ; Raina; Sunil; (Manchester,
CT) ; Scheideman; Fred C.; (Windsor Locks, CT)
; Lewis, JR.; Floyd J.; (Longmeadow, MA) |
Correspondence
Address: |
ALIX YALE & RISTAS LLP
750 MAIN STREET, SUITE 1400
HARTFORD
CT
06103
US
|
Family ID: |
40787208 |
Appl. No.: |
12/316715 |
Filed: |
December 16, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61008807 |
Dec 21, 2007 |
|
|
|
Current U.S.
Class: |
165/154 ;
165/177; 29/890.03 |
Current CPC
Class: |
B21C 37/207 20130101;
F28F 2210/06 20130101; F28F 1/08 20130101; Y10T 29/4935 20150115;
F28F 1/06 20130101; F28D 7/106 20130101; F28F 1/36 20130101; F28D
7/022 20130101; F28F 21/086 20130101 |
Class at
Publication: |
165/154 ;
165/177; 29/890.03 |
International
Class: |
F28D 7/10 20060101
F28D007/10; F28F 1/00 20060101 F28F001/00; B21D 53/02 20060101
B21D053/02 |
Claims
1. A heat exchanger tube comprising a first portion, a twisted
portion, and a transition portion between the first portion and the
twisted portion, the transition portion including a reinforcing
sleeve.
2. The heat exchanger tube of claim 1, wherein the reinforcing
sleeve is positioned over the transition portion.
3. The heat exchanger tube of claim 2, wherein the first portion
comprises straight tube material.
4. The heat exchanger tube of claim 1, wherein the first portion,
twisted portion and transition portion comprise titanium.
5. The heat exchanger of claim 4, wherein the reinforcing sleeve
comprises titanium.
6. A heat exchanger comprising an outer tube and an inner tube
defining an annular opening therebetween, the inner tube including
a first portion, a twisted portion, and a transition portion
between the first portion and the twisted portion including a
reinforcing sleeve formed thereon, the inner tube being configured
to withstand a hydrostatic test pressure of at least 2600 psig for
at least 2 minutes without mechanical failure.
7. The heat exchanger of claim 6, wherein the heat exchanger is
configured to receive a first fluid in the inner tube and second
fluid in the annular portion, and the reinforcing sleeve enables to
heat exchanger to operate with a pressure difference of at least
300 psi between the first and second fluids.
8. The heat exchanger of claim 6, wherein the inner tube is
configured to withstand a hydrostatic test pressure of at least
3000 psig for at least 2 minutes without mechanical failure.
9. The heat exchanger of claim 6, wherein the outer tube is
coiled.
10. The heat exchanger of claim 6, wherein the heat exchanger
contains a refrigerant fluid in the inner tube and a second fluid
in the annular space between the inner tube and outer tube.
11. The heat exchanger of claim 10, wherein the refrigerant is at
least one of R410A, R-410b, R-417a, R-134a and R-407a.
12. The heat exchanger of claim 10, wherein the second fluid
comprises water.
13. The heat exchanger of claim 10, wherein the second fluid
comprises chlorinated water.
14. A heat pump comprising the heat exchanger of claim 6.
15. A heat exchanger comprising an outer tube and an inner tube
defining an annular opening therebetween, the inner tube including
a first portion, a twisted portion, and a transition portion
between the first portion and the twisted portion including a
reinforcing sleeve formed thereon, the inner tube being configured
to pass a fatigue test of 250,000 cycles between 118 psig and 418
psig at a rate of 0.5 cycles/second without mechanical failure.
16. The heat exchanger of claim 15, wherein the heat exchanger is
configured to receive a first fluid in the inner tube and second
fluid in the annular portion, and the reinforcing sleeve enables to
heat exchanger to operate with a pressure difference of at least
300 psi between the first and second fluids.
17. A method of making a heat exchanger tube comprising: forming a
inner tube comprising a first portion, a twisted portion, and a
transition portion between the first portion and the twisted
portion, and forming a reinforcing sleeve over the transition
portion.
18. The method of claim 17, further comprising disposing the inner
tube and reinforcing sleeve in an outer tube to form an annular
opening between the inner tube and the outer tube.
19. The method of claim 17 wherein the inner tube and the
reinforcing sleeve comprise titanium.
20. The method of claim 17 wherein the first portion, twisted
portion and transition portion are formed from a continuous segment
of tube material.
21. The method of claim 17 wherein the transition portion includes
a section of straight tube material and a section of twisted tube
material, and the reinforcing sleeve is configured to protect a
portion of the section of twisted tube material from fluid
impingement.
Description
RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Patent Application No. 61/008,807 filed Dec. 21, 2007.
BACKGROUND
[0002] Tube-in-tube heat exchangers are used in a variety of
applications for transferring heat from one fluid to another.
Particular configurations of tube-in-tube heat exchangers are
described in U.S. Pat. Nos. 5,004,047 and 6,012,514.
[0003] Traditionally, tube-in-tube heat exchangers used for
swimming pool heat pumps had CuNi inner tubes enclosed in a copper
or steel jacket. Later, titanium alloys were used to form the inner
tubes in order to provide improved chlorine resistance, and the
outer shells were made of polyvinyl chloride.
[0004] Currently, swimming pool heat pumps are available that have
heat exchangers formed from an inner tube of twisted titanium in a
plastic polyvinyl chloride jacket. The heat exchangers are suitable
for use with R-22 refrigerant. The twisted titanium tube is
connected to a copper tube transition with a lock ring
connector.
[0005] It would be useful to further improve the efficiency of heat
exchangers used in corrosive environments, including but not
limited to swimming pool heat exchangers.
SUMMARY
[0006] One embodiment is a heat exchanger tube comprising a first
portion, a twisted portion, and a transition portion between the
first portion and the twisted portion, the transition portion
including a reinforcing sleeve.
[0007] Another embodiment is a heat exchanger comprising an outer
tube and an inner tube defining an annular opening therebetween,
the inner tube including a first portion, a twisted portion, and a
transition portion between the first portion and the twisted
portion including a reinforcing sleeve formed thereon, the inner
tube being configured to withstand a hydrostatic test pressure of
at least 2600 psig for at least 2 minutes without mechanical
failure.
[0008] Yet another embodiment is a heat exchanger comprising an
outer tube and an inner tube defining an annular opening
therebetween, the inner tube including a first portion, a twisted
portion, and a transition portion between the first portion and the
twisted portion including a reinforcing sleeve formed thereon, the
inner tube being configured to pass a fatigue test of 250,000
cycles between 118 psig and 418 psig at a rate of 0.5 cycles/second
without mechanical failure.
[0009] Another embodiment is a method of making a heat exchanger
tube comprising forming a inner tube comprising a first portion, a
twisted portion, and a transition portion between the first portion
and the twisted portion, and forming a reinforcing sleeve over the
transition portion.
[0010] Yet another embodiment is a heat exchanger comprising an
inner tube comprising a first portion, a twisted portion, and a
transition portion between the first portion and the twisted
portion including reinforcing sleeve, and an outer tube or shell
surrounding the inner tube.
[0011] A further embodiment is a method of extending the useful
life of a heat exchanger tube comprising a first portion connected
to a twisted portion, the method comprising forming a reinforcing
sleeve over the connection between the first portion and the
twisted portion.
[0012] Yet another embodiment is a method of forming a heat
exchanger tube capable of use at test pressures up to at least 2600
psig, comprising forming a heat exchanger tube comprising a first
portion, a twisted portion, and a transition portion between the
first portion and the twisted portion, and forming a reinforcing
sleeve over the transition portion.
[0013] Another embodiment is a method of forming a heat exchanger
tube capable of use at operating pressures up to at least 500 psig,
comprising forming a heat exchanger tube comprising a first
portion, a twisted portion, and a transition portion between the
first portion and the twisted portion, and forming a reinforcing
sleeve over the transition portion.
[0014] A further embodiment is a method of protecting a twisted
heat exchanger tube from fluid impingement on its outer surface,
comprising forming a reinforcing sleeve over the upstream part of
the twisted portion of the tube.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a side view of a sleeved tube segment in
accordance with certain embodiments.
[0016] FIG. 2 is a side view of a tube segment with the outer
layers cut away to show the transition portion beneath the
sleeve.
[0017] FIG. 3 is a section view of the sleeved tube segment of FIG.
1.
[0018] FIG. 4 is a perspective view of a heat exchanger tube
containing the sleeved tube segment of FIG. 1.
[0019] FIG. 5 is a side view of a segment of the heat exchanger
tube with the outer layer cut away to show the sleeved tube
segment.
DETAILED DESCRIPTION
[0020] A new and improved heat exchanger tube has been developed
that enables environmentally favorable and efficient refrigerants
to be used in corrosive environments, including in the presence of
chlorinated swimming pool water. The new heat exchanger tube can be
used at pressures up to 500 psig or more, or 600 psig or more, and
is particularly useful when the pressure difference on opposite
sides of the tube wall is 300 psig or more. The tube can be used
with R-410A refrigerant, which has a zero Ozone Depleting
Potential, as well as other refrigerants requiring high pressures.
The new tube can be fabricated in a variety of sizes and shapes.
Typically, the twisted tube is coiled and is enclosed a hard
coil-shaped tube made of plastic or another suitable material. The
coils can have various diameters, and various numbers of turns per
linear meter.
Definitions
[0021] As used herein, a "twisted portion" of a tube is a portion
that has improved heat transfer resulting from increased surface
area per unit length of the tube by twisting the tube. A twisted
portion of tube material has one or more visible flutes on one or
both of its inner and outer surfaces. As used herein, a "smooth
portion" and a "straight portion" of a tube are non-twisted
portions of a tube. As used herein, "mechanical failure" refers to
a fracture or rupture of the tube.
[0022] Referring first to FIG. 1, a side view of a tube is shown
and is generally designated as 10. The tube 10 includes a first
portion 12 (which usually but not necessarily is a non-twisted or
straight portion), a twisted portion 14 and a transition portion 18
between the straight portion 12 and the twisted portion 14. A
reinforcing sleeve 16 is mounted over the transition portion 18.
The reinforcing sleeve 16 usually is formed from straight tube
material, however other configurations of tube material can be
used.
[0023] The twisted portion 14 of the tube 10 includes a spiraling
flute 17 and a corresponding valley 19, both of which spiral along
the length of the twisted portion 14 of the tube 10. Tube
configurations having multiple flutes and valleys also can be
used.
[0024] The first portion 12 and twisted portion 14 usually comprise
titanium and often are made from a titanium alloy. The sleeve 16
typically is formed from titanium or a titanium alloy. The sleeve
prevents mechanical failure of the twisted portion 14 of the tube
material at and near the connection with the first portion 12 of
the tube material when the heat exchanger is operated at a 500 or
520 psig (or higher) working pressure. The sleeve also prevents
mechanical failure of the twisted portion 14 of the tube material
at and near the connection with the first portion 12 of the tube
material when the tube 10 is tested at a test pressure of, e.g.
2500-3000 psig for 2-6 minutes.
[0025] For a swimming pool or spa heat exchanger, the sleeve
typically has an outer diameter in the range of about 0.75 inch to
1.25 inch, and a length of about 5-7 inches. It is noted that
tubing with larger and smaller dimensions can be used, and that
sleeves of longer and shorter lengths can be used. The flutes
typically have a peak-to-valley height of about 0.145'' to 0.150''
and a length of approximately 0.375'' per rotation. The twisted
portion of the tube often has an average wall thickness in the
range of 0.018'' to 0.025''. The thinness of the tube wall provides
for effective heat transfer between the fluids on opposite sides of
the tube wall. The ratio of the length to the outer diameter of the
sleeve typically, but not necessarily, is in the range of 6-8, and
often is in the range of 6.5 to 7.0.
[0026] FIG. 2 shows the portion of a tube 10' that is connected to
other tubing. In this embodiment, the first portion 12' is
connected to a second tube 21 which typically is formed from a
different material, such as copper. The second tube 21 and a
connector 23 typically are positioned beside (not within) an outer
heat exchanger tube (not shown). The connector 23 typically
comprises brass or another suitable material and connects the first
portion 12' to the second tube 21.
[0027] In FIG. 2, the sleeve 16' is cut away to show further
details of the transition portion 18'. In the particular embodiment
shown in FIG. 2, a first section 13 of the transition portion 18'
is straight and a second section 15 is twisted. The first and
second sections 13 and 15 typically are part of a continuous piece
of tube material. In the embodiment shown in FIG. 2, about one
quarter of the length of the tube material covered by the sleeve
16' is straight tube, and about three quarters of the length of
tube material covered by the sleeve 16' is twisted tube. Inner wall
25 of sleeve 16' is adjacent to the flute 17'. The inner wall 25 of
sleeve 16' is also configured to fit closely around the outer wall
24 of first portion 12'. In embodiments in which the twisted
portion 14' of the tube 10' has a larger outer diameter than the
first portion 12', the sleeve will be slightly tapered to
accommodate these dimensions.
[0028] FIG. 3 shows a cross-sectional view of the tube 10 of FIG. 1
taken along line 3-3 of FIG. 1. The flute 17 on the outer surface
of the twisted portion 14 of the second section 15 forms a
complementary channel 27 inside the twisted portion 14 of the tube
10. The valley 19 on the outer surface of the twisted portion forms
a corresponding, inwardly projecting portion 29 inside the twisted
portion 14 of the tube 10. This configuration promotes mixing on
both sides of the twisted tube wall.
[0029] FIGS. 4 and 5 show a tube-in-tube heat exchanger 100. The
heat exchanger 100 has a helically coiled outer tube 102 which
contains an inner tube 110, which preferably but not necessarily is
coaxial with the outer tube 102, forming an annular opening 104
therebetween configured for flow of a heat transfer fluid
therethrough. A sleeve 116 is positioned over the transition
between a first portion 112 and a twisted portion 114 of the tube
110. The twisted portion 114 has a flute 117 and a valley 119. The
inner tube 110 generally has the configuration of the tube shown in
FIG. 1. The heat exchanger 100 has a water inlet 132, a water
outlet (not shown), a refrigerant inlet section with a refrigerant
inlet (not shown), and a refrigerant outlet section 140 with a
refrigerant outlet 142.
[0030] The outer tube 102 can be made of a material that is
resistant to corrosion by the fluid that flows in the annular
opening 104. When the fluid is chlorinated water, a hard plastic
material such as polyvinyl chloride can be used. The reinforcing
sleeve provides for use of the tube in a tube-in-tube heat
exchanger in which the pressure difference between the inside and
the outside of the tube is at least 300 psi. or at least 450 psi,
or at least 550 psi. When a refrigerant such as R-410A is used, the
pressure on the inside of the inner tube typically reaches a
maximum of 600 psig and the pressure on the outside of the inner
tube typically is in the range of 25 to 100.
[0031] Various tests were conducted during the process of forming
the new heat exchanger tubing. Test procedures and results are
shown in Examples 1-3. The examples are included to illustrate
features of the invention but are not intended to be limiting.
EXAMPLE 1
Fatigue Testing
[0032] Seven different sets of tubes having a straight portion and
a twisted portion (Samples 1-6 and 9) were tested using fatigue
test UL 1995 to determine their suitability for use in a heat
exchanger operating with R-410A refrigerant. Two sets of tube
material that only contained smooth tubing also were tested
(Samples 7-8). The twisted tubes were formed from a titanium alloy
and had the following general dimensions: 7/8 inch outer diameter,
0.020 wall thickness along the straight portion, and 0.020 average
wall thickness along the twisted portion. The fluted portion had an
outer diameter of about 0.810-0.850, a height of about 0.145 from
flute to valley as measured on the outer wall, and approximately 33
turns per linear foot. According to the literature, the titanium
alloy used in making the tube material has an ultimate tensile
strength of approximately 65 ksi, a yield strength of approximately
50 ksi and a nominal composition typical of type 2 titanium. The
smooth tubes had the same composition as the twisted tube and the
same dimensions as the smooth portion of the twisted tubes.
[0033] In the fatigue test (as per UL 1995), the tubes were cycled
between 118 psig and 418 psig for 250,000 cycles. Hydraulic oil was
used as the test fluid. The outer surface of the tube was
maintained at atmospheric pressure. To pass the test, no failure
can occur. The hydraulic system was controlled by a servo valve to
pressurize the test articles. The system included a hydraulic pump,
interconnecting piping, on/off valves, servo valve, filters,
accumulator and PLC electronic controls. UL 1995 requires that the
high and low pressure in any cycle be maintained for at least 0.10
seconds. Tests were run at around 0.5 cycles/sec or 2
sec/cycle.
[0034] As is shown on Table 1 below, none of the twisted tube
Samples 1-6 and 9 passed the fatigue test. Both of the smooth tube
Samples 7-8 passed the test, showing that the non-twisted material
is acceptable for use at the pressures required for R-410A
refrigerant.
EXAMPLE 2
Hydrostatic Strength Testing
[0035] Five different types of tubes having a straight portion and
a twisted portion (Samples 10-14) were tested using a hydrostatic
strength test to determine their suitability for use in a heat
exchanger operating with R-410A refrigerant. The twisted tubes were
formed from a titanium alloy and had the following general
dimensions: 7/8 inch outer diameter, 0.020'' wall thickness along
the straight portion, and 0.020'' average wall thickness along the
twisted portion. The fluted portion had an outer diameter of about
0.810-0.850'', a height of about 0.134'' from flute to valley as
measured on the outer wall, and approximately 33 turns per lineal
foot. According to the literature, the titanium alloy used in
making the tube material has an ultimate tensile strength of
approximately 65 ksi, a yield strength of approximately 50 ksi and
a nominal composition typical of type 2 titanium.
[0036] To pass the hydrostatic strength test, a tube is required to
withstand 5 times the desired working pressure for a minimum of 2
minutes. Thus, for a desired working pressure of 520 psi the test
is run at 2600 psi, and for a desired working pressure or 600 psi
the test is run at 3000 psi. Pressure outside the tube was
atmospheric. Water was used as the fluid in the high pressure
test.
[0037] As is shown on Table 1 below, none of Samples 10-14 passed
the hydrostatic strength test at 2600 psig, thus showing the
difficulty in using twisted tube material in high pressure
environments.
TABLE-US-00001 TABLE I Required Acceptance Samples Test Task
Procedure/Method Task Description Criteria Location Tested Result 1
Fatigue Test-UL 1995 Turbotec Laboratory 250K cycles Turbotec 3
Fail R410A TR2004-134 without failure Inc. 2 Fatigue Test-UL 1995
Turbotec Laboratory 250K cycles Turbotec 3 Fail R410A TR2004-135
without failure Inc. 3 Fatigue Test-UL 1995 Turbotec Laboratory
250K cycles Turbotec 3 Fail R410A TR2006-091 without failure Inc. 4
Fatigue Test-UL 1995 Turbotec Laboratory 250K cycles Turbotec 3
Fail R410A TR2006-101 without failure Inc. 5 Fatigue Test-UL 1995
Turbotec Laboratory 250K cycles Turbotec 3 Fail R410A TR2006-127
without failure Inc. 6 Fatigue Test-UL 1995 Turbotec Laboratory
250K cycles Turbotec 3 Fail R410A TR2006-142 without failure Inc. 7
Fatigue Test-UL 1995 Turbotec Laboratory 250K cycles Turbotec 3
Pass R410A TR2006-177 without failure Inc. 8 Fatigue Test-UL 1995
Turbotec Laboratory 250K cycles Turbotec 3 Pass R410A TR2006-178
without failure Inc. 9 Fatigue Test-UL 1995 Turbotec Laboratory
250K cycles Turbotec 3 Fail R410A TR2006-192 without failure Inc.
10 Hydostatic Pressure Turbotec Laboratory 2600 psig Turbotec 2
Fail Tube Side R410A TR2006-197 Inc. 11 Hydostatic Pressure
Turbotec Laboratory 2600 psig Turbotec 2 Fail Tube Side R410A
TR2006-206 Inc. 12 Hydostatic Pressure Turbotec Laboratory 2600
psig Turbotec 2 Fail Tube Side R410A TR2006-214 Inc. 13 Hydostatic
Pressure Turbotec Laboratory 2600 psig Turbotec 2 Fail Tube Side
R410A TR2006-220 Inc. 14 Hydostatic Pressure Turbotec Laboratory
2600 psig Turbotec 2 Fail Tube Side R410A TR2007-007 Inc. 15
Hydostatic Pressure Turbotec Laboratory 3000 psig Turbotec 2 Fail
Tube Side R410A TR2007-024 Inc. 16 Hydostatic Pressure Turbotec
Laboratory 3000 psig Turbotec 2 Pass Tube Side R410A TR2007-039
Inc. 17 Fatigue Test-UL 1995 R Turbotec Laboratory 250K cycles
Turbotec In 3 Pass TF2007-041 without failure
EXAMPLE 3
Twisted Tube with Reinforcing Sleeve
[0038] Reinforcing sleeves made of type 2 titanium alloy having an
inner diameter of about 7/8 inch and a length of 6 inches were
placed (swaged) around the transition point from smooth tubing to
twisted tubing of several samples of the same type of tube material
of the same dimensions as was used in Example 2. The tubes with the
reinforcing sleeves were subjected to the hydrostatic strength test
described above in Example 2 using water as the high pressure test
fluid. The inside of the twisted tube was brought to a pressure of
2,600 psig, and this pressure was maintained for 2 minutes.
Subsequently, the pressure was increased to 2,700 psig for 2
additional minutes, and the pressure was then increased to 3,000
psig for 2 more minutes. The outer surface of the tube was at
atmospheric pressure. The twisted tube was then examined for
failures.
[0039] For Sample set 15 (TR 2007-024) which included the
reinforcing sleeve, no failures were detected at 2600 psig but
failure occurred at 3000 psig. For tube sample TR 2007-039, which
included both a reinforcing sleeve and a tight fit reducer bushing
positioned around the plain end, no failure occurred even at 3000
psig.
EXAMPLE 4
[0040] The same type of tube samples as were used in Example 3,
Sample 16, were subjected to a fatigue test in accordance with
UL1995, described above in Example 1, using hydraulic oil as the
test fluid. The set of samples passed two full rounds of testing
without any failures. The results are shown in Table 1 as Sample 17
(Example TR-2007 041).
[0041] An important advantage of the embodiments disclosed herein
is that the twisted tubes can be used in conjunction with
refrigerants that replace HCFCs. Nonlimiting examples of
refrigerants that can be used with the embodiments described herein
are provided below on Table 2.
TABLE-US-00002 TABLE 2 Refrigerants Refrigerant Substitute (Name
Used in Trade Being Retrofit/ the Federal Register) Name Replaced
New HFC-134a 22 N THR-03 22 N ISCEON 59, NU-22, R- Isceon 59, 22 R,
N 417A NU-22 R-410A, R-410B AZ-20, 22 N Suva 9100, Puron R-407C
Suva 9000, 22 R, N Klea 66 R-507, R-507A AZ-50 22 R, N NU-22 NU-22
22 R, N Ammonia Absorption 22 N Evaporative/Desiccant all HCFCs N
Cooling R-404A HP62 22 R, N R-125/134a/600a 22 R, N (28.1/70.0/1.9)
RS-44 RS-44 22 R, N R-421A Choice 22 R, N R421A R-422D ISCEON 22 R,
N MO29 R-424A RS-44 22 R, N R-125/290/134a/600a ICOR AT- 22 R, N
(55.0/1.0/42.5/1.5) 22 R-422C ICOR 22 R, N XLT1 R-422B ICOR 22 R, N
XAC1 KDD5 KDD5 22 R, N RS-45 (ASHRAE RS-45 22 R, N proposed
designation: R- 434A) R-125/290/134a/600a ICOR AT- 22 R, N
(55.0/1.0/42.5/1.5) 22 R-422B XAC1, 22 R, N NU-22B R-422C XLT1 22,
402A, R, N 402B, 408A Key: R = Retrofit Uses, N = New Uses
[0042] It will be appreciated that features disclosed above and
other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Furthermore, currently unforeseen or unanticipated
alternatives, modifications, variations or improvements therein may
be subsequently made by those skilled in the art which are also
intended to be encompassed by the following claims.
* * * * *