U.S. patent application number 11/120946 was filed with the patent office on 2005-09-08 for system and method for selective heating and cooling.
Invention is credited to Wells, David N..
Application Number | 20050193758 11/120946 |
Document ID | / |
Family ID | 46304508 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050193758 |
Kind Code |
A1 |
Wells, David N. |
September 8, 2005 |
System and method for selective heating and cooling
Abstract
A combined heating/cooling system and method is provided wherein
an absorption tank (20) houses a refrigerant and absorbant mixture
composition. A boiler (50) heats the pressurized mixture
composition and vaporizes the refrigerant. Heated absorbant is
passed back through a heat exchanger (40) to be delivered back into
absorption tank (20) and the vaporized refrigerant is directed to a
closed-loop thermal exchange system for selectively heating and
cooling ambient air. The mixture may be a composition of NMP as the
absorbant and HFC-245fa as the refrigerant. When such a composition
is employed, pressure may be reduced such that less expensive
construction materials, such as aluminum, may be incorporated into
the boiler fluid circuit, such as in the heat exchanger (40).
Inventors: |
Wells, David N.; (Silver
Spring, MD) |
Correspondence
Address: |
ROSENBERG, KLEIN & LEE
3458 ELLICOTT CENTER DRIVE-SUITE 101
ELLICOTT CITY
MD
21043
US
|
Family ID: |
46304508 |
Appl. No.: |
11/120946 |
Filed: |
May 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11120946 |
May 4, 2005 |
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10910294 |
Aug 4, 2004 |
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60543929 |
Feb 13, 2004 |
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60571938 |
May 18, 2004 |
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60562546 |
Apr 16, 2004 |
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60523679 |
Nov 21, 2003 |
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60513999 |
Oct 27, 2003 |
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Current U.S.
Class: |
62/324.2 ;
62/222; 62/476; 62/513 |
Current CPC
Class: |
F25B 15/02 20130101;
Y02A 30/27 20180101; F25B 25/02 20130101; F25B 2400/141 20130101;
Y02A 30/277 20180101; F25B 2315/006 20130101; Y02B 30/62
20130101 |
Class at
Publication: |
062/324.2 ;
062/476; 062/513; 062/222 |
International
Class: |
F25B 041/04; F25B
043/04; F25B 013/00; F25B 015/00; F25B 041/00 |
Claims
What is claimed is:
1. A combined heating/cooling system comprising: (a) an absorption
tank for containing a refrigerant and an absorbant mixture
composition, (b) a pump in fluid communication with said absorption
tank for pressurizing said mixture composition to produce a high
pressure mixture composition; (c) a heat exchanger fluidly coupled
to said pump for passing said high pressure mixture composition
therethrough; (d) a boiler for heating said high pressure mixture
composition, said boiler vaporizing said refrigerant and egressing
on a first boiler conduit line, said heated absorbant being passed
to said heat exchanger on a second boiler conduit line for insert
into said absorption tank; (e) a closed-loop thermal exchange
system for selectively heating and cooling ambient air.
2. The combined heating/cooling system as recited in claim 1
further comprising an expansion valve being positioned between said
heat exchanger and said absorption tank, whereby said heated
absorbant passes through said expansion valve prior to reinsertion
in said absorbant tank.
3. The combined heating/cooling system as recited in claim 1
wherein said closed-loop thermal exchange system comprises: (a) a
first selector valve for diverting the vaporized refrigerant from
said scroll expander through (1) a cooling cycle or (2) a heating
cycle; (b) a first liquid-vapor converter fluidly coupled to said
first converter valve for (1) converting said refrigerant vapor to
a liquid in said cooling cycle and (2) converting said liquid
refrigerant to a vapor in the heating cycle; (c) a second
liquid-vapor converter fluidly coupled to said first liquid vapor
converter for (1) converting said liquid refrigerant to a vapor in
the cooling cycle and (2) converting the vapor refrigerant to a
liquid refrigerant in the heating cycle; (d) a second selector
valve fluidly coupled to said second liquid-vapor converter for (1)
receiving refrigerant vapor in said cooling cycle and directing
said refrigerant vapor into said absorption tank, and (2) diverting
said refrigerant vapor from said first selector valve to said
second liquid-vapor converter in said heating cycle; (e) a first
air to liquid contactor member for receiving (1) a heated brine
solution from said first liquid-vapor connector and expelling
heated air in cooling cycle and (2) a cooled brine solution from
said first liquid-vapor converter and expelling cooled air, said
brine solution being heated in the heating cycle; (f) a second heat
exchanger coupled to said first air to liquid contactor and said
liquid-vapor converter for (1) cooling said brine solution in said
cooling cycle and (2) heating said brine solution in said heating
cycle; and, (g) a second air to liquid contactor fluidly coupled to
said second liquid-vapor converter for (1) inputting cooled brine
solution and expelling cooling air in the cooling cycle and (2)
inputting heated brine solution and expelling heated air.
4. The combined heating/cooling system as recited in claim 3
further comprising a first expansion valve being positioned between
said heat exchanger and said absorption tank, whereby said heated
absorbant passes through said expansion valve prior to reinsertion
in said absorbant tank.
5. The combined heating/cooling system as recited in claim 3
wherein a second expansion valve is fluidly connected between said
first liquid-vapor converter and said second liquid-vapor
converter.
6. The combined heating/cooling system as recited in claim 3
further comprising a pump for driving brine solution through said
second liquid-vapor converter.
7. The combined heating/cooling system as recited in claim 1
wherein said refrigerant and absorbant mixture composition has a
refrigerant concentration in the range of 30 to 50%.
8. The combined heating/cooling system as recited in claim 1
wherein said heat exchanger heats said refrigerant and absorbant
mixture composition to approximately 100.degree. C.
9. The combined heating/cooling system as recited in claim 1
wherein said vaporized refrigerant is super-heated by said boiler
to a temperature in the range of 20 to 30.degree. C. above the
saturation temperature of said vaporized refrigerant.
10. The combined heating/cooling system as recited in claim 3
wherein said brine solution comprises a salt dissolved in
water.
11. The combined heating/cooling system as recited in claim 10
wherein said salt is selected from the group consisting of: lithium
chloride, lithium bromide, magnesium chloride, calcium chloride and
glycol.
12. The combined heating/cooling system as recited in claim 3
wherein said first and second air to liquid contactor members are
formed of honeycombed absorptive material.
13. The combined heating/cooling system as recited in claim 1
wherein said refrigerant is an HFC-245fa.
14. The combined heating/cooling system as recited in claim 1
wherein said absorbant includes NMP.
15. The combined heating/cooling system as recited in claim 14
wherein said absorbant further includes at least one
stabilizer.
16. The combined heating/cooling system as recited in claim 1
further comprising: (a) a scroll expander fluidly coupled to said
boiler for receiving said vaporized refrigerant; and, (b) an
induction generator rotationally coupled to said scroll expander
for producing electrical power.
17. The combined heating/cooling system as recited in claim 3
further comprising: (a) a scroll expander fluidly coupled to said
boiler for receiving said vaporized refrigerant; and, (b) an
induction generator rotationally coupled to said scroll expander
for producing electrical power.
18. The combined heating/cooling system as recited in claim 15
wherein said at least one stabilizer is selected from the group
consisting of: microalkanes and phosphates.
19. The combined heating/cooling system as recited in claim 1,
wherein both of said high pressure mixture composition and said
heated absorbant passing through said heat exchanger is maintained
at a pressure of below 100 psi.
20. The combined heating/cooling system as recited in claim 19,
wherein said absorbant includes NMP and said refrigerant includes
HFC-245fa.
21. The combined heating/cooling system as recited in claim 20,
wherein said heat exchanger is constructed from aluminum.
22. The combined heating/cooling system as recited in claim 21,
wherein said aluminum has been treated by etching and
passivation.
23. The combined heating/cooling system as recited in claim 22,
wherein said aluminum was passivated through the application of one
of the group consisting of a chromic acid, a non-chromic acid,
nitric acid, and fluorine gas.
24. The combined heating/cooling system as recited in claim 22,
wherein said passivated surface is sealed by one of the group
consisting of a saline surface treatment, a sol-gel, and a
paint.
25. A method of heating/cooling including the steps of: (a)
providing a mixture of a refrigerant composition and an absorbant;
(b) heating said refrigerant and absorbant mixture; (c) vaporizing
said refrigerant composition; (d) selectively passing said
vaporized refrigerant through (1) a cooling cycle for exiting
cooled air, and (2) a heating cycle for exiting heated air.
26. The method of heating/cooling as recited in claim 20 further
comprising the steps of: (a) providing a first liquid-vapor
converter; (b) converting said (1) refrigerant vapor to a liquid in
said cooling cycle within said first liquid-vapor converter, and
(2) liquid refrigerant to a vapor in the heating cycle within said
first liquid-vapor converter; (c) providing a second liquid-vapor
converter; (d) converting said (1) liquid refrigerant to a vapor in
the cooling cycle within said second liquid-vapor converter, and
(2) refrigerant vapor to a liquid refrigerant in the heating cycle
within said second liquid-vapor converter; (e) directing (1) said
refrigerant vapor into said heated refrigerant and absorbant
mixture in said cooling cycle, and (2) said refrigerant vapor to
said second liquid-vapor converter in said heating cycle; (f)
providing first and second air to liquid contactor members; (g)
providing a brine solution; (h) passing said brine solution through
said first air to liquid contactor member, (1) heated air being
expelled in said cooling cycle, and (2) cooled air being expelled
in said heating cycle; (i) (1) cooling said brine solution in said
cooling cycle, and (2) heating said brine solution in said heating
cycle; (j) passing (1) cooled brine solution through said second
air to liquid contactor member in said cooling cycle and expelling
cooled air, and (2) heated brine solution through said second air
to liquid contactor member in said heating cycle and expelling
heated air.
27. The method of heating/cooling as recited in claim 25 wherein,
following said step of vaporizing said refrigerant composition,
said absorbant is collected.
28. The method of heating/cooling as recited in claim 27 wherein,
prior to collection of said absorbant, said absorbant is
depressurized.
29. The method of heating/cooling as recited in claim 26 further
comprising the step of providing a fluid pump.
30. The method of heating/cooling as recited in claim 29 wherein
said brine solution is charged by said fluid pump and directed
through said second liquid-vapor converter.
31. The method of heating/cooling as recited in claim 26 further
comprising the step of providing an expansion valve fluidly
connected to said first and second liquid-vapor converters.
32. The method of heating/cooling as recited in claim 31 wherein
said expansion valve depressurizes said liquid refrigerant flowing
therethrough.
33. The method of heating/cooling as recited in claim 25 further
comprising the steps of: (a) following the step of vaporizing said
refrigerant composition, passing said vaporized refrigerant
composition through a scroll expander; and, (b) generating
electrical power from a generator connected to said scroll
expander.
34. The method of heating/cooling as recited in claim 26 further
comprising the steps of: (a) following the step of vaporizing said
refrigerant composition, passing said vaporized refrigerant
composition through a scroll expander; and, (b) generating
electrical power from a generator connected to said scroll
expander.
35. The method of heating/cooling as recited in claim 25 where said
mixture providing step includes the step of providing HFC-245fa to
said refrigerant composition and NMP to said absorbant.
36. The method of heating/cooling as recited in claim 35 further
including the steps of: providing a heat exchanger; and preheating
said refrigerant and absorbant mixture in said heat exchanger prior
to said refrigerant and absorbant mixture heating step.
37. The method of heating/cooling as recited in claim 36 where said
heat exchanger providing step includes the step of constructing
said heat exchanger from aluminum.
38. The method of heating/cooling as recited in claim 37 where said
heat exchanger construction step includes the steps of etching and
passivating exposed surfaces of the aluminum.
39. The method of heating/cooling as recited in claim 38 where said
passivating step includes the step of applying one of the group
consisting of chromic acid, non-chromic acid, nitric acid and
fluorine gas.
40. The method of heating/cooling as recited in claim 38 further
including the step of sealing said passivated aluminum by one of
the group consisting of silane surface treatment, sol-gel treatment
and painting.
41. A combined heating/cooling system comprising: (a) an absorption
tank for containing a refrigerant and an absorbant mixture
composition, (b) a pump in fluid communication with said absorption
tank for pressurizing said mixture composition to produce a high
pressure mixture composition; (c) a heat exchanger fluidly coupled
to said pump for passing said high pressure mixture composition
therethrough; (d) a boiler for heating said high pressure mixture
composition, said boiler vaporizing said refrigerant and egressing
on a first boiler conduit line, said heated absorbant being passed
to said heat exchanger on a second boiler conduit line for insert
into said absorption tank, said refrigerant and said absorbant both
passing back through said boiler prior exiting said boiler, said
absorbant and said refrigerant releasing thermal energy within said
boiler; (e) a condenser for receiving said vaporized refrigerant
and condensing said vaporized refrigerant into a liquid
refrigerant, ambient air passing through said condenser and
removing thermal energy released during the condensation of said
refrigerant; (f) an expansion valve for receiving said liquid
refrigerant, said expansion valve depressurizing said liquid
refrigerant and creating a mixture of vaporized refrigerant and
liquid refrigerant; (g) an evaporator for receiving said mixture of
vaporized refrigerant and liquid refrigerant, said evaporator
converting said mixture into pure vaporized refrigerant, ambient
air passing through said evaporator, said ambient air being cooled
by said conversion into said pure vaporized refrigerant, said
evaporator expelling cooled air into the environment, said pure
vaporized refrigerant being delivered back into said absorption
tank.
42. The combined heating/cooling system as recited in claim 41
wherein said refrigerant is an HFC-245fa.
43. The combined heating/cooling system as recited in claim 41
wherein said absorbant includes NMP.
44. The combined heating/cooling system as recited in claim 43
wherein said absorbant further includes at least one
stabilizer.
45. The combined heating/cooling system as recited in claim 43
wherein said at least one stabilizer is selected from the group
consisting of: nitroalkanes and phosphates.
46. The combined heating/cooling system as recited in claim 41,
wherein both of said high pressure mixture composition in said
heated absorbant passing through said heat exchanger is maintained
at a pressure of below 100 psi.
47. The combined heating/cooling system as recited in claim 46,
wherein said absorbant includes NMP and said refrigerant includes
HFC-245fa.
48. The combined heating/cooling system as recited in claim 47,
wherein said heat exchanger is constructed from aluminum.
49. The combined heating/cooling system as recited in claim 47,
wherein said aluminum has been treated by etching and
passivation.
50. The combined heating/cooling system as recited in claim 49,
wherein said aluminum was passivated by the application of one of
the group consisting of chromic acid, non-chromic acid, nitric acid
and fluorine gas.
51. The combined heating/cooling system as recited in claim 49,
wherein said passivated surface is sealed by one of the group
consisting of a silane surface treatment, a sol-gel, and a
paint.
52. A combined heating/cooling system comprising: (a) an absorption
tank for containing a refrigerant and an absorbant mixture
composition, (b) a pump in fluid communication with said absorption
tank for pressurizing said mixture composition to produce a high
pressure mixture composition; (c) a heat exchanger fluidly coupled
to said pump for passing said high pressure mixture composition
therethrough; (d) a boiler for heating said high pressure mixture
composition, said boiler vaporizing said refrigerant and egressing
on a first boiler conduit line, said heated absorbant being passed
to said heat exchanger on a second boiler conduit line for insert
into said absorption tank; (e) a scroll expander for receiving said
vaporized refrigerant, said vaporized refrigerant driving said
scroll expander; (f) a compressor mechanically driven by said
scroll expander, said compressor pressurizing said vaporized
refrigerant; (g) a condenser for receiving said pressurized
vaporized refrigerant output by said compressor, said condenser
condensing said pressurized vaporized refrigerant to form liquid
refrigerant; (h) an expansion valve for receiving said liquid
refrigerant, said expansion valve reducing pressure of said liquid
refrigerant; (i) an evaporator for receiving said liquid
refrigerant and vaporizing said liquid refrigerant, said evaporator
expelling vaporized refrigerant which is driven back to said
compressor.
53. The combined heating/cooling system as recited in claim 52
further comprising: (a) a first selector valve for receiving said
vaporized refrigerant from said scroll expander, said first
selector valve directing said vaporized refrigerant to said
condenser, said condenser converting said vaporized refrigerant
into liquid refrigerant; (b) a second expansion valve for receiving
said liquid refrigerant from said condenser, said second expansion
valve decreasing pressure of said liquid refrigerant and directing
said liquid refrigerant to said evaporator, said evaporator
vaporizing said liquid refrigerant and delivering said vaporized
refrigerant to said absorption tank.
54. The combined heating/cooling system as recited in claim 52
wherein said refrigerant is HFC-245fa.
55. The combined heating/cooling system as recited in claim 52
wherein said absorbant includes NMP.
56. The combined heating/cooling system as recited in claim 55
wherein said absorbant further includes at least one
stabilizer.
57. The combined heating/cooling system as recited in claim 56
wherein said at least one stabilizer is selected from the group
consisting of: nitroalkanes and phosphates.
58. The combined heating/cooling system as recited in claim 52,
wherein said absorbant includes NMP and said refrigerant includes
HFC-245fa.
59. The combined heating/cooling system as recited in claim 58,
wherein said heat exchanger is constructed from aluminum.
60. The combined heating/cooling system as recited in claim 59,
wherein said aluminum is treated by etching and passivation.
61. The combined heating/cooling system as recited in claim 60,
wherein said aluminum has been passivated by the application of one
of the group consisting of chromic acid, non-chromic acid, nitric
acid and fluorine gas.
62. The combined heating/cooling system as recited in claim 60,
wherein said passivated surface is sealed by one of the group
consisting of a silane treatment, a sol-gel, and a paint.
63. A cooling and power generation system comprising: (a) an
absorption tank for containing a refrigerant and an absorbant
mixture composition, (b) a pump in fluid communication with said
absorption tank for pressurizing said mixture composition to
produce a high pressure mixture composition; (c) a heat exchanger
fluidly coupled to said pump for passing said high pressure mixture
composition therethrough; (d) a boiler for heating said high
pressure mixture composition, said boiler vaporizing said
refrigerant and egressing on a first boiler conduit line, said
heated absorbant being passed to said heat exchanger on a second
boiler conduit line for insert into said absorption tank; (e) a
scroll expander fluidly coupled to said boiler for receiving said
vaporized refrigerant; (f) an induction generator rotationally
coupled to said scroll expander for producing electrical power; (g)
a condenser for receiving said vaporized refrigerant, said
condenser converting said vaporized refrigerant to liquid
refrigerant; (h) an evaporator for receiving said liquid
refrigerant, said evaporator converting said liquid refrigerant
back to said vaporized refrigerant, said conversion of said liquid
refrigerant to said vaporized refrigerant drawing thermal energy
from the environment, said vaporized refrigerant being returned to
said absorption tank to remix with said absorbant.
64. The cooling and power generation system as recited in claim 63
wherein said absorption tank includes an air-to-liquid contactor
member for drawing thermal energy from said absorption tank.
65. The cooling and power generation system as recited in claim 63
wherein a portion of said liquid absorbant released by said boiler
is routed to said scroll expander for lubricating and cooling said
scroll expander.
66. The cooling and power generation system as recited in claim 63
wherein an expansion valve is positioned between said heat
exchanger and said absorption tank to depressurize said absorbant
prior to re-insert in said absorption tank.
67. The cooling and power generation system as recited in claim 63
wherein an expansion valve is positioned between said condenser and
said evaporator to depressurize said liquid refrigerant prior to
entry in said evaporator.
68. The cooling and power generation system as recited in claim 63
wherein said refrigerant is HFC-245fa.
69. The cooling and power generation system as recited in claim 63
wherein said absorbant includes NMP.
70. The cooling and power generation system as recited in claim 69
wherein said absorbant further includes at least one
stabilizer.
71. The cooling and power generation system as recited in claim 70
wherein said at least one stabilizer is selected from the group
consisting of: nitroalkanes and phosphates.
72. The cooling and power generation system as recited in claim 63,
wherein said absorbant includes NMP and said refrigerant includes
HFC-245fa.
73. The cooling and power generation system as recited in claim 72,
wherein said heat exchanger is constructed from aluminum.
74. The cooling and power generation system as recited in claim 73,
wherein said aluminum is treated by etching and passivation.
75. The cooling and power generation system as recited in claim 74,
wherein said aluminum has been passivated by the application of one
of the group consisting of chromic acid, non-chromic acid, nitric
acid and fluorine gas.
76. The cooling and power generation system as recited in claim 74,
wherein said passivated surface is sealed by one of the group
consisting of a silane treatment, a sol-gel, and a paint.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a Continuation-in-part
Application of application Ser. No. 10/910,294, filed on 4 Aug.
2004, currently pending, which is based on Provisional Applications
Ser. No. 60/543,929, filed on 13 Feb. 2004; Ser. No. 60/571,938,
filed 18 May 2004; Ser. No. 60/562,546, filed 16 Apr. 2004; Ser.
No. 60/523,679 filed 21 Nov. 2003; and Ser. No. 60/513,999 filed on
27 Oct. 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The subject invention relates to a system and method for
selective heating and cooling. In particular, the present invention
directs itself to a system utilizing a refrigerant and absorbant
mixture composition held within an absorption tank. More
particularly, a boiler is provided for heating the mixture
composition such that the boiler vaporizes the refrigerant and the
liquid absorbant is delivered back into the absorption tank for
reuse. Further, the vaporized refrigerant is delivered to a
closed-loop thermal exchange system for selectively heating and
cooling ambient air.
[0004] The present invention system and method further directs
itself to providing a novel mixture of refrigerants and an
absorbant composition allowing the system to act as both a heating
and cooling system. More particularly, the mixture of refrigerants
and the absorbant provide an environmentally friendly composition,
which further allows the system to be hermetically sealed.
Additionally, the heating and cooling system may further be
utilized as a power generation system.
[0005] Furthermore, the inventive mixture of refrigerants have
pressure and corrosion characteristics that advantageously allow
the utilization of lower-cost aluminum heat exchangers. The
aluminum heat exchangers may also be surface-treated, such as by
anodization or passivation, particularly on those surfaces exposed
to the refrigerant mixture to further protect the heat exchanger
and thereby extend the usable lifetime thereof. The use of aluminum
components in the boiler fluid circuit of the present invention is
a clear advantage of the present invention over existing
high-pressure ammonia-water absorption systems.
[0006] The system and method of the present invention is further
directed to the use of a refrigerant consisting of substantially
pure 1, 1, 1, 3, 3 pentafluoropropane (HFC-245fa) and an absorption
material consisting of substantially pure n-methyl, 2-pyrrolidone
(NMP) with small amounts (ranging within 0.1-1% by volume) of one
or more stabilizers selected from the group of nitroalkanes such as
nitromethane, phosphates such as tributyl phosphate, zinc
dithiophosphate, or other stabilizers. Furthermore, the present
system employs the additional steps 1) passivation and 2) silicone
sealing of the aluminum system components to make these stabilizers
even more effective.
[0007] 2. Brief Description of the Prior Art
[0008] Heating and cooling systems are well-known in the art. In
general, such prior art systems generally utilize two different
sets of heating and cooling sub-systems. The system of the subject
patent application, however, provides for a single closed-loop
thermal exchange system allowing selection of a heating cycle or a
cooling cycle, where both cycles involve common system components
in their respective executions. The system is sealed and utilizes
heating/cooling solution mixtures which may be reused in the
heating and cooling cycles.
[0009] Given present thermal exchange systems, a need exists in the
market for a system that produces a heat pump or cooling effect, or
producing both electric power and a cooling effect utilizing heat
input. The system should be both efficient and inexpensive. Such a
system would preferably use substantially "off-the-shelf"
components. For example, stock automotive fuel pumps might act as a
system liquid pump. Stock air conditioning electric refrigeration
compressors, particularly of the scroll type, might act as the
system expander/power producing element if the scroll compressor
were modified by simply removing the check valve that is installed
in typical air conditioning service. The present inventive system
concept is directed to utilizing such "off-the-shelf" components
and, in particular, is directed at a novel and unique selection of
working fluid and absorption materials which are compatible with
the system components.
[0010] Systems utilizing isoparaffins as absorption materials for
use with butane refrigerants are well-known in the art. The present
system provides an improvement over prior art systems in that it
employs working fluid refrigerants, which are both non-flammable
and non-toxic, and absorption materials which have an
advantageously high boiling point. The refrigerant and absorption
materials are chemically non-reactive with lower-cost construction
materials designed for medium-pressure systems, such as lightweight
aluminum heat exchangers. The ability to incorporate lower-cost
materials such as aluminum into the boiler fluid circuit of the
present invention is a significant advancement over similar systems
of the prior art. Moreover, as the refrigerants utilized by the
present system are non-flammable and operate at only moderate
pressure, operational safety is enhanced.
[0011] Systems implementing scroll compressors which are run in
reverse as expansion engines are known. Among the many advantageous
features of the present system is the use of such an expansion
engine to drive an electric power generation system. Thus, some of
the energy dissipated to the surrounding environment during
expansion by prior art systems is converted by the inventive system
into electric power.
SUMMARY OF THE INVENTION
[0012] The present invention provides for a combined
heating/cooling system. The heating/cooling system utilizes a
refrigerant and absorbant mixture composition held, initially, in
an absorption tank. A pump in fluid communication with the
absorption tank pressurizes the mixture composition and delivers it
to a first heat exchanger. A boiler is provided for receiving the
high pressure mixture composition, with the boiler vaporizing the
refrigerant and delivering the liquid absorbant back into the
absorption tank for later reuse. The vaporized refrigerant is
delivered to a closed-loop thermal exchange system for selective
heating and cooling of ambient air.
[0013] It is a principal objective of the subject heating/cooling
system to provide an optimized refrigerant and absorbant mixture
composition.
[0014] It is a further objective of the subject heating/cooling
system to provide a boiler for heating a high pressure mixture
composition in order to vaporize the refrigerant component of the
mixture.
[0015] It is a further objective of the subject invention to
provide means for retrieving the liquid absorbant from the boiler
in order to reuse the absorbant in the absorbant/refrigerant
mixture.
[0016] It is yet a further objective of the present invention to
provide a closed-loop thermal exchange system for selectively
heating and cooling ambient air.
[0017] It is a further objective of the present invention to
provide a closed-loop thermal exchange system utilizing HFC-245fa
as a refrigerant.
[0018] It is another objective of the present invention system to
provide NMP as an absorption material.
[0019] It is yet a further objective of the present invention
system to provide improved compatibility of the working fluid
mixtures to aluminum component parts, such as aluminum heat
exchangers, by providing relatively low corrosion characteristics
and lower operating pressure. It is a further objective of the
present invention to subject the aluminum components to surface
treatments to extend system lifetime over that of untreated
aluminum components alone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic representation of the preferred
embodiment of the subject heating/cooling and power generation
system;
[0021] FIG. 2 is a schematic representation of an alternative
embodiment of the subject heating/cooling system in a cooling
cycle;
[0022] FIG. 3 is a schematic diagram of an alternative embodiment
of the subject heating/cooling system in a heating cycle;
[0023] FIG. 4 is a schematic diagram of an alternative embodiment
of the heating/cooling system utilizing a single-effect absorption
cycle; and,
[0024] FIG. 5 is an alternative embodiment of the subject
heating/cooling system utilizing a mechanical compressor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] I. Overview
[0026] Referring to FIGS. 2 and 3 of the Drawings, there is shown a
system for combined heating/cooling of an edifice. The basic system
10 includes an absorption tank 20 for containing a mixture composed
of a refrigerant and an absorbant. The refrigerant and absorbant
materials themselves will be discussed in greater detail below. The
refrigerant and absorbant mixture composition is drawn from
absorption tank 20 by pump 30 and is delivered to first heat
exchanger 40. Pump 30 drives the high pressure mixture through heat
exchanger 40 in order to pre-heat the mixture in the manner typical
of heat-exchangers. The pre-heated mixture flows from heat
exchanger 40 into boiler 50. In boiler 50, the refrigerant is
vaporized and is drawn off in gaseous form (represented by the
dashed line in the Figure). The liquid absorbant is removed from
boiler 50 and drawn back into heat exchanger 40 where it is cooled.
The liquid absorbant then passes through an expansion valve 60,
where it is depressurized and lowered in temperature, and then
flows back into absorption tank 20.
[0027] The vaporized refrigerant may pass into a power generation
sub-system 70. In power generation sub-system 70, the vaporized
refrigerant flows into a scroll expander 80, causing the scroll
expander 80 to rotate and drive generator 90 via the rotation of
shaft 100. The power generation sub-system 70 is optional and may
be bypassed, with the vaporized refrigerant passing directly into a
closed-loop thermal exchange system for selectively heating or
cooling ambient air. The closed-loop thermal exchange system will
be discussed, for both a heating cycle and a cooling cycle, in
greater detail below.
[0028] II. Exemplary Embodiment for Hybrid Organic
Absorption/Rankine Scroll Electric System Based on HFC-245fa and
NMP
[0029] The thermal exchange system 500 shown in FIG. 1 includes an
absorption tank 510 for containing a mixture of a refrigerant and
an absorbant composition. In certain advantageous embodiments, the
refrigerant consists of substantially pure 1,1,1,3,3
pentafluoropropane (HFC-245fa). The refrigerant may also consist of
1,1,1,2 tetrafluoroethane (HFC-134a) in combination with HFC-245fa.
The refrigerant may also be a chlorinated alkane such as 1-chloro,
1,2,2, 2-tetrafluoroethane, also known as HCFC-124. The refrigerant
may further be methylene chloride, also known as dichloromethane,
or mixtures of these, or further other HCFC, HFC compositions or
chloroalkanes.
[0030] The absorption material and refrigerant mixture, in certain
beneficial embodiments, consists substantially of pure n-methyl,
2-pyrrolidone (NMP) with small amounts (in the range of 0.1-1% by
volume) of one or more stabilizers selected from the group of
nitroalkanes, such as nitromethane, phosphates such as tributyl
phosphite, zinc dithiophosphate, or other suitable stabilizer.
[0031] As an alternative, a polyglycol dibutyl ether, such as
Genosorb.RTM. 1843, may be utilized as the absorbant. An
advantageous characteristic of Genosorb.RTM.1843 is that it
physically absorbs non-polar compounds, such as aromatics and
hydrocarbons. The specific compositions for the absorbant and
refrigerant are further discussed in Section V of the application,
related to the specific compositions.
[0032] Referring to FIG. 1, a pump 520 pumps the mixture of
absorbant and refrigerant from absorption tank 510, with the
mixture being pressurized to a pressure of approximately 30-70
psia.
[0033] The mixture is delivered to a counter-flow liquid-liquid
heat exchanger 530, where the mixture is pre-heated. When the
mixture exits heat exchanger 530, the mixture has a temperature of
approximately 90.degree. C.
[0034] The mixture is delivered to boiler 540, which boils the
mixture of refrigerant and absorbant at a pressure of approximately
30-70 psia. Because the HFC-245fa is dissolved in the NMP, it is
maintained at a pressure lower than that of pure HFC-245fa at the
same temperature. As HFC-245fa is removed from the mixture by
evaporation, the solution must be heated to a higher temperature in
order to continue to drive the HFC-245fa out. Optimally, the liquid
mixture exiting the boiler contains HFC-245fa in a concentration of
approximately 10-20%. As shown in FIG. 1, the liquid is then
delivered back into the heat exchanger 530 in counter-flow to the
mixture pumped from the absorption tank 510. Some of the energy of
the heated mixture is transferred in heat exchanger 530 to the
pumped mixture in known fashion for heat exchangers.
[0035] Superheated dry HFC-245fa vapor exits the boiler 540 and is
delivered to the scroll expander 550. The superheated HFC-245fa
enters the scroll expander and expands with a volumetric expansion
ratio of approximately 3. Due to the properties of HFC-245fa, the
pressure ratio achieved is approximately 3.0.
[0036] The HFC-245fa temperature upon exit from the scroll expander
550 has dropped, at this point in the cycle, to approximately
70.degree. C. The lower temperature HFC-245fa vapor may be used, in
certain embodiments of the invention, to cool the windings of
electric generator 560, which is coupled to scroll expander 550 by
shaft 570. The shaft-driven generator 560 may be used to generate
electrical power. The generator 560 is, in certain embodiments,
cooled by the ambient air in which it is operated.
[0037] In order to improve the lifetime of system 500, a portion of
the cooled NMP absorption composition, which has exited boiler 540
and re-entered heat exchanger 530, is routed through a regulator
valve 580 so as to meter out a small portion of the composition
material into scroll expander 550, thereby providing lubrication
thereto.
[0038] NMP is chosen as a preferred absorbant in certain
embodiments because NMP compositions exhibit exceptional thermally
stability. However, NMP also has a relatively high electrical
conductivity. As a result, scroll expander 550 is preferably
coupled to electrical generator while separated from the system
working fluids via a hermetic shaft seal. The shaft seal may be
constructed of either silicone rubber or butyl rubber, both of
which show excellent resistance to both the NMP and the
HFC-245fa.
[0039] The thermal stability of the absorbant/refrigerant mixture
can be substantially improved by adding certain well-known chemical
additives. For example, the additive may be a phosphate, a
phosphite, a borate, or a zinc dialkyldithiophosphate (ZDDP)
compound, such as OLOA 262, manufactured by the Chevron
Corporation. The additives may also be any of the many well-known
oil anti-oxidants. These oil additives act to coat surfaces of
metal and reduce the tendency of the metal surfaces to catalyze the
reaction of the decomposition of the adsorption material and the
refrigerant.
[0040] The performance of such additives described above,
particularly when aluminum is employed, is dramatically enhanced by
first pre-treating the aluminum surfaces, such as by chromate
conversion with, for example, well-known Alodine.RTM. treatment, by
anodization, or by passivation techniques including, but not
limited to: fluorine treatment, ozone treatment, nitric acid
treatment, vanadate treatment, or sol-gel surface treatment.
Surface treatment of system components is discussed further below
in Section VIII.
[0041] Returning to the system 500 of FIG. 1, a larger portion of
the concentrated NMP material exiting heat exchanger 530 enters a
second pressure reduction valve 590, where the pressure is stepped
down to the pressure of the HFC-245fa cooler/evaporator 620,
further described below.
[0042] Returning to the scroll expander 550, HFC-245fa vapor exits
the scroll expander 550 at approximately 2-6 atmospheres of
pressure. This relatively moderate pressure allows the main
condenser 600 to be compact. The condenser may be cooled by air or
water, shown by arrow 650. The refrigerant vapor exits the scroll
expander 550 and enters condenser 600, where the refrigerant is
converted to a liquid by the cooling action of condenser 600. The
cooled and condensed liquid HFC-245fa exits the condenser and is
directed to a refrigeration expansion valve 610, where the liquid
steps down in pressure to approximately 0.5-2.5 atmospheres. The
depressurized liquid exits the expansion valve 610 and enters
evaporator 620. Evaporator 620 converts the liquid refrigerant to a
vaporized refrigerant. The vaporization process is endothermic
thereby effecting a cooling of the air or water flowing through
evaporator 620, as illustrated by the arrows 640. The cooled air or
liquid 640 exiting evaporator 620 can be routed through a home,
building, or other edifice, thus providing a cooling effect.
[0043] The absorption tank 510 may be provided with an air-cooled
contactor to allow intimate mixing of the HFC-245fa vapor and the
cool, concentrated NMP absorption solution. The vaporized
refrigerant is drawn from evaporator 620 back into the absorption
tank 510, containing the air-cooled contactor. The absorption tank
510 further holds the liquid absorbant drawn from the boiler 540
and through valve 590.
[0044] The adsorption process of the vaporized refrigerant mixing
with the liquid absorbant produces heat, and a fluid material such
as air or water flows through the contactor, illustrated by the
arrows 630, in order to remove this excess thermal energy.
Typically, the contactor performance is improved by operating at as
low a temperature as possible. Thus, the air or other fluid 630
entering the contactor within absorption tank 510 is preferably
cooled first by, for example, a wick-type water evaporation
cooler.
[0045] After entering the contactor, the NMP material and HFC-245fa
have formed the original mixture, which began the cooling cycle,
and the mixture, once again, exits the contactor to enter pump 520,
thus restarting the cycle.
[0046] Due to the fact that the HFC-245fa is superheated and
expanded at a pressure ratio of approximately 3, the thermodynamic
efficiency of the scroll Rankine cycle is expected to be between 7
and 10%. Higher efficiency results if the condenser 600 is operated
on a cool day.
[0047] As an absorption system, the expected coefficient of
performance of system 500 is similar to any other efficient
single-effect absorption unit, i.e., approximately 0.6-0.9.
[0048] If the electric power produced by generator 560 is produced
at an efficiency of approximately 7 to 9%, and is coupled to an
electric compressor and used with conventional equipment with an
electrical-to-cooling coefficient of performance (COP) of
approximately 3.0, the net effect of the overall system in terms of
COP is the sum of the absorption unit, 0.6, and the
Rankine/electric unit, 0.4, thus giving a net system COP of
approximately 1.0.
[0049] It should be noted that the boiler temperature of system 500
is substantially higher than would be required of the system
operating with only pure HFC-245fa as the working fluid.
[0050] Pump 520 may be a chemically compatible centrifugal pump,
such as a polypropylene magnetically-coupled pump. Furthermore, the
centrifugal pump may be operated in an intermittent mode by
providing a check valve after the pump, and a hydraulic accumulator
on the high-pressure side of the system.
[0051] III. Cooling Cycle
[0052] FIG. 2 illustrates an exemplary cooling cycle as implemented
by certain embodiments of the heating/cooling system 10. As shown
in FIG. 2, following the vaporization of the refrigerant in boiler
50, the vaporized refrigerant is passed through a first selector
valve 110. In the cooling cycle of FIG. 2, the selector valve 110
diverts the vaporized refrigerant into a first liquid-vapor
converter 130. The liquid-vapor converter acts, essentially, as a
condenser and condenses the vaporized refrigerant into a
liquid.
[0053] The liquid refrigerant is passed through a second expansion
valve 140 where the pressure of the liquid refrigerant is dropped
to slightly below atmospheric pressure. The depressurized liquid
refrigerant passes from the second expansion valve 140 into a
second liquid-vapor converter 150. The second liquid-vapor
converter 150 re-vaporizes the liquid refrigerant and passes the
vaporized refrigerant through a second selector valve 120, which in
the cooling cycle, passes the vaporized refrigerant back into
absorption tank 20 to form the refrigerant and absorbant mixture
composition.
[0054] A salt or brine solution is provided with the brine solution
passing through liquid-vapor converter 130. When the vaporized
refrigerant condenses into the liquid refrigerant within
liquid-vapor converter 130, the heat of the vaporized refrigerant
is released. This heat is used to heat the brine solution. This
heated brine solution then passes into a first air-to-liquid
contactor member 170.
[0055] When the cooling/heating system 10 is installed in a home or
other edifice, the first air-to-liquid contactor member 170 is
positioned external to the edifice. Ambient or environmental air is
drawn into the first air-to-liquid contactor member 170 and the
heated brine solution causes the ambient air to be heated, with the
air-to-liquid contactor member 170 expelling heated air into the
environment. A fan or blower (not shown) may be used to force air
through air-to-liquid contact member 170.
[0056] The now-cooled brine solution is driven through second heat
exchanger 160 by fluid pump 180. The second heat exchanger 160
further cools the brine solution as it is being drawn therethrough
by pump 180. The cooled brine solution is then passed into second
liquid-vapor converter 150.
[0057] The second liquid-vapor converter 150 vaporizes the liquid
refrigerant, thus requiring thermal energy to be added thereto.
This thermal energy comes from the brine solution driven by pump
180, the transfer of which causes the brine solution to be further
cooled as it passes through second liquid-vapor converter 150.
[0058] This cooled brine solution is then driven through second
air-to-liquid contactor 190. When the cooling/heating system 10 is
installed in a home or other edifice, the second air-to-liquid
contactor 190 is installed within the home or edifice and draws in
ambient air. The ambient air is cooled by the now-cooled brine
solution passing through contactor 190, thus allowing the second
air-to-liquid contactor 190 to provide cooled air to home or
edifice. Again, as was indicated for air-to-liquid contactor member
170, a fan or blower (not shown) may be installed adjacent to
contactor 190 to force air therethrough.
[0059] The brine solution passes from the second air-to-liquid
contactor 190 through absorption tank 20, thus heating the brine
solution, where it can then be passed through second heat exchanger
160 in order to start the cycle over again.
[0060] The heat of condensation of the vapor is transferred to the
brine solution passing through condenser 130. As the brine enters
the condenser 130, the brine is somewhat water-saturated, and that
water-saturated brine is heated by the action of the condenser.
When the brine exits condenser 130, it is heated and enters the
liquid contactor 170. The air-to-liquid contactor 170 may be
constructed of a honeycomb absorptive paper or other similar kind
of pad material. Since the brine, at this point, is heated, the
brine loses water to the ambient air such that the air exiting the
contactor 170 is saturated with water vapor and is further heated.
Thus, brine solution exiting contactor 170 is substantially
depleted of water and has a far higher concentration of salt. Upon
entering the heat exchanger 160, the brine solution transfers its
remaining thermal energy to the incoming water-rich brine solution,
thus pre-heating the water-rich brine within heat exchanger
160.
[0061] When the water is depleted, brine solution exits heat
exchanger 160 in a near ambient-temperature state, where upon it
enters brine pump 180. Brine pump 180 directs the brine solution
into liquid-vapor converter 150 and as the refrigerant is
evaporated, the brine is cooled well below room temperature so that
the brine exits on the right-hand side of 150 (in FIG. 2) in a
somewhat cold state and is depleted of any moisture.
[0062] When the brine solution enters contactor 190, which is
located within the building or edifice, the air from the building
is blown over the high concentration salt water brine and the air
from the building gives up its moisture to the cold brine solution,
thus effecting both dehumidification and cooling on the air going
through the contactor 190.
[0063] Upon exiting contactor 190, the brine solution is slightly
cooled and water-rich, where it is then directed to the absorption
tank 20. The heat of absorption is removed by the brine solution in
the absorption tank 20, and the brine solution exits absorption
tank 20 at a temperature of approximately 100.degree. F. The brine
solution then flows back into heat exchanger 160 to start the cycle
over again.
[0064] IV. Heating Cycle
[0065] An exemplary heating cycle of certain embodiments of
cooling/heating system 10 is shown diagrammatically in FIG. 3. As
shown in FIG. 3, the vaporized refrigerant, having been vaporized
in boiler 50, is passed through first selector valve 110. In the
heating cycle, the first selector valve 110 diverts the flow of the
vaporized refrigerant through second selector valve 120.
[0066] The second selector valve 120 directs the vaporized
refrigerant through liquid-vapor converter 150. The second
liquid-vapor converter 150 acts, essentially, as a condenser and
converts the vaporized refrigerant to a liquid refrigerant. The
liquid refrigerant is then passed through the second expansion
valve 140 where it is depressurized.
[0067] The newly-depressurized liquid refrigerant is then driven
through the first liquid-vapor converter 130 where the refrigerant
is re-vaporized. The re-vaporized refrigerant then passes back
through first selector valve 110 where it is directed to second
selector valve 120. Second selector valve 120 passes the vaporized
refrigerant back into absorption tank 20, where it mixes with the
absorbant to form the refrigerant and absorbant mixture
composition.
[0068] When the liquid refrigerant passes through the first
liquid-vapor converter 130, thereby vaporizing the liquid
refrigerant, an addition of thermal energy is required. This energy
is provided by the brine solution as it passes through the
liquid-vapor converter 130.
[0069] The now-cooled brine solution passes through the first
air-to-liquid contactor member 170. When the cooling/heating system
10 is installed in a home or other edifice, the first air-to-liquid
contactor member 170 is positioned external to the home or edifice.
Ambient air is drawn through the first air-to-liquid contactor
member 170 and the cooled brine solution causes the air-to-liquid
contactor member 170 to expel cooled air, thereby heating the brine
solution.
[0070] The now-heated brine solution is passed through second heat
exchanger 160, which heats the brine solution. The heated brine
solution is driven by pump 14 into second liquid-vapor converter
150. As the vaporized refrigerant passes through second
liquid-vapor converter 150, converting the vaporized refrigerant
into a liquid, thermal energy is transferred to the brine solution,
which is then driven into second air-to-liquid contactor member
190.
[0071] When the cooling/heating system 10 is installed in a home or
other edifice, the second air-to-liquid contactor member 190 may be
installed therein. The heated brine solution in the second
air-to-liquid contactor 190 heats the air drawn therethrough. The
heated air is then provided to the home or edifice.
[0072] From the contactor member 190, the brine solution passes
back through absorption tank 20, where it is further cooled. The
brine solution is transferred back to heat exchanger 160 whereupon
a new cycle may begin.
[0073] In the heating cycle, the condensing vapor in liquid-vapor
converter 150 gives up its heat to the water-rich brine entering
the converter 150. The water-rich brine is heated at this point.
Similarly, the evaporator 130 of the heating cycle chills the
concentrated brine solution. The concentrated brine at this point
is quite cold and exits the liquid-vapor converter 130, flowing
into the ambient air-to-liquid contactor 170 (similar to the flow
of the cooling cycle) in its cold state and, further, depleted of
water. Ambient air in the air contactor 170 flows over the cold and
water-depleted brine solution, allowing the brine solution to
absorb heat and absorb water vapor from the ambient air, thus
resulting in a heated brine solution with an increased water
content.
[0074] The brine solution exits the contactor 170 and enters heat
exchanger 160, which acts to pre-heat the brine solution as it is
pumped from the upper left-hand side (referring to FIG. 3) to the
bottom left-hand side of heat exchanger 160 by pump 180. Pump 180
forces the brine solution into condenser 150, where the brine is
heated even further by the condensation of the water vapor, thus
allowing heated water-rich brine to exit the liquid-vapor converter
150. This heated water-rich brine solution passes to contactor 190
where the ambient air receives the heat of the brine solution. The
air is also humidified by the water-rich brine solution, and
humidified warm air may then be provided to the building or
edifice. The brine solution then follows a return path through the
absorption tank 20, similar to that of the cooling cycle.
[0075] V. Specific Compositions of Absorbant and Refrigerant
[0076] The absorbant, in certain embodiments, consists
substantially of pure NMP with small amounts (ranging from 0.1-1%
by volume) of one or more stabilizers selected from the group of
nitroalkanes, such as nitromethane, phosphates such as tributyl
phosphate, zinc dithiophosphate, or other stabilizers. The
absorbant may, in the alternative, be a liquid polymer containing
triethylene glycol dibutyl ether. A polyglycol dibutyl ether, such
as Genosorb.RTM. 1843 may also be utilized. Genosorb.RTM. 1843 is
hydrophobic and contains a stabilizer and is used to physically
absorb nonpolar compounds, such as aromatics and hydrocarbons.
Genosorb.RTM. 1843 is a product of the Clariant Corporation of
Mount Holly, N.C.
[0077] The refrigerant may be a hydrofluorocarbon or a
hydrochlorofluorocarbon refrigerant composition. The refrigerant
may consist of HFC134a, HFC245fa, or a combination of the two. In
certain embodiments, the refrigerant is substantially pure
HFC-245fa. Further, the refrigerant may be any of the following
compounds: trichlorofluoromethane, dichlorodifluoromethane,
chlorodifluoro-methane, difluoromethane,
1,1,2-trichlorotrifluoroethane, 1,2-dichlorotetra-fluoro- ethane,
chloropentafluoroethane, 1,1,1,2-tetrafluoroethane,
1,1-dichloro-1-fluoroethane, 1,1-difluoroethane, and methylene
chloride.
[0078] When the absorbent is not NMP, the refrigerant may be
selected from the above group based upon the refrigerant's affinity
for the selected absorbant. For example, the substances
chlorodifluoromethane, difluoromethane, and methylene chloride are
non-NMP refrigerants having the highest affinities for
Genosorb.RTM. 1843.
[0079] The refrigerant may further be a mixture of 10%
1,1-difluoroethane (R152a) and 90% 1, 1, 1, 3, 3-pentafluoropropane
(R245fa).
[0080] The ozone depletion potential (ODP) and global warming
potential (GWP) of various refrigerants is a key issue of concern.
R245fa may be used as a low ODP working fluid in a Rankine power
cycle. However, R245fa has a substantial GWP of around 990 in
comparison to carbon dioxide. Additionally, R245fa is
non-flammable. Thus, the possibility exists for using R245fa as a
refrigerant, but it has a boiling point of around 15.degree. C.,
which is generally considered to be too high for most air
conditioning applications, where the typical evaporation
temperature is desired to be around 10.degree. C.
[0081] R152a, or HFC 152a, has the advantage of having zero ODP and
a GWP of 140. However, HFC 152a is a flammable gas. A container of
pure HFC 152a can easily be ignited and the product of ignition is
the hazardous material hydrogen fluoride, which is harmful to
humans and is also corrosive. Pure R152a has low toxicity and its
OSHA limit of exposure is equal to other non-toxic Freon gases;
i.e., approximately 1000 ppm. However, in a mixture ratio of
approximately 5% to 25% of R152a with approximately 95% to 75%
R245fa, with the most preferable ratio being approximately 10%
R152a and 90% R245fa, the mixture of R152a and R245fa produces an
optimal refrigerant mixture. The mixture is essentially
non-flammable, i.e., far less flammable than R152a on its own, and
the mixture has a substantially lower boiling point than R245fa on
its own. In the ratio described above, the mixture has a boiling
point of approximately 2.degree. to 4.degree. C. Additionally, the
vapor pressure of the mixture is slightly above atmospheric
pressure, over the "glide" range, of approximately 30 to
approximately 10.degree. C. Moreover, both R152a and R245fa are
absorbed efficiently by the Genosorb.RTM. 1843.
[0082] The GWP of the mixture is substantially lower than the GWP
of pure R245fa and when used in conjunction with Genosorb.RTM.
1843, the resulting system pressure is slightly below atmospheric
pressure during times when the system is not in operation. Thus,
the loss of the mixture is essentially zero during the time of
non-operation, which represents the vast majority of hours over the
life of a typical air conditioning system.
[0083] The vapor pressure of the refrigerant mixture is higher than
the vapor pressure of pure R245fa, thereby increasing the
mechanical output power of the expander device 80 of system 10.
This results in a lower cost of generated electrical power by
generator 90 and thus a more economical system.
[0084] The proportions of the refrigerant mixture can be optimized
for particular locations. For example, in cold climates, the ratio
of R152a may be increased to approximately 13% to 20%. In warm
climates, the optimal mixture will have a lower concentration of
R152a, typically from approximately 3% to 9%. It should be apparent
that such "tuning" of the refrigerant would be impossible in
systems utilizing only a single pure material, such as R245fa or
R152a alone.
[0085] Another advantage of using the refrigerant mixture is that
the toxicity thereof is lower than the toxicity of pure R245fa. The
mixture is further particularly advantageous for systems where a
vapor ejector is used as the device for converting the expansion
energy. This is because the average molecular weight of the hot
vapor is nearly equal to the molecular weight of pure R245fa, while
the average molecular weight of the "pumped gas" can be arranged to
be closer to the molecular weight of R152a. A prudently selected
absorption material, such as Genosorb.RTM. 1843, will have a higher
affinity for R245fa than for R152a, and as a result, the working
mixture in the lower pressure environment of the evaporator will
have a higher concentration of R152a than of R245fa. The molecular
weight of R152a is only 33, while the molecular weight of R245fa is
134, and the large difference in molecular weight results in highly
efficient pumping of R152a refrigerant by the motive gas consisting
primarily of R245fa.
[0086] Additionally, the change in entropy of the mixture as a
function of pressure change is such that entropy decreases as
pressure decreases. This means that the mixture is "dry" as it
expands in either the scroll expander or a vapor jet pump.
[0087] As a further advantage, the mixture of R245fa, R152a, and
Genosorb.RTM. 1843 is completely compatible with all materials of
construction of the system 10. Therefore, the system can be
entirely hermetically sealed. The specific characteristics of a
polyglycol dibutyl ether such as Genosorb.RTM.1843 and those of the
refrigerants include very low electrical conductivity, and no
tendency to attack materials such as wires, insulation, bearings,
etc.
[0088] In one embodiment, chlorotetrafluoroethane (HCFC 124) is
used as the refrigerant. Though HCF 245fa may be utilized, as
described above, in combination with Genosorb.RTM. 1843, HFC 245fa
has a poor attraction to the Genosorb.RTM. 1843 molecule. Neither
the HFC 152a nor the HFC 245fa have chlorine molecules in their
molecular make-up.
[0089] Chloride-containing refrigerant molecules result in far
greater attraction between a refrigerant and other molecules
because the hydrogen bond is stronger. Thus, HFC 124a will provide
a stronger attraction, and thus better refrigerant qualities in the
mixture, with Genosorb.RTM. 1843. Additionally, compounds such as
phosphites and zinc compounds may be utilized as additives in order
to reduce interaction between the refrigerant and absorption
compounds.
[0090] With regard to the brine solution, the brine solution may be
a salt dissolved in water. The salt may be lithium chloride,
lithium bromide, magnesium chloride, calcium chloride, or
glycol.
[0091] In the certain embodiments utilizing HFC-245fa as a
refrigerant and NMP as an absorption material, lower temperatures
may be produced than are produced by the alternate compositions
described above. The HFC-245fa/NMP working pair further has
desirable properties such as low ozone depletion potential, high
thermal conductivity, stability, virtually zero loss of refrigerant
during shut-down mode and low production costs.
[0092] VI. Single-Effect Absorption Cycle
[0093] FIG. 4 illustrates an alternative embodiment of the
inventive cooling system utilizing the specific absorbant and
refrigerant compounds discussed above in Section V. As shown in
FIG. 4, the absorbant and refrigerant mixture is pressurized by a
pump 230, similar to the pump used in system 10 of FIGS. 2 and 3.
The initial pumping occurs at essentially constant temperature
(approximately 40.degree. C.) and enthalpy. The mixture is held at
a pressure of approximately 4 atmospheres absolute, or
approximately 3 atmospheres "gage" pressure, which is approximately
45 psig.
[0094] The mixture is passed through heat exchanger 240 into boiler
250. Once in the boiler 250, the refrigerant described above in
Section V, is driven off from the absorption fluid. The
concentration of the refrigerant is reduced from approximately 40%
refrigerant to approximately 12.5% refrigerant. This process
requires considerably higher temperature than the temperature
required for boiling pure fluid, because the refrigerant
concentration is only present in a relatively small fraction (one
part in 1.5, at the start, and about one part in 9 at the end of
the process).
[0095] As an approximation, the "activity" of the refrigerant is
about 1.0. To produce an absolute pressure of 4 atmospheres with a
concentration of 40%, the refrigerant must be heated to a
temperature where the pure material is (1/0.4).times.4 atm=10 atm.
These conditions occur at a temperature of approximately 75.degree.
C. The refrigerant at this temperature begins to give off
refrigerant vapor at 4 atmospheres of pressure. At the end of the
boiling process, the effective temperature must be such that the
effective pure refrigerant has a vapor pressure of
(1/0.125).times.4 atm=32 atm. This occurs when the pure refrigerant
temperature is approximately 135.degree. C.
[0096] As shown in FIG. 4, boiler 250 is constructed such that the
exiting hot vapor loops back through the boiler, allowing the hot
vapor to cool and give up its heat to the boiler process.
Similarly, the liquid exiting at the hot end of the boiler also
gives up its heat by looping back through the boiler 250.
[0097] Upon exiting the boiler, the refrigerant vapor is
superheated to approximately 80.degree. C. Superheated vapor exits
the boiler and enters the condenser device 260, which is similar in
construction to the liquid-vapor converter 130 of the embodiment of
FIGS. 2 and 3. The liquid absorbant is drawn from boiler 250 back
through the heat exchanger 240 and through expansion valve 270 in
order to return to the absorption tank 220, in a similar process to
that shown in FIGS. 2 and 3.
[0098] Once in the liquid-vapor converter or condenser 260, the
vapor is condensed and heat is given up to the environment by air
flowing through the condenser 260. Exiting the condenser, the
liquid refrigerant mix expands adiabatically and at constant
enthalpy in expansion valve 280.
[0099] The vapor mixture is now at a state between liquid and
vapor. The "quality" of this mixture is estimated to be
approximately 80% liquid and 20% vapor at a temperature of
approximately 2.degree. C. and at a pressure of 1 atmosphere. The
cool mixture evaporates completely with an evaporator 290, which is
similar to the second liquid-vapor converter 150 of the embodiment
shown in FIGS. 2 and 3. The pressure of the evaporant remains at 1
atmosphere.
[0100] The refrigerant reaches a total vapor state after its
temperature is increased from approximately 2.degree. C. to
approximately 10.degree. C. This expansion process absorbs heat,
thus creating a cooling effect for air passing through the
evaporator 290. The vapor mixture at this point is at approximately
1 atmosphere of pressure and approximately 10.degree. C., and has a
"quality" of 100%.
[0101] The vapor is then directed back into the absorption tank
220, where it mixes with the NMP, which is also at a pressure of
approximately 1 atmosphere, and at near room temperature.
[0102] The NMP, at this point, has been depleted to approximately
10% refrigerant by the boiling process. The NMP then absorbs the
refrigerant, releasing heat. The final concentration of the
refrigerant in the NMP material is approximately 40%. The mixture
of refrigerant and NMP is then pressurized by the pump 230 from
approximately 1 atmosphere to about 4 atmospheres, and the process
is repeated.
[0103] VII. Shaft-Coupled Mechanical Compressor System
[0104] In the embodiment shown in FIGS. 2 and 3, a scroll expander
80 is coupled to an induction generator 90 by shaft 100. In the
alternative embodiment shown in FIG. 5, the mechanical output of a
scroll compressor is used to drive a mechanical compressor, which
may be of the scroll type.
[0105] In a cooling mode, a mixture of refrigerant and absorbant,
as described above with regard to FIGS. 2 and 3, and in the
embodiment of FIG. 4, is held within an absorption tank 320. The
mixture is driven by pump 330 through a heat exchanger 340. The
mixture is then delivered to a boiler unit 350 where the
refrigerant is vaporized and the liquid absorbant is driven back
through heat exchanger 340, through expansion valve 360 and back
into the absorption tank 320. This process is the same as in the
embodiments of FIGS. 2 and 3, and in the embodiment of FIG. 4.
[0106] In the embodiment of FIG. 5, the vaporized refrigerant is
delivered to a scroll expander 370 which drives a compressor 380
via shaft 450. The compressor 380 elevates the pressure from
approximately 1 atmosphere to about 2 to 4 atmospheres, and gaseous
refrigerant is transported by compressor 380 to condenser 410,
which is similar to the liquid-vapor converter 130 of the
embodiment shown in FIGS. 2 and 3. The condenser 410 liquefies the
vaporized refrigerant, thus releasing heat into ambient air
circulating over condenser 410. The condensed refrigerant is then
directed to an expansion valve 420 where the pressure is decreased
to approximately 1 atmosphere. The refrigerant passes from the
expansion valve 420 to an evaporator 430, which is similar to the
second liquid-vapor converter 150 of the embodiment shown in FIGS.
2 and 3. In the evaporator 430, the liquid refrigerant evaporates
and absorbs heat. The vapor exits the evaporator 430 and is
returned to compressor 380 to begin the cycle over again.
[0107] Gaseous refrigerant exiting scroll expander 370 is directed,
through first selector valve 390 into condenser 410. As in the
embodiment shown in FIGS. 2 and 3, through use of the selector
valves 390 and 400, the system can be switched between a heating
and cooling mode.
[0108] Liquid refrigerant exiting the condenser 410 enters an
expansion valve 440, where the liquid refrigerant is depressurized
from approximately 4 atmospheres to approximately 1 atmosphere. The
liquid refrigerant evaporates within evaporator 430, producing
gaseous or vaporized refrigerant.
[0109] The vaporized refrigerant then passes through the second
selector valve 400 to be input back into the absorbant tank 320,
where it is mixed with the absorbant to form the mixture of
refrigerant and absorbant.
[0110] Following the process of this embodiment, mechanical power
is produced, representing approximately 10% of the input heat
energy. A typical mechanical compressor using a scroll-type design
operates with a mechanical coefficient of performance (COP) of
approximately 4 to 6. Thus, in considering the effective
refrigeration output vs. heat input, the mechanical "Rankine" cycle
portion operates with an effective COP of approximately 0.5.
[0111] In addition to the cooling effect produced by the mechanical
compressor, cooling is produced in the absorption section. As shown
in FIG. 5, air is passed through an air-to-liquid contactor member
460 in communication with the absorption tank 320, in order to
produce cooled air. In the heating mode, it is understood that this
would produce a heated air effect.
[0112] VIII. Alternative Construction Materials
[0113] As previously stated, the implementation of various
components through lower-cost materials is among the many
beneficial features the present invention. For example, the
utilization of NMP as an absorbant in combination with a
refrigerant containing HFC-245fa allows boiler fluid operating
pressures below 100 psi. At such moderate pressures, certain
components in the boiler fluid circuit, such as the heat exchanger,
may be constructed from a lighter material, such as aluminum. It
should be apparent to the skilled artisan that significant savings
in construction costs may be secured by the use of alternative
materials such as aluminum.
[0114] In certain embodiments of the present invention, the
components constructed from lower-cost materials may be treated on
the surface thereof to further protect the component from corrosion
by exposure to the absorbant/refrigerant mixture. For example,
where aluminum is used, the surface of components may be treated by
processes that include one or more of the steps of: etching,
passivation and sealing. Such processes are well-known and an
exemplary treatment of aluminum is provided in U.S. Pat. No.
6,579,472, issued to Chung, et al.
[0115] In certain embodiments, aluminum components, such as heat
exchangers and boiler fluid tubing, are etched by an etchant, such
as phosphoric acid. The etchant is rinsed off and the components
are subjected to passivation. The surface of the components are
passivated by a chromic acid based conversion coating such as
Alodine.RTM. 1200, (Alodine is a registered trademark of the
American Chemical Paint Company). Alternatively, the component may
be treated by a non-chromic conversion coating, such as
Alodine.RTM. 5200. The aluminum components may be passivated, also,
by nitric acid, fluorine gas or other chemicals known in the art
that are compatible for use with the absorbant/refrigerant
mixture.
[0116] Once the surface conversion treatment has been completed,
the surface of the components may be sealed using, for example: a
silane surface treatment, such as Z-6040 manufactured by Dow
Corning.RTM., a sol-gel, such as that disclosed in the
above-referenced U.S. patent issued to Chung, et al., or a paint,
such as a silicon based paint.
[0117] It should be noted that it is not required that all
components of the inventive system be surface treated in the same
way, i.e., components having different surface characteristics may
be incorporated in any given system. This allows flexibility for
particular field installations. Furthermore, it should be noted
that the list of exemplary surface treatments provided above is not
exhaustive. Other treatments are, and will be available that are
compatible with a particular absorbent/refrigerant mixture of the
present invention.
[0118] Although this invention has been described in connection
with specific forms and embodiments thereof, it will be appreciated
that various modifications other than those discussed above may be
resorted to without departing from the spirit or scope of the
invention. For example, functionally equivalent elements may be
substituted for those specifically shown and described,
proportional quantities of the elements shown and described may be
varied, and in the method steps described, particular steps may be
reversed or interposed, all without departing from the spirit or
scope of the invention as defined in the appended claims.
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