U.S. patent application number 13/415796 was filed with the patent office on 2013-03-14 for helium charged refrigerator.
This patent application is currently assigned to Atwood Mobile Products LLC. The applicant listed for this patent is Marco Jiang, David William Leistner. Invention is credited to Marco Jiang, David William Leistner.
Application Number | 20130061629 13/415796 |
Document ID | / |
Family ID | 46798818 |
Filed Date | 2013-03-14 |
United States Patent
Application |
20130061629 |
Kind Code |
A1 |
Leistner; David William ; et
al. |
March 14, 2013 |
HELIUM CHARGED REFRIGERATOR
Abstract
A helium charged refrigerator is capable of cooling a
refrigerator box to a temperature of 6.degree. C. (43.degree. F.)
and the freezer compartment to a temperature of -9.degree. C.
(15.degree. F.) when the ambient is at a temperature of 43.degree.
C. (110.degree. F.). The total cubic area cooled is greater than or
equal to six cubic feet. The unit includes a condenser, an
evaporator, a liquid ammonia tube, and a gas heat exchanger. The
liquid ammonia tube includes two vertical sections. The second
section is downstream of the first and is noncontiguous with the
heat exchanger so that no heat is exchanged between flowable fluids
flowing in the second vertical section and in the heat exchanger.
The heat exchanger includes modifications to its inner and outer
tubes to produce an increase in surface area of the corresponding
surface.
Inventors: |
Leistner; David William;
(Sidney, OH) ; Jiang; Marco; (Qingdao,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Leistner; David William
Jiang; Marco |
Sidney
Qingdao |
OH |
US
CN |
|
|
Assignee: |
Atwood Mobile Products LLC
Elkhart
IN
|
Family ID: |
46798818 |
Appl. No.: |
13/415796 |
Filed: |
March 8, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61450237 |
Mar 8, 2011 |
|
|
|
Current U.S.
Class: |
62/490 |
Current CPC
Class: |
F25D 11/027 20130101;
F25B 15/10 20130101 |
Class at
Publication: |
62/490 |
International
Class: |
F25B 15/10 20060101
F25B015/10 |
Claims
1. A refrigerator having a diffusion-absorption refrigeration
assembly that uses helium as a diffusion gas, the refrigeration
assembly comprising, a condenser, an evaporator, a liquid ammonia
tube, and a gas heat exchanger, wherein the liquid ammonia tube
comprising a first vertical section with an inlet, and a second
vertical section downstream of the first.
2. A refrigerator according to claim 1, wherein the second vertical
section of the liquid ammonia tube being noncontiguous with said
heat exchanger, wherein no heat is exchanged between flowable
fluids flowing in said second vertical section and in said heat
exchanger.
3. A refrigerator according to claim 1, wherein said liquid ammonia
tube further comprising an intermediate section downstream of the
second vertical section, said intermediate section being contiguous
with said heat exchanger, wherein heat is exchanged between
flowable fluids flowing in said intermediate section and in said
heat exchanger.
4. A refrigerator according to claim 3, wherein said liquid ammonia
tube further comprising a freezer section upstream of the
intermediate section, said freezer section being contiguous with
said heat exchanger, wherein heat is exchanged between flowable
fluids flowing in said freezer section and in said heat
exchanger.
5. A refrigerator according to claim 4, wherein the second vertical
section of the liquid ammonia tube being noncontiguous with said
heat exchanger, wherein no heat is exchanged between flowable
fluids flowing in said second vertical section and in said heat
exchanger.
6. A refrigerator having a diffusion-absorption refrigeration
assembly that uses helium as a diffusion gas, the refrigeration
assembly comprising, a condenser, an evaporator, a liquid ammonia
tube, and a gas heat exchanger, wherein the liquid ammonia tube
comprising a first vertical section with an inlet, and a second
vertical section downstream of the first, said refrigerator having
a freezer box defining a first cubic area, and a refrigerator box
defining a second cubic area, the sum of said first and second
cubic areas being equal to or greater than six cubic feet, wherein
said assembly being capable of cooling the refrigerator box to a
temperature of 6.degree. C. (43.degree. F.) and the freezer
compartment to a temperature of -9.degree. C. (15.degree. F.) when
the ambient is at a temperature of 43.degree. C. (110.degree.
F.).
7. A refrigerator according to claim 6, wherein the heat exchanger
includes inner and outer tubes, said inner tube having an outer
surface, and said outer tube having an inner surface, said outer
and inner surfaces each being shaped to produce an increase in
surface area of the corresponding surface.
8. A refrigerator having a diffusion-absorption refrigeration
assembly that uses helium as a diffusion gas, the refrigeration
assembly comprising, a condenser, an evaporator, a liquid ammonia
tube, a gas heat exchanger, wherein the liquid ammonia tube
comprising a first vertical section with an inlet, and a second
vertical section downstream of the first, said refrigerator having
a freezer box defining a first cubic area, and a refrigerator box
defining a second cubic area, the sum of said first and second
cubic areas being equal to or greater than six cubic feet, wherein
said assembly being capable of cooling the refrigerator box to a
temperature of 6.degree. C. (43.degree. F.) and the freezer
compartment to a temperature of -9.degree. C. (15.degree. F.) when
the ambient is at a temperature of 43.degree. C. (110.degree. F.),
wherein the second vertical section of the liquid ammonia tube
being noncontiguous with said heat exchanger, wherein no heat is
exchanged between flowable fluids flowing in said second vertical
section and in said heat exchanger.
9. A refrigerator according to claim 8, wherein the heat exchanger
includes inner and outer tubes, said inner tube having an outer
surface, and said outer tube having an inner surface, said outer
and inner surfaces each having serrations to produce an increase in
surface area of the corresponding surface.
10. A refrigerator according to claim 9, wherein said liquid
ammonia tube further comprising an intermediate section downstream
of the second vertical section, said intermediate section being
contiguous with said heat exchanger, wherein heat is exchanged
between flowable fluids flowing in said intermediate section and in
said heat exchanger.
11. A refrigerator according to claim 10, wherein the second
vertical section of the liquid ammonia tube being noncontiguous
with said heat exchanger, wherein no heat is exchanged between
flowable fluids flowing in said second vertical section and in said
heat exchanger.
12. A refrigerator having a diffusion-absorption refrigeration
assembly that uses helium as a diffusion gas, the refrigeration
assembly comprising, a condenser, an evaporator, a liquid ammonia
tube, and a gas heat exchanger, wherein the gas heat exchanger
comprising an inner tube having and outer diameter of between about
14 and about 16 millimeters and an outer tube having an outer
diameter of between about 25 and 27 millimeters, said refrigerator
having a freezer box defining a first cubic area, and a
refrigerator box defining a second cubic area, the sum of said
first and second cubic areas being equal to or greater than six
cubic feet, wherein said assembly being capable of cooling the
refrigerator box to a temperature of 6.degree. C. (43.degree. F.)
and the freezer compartment to a temperature of -9.degree. C.
(15.degree. F.) when the ambient is at a temperature of 43.degree.
C. (110.degree. F.).
13. A refrigerator according to claim 12, wherein the liquid
ammonia tube comprising a first vertical section with an inlet, and
a second vertical section downstream of the first, wherein the
second vertical section being noncontiguous with said heat
exchanger, wherein no heat is exchanged between flowable fluids
flowing in said second vertical section and in said heat
exchanger.
14. A refrigerator according to claim 13, wherein said liquid
ammonia tube further comprising an intermediate section downstream
of the second vertical section, said intermediate section being
contiguous with said heat exchanger, wherein heat is exchanged
between flowable fluids flowing in said intermediate section and in
said heat exchanger.
15. A refrigerator according to claim 14, wherein said liquid
ammonia tube further comprising a freezer section upstream of the
intermediate section, said freezer section being contiguous with
said heat exchanger, wherein heat is exchanged between flowable
fluids flowing in said freezer section and in said heat
exchanger.
16. A refrigerator according to claim 15, wherein said inner tube
of the heat exchanger includes an outer surface, and said outer
tube includes an inner surface, said outer and inner surfaces each
having serrations to produce an increase in surface area of the
corresponding surface.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application No. 61/450,237, filed Mar. 8, 2011, which is hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to gas absorption
refrigeration cooling systems and specifically to a helium gas
charged refrigerator for a recreational vehicle (RV).
[0004] 2. Description of the Prior Art
[0005] The cooling cycle of the typical diffusion-absorption
refrigeration system starts with liquefied ammonia entering an
evaporator at room temperature. The ammonia is mixed in the
evaporator with hydrogen. The partial pressure of the hydrogen is
used to regulate the total pressure, which in turn regulates the
vapor pressure and thus the boiling point of the ammonia. The
ammonia boils in the evaporator, providing the cooling required.
The fluids are endlessly recirculated by gravity.
[0006] Hydrogen is assumed to be the optimum diffusion gas used in
diffusion-absorption cooling systems because it is the lightest
element of the periodic table. It has an atomic weight of one, and
its molecular weight is about the same. Hydrogen has always been
the preferred diffusion agent because its partial pressure, which
regulates the overall pressure of the closed system, is small and
easily calculable. Hydrogen is predictable as the element moves
between phase changes and solution in the system as well.
[0007] Helium, on the other hand, has an atomic weight of two and
is considered ineffective as a diffusion gas for such cooling
systems. The more weighty helium has a different partial pressure
and requires a higher boiling temperature for the ammonia in a
helium charged system. Refrigerators that operate outdoors at
higher ambient temperatures have difficulty reaching desirable
cooling temperatures. Normal-sized diffusion-absorption type
refrigerators where the total area chilled is about eight cubic
feet, for example, cannot use helium and meet applicable ANSI
standards.
[0008] Hydrogen, however, is volatile and extremely dangerous. Fire
and explosion have produced a need for an alternative diffusion or
charging gas. Prior refrigerators that use helium as a charging
gas, e.g., hotel mini bar refrigerators, are for low ambient
temperatures (i.e., 32.degree. C. (90.degree. F.) or lower). Such
applications have a nominal ambient temperature rating of
25.degree. C. (77.degree. F.). The ANSI standard applicable to RV
gas absorption refrigeration cooling systems, however, requires the
following specifications at an ambient temperature of 43.degree. C.
(110.degree. F.): (i) the refrigerator compartment cooled to a
temperature of at least 6.degree. C. (43.degree. F.) and (ii) the
freezer compartment cooled to a temperature of at least -9.degree.
C. (15.degree. F.).
[0009] The invention has overcome the perceived barriers to using
helium as a diffusion gas for normal-sized refrigerators and
results in a refrigerator that meets the applicable ANSI
standards--that is, the inventive helium charged system provides
desirable freezer/refrigeration temperatures for larger
refrigerators operative where the ambient is not temperature
controlled.
SUMMARY OF THE INVENTION
[0010] The disadvantages heretofore associated with the prior art
are overcome by the inventive RV refrigeration cooling system using
helium as the charging gas. The novel system is for a refrigerator
of the type that relies upon gravity to move fluid through a closed
fluid system for heat exchange between an ammonia solution and a
diffusion or charging gas. Such a refrigerator has a freezer
evaporator, including a freezer box, a cabinet evaporator,
including a refrigerator box, an absorber vessel downstream of the
freezer and cabinet evaporators, and a liquid heat exchanger
downstream of the absorber vessel.
[0011] The new refrigerator includes a diffusion-absorption
refrigeration assembly that uses helium as a diffusion gas. The
refrigeration assembly includes a condenser, an evaporator, a
liquid ammonia tube, and a gas heat exchanger.
[0012] In one aspect of the invention, the liquid ammonia tube may
include a first vertical section with an inlet and a second
vertical section downstream of the first. The refrigerator may
include a freezer box defining a first cubic area and a
refrigerator box defining a second cubic area.
[0013] In another aspect, the sum of the first and second cubic
areas may be equal to or greater than six cubic feet such that the
assembly is capable of cooling the refrigerator box to a
temperature of 6.degree. C. (43.degree. F.) and the freezer
compartment to a temperature of -9.degree. C. (15.degree. F.) when
the ambient is at a temperature of 43.degree. C. (110.degree.
F.).
[0014] In yet another aspect, the heat exchanger includes inner and
outer tubes, said inner tube having an outer surface, and said
outer tube having an inner surface, said outer and inner surfaces
each being shaped to produce an increase in surface area of the
corresponding surface.
[0015] One object of the invention is to provide a novel
refrigerator having a diffusion-absorption refrigeration assembly
that uses helium as a diffusion gas instead of hydrogen and thus is
safe if the system is ruptured and gas escapes. It has heretofore
not been possible for a helium charged refrigerator to cool eight
(8) cubic feet, that is, the size of the refrigerator box to a
temperature of 6.degree. C. (43.degree. F.) and the size of the
freezer compartment to a temperature of -9.degree. C. (15.degree.
F.) when the ambient is at a temperature of 43.degree. C.
(110.degree. F.). In other words, the new refrigerator meets ANSI
standards for cooling larger refrigerators where the ambient is not
temperature controlled. Related objects and advantages of the
invention will be apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The details of the invention, both as to its structure and
operation, may be obtained by a review of the accompanying
drawings, in which:
[0017] FIG. 1 is an isometric view of a refrigerator of the
invention showing the freezer box and the refrigerator box;
[0018] FIG. 2 is a diagrammatic illustration of a typical prior art
absorption system;
[0019] FIG. 3 is a diagrammatic drawing of the diffusion-absorption
refrigeration assembly of the invention;
[0020] FIG. 4 is a partial cutaway isometric view of an embodiment
of the heat exchanger of the invention;
[0021] FIG. 4A is an enlarged view of the outer surface of the
inner tube of the heat exchanger of the invention; and
[0022] FIG. 4B is an enlarged view of the inner surface of the
outer tube of the heat exchanger of the invention.
DETAILED DESCRIPTION OF INVENTION
[0023] The invention is a refrigerator 10 having a
diffusion-absorption refrigeration assembly 20 that uses helium as
a diffusion gas instead of hydrogen. As shown in FIG. 3, the
refrigeration assembly includes a condenser 22, an evaporator
(freezer 24, cabinet 26), a liquid ammonia tube 25, and a gas heat
exchanger 27. The liquid ammonia tube has a first vertical section
30 with an inlet 31, a second vertical section 32 downstream of the
first, and an intermediate section 34 downstream of the second
vertical section.
[0024] The second vertical section 32 does not touch the heat
exchanger 27. No heat is exchanged between flowable fluids flowing
in the second vertical section and in the heat exchanger as a
result. Additionally, the intermediate section 34 is contiguous
with the heat exchanger 27 so that heat is exchanged between
flowable fluids flowing in the intermediate section and in the heat
exchanger.
[0025] Referring to FIG. 1, the refrigerator 10 has a freezer box
12 defining a first cubic area and a refrigerator box 14 defining a
second cubic area. In one embodiment, the sum of the first and
second cubic areas is equal to about six (6) cubic feet. In a more
preferred embodiment the sum of the first and second cubic areas is
equal to about eight (8) cubic feet.
[0026] With reference to FIG. 2, the function of a typical
absorption system will now be described. The rich solution leaves
the absorber vessel 210 and passes through the liquid heat
exchanger 212 to the bottom of the pump tube 214. The heat source
(gas or electric) 216 causes the temperature of the solution to
rise. This temperature increase causes ammonia and some water vapor
to be driven out of the solution, forming vapor bubbles which push
columns of liquid up the pump tube. The liquid falls downward
through the rectifier 218 where the temperature is increased
causing additional ammonia vapor to be released. The remaining
liquid is now a weak ammonia solution and flows through the
external shell of the liquid heat exchanger 212 where it transfers
its residual heat to the rich solution and enters the top of the
absorber coil 220 at a reduced temperature.
[0027] The ammonia/water vapor passes through the water separator
222 whose reduced temperature causes any water vapor to liquefy and
join the weak solution in the boiler 224. The ammonia vapor enters
the condenser 226 where it condenses to hot liquid ammonia. The
liquid ammonia enters the tubular coil of the freezer and cabinet
evaporators 228, 230 and wets the internal surface of the
tubes.
[0028] As the weak gas passes over the wetted surface of the
evaporator tubing, the liquid ammonia evaporates into the hydrogen,
creating an initial refrigeration temperature of about -20.degree.
F. The weight of the hydrogen and ammonia mixture is heavier than
that of weak gas. Consequently, it falls through the gas heat
exchanger into the top of the absorber vessel 210. From this point
it enters the bottom of the absorber coil.
[0029] As this mixture travels up through the absorber it contacts
the weak solution entering the top of the absorber from the boiler.
As the weak solution drops through the absorber it absorbs the
ammonia from the ammonia/hydrogen mixture. The relatively pure
hydrogen passes through the hydrogen circuit to the evaporator and
now the rich solution falls to the bottom on the absorber vessel
where the cycle starts again.
[0030] Referring to FIG. 3, the rich ammonia water solution leaves
the absorber vessel 40 and passes through the liquid heat exchanger
to the bottom of the pump tube. The heat source (gas or electric)
44 causes the temperature of the solution to rise. This temperature
increase causes ammonia and some water vapor to be driven out of
the solution, forming vapor bubbles, which push columns of liquid
up the pump tube. The liquid falls downward through the rectifier
46 where the temperature is increased causing additional ammonia
vapor to be released. The remaining liquid is now a weak ammonia
solution and flows through the external shell of the liquid heat
exchanger 42 where it transfers its residual heat to the rich
solution and enters the top of the absorber coil at a reduced
temperature.
[0031] The ammonia/water vapor passes through the water separator
48 whose reduced temperature causes a water vapor to liquefy and
join the weak solution in the boiler 50. The ammonia vapor enters
the condenser 22 where it condenses to hot liquid ammonia. The
liquid ammonia enters the tubular coil of the freezer and cabinet
evaporators 24, 26 and wets the internal surface of the tubes.
Referring to FIGS. 4, 4A and 4B, the increased tube volume of
Applicant's device accommodates the increased weight of the helium
over hydrogen. Smaller heat exchange tubes suitable for hydrogen
provide restriction for the larger helium molecules.
[0032] Additionally, a second heat exchanger 60 is between the
freezer and the cabinet evaporators 24, 26. In one embodiment, the
new heat exchange conduit section 60 includes a first tube 61
having an outer surface 62 and a second tube 63 having an inner
surface 64. The new heat exchange conduit section 60 is connected
"stream wise" into the overall absorption system. The first tube 61
has an outer diameter smaller than the inner diameter of the second
tube 63 so that the first tube can be positioned inside the second
to define a space that has a cross sectional area and a length.
Applicant's have discovered that to meet the ANSI RV refrigeration
standards (i.e., the refrigerator compartment cooled to at least
6.degree. C. (43.degree. F.) and the freezer compartment cooled to
at least -9.degree. C. (15.degree. F.) when the ambient is at
43.degree. C. (110.degree. F.)), the inner diameters of the tubes
have to be substantially modified if helium is used as the
diffusion gas.
[0033] In one embodiment, therefore, the cross sectional area
between the inner surface of the outer tube and the outer surface
of the inner tube is about 200 square millimeters. In another
embodiment, the outer diameter of the inner tube is increased, thus
reducing the cross-sectional area between the inner and outer tubes
by twenty percent (20%). In a more preferred embodiment, the outer
diameter of the inner tube 61 is between about 14 and 16
millimeters and the outer diameter of the outer tube 63 is between
about 25 and 27 millimeters; however, other combinations of inner
and outer tube diameters may be derived that would serve to
compensate for the larger helium molecules. Thus, the evaporator
tubes of the new system are specially sized in proportion to the
other tubes so that the larger gaseous helium molecules are
effective in replacing hydrogen as the diffusion gas.
[0034] The assembly 20, is thus capable of cooling the refrigerator
box 14 to a temperature of 6.degree. C. (43.degree. F.) and the
freezer box 12 to a temperature of -9.degree. C. (15.degree. F.)
when the ambient is at a temperature of 43.degree. C. (110.degree.
F.). The assembly meets applicable ANSI standards.
[0035] The outer and inner surfaces 62, 64 are preferably shaped,
respectively, in a manner to increase their area. The example shown
in FIGS. 4A and 4B may be construed as a serrated shape. Those
skilled in the art will appreciate that any one of a number of
shapes may be formed in the surfaces to increase their surface
area. Fins may be another example of a shape contemplated.
[0036] The shaped outer surface of the tubes increase the surface
area exposed, as shown in FIGS. 4A-4B. As the weak gas passes over
the wetted surface of the evaporator tubing, the liquid ammonia
evaporates into the helium. As the ammonia continues to evaporate
into the helium, the partial pressure of ammonia continues to rise
slowly. As the ammonia pressure rises, the evaporation temperature
also rises.
[0037] The new heat exchanger conduit section 60 of the new system
between the refrigerator and freezer compartments pre-cools the
liquid ammonia before it enters the freezer's evaporators section.
This prevents hot liquid ammonia from injecting heat into the
coldest portion of the evaporator and helps lower the temperature
in the evaporator, which improves the overall cooling
performance.
[0038] As the ammonia continues to evaporate into the helium, the
partial pressure of ammonia continues to rise slowly. As the
ammonia pressure rises the evaporation temperature also rises. This
increase in ammonia partial pressure raises the evaporation
temperature steadily down through the evaporator. The weight of the
helium and ammonia mixture is heavier than that of a weak gas.
Hence, it falls through the gas heat exchanger into the top of the
absorber vessel. From this point it enters the bottom of the
absorber coil.
[0039] As this mixture travels up through the absorber it contacts
the weak solution entering the top of the absorber from the boiler.
As the weak solution drops through the absorber, it absorbs the
ammonia from the ammonia/helium mixture. The relatively pure helium
passes through the helium circuit to the evaporator and now the
rich solution falls to the bottom of the absorber vessel where the
cycle starts again.
[0040] A significant advantage of the new helium charged cooling
system in RV refrigeration applications is the increased safety of
the refrigerator 10. A hydrogen charged gas absorption system may
create a serious fire or explosion if the closed fluid system is
compromised.
[0041] For the purposes of promoting an understanding of the
principles of the invention, specific embodiments have been
described. It should nevertheless be understood that the
description is intended to be illustrative and not restrictive in
character, and that no limitation of the scope of the invention is
intended. Any alterations and further modifications in the
described components, elements, processes, or devices, and any
further applications of the principles of the invention as
described herein, are contemplated as would normally occur to one
skilled in the art to which the invention relates.
* * * * *