U.S. patent application number 11/908622 was filed with the patent office on 2008-10-23 for condensate heat transfer for transcritical carbon dioxide refrigeration system.
This patent application is currently assigned to CARRIER COMMERCIAL REFRIGERATION, INC.. Invention is credited to Yu Chen, Hans-Joachim Huff, Tobias H. Sienel, Parmesh Verma.
Application Number | 20080256974 11/908622 |
Document ID | / |
Family ID | 37024106 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080256974 |
Kind Code |
A1 |
Verma; Parmesh ; et
al. |
October 23, 2008 |
Condensate Heat Transfer for Transcritical Carbon Dioxide
Refrigeration System
Abstract
A bottle cooler system includes means for using atmospheric
water condensate from the evaporator to draw heat from the
condenser.
Inventors: |
Verma; Parmesh; (Manchester,
CT) ; Sienel; Tobias H.; (East Hampton, MA) ;
Huff; Hans-Joachim; (West Hartford, CT) ; Chen;
Yu; (East Hartford, CT) |
Correspondence
Address: |
BACHMAN & LAPOINTE, P.C. (UTC)
900 CHAPEL STREET, SUITE 1201
NEW HAVEN
CT
06510-2802
US
|
Assignee: |
CARRIER COMMERCIAL REFRIGERATION,
INC.
Charlotte
NC
|
Family ID: |
37024106 |
Appl. No.: |
11/908622 |
Filed: |
December 30, 2005 |
PCT Filed: |
December 30, 2005 |
PCT NO: |
PCT/US05/47526 |
371 Date: |
September 14, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60663912 |
Mar 18, 2005 |
|
|
|
Current U.S.
Class: |
62/498 |
Current CPC
Class: |
F25D 21/14 20130101;
F25D 2317/0661 20130101; F25B 2339/047 20130101; F25D 2323/00264
20130101; F25B 6/04 20130101; F25D 2321/147 20130101; F25B 9/008
20130101; F25D 2317/0651 20130101; F25D 31/007 20130101; F25D
2323/00271 20130101; F25B 2339/041 20130101; F25D 2321/146
20130101; F25D 23/003 20130101; F25D 19/02 20130101 |
Class at
Publication: |
62/498 |
International
Class: |
F25B 1/00 20060101
F25B001/00 |
Claims
1. A cooler system comprising: a compressor (22) for driving a
refrigerant along a flow path in at least a first mode of system
operation; a first heat exchanger (102) along the flow path
downstream of the compressor in the first mode so as to act as a
condenser; a second heat exchanger (28) along the flow path
upstream of the compressor in the first mode so as to act as an
evaporator to cool contents of an interior volume of the system;
and means for using atmospheric water condensate from the second
heat exchanger to draw heat from a downstream portion of the first
heat exchanger.
2. The system of claim 1 wherein the means comprises: immersion of
said downstream portion (106) of the first heat exchanger (102) in
a drain pan (122) of the second heat exchanger (28).
3. The system of claim 1 wherein the means comprises at least one
of: a wick conveying the water condensate to said downstream
portion; a wick conveying the water condensate to an airflow
flowing over said downstream portion; at least a first subportion
of the downstream portion of the first heat exchanger extending
upward to receive a flow of the water condendsate and guide said
flow to a drain pan; and at least a first subportion of the
downstream portion of the first heat exchanger extending upward to
receive a flow of the water condensate and guide said flow to a
drain pan with a second subportion in the pan.
4. The system of claim 1 wherein the means comprises: a sprayer for
spraying the water condensate onto the first heat exchanger.
5. The system of claim 1 wherein the means comprises: a counterflow
heat exchange between refrigerant and a flow of the water
condensate.
6. The system of claim 1 being a self-contained externally
electrically powered beverage cooler positioned outdoors.
7. The system of claim 1 wherein: the refrigerant comprises, in
major mass part, CO.sub.2; and the first and second heat exchangers
are refrigerant-air heat exchangers.
8. The system of claim 1 wherein: the refrigerant consists
essentially of CO.sub.2; and the first and second heat exchangers
are refrigerant-air heat exchangers each having an associated fan,
an air flow across the first heat exchanger being an external to
external flow and an airflow across the second heat exchanger being
a recirculating internal flow.
9. The system of claim 1 in combination with said contents which
include: a plurality of beverage containers in a 0.3-4.0 liter size
range.
10. The system of claim 9 being selected from the group consisting
of: a cash-operated vending machine; a transparent door front,
closed back, display case; and a top access cooler chest.
11. The system of claim 1 being a transcritical system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Benefit is claimed of U.S. Patent Application 60/663,912,
entitled "CONDENSATE HEAT TRANSFER FOR TRANSCRITICAL CARBON DIOXIDE
REFRIGERATION SYSTEM" and filed Mar. 18, 2005. Copending
application docket 05-258, entitled HIGH SIDE PRESSURE REGULATION
FOR TRANSCRITICAL VAPOR COMPRESSION SYSTEM and filed on even date
herewith, discloses prior art and inventive cooler systems. The
present application discloses possible modifications to such
systems. The disclosures of said applications are incorporated by
reference herein as if set forth at length.
BACKGROUND OF THE INVENTION
[0002] The invention relates to refrigeration. More particularly,
the invention relates to beverage coolers.
[0003] As a natural and environmentally benign refrigerant,
CO.sub.2 (R-744) is attracting significant attention. In most
air-conditioning operating ranges, CO.sub.2 systems operate in
transcritical mode. An example of a transcritical vapor compression
system utilizing CO.sub.2 as working fluid comprises a compressor,
a gas cooler, an expansion device, an evaporator and the like (see
FIG. 1). The major difference between transcritical and
conventional operation is that heat rejection in the gas cooler is
in the supercritical region because the critical temperature for
CO.sub.2 is 87.8 F. Consequently, pressure is not solely dependent
on temperature and this opens additional control and optimization
issues for system operation.
[0004] FIG. 1 schematically shows transcritical vapor compression
system 20 utilizing CO.sub.2 as working fluid. The system comprises
a compressor 22, a gas cooler 24, an expansion device 26, and an
evaporator 28. The exemplary gas cooler and evaporator may each
take the form of a refrigerant-to-air heat exchanger. Airflows
across one or both of these heat exchangers may be forced. For
example, one or more fans 30 and 32 may drive respective airflows
34 and 36 across the two heat exchangers. A refrigerant flow path
40 includes a suction line extending from an outlet of the
evaporator 28 to an inlet 42 of the compressor 22. A discharge line
extends from an outlet 44 of the compressor to an inlet of the gas
cooler. Additional lines connect the gas cooler outlet to expansion
device inlet and expansion device outlet to evaporator inlet.
[0005] An electronic expansion valve is usually used as the device
26 to control the high side pressure to optimize the COP of the
CO.sub.2 vapor compression system. An electronic expansion valve
typically comprises a stepper motor attached to a needle valve to
vary the effective valve opening or flow capacity to a large number
of possible positions (typically over one hundred). This provides
good control of the high side pressure over a large range of
operating conditions. The opening of the valve is electronically
controlled by a controller 50 to match the actual high side
pressure to the desired set point. The controller 50 is coupled to
a sensor 52 for measuring the high side pressure.
[0006] As the airflow 36 passes over the heat exchanger 28, cooling
of the airflow 36 causes the condensation of water out of that
airflow. Disposal of that water may need to be addressed. One way
involves using the heat rejection heat exchanger to heat the water
to induce its evaporation. An example of such a system 60 is shown
in FIG. 2.
[0007] In the illustrated system 60, components similar to those of
the system 20 are shown with like numerals. For illustration, the
control and sensor components are hidden. The gas cooler 62 is
split into first and second sections 64 and 66. Along the
refrigerant flowpath 66, the first section 64 is upstream of the
second section 66. The sections 64 and 66 may be along a common air
flowpath to receive a common airflow 68 (e.g., driven by a fan 70)
or may be on separate air flowpaths (e.g., driven by separate
fans). If on a common air flowpath, the first section may be
upstream/downstream of the second section.
[0008] Water condensed from the airflow 36 is collected by a
collection system 80. An exemplary system 80 includes a pan 82 to
which the water is delivered. A portion of the first section 64 is
positioned to be immersed in a water accumulation in the pan.
Heating of the water by the first section 64 encourages evaporation
of the water.
SUMMARY OF THE INVENTION
[0009] For advantageous performance, however, the condensate may
preferably be exposed to a more downstream section of the heat
rejection heat exchanger. A bottle cooler system includes means for
using atmospheric water condensate from the evaporator to draw heat
from the condenser.
[0010] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic view of a prior art refrigeration
system.
[0012] FIG. 2 is a schematic view of another prior art
refrigeration system.
[0013] FIG. 3 is a schematic view of an inventive refrigeration
system.
[0014] FIG. 4 is a side schematic view of a display case bottle
cooler including a refrigeration and air management cassette.
[0015] FIG. 5 is a view of a refrigeration and air management
cassette.
[0016] FIG. 6 is a partial side schematic view of an alternative
cassette.
[0017] FIG. 7 is a partial side schematic view of an alternative
cassette.
[0018] FIG. 8 is a partial side schematic view of an alternative
cassette.
[0019] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0020] FIG. 3 shows a system 100 having a compressor 22, expansion
device 26, and heat absorption heat exchanger (evaporator) 28.
These may be similar to corresponding components of the systems of
FIGS. 1 and 2. For illustration, the control and sensor components
are hidden. The gas cooler 102 is split into first and second
sections 104 and 106. Along the refrigerant flowpath 66, the first
section 104 is upstream of the second section 106. The sections 104
and 106 may be along a common air flowpath to receive a common
airflow 108 (e.g., driven by a fan 110) or may be on separate air
flowpaths (e.g., driven by separate fans). In the exemplary system,
the first section 104 is upstream of the second section 106 with
the fan 110 intervening.
[0021] Water condensed from the airflow 36 is collected by a
collection system 112. An exemplary system 112 includes a pan 122
to which the water is delivered. A portion of the second section
106 is positioned to be immersed in a water accumulation in the pan
122. Heating of the water by the second section 64 may encourage
evaporation of the water. Contrasted with the system of FIG. 2, the
section of the gas cooler which gives up heat to the condensate is
relatively downstream along the refrigerant flow path (e.g., in the
cooler half or quarter of the temperature drop prior to the
expansion device). This is intended to reduce the refrigerant
temperature as much as possible by exposing the coldest refrigerant
to the condensate. For a transcritical CO.sub.2 refrigeration
system, to maintain peak efficiencies it is critical to minimize
the temperature at the exit of the high-side (gas cooler) heat
exchanger.
[0022] It is even more critical to minimize this exit temperature
for a CO.sub.2 bottle cooler refrigeration system. Manufacture
costs are of particular concern. The result is that low
cost/relatively lower efficiency heat exchangers (including but not
limiting to wire-on-tube heat exchanger, plate-on-tube heat
exchanger, finless heat exchanger etc.) are particularly useful for
to control bottle cooler manufacture costs.
[0023] Thus, a particular area for implementation of the condensate
heat exchange is in bottle coolers, including those which may be
positioned outdoors or must have the capability to be outdoors
(presenting large variations in ambient temperature). FIG. 4 shows
an exemplary cooler 200 having a removable cassette 202 containing
the refrigerant and air handling systems. The exemplary cassette
202 is mounted in a compartment of a base 204 of a housing. The
housing has an interior volume 206 between left and right side
walls, a rear wall/duct 216, a top wall/duct 218, a front door 220,
and the base compartment. The interior contains a vertical array of
shelves 222 holding beverage containers 224.
[0024] The exemplary cassette 202 draws the air flow 108 through a
front grille in the base 224 and discharges the air flow 108 from a
rear of the base. The cassette may be extractable through the base
front by removing or opening the grille. The exemplary cassette
drives the air flow 36 on a recirculating flow path through the
interior 206 via the rear duct 210 and top duct 218.
[0025] FIG. 5 shows further details of an exemplary cassette 202.
The heat exchanger 28 is positioned in a well 240 defined by an
insulated wall 242. The heat exchanger 28 is shown positioned
mostly in an upper rear quadrant of the cassette and oriented to
pass the air flow 36 generally rearwardly, with an upturn after
exiting the heat exchanger so as to discharge from a rear portion o
the cassette upper end. A drain 250 may extend through a bottom of
the wall 242 to pass water condensed from the flow 36 to the drain
pan 122. A water accumulation 254 is shown in the pan 122. The pan
122 is along an air duct 256 passing the flow 108 downstream of the
heat exchanger first section 104. The heat exchanger second section
106 is positioned to be at least partially immersed in the
accumulation 254. Exposure of the accumulation 254 to the immersed
second section 106 and to the heated air in the flow 108 may
encourage evaporation.
[0026] In an exemplary, coil routing of the second section 106, the
second section is divided into a first portion normally above the
accumulation and in the airflow 108 and a second portion normally
immersed. The refrigerant flow path may pass generally downstream
along the air flow 108 through the first portion and then pass into
the second portion before proceeding to the expansion device.
[0027] The FIG. 5 arrangement is consistent with a basic
reengineering of a baseline cassette having a single heat rejection
heat exchanger located where the first section 104 is and nothing
where the second section 106 is. It is also consistent with a
reengineering of a split system where the hotter section is in that
latter position. However, the illustrated configuration has the
disadvantage that the cooler section is downstream of the hotter
section along the air flow path. Accordingly, it may be desirable
to reverse the air flow to become back-to-front. A portion of this
back-to-front air flow could be directed to flow over the cooler
door window to avoid window fogging.
[0028] An alternative implementation might eliminate the physical
separateness of the first section 104. One example would be to only
have a single heat rejecting heat exchanger unit positioned as
represented by the second section 106 in FIG. 5. The immersed
portion of that exchanger unit could serve the role of the second
section 106 while the exposed portion could serve the role of the
first section 104 (see FIG. 6 below). Another simple variation
could involve heat exchanger positioning so that water dripping
from the drain flows over a leading portion of the heat exchanger
(i.e., at the upstream end of the warm air flow).
[0029] Various implementations may further maximize heat transfer
via a counterflow exchange of condensate water and the refrigerant.
This counterflow may be the exclusive method of heat exchange
between the condensate and the refrigerant, or may supplement pan
immersion or another mechanism. FIG. 6 shows such a system, wherein
the drain 250 having an outlet 260. A length 262 of the refrigerant
line extends upward to the outlet. The length 262 is positioned to
guide/wick droplets of water from the outlet 260 downwardly along
the length 262 to the drain pan. With refrigerant flowing upward
through the length 324, the refrigerant and water are in
counterflow heat exchange. A more upstream (along the refrigerant
flow path) length 264 (or portion of the heat rejection heat
exchanger) may be immersed in the water 254 in the pan. a yet more
upstream portion 270 may be in the air flow
[0030] In another example of a supplementary situation, a
relatively small downstream section of the gas cooler may run
through/in the drain pan 122. A smaller yet more downstream portion
may run up into the to evaporator drain in a counterflow heat
exchange (both along its length and/or merely a two step
counterflow in combination with the portion in the pan). In the
FIG. 7 example, the drain 250 is replaced by a more convoluted
drain 300. The drain 300 has an upwardly directed U-portion 302
defining a water trap containing a water slug 304. The drain 300
and slug 304 may prevent air leakage between the hot and cold air
flows and might be used independently in place of the simpler drain
250. The slug is continuously replenished by condensate flowing
into the drain 300 and continuously discharges condensate down
toward the pan 122. A portion 306 of the refrigerant line extends
from a remainder of the second section 106 and through the drain
300. The expansion device (not shown) may be positioned between the
downstream end of the line portion 306 and the evaporator 28. Thus
refrigerant flowing through the line portion 306 is in counterflow
heat exchange with the condensate flowing through the drain 300.
Although shown piercing the drain 300, the line portion 306 may
enter the drain outlet 308 and/or exit the drain inlet 310 and more
closely follow the path of the drain.
[0031] FIG. 8 shows an alternate drain 320 having an outlet 322. A
length 324 of the refrigerant line extends upward to the outlet.
The length 324 is positioned to guide/wick droplets of water from
the outlet 322 downwardly along the length 324 to the drain pan.
With refrigerant flowing upward through the length 324, the
refrigerant and water are in counterflow heat exchange. A more
upstream (along the refrigerant flow path) portion of the heat
rejection heat exchanger may be immersed in the water in the
pan.
[0032] In other implementations, the condensate could be delivered
to air flow (e.g., 108) just prior to its passing over the last
portion of the heat rejecting heat exchanger (i.e., the gas cooler
which would be a condenser if conditions were appropriate) so that
the heat transfer is enhanced and hence the refrigerant temperature
is reduced. This may be particularly effective in dry climates
where evaporative cooling of the air flow is particularly
relevant.
[0033] This condensate to air delivery could be done in several
ways. A wick could be placed upstream of the relevant section of
the heat exchanger along the air flow. A spray device could be
similarly positioned to introduce the spray of condensate to the
air flow. Such a spray could also or alternatively directly contact
the relevant heat exchanger portion to cool via evaporative or
conventional cooling. Similarly, a wick could contact the heat
exchanger to transport the water and provide conventional and/or
evaporative cooling.
[0034] Thus, it is seen that for transcritical bottle cooler
applications, the water being condensed on evaporator surfaces is
useful for refrigerant cooling to maintain efficiency. This
approach especially provides additional efficiency for low cost,
fouling resistant, heat exchangers like wire-on-tube,
plate-on-tube, finless heat exchangers, and the like. This may
enable performance comparable to high efficiency finned-tube
conventional heat exchangers currently being used for bottle cooler
applications. The protective coating typically present on low cost
heat exchangers (wire-on-tube, plate-on-tube, etc.) may provide
effective resistance to corrosion from the condensate to which the
heat exchanger is exposed.
[0035] One or more embodiments of the present invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. For example, when implemented as a
remanufacturing of an existing system or reengineering of an
existing system configuration, details of the existing
configuration may influence details of the implementation.
Exemplary baseline systems could be transcritical CO2 systems or
could have other operational domains and/or other refrigerants.
Accordingly, other embodiments are within the scope of the
following claims.
* * * * *