U.S. patent application number 12/809639 was filed with the patent office on 2010-12-02 for refrigerating circuit and method of selectively cooling or defrosting an evaporator thereof.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Bernd Heinbokel.
Application Number | 20100300122 12/809639 |
Document ID | / |
Family ID | 40935739 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100300122 |
Kind Code |
A1 |
Heinbokel; Bernd |
December 2, 2010 |
Refrigerating Circuit And Method Of Selectively Cooling Or
Defrosting An Evaporator Thereof
Abstract
A Refrigerating circuit according to the invention comprises a
compressor, a condenser/gas cooler, an expansion device (2), an
evaporator (4), and refrigerant conduits circulating a refrigerant
therethrough. The evaporator (4) comprises refrigerant piping
comprising a plurality of substantially horizontal layers (8, 10)
each layer comprising a plurality of pipes (8a-8h, 10a-10h) the
pipes being substantially perpendicular to an air flow direction
(12) from an air inlet region to an air outlet region of the
evaporator (4). A pipe selected from the group of the second pipe
(8b) to the last but one pipe (8g) in the bottom layer (8) forms
the entry pipe (8c) of the evaporator (4). The entry pipe (8c) is
connectable with the expansion device (2) to provide a
refrigerating mode, and the entry pipe (8c) is connectable with a
hot gas conduit (6) to provide a defrosting mode for the evaporator
(4).
Inventors: |
Heinbokel; Bernd; (Koeln,
DE) |
Correspondence
Address: |
Cantor Colburn LLP - Carrier
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
CARRIER CORPORATION
Farmington
CT
|
Family ID: |
40935739 |
Appl. No.: |
12/809639 |
Filed: |
February 16, 2009 |
PCT Filed: |
February 16, 2009 |
PCT NO: |
PCT/EP09/01062 |
371 Date: |
June 21, 2010 |
Current U.S.
Class: |
62/81 ;
62/498 |
Current CPC
Class: |
F25B 39/02 20130101;
F25B 47/02 20130101 |
Class at
Publication: |
62/81 ;
62/498 |
International
Class: |
F25B 41/00 20060101
F25B041/00; F25B 1/00 20060101 F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2008 |
EP |
PCT/EP2008/001367 |
Claims
1-16. (canceled)
17. Refrigerating circuit comprising a compressor, a condenser/gas
cooler, an expansion device, an evaporator, and refrigerant
conduits circulating a refrigerant therethrough, wherein the
evaporator comprises refrigerant piping comprising a plurality of
substantially horizontal layers each layer comprising a plurality
of pipes the pipes being substantially perpendicular to an air flow
direction from an air inlet region to an air outlet region of the
evaporator, wherein a pipe selected from the group of the second
pipe to the last but one pipe in the bottom layer forms the entry
pipe of the evaporator, wherein the entry pipe is connectable with
the expansion device to provide a refrigerating mode, wherein the
entry pipe is connectable with a hot gas conduit to provide a
defrosting mode for the evaporator, and wherein a first section of
the refrigerant piping of the evaporator comprises the entry pipe
and the pipes on the bottom layer that are downstream of the entry
pipe with regard to the air flow direction.
18. Refrigerating circuit according to claim 17, wherein the hot
gas conduit is a by-pass conduit originating between the compressor
and the expansion device and ending between the expansion device
and the evaporator.
19. Refrigerating circuit according to claim 17, wherein the
refrigerant entry pipe is a pipe in the first half of the
evaporator in the air flow direction.
20. Refrigerating circuit according to claim 17, wherein first
connection elements connect respective adjacent pipes of the first
section of the refrigerant piping of the evaporator, such that in
operation the refrigerant flows in a co-flow relationship with the
air flow direction in the first connection elements.
21. Refrigerating circuit according to claim 17, wherein a second
section of the refrigerant piping of the evaporator comprises the
pipes on the level of and downstream from the entry pipe with
regard to the air flow direction above the bottom layer.
22. Refrigerating circuit according to claim 21, wherein second
connection elements connect the pipes of the second section of the
refrigerant piping of the evaporator, such that in operation the
refrigerant flows in an overall counter-flow relationship with the
air flow direction in the second connection elements.
23. Refrigerating circuit according to claim 17, wherein the first
pipe in the air flow direction in the bottom layer is an exit
pipe.
24. Refrigerating circuit according to claim 21, wherein a third
section of the refrigerant piping of the evaporator comprises the
pipes upstream of the refrigerant entry pipe with regard to the air
flow direction.
25. Refrigerating circuit according to claim 17, wherein the
refrigerant piping of the evaporator comprises 2 or 3 layers.
26. Refrigerating circuit according to claim 17, wherein each layer
of the refrigerant piping of the evaporator comprises 5 to 10
pipes, particularly 6 to 8 pipes.
27. Refrigerating circuit according to claim 17, wherein the
refrigerant entry pipe is the second or third pipe in the air flow
direction in the bottom layer of the refrigerant piping of the
evaporator.
28. Refrigerating circuit according to claim 17, wherein the
refrigerant is
29. Refrigerating circuit according to claim 17, wherein the air
flow in the evaporator is in the refrigerating mode cooled down to
a temperature below 0.degree. C.
30. Refrigerating circuit according to claim 17, wherein the
refrigerating circuit comprises two expansion devices and two
evaporators, a first expansion device and a first evaporator
forming a below 0.degree. C. refrigerating portion of the
refrigerating circuit, the second expansion device and the second
evaporator forming an above 0.degree. C. refrigerating portion of
the refrigerating circuit.
31. Method of selectively cooling or defrosting an evaporator of a
refrigerating circuit, the method comprising: compressing a
refrigerant, flowing the refrigerant through a gas cooler/condenser
and an expansion device, when cooling is selected, or flowing the
refrigerant through a hot gas by-pass conduit, when defrosting is
selected, flowing the refrigerant through refrigerant piping of the
evaporator, the refrigerant piping comprising a plurality of
substantially horizontal layers each layer comprising a plurality
of pipes, and flowing air through the evaporator with the air flow
direction being substantially perpendicular to the orientation of
the pipes, wherein the refrigerant enters the refrigerant piping of
the evaporator at a pipe of the group from the second pipe to the
last but one pipe in the bottom layer, and wherein the refrigerant
flows through a first section of the refrigerant piping of the
evaporator comprising the entry pipe and the pipes on the bottom
layer that are downstream of the entry pipe with regard to the air
flow direction.
Description
[0001] The invention relates to a refrigerating circuit and to a
method of selectively cooling or defrosting an evaporator of a
refrigerating circuit.
[0002] Refrigerating system evaporators having a plurality of
refrigerant pipes are well-known in the art. Refrigerant is flown
through these pipes for effecting a heat exchange with an ambient
air flow. Refrigerant flow direction and air flow direction often
constitute a counter-flow relationship. It is also known to use the
same pipes in a defrosting operation by flowing a hot gas
therethrough. During a defrosting operation, however, the problem
arises that one side of the evaporator (hot gas outlet) is not
fully defrosted and the ice build up at this side remains unmelted.
Moreover, at the other side of the evaporator (hot gas inlet) some
of the water generated in the defrosting procedure normally
evaporates, which leads to heavy ice build-up in parts of the
refrigerating system that are still below 0.degree. C.
Refrigerating systems often comprise a Cu pipe serpentine, which is
for example located in the floor of the refrigerating system, to
which the evaporator is mounted, and helps in the defrosting
operation by carrying hot fluid.
[0003] Accordingly, it would be beneficial to provide a
refrigerating circuit having an evaporator, whose defrosting can be
carried out in an energy-efficient manner.
[0004] Exemplary embodiments of the invention include a
refrigerating circuit comprising a compressor, a condenser/gas
cooler, an expansion device, an evaporator, and refrigerant
conduits circulating a refrigerant therethrough. The evaporator
comprises refrigerant piping comprising a plurality of
substantially horizontal layers, each layer comprising a plurality
of pipes, the pipes being substantially perpendicular to an air
flow direction from an air inlet region to an air outlet region of
the evaporator. A pipe selected from the group of the second pipe
to the last but one pipe in the air flow direction in the bottom
layer forms the entry pipe of the evaporator. The entry pipe is
connectable with the expansion device to provide a refrigerating
mode, and the entry pipe is connectable with a hot gas conduit to
provide a defrosting mode for the evaporator.
[0005] Exemplary embodiments of the invention further include a
method of selectively cooling or defrosting an evaporator of a
refrigerating circuit, the method comprising the steps of
compressing a refrigerant; flowing the refrigerant through a gas
cooler/condenser and an expansion device, when cooling is selected,
or flowing the refrigerant through a hot gas by-pass conduit, when
defrosting is selected; flowing the refrigerant through refrigerant
piping of the evaporator, the refrigerant piping comprising a
plurality of substantially horizontal layers, each layer comprising
a plurality of pipes; and flowing air through the evaporator with
the air flow direction being substantially perpendicular to the
orientation of the pipes. The refrigerant enters the refrigerant
piping of the evaporator at a pipe of the group from the second
pipe to the last but one pipe in the bottom layer.
[0006] Embodiments of the invention are described in greater detail
below with reference to the Figures wherein:
[0007] FIG. 1 shows a schematic of an exemplary evaporator and its
integration in a refrigerating circuit in accordance with the
present invention.
[0008] FIG. 1 shows a portion of a refrigerating circuit in
accordance with an embodiment of the present invention in a
schematic manner. As the compressor and the condenser/gas cooler
are well-known elements in the art, they have been omitted from
FIG. 1 for easy readability.
[0009] The evaporator 4 is shown in detail. It comprises two layers
(8, 10) of refrigerant pipes (8a-8h, 10a-10h). As such evaporators
are often disposed in the floor region of a refrigerating sales
furniture, for example an island freezer, layer 8 is hereinafter
also referred to as the bottom layer, whereas layer 10 is
hereinafter also referred to as the top layer. Each layer comprises
eight refrigerant pipes, which are shown as circles giving their
representation a cross-sectional appearance, which indicates that
the pipes run perpendicular to the drawing plane. The pipes are
numbered with regard to the air flow direction 12, which is from
left to right in the schematic of FIG. 1. 8a is the first pipe with
regard to the air flow direction, 8b the second pipe, . . . , and
8h is the eighth and last pipe with regard to the air flow
direction. An analogous numbering is adhered to for the top layer
10.
[0010] The refrigerant pipes are interconnected by connection
elements, which are schematically depicted by solid lines and
dashed lines. The solid lines represent connection elements that
are disposed towards the user from the drawing plane, whereas the
dashed lines represent connection elements behind the drawing
plane. In this manner, the pipes 8a to 8h and 10a to 10h combine
with the connection elements to form a refrigerant serpentine whose
long legs run back and forth through the drawing plane. This piping
is used to flow a refrigerant through the evaporator, with the
detailed description of the connection setup and the resulting
refrigerant flow given below.
[0011] The third pipe with regard to the air flow direction 12 in
the bottom layer 8, i.e. pipe 8c, hereinafter also referred to as
entry pipe, is in connection to an evaporator inlet section 14 of
the refrigerant conduits. Said evaporator inlet section is
selectively connected to a hot gas conduit 6 or the expansion
device 2 of the refrigerating circuit. According means (not shown)
for enabling a flow connection between the evaporator inlet section
14 and either the expansion device 2 or the hot gas conduit 6 and
blocking the respective other of the expansion device 2 and the hot
gas conduit 6 are well-known in the art and therefore not described
in detail. The connection with the expansion device 2 is selected
for a refrigerating mode, whereas the connection with the hot gas
conduit 6 is selected for a defrosting mode.
[0012] In the embodiment shown in FIG. 1 the hot gas conduit 6
originates between the compressor and the condenser/gas cooler.
Thus, it establishes a by-pass conduit, diverting the refrigerant
after its compression and before its cooling in the condenser/gas
cooler from the conventional refrigerating circuit. It is apparent
that the junction between the compressor and the condenser/gas
cooler may comprise appropriate means for guiding the refrigerant
either into the hot gas conduit 6 or towards the condenser/gas
cooler. The hot gas conduit 6 may also comprise an expansion device
for controlling the temperature/pressure of the refrigerant upon
entering the evaporator 4 in the defrosting mode.
[0013] As mentioned above, the refrigerant enters the evaporator 4
at the entry pipe 8c. From there it is flown through a first
section 18 of the refrigerant piping of the evaporator 4. The first
section comprises the pipes 8c, 8d, . . . , 8g, and 8h, which are
the entry pipe 8c and all pipes on the bottom layer that are
downstream thereof. These pipes are interconnected by first
connection elements 20. The refrigerant is flown substantially
perpendicular to the air flow direction in the pipes and
substantially in a co-flow relationship with the air flow direction
12 in the first connection elements 20 towards the end of the
evaporator 4.
[0014] From pipe 8h the refrigerant is flown through the second
section 22 of the refrigerant piping of evaporator 4. The second
section 22 of refrigerant piping comprises the pipes on the top
layer from the end of the evaporator 4 to the pipe that is on the
same level as the entry pipe with regards to the air flow direction
12, in this embodiment the pipe 10c. The pipes of the second
section 22 of the refrigerant piping are interconnected by second
connection elements 24. The refrigerant flow in the pipes 10c to
10h of the second section 22 of refrigerant piping is substantially
perpendicular to the air flow direction 12. The refrigerant flow in
the second connection elements 24 exhibits a substantially
counter-flow relationship with the air flow direction 12.
[0015] From pipe 10c the refrigerant is flown through a third
section 26 of the refrigerant piping of evaporator 4, which is--in
refrigerant flow direction--comprised of the pipes 8b, 10b, 10a,
and 8a. Accordingly, pipe 8a is the exit pipe of the evaporator. It
is connected to the evaporator outlet section 16 of the refrigerant
conduits, which leads the refrigerant back to the compressor.
[0016] The above-described structure of the evaporator 4 according
to an exemplary embodiment of the invention has a number of
implications for the defrosting and the refrigerating modes. In the
refrigerating mode it is the primary objective to generate a heat
transfer between the refrigerant and the air flow that is as
efficient as possible. The counter-flow relationship between the
refrigerant and the air flow direction 12 in the second section 22
of the refrigerant piping provides for very good heat transfer
conditions. Moreover, the third section 26 of the refrigerant
piping provides for an extended region, where the refrigerant is at
its warmest in the evaporator and the air flow is also at its
warmest right after entering the evaporator 4. This set-up provides
for a maximum heating of the refrigerant and thus for a maximum
heat transfer from the air flow before the refrigerant leaves the
evaporator 4 through the exit pipe 8a. In the case that the
refrigerant has been evaporated in the first or second section (18,
22) of the refrigerant piping, the third section 26 allows for a
maximum amount of super-heating of the gaseous refrigerant.
[0017] In the defrosting mode the above-described structure of the
evaporator 4 is particularly efficient for a number of reasons. In
the exemplary embodiment of FIG. 1, the hot refrigerant, after
by-passing the condenser/gas cooler and the expansion device 2,
enters the evaporator 4 at entry pipe 8c. At the point of entry the
refrigerant is the warmest and has the biggest effect in melting
the ice build-up in the evaporator 4. Thus, the region around the
entry pipe 8c and the downstream portion thereof in the bottom
layer receive the most heat, especially in the beginning stages of
the defrosting operation. An advantageous effect thereof is that
the support structure to which the evaporator 4 is attached, for
example the floor portion of an island freezer, is warmed up
starting in the middle region and expanding to the sides. A warming
of the support structure at an early stage of the defrosting
operation prevents a scenario wherein ice is melted somewhere in
the evaporator 4 and the water is re-frozen at the support
structure, when supposed to drain out of the evaporator 4. The
set-up provides for the support structure, which may be slightly
inclined, to be an ideal gutter for water generated by melting the
ice in all parts of the evaporator 4 at later stages of the
defrosting operation. Another advantage is that water vapour which
may be generated around the entry pipe 8c, where continuous heating
is effected by flowing hot fluid through the refrigerant piping,
cannot easily leave the evaporator 4 and re-freeze in other parts
of the refrigerating system, where the temperature is still below
0.degree. C. In other words, instead of generating ice build-up
outside of the evaporator 4, the water vapour helps in defrosting
the evaporator 4 from the middle region towards the sides.
[0018] The foregoing discussion shows that the evaporator 4 of the
exemplary embodiment of the invention in FIG. 1 has a structure
that allows for extremely energy-efficient defrosting of the
evaporator 4. This even allows basing the defrosting of the
evaporator solely on the by-pass conduit, when CO.sub.2 is used as
a refrigerant. The refrigerant piping of the evaporator 4 of the
exemplary embodiment is not designed in a way to sustain CO.sub.2
in a liquid phase. That means that, when CO.sub.2 is used as
refrigerant, the condensation energy is not at the disposal of the
defrosting process, which is compensated for by the
energy-efficient layout of the evaporator 4.
[0019] As mentioned before, the hot gas conduit 6 may be a by-pass
conduit to the refrigerating circuit. It may also be part of an
independent defrosting circuit. It is apparent that in addition to
the flow switching means between the expansion device 2 and the hot
gas conduit 6, second guiding means would be necessary to direct
the fluid coming out of the evaporator 4 into the defrosting
circuit or the refrigerant circuit. The defrosting circuit would in
that case need additional means for generating fluid circulation,
for example a compressor.
[0020] The hot gas conduit 6 may carry a fluid in a liquid or
gaseous state to the evaporator, depending on the specific
embodiment of the invention.
[0021] Instead of comprising two layers the evaporator 4 may
comprise three or more layers as well. This would lead to some
changes as to how the pipes are connected with connection elements.
Assume an evaporator having the two layers 8 and 10, as depicted,
as well as an additional third layer. Assume that the eight pipes
of the third layer are denoted 30a, 30b, . . . , 30g, and 30h, in
analogy with the first layer 8 and the second layer 10. The first
section 18 of the refrigerant piping would have the same structure
as in the exemplary embodiment of FIG. 1. However, the second
section 22 of the refrigerant piping would have a fairly different
layout. It would comprise the pipes 10c to 10h of the intermediate
layer and the pipes 30c to 30h of the third layer. A plurality of
options can be thought of as to how to connect these pipes with
each other. A first option would be connecting--in refrigerant flow
direction--pipes 10a, 30h, 10b, 30g, 10f, etc., forming a kind of
sawtooth wave shape of the connection elements.
[0022] Another option would be connecting--in refrigerant flow
direction--pipes 10h, 30h, 30g, 10g, 10f, 30f, etc., forming a kind
of square wave shape of the connection elements. Both options have
in common that the refrigerant flows in a generally counter-flow
relationship with respect to the air flow direction 12 in the
second section 22 of the refrigerant piping. Additional options,
for example options combining the two above-described ways of
connecting the individual pipes, can be thought of. It is apparent
that the connection options increase with the number of layers of
refrigerant pipes. As far as the third section 26 of the
refrigerant piping is concerned, a lot of options for connections
starting at the last pipe of the second section 22, i.e. either 10c
or 30c, to the exit pipe 8a exist. As is clear from simple
geometric considerations, there is no possibility of connecting all
pipes without any connection elements exhibiting co-flow
relationship with the air flow direction 12. Therefore, a lot of
secondary considerations are left to be considered by the designer
when establishing the connection element layout.
[0023] Exemplary embodiments of the invention, as described above,
allow for energy-efficient cooling of the air flow through an
evaporator in a refrigerating mode as well as for energy-efficient
defrosting of said evaporator in a defrosting mode. Introducing the
hot gas into a pipe in the middle portion of the bottom layer of
the evaporator in the defrosting mode provides for a number of
advantages. The region around the point of entry of the hot gas
will be heated most and will be defrosted quickest. Therefore, the
support structure, to which the evaporator is mounted, will be
defrosted in the beginning stages of a defrosting operation and
thus will provide for an ice-free surface, which is ideal for
receiving and draining the water that is generated throughout the
defrosting process. Moreover, the water vapour, which is generated
in the most heated portion of the evaporator during the defrosting
process, will not be able to leave the evaporator, as it will not
stay a vapour on its way to the end portions of the evaporator.
Thus, energy losses due to the heated vapour leaving the evaporator
to be defrosted are minimized and ice built-up in other parts of
the refrigerating system, caused by said water vapour, is
prevented. These aspects allow for a highly efficient defrosting of
the evaporator, eliminating the need for or at least reducing the
extent of additional means for defrosting in the support structure
or in the evaporator itself. This even holds true, when CO.sub.2 is
used as the hot gas in the defrosting operation, which is
fundamentally less attractive for use in defrosting, as no
condensation takes place at pressures common to these evaporators.
The defrosting operation in a refrigerant circuit in accordance
with an embodiment of the invention is so energy-efficient that
shorter defrosting times can be achieved than with electric
defrosting. This time duration advantage is paired with the overall
simplification of not having an additional electric defrosting
system integrated into a refrigerating system.
[0024] In a further embodiment of the invention, the hot gas
conduit is a by-pass conduit originating between the compressor and
the expansion device and ending between the expansion device and
the evaporator. This structure allows for using the same fluid for
the refrigerating operation as well as for the defrosting
operation, which is very cost-efficient. It also eliminates the
need for having a full second fluid circuit for the fluid of the
defrosting operation and eliminates the need for ensuring a strict
separation of the refrigerating fluid and the defrosting fluid.
This layout also allows for a minimum amount of piping used and
thus for a very compact design of the refrigerating circuit.
[0025] Furthermore, the refrigerant entry pipe may be a pipe in the
first half of the evaporator in the air flow direction. It is also
possible that a first section of the refrigerant piping of the
evaporator comprises the entry pipe and the pipes on the bottom
layer that are downstream of the entry pipe with regard to the air
flow direction. This allows for an early and thorough heating of
the bottom region of the evaporator in the defrosting process,
which is beneficial to the draining of the melted water during the
later stages of the defrosting. This first section leaves the
beginning of the evaporator in the air flow direction out, which
leaves the option of flowing the refrigerant therethrough shortly
before leaving the evaporator, which in turn is beneficial in the
refrigerating mode. Therefore, this layout is a good basis for
achieving an excellent trade-off between the refrigerating and the
defrosting modes.
[0026] It is furthermore possible that first connection elements
connect respective adjacent pipes of the first section of the
refrigerant piping of the evaporator, such that in operation the
refrigerant flows in a co-flow relationship with the air flow
direction in the first connection elements. This allows for an
advantageous heating of the bottom layer, and therefore of the
underlying support structure, from a middle region towards an end
region of the evaporator.
[0027] In another embodiment of the invention, a second section of
the refrigerant piping of the evaporator comprises the pipes on the
level of and downstream from the entry pipe with regard to the air
flow direction above the bottom layer. It is also possible that
second connection elements connect the pipes of the second section
of the refrigerant piping of the evaporator, such that in operation
the refrigerant flows in an overall counter-flow relationship with
the air flow direction in the second connection elements. This
allows for using an advantageous counter-flow relationship between
the refrigerant and the air flow in the refrigerating mode. This
layout furthermore allows for implementing the beneficial
counter-flow for one or a plurality of layers above the bottom
layer, i. e. in the second section of the refrigerant piping.
[0028] Moreover, it is possible that the first pipe in the air flow
direction in the bottom layer is an exit pipe. This exit pipe may
be connected to an evaporator outlet section of the refrigerant
conduits. Having the refrigerant leave the evaporator in the first
pipe in the air flow direction in the bottom layer ensures that the
refrigerant flows last through the inlet region of the evaporator
with regard to the air flow. In the refrigerating mode, this leads
to a region of heat exchange between the air flow and the
refrigerant, when they are both in their warmest state throughout
the evaporator. This allows for the maximum amount of superheating
of the refrigerant, when in gaseous form already, which provides
for maximum use of the energetic capacity of the refrigerant in the
refrigerating process.
[0029] In a further embodiment, a third section of the refrigerant
piping of the evaporator comprises the pipes upstream of the
refrigerant entry pipe with regard to the air flow direction. This
allows for an extended region of heat transfer between the air flow
and the refrigerant, where they are both at their substantially
warmest in the refrigerating mode. It allows for that region to
include all layers, forming a heat exchange region with above
described properties across the hole cross-section of the air
flow.
[0030] The refrigerant piping of the evaporator may comprise two or
three layers. An evaporator having four, five or more layers can
also be thought of. Each layer of the refrigerant piping of the
evaporator may comprise five to ten pipes, particularly six to
eight pipes. These numbers of pipes have been found to be
beneficial for an efficient heat exchange both in the refrigerating
and the defrosting mode. Depending on the application, less than
five pipes or more than ten pipes may also constitute a good layer
size.
[0031] In a further embodiment, the refrigerant entry pipe is the
second or third pipe in the air flow direction in the bottom layer
of the refrigerant piping of the evaporator. This allows for the
hot gas entering the evaporator towards the middle in the
refrigerating mode, advantageously heating the middle portion of
the bottom region of the evaporator first in a defrosting mode. It
also leaves room for having a heat exchange area of relatively warm
refrigerant and relatively warm air flow in the beginning of the
evaporator with regard to the air flow direction, when the system
is operated in the refrigerating mode.
[0032] The refrigerant may be CO.sub.2. It can also be R22 or R404A
or any other refrigerant suitable to the refrigerating circuit.
[0033] In an exemplary embodiment, the air flow in the evaporator
is in the refrigerating mode cooled down to a temperature below
0.degree. C. In other words, the invention is suitable for freezers
and below 0.degree. C. refrigerating systems, where defrosting is a
big issue.
[0034] It is also possible that the refrigerating circuit comprises
two expansion devices and two evaporators, a first expansion device
and a first evaporator forming a below 0.degree. C. refrigerating
portion of the refrigerating circuit, the second expansion device
and the second evaporator forming an above 0.degree. C.
refrigerating portion of the refrigerating circuit. Accordingly,
the invention can be applied to a dual system including a freezer
and a refrigerator. In this case, the defrosting may be carried out
on the freezing portion or on the refrigerating portion or on both
portions. It is apparent that according piping and according
compressing means will be necessary.
[0035] With the method of selectively cooling or defrosting an
evaporator of a refrigerating circuit according to exemplary
embodiments of the invention, as described above, the same
advantages can be attained as with the refrigerating circuit. This
method can be developed further by method steps corresponding to
the features as described with regard to the refrigerating circuit.
In order to avoid redundancy such embodiments and developments of
the method of selectively cooling or defrosting an evaporator of a
refrigerating circuit are not repeated.
[0036] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
REFERENCE NUMERALS
[0037] 2 Expansion device [0038] 4 Evaporator [0039] 6 Hot gas
conduit [0040] 8 Bottom layer of refrigerant piping of evaporator
[0041] 10 Top layer of refrigerant piping of evaporator [0042] 12
Air flow direction [0043] 14 Evaporator inlet section of
refrigerant conduits [0044] 16 Evaporator outlet section of
refrigerant conduits [0045] 18 First section of refrigerant piping
of evaporator [0046] 20 First connection elements [0047] 22 Second
section of refrigerant piping of evaporator [0048] 24 Second
connection elements [0049] 26 Third section of refrigerant piping
of evaporator
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