US20070056312A1

US20070056312A1 - Cooling System

Info

Publication number: US20070056312A1
Application number: US11/530,459
Authority: US
Inventors: Makoto Kobayashi
Original assignee: Individual
Current assignee: Sanden Corp
Priority date: 2005-09-09
Filing date: 2006-09-09
Publication date: 2007-03-15
Also published as: CN1928461A; JP2007071519A

Abstract

A cooling system provided with a first freezing circuit which comprises a first compressor, a first condenser, a first expansion mechanism and a first heat exchanger and in which a first refrigerant is circulated; a second freezing circuit which comprises a second compressor, a second heat exchanger, a second expansion mechanism and an evaporator and in which a second refrigerant is circulated; and a heat medium circuit in which a heat medium for exchanging heat between the first refrigerant of the first heat exchanger and the second refrigerant of the second heat exchanger is circulated, wherein the first freezing circuit is arranged on the exterior side and the second freezing circuit is arranged in the machinery room of a thermal system on the interior side.

Description

BACKGROUND OF THE INVENTION

(i) Field of the Invention
The present invention relates to a cooling system for use in air conditioning systems, freezers, refrigerators, refrigerated showcases and the like.
(ii) Description of the Related Art
Previously, the refrigerant generally used in cooling systems for use in air conditioning systems, freezers, refrigerators, refrigerated showcases and the like was chlorofluorocarbon (CFC). However, the depletion of the ozone layer surrounding the earth by CFC has posed an environmental problem. To address this problem, cooling systems using a natural refrigerant, such as ammonia or carbon dioxide, as an alternative to CFC have come into use in recent years. Known such cooling systems include, for instance, a unified cooling system having a compressor, a condenser, an expansion valve and an evaporator which are installed in a refrigerated showcase, but such a unified cooling system is poor in freezing efficiency.
In this connection, as a solution to the problem with the unified cooling system, there are known a cooling system shown in FIG. 3 and a dual cooling system shown in FIG. 4.
Each of the cooling systems shown in FIG. 3 and FIG. 4 is configured of an ammonia circuit 51 and a carbon dioxide circuit 52. The ammonia circuit 51 is further provided with a compressor 51 a, a condenser 51 b, an expansion valve 51 c and an external heat exchanger 53. The refrigerant used by the ammonia circuit 51 is ammonia. The carbon dioxide circuit 52 is further provided with a compressor 52 a, an expansion valve 52 b, an evaporator 52 c and the external heat exchanger 53. The refrigerant used by the carbon dioxide circuit 52 is carbon dioxide. The compressor 52 a and the external heat exchanger 53 are connected to each other by piping 53 a, and the expansion valve 52 b and the external heat exchanger 53 are connected to each other by piping 53 b.
The cooling system shown in FIG. 3, configured in this way, has the compressor 52 a, the expansion valve 52 b and the evaporator 52 c arranged in a refrigerated showcase C arranged on an interior A side (indicated by double-dot chain lines in FIG. 3). The cooling system shown in FIG. 4 has the expansion valve 52 b and the evaporator 52 c in a refrigerated showcase C arranged on the interior A side (indicated by double-dot chain lines in FIG. 4). Further, each of the cooling systems shown in FIG. 3 and FIG. 4 has the ammonia circuit 51 on an exterior B side.
However, each of the cooling systems shown in FIG. 3 and FIG. 4 has the piping 53 a within which a high-temperature high-pressure refrigerant flows or the piping 53 b within which a high-pressure refrigerant flows arranged in the state of being exposed on the interior A. The arrangement of the piping 53 a and the piping 53 b arranged in the state of being exposed on the interior A makes the cooling systems shown in FIG. 3 and FIG. 4 subject to the fear of allowing the refrigerant to leak out indoors.
Also, in each of the cooling systems shown in FIG. 3 and FIG. 4 may need long-extended piping 53 a or 53 b depending on the location of the refrigerated showcase C placed on the interior A side. Where the piping 53 a or 53 b is long, the required quantity of the refrigerant to be sealed in increases correspondingly. Therefore, in the cooling system shown in FIG. 3 and FIG. 4, if the high-pressure refrigerant leaks to the interior A, a large quantity of the refrigerant may leak out to the interior A.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a safe cooling system which can prevent its refrigerant from leaking into the room (except the machinery room for the indoor unit of the thermal system).
In order to achieve the object stated above, the cooling system according to the invention is provided with a first freezing circuit which comprises a first compressor, a first condenser, a first expansion mechanism and a first heat exchanger and in which a first refrigerant is circulated; a second freezing circuit which comprises a second compressor, a second heat exchanger, a second expansion mechanism and an evaporator and in which a second refrigerant is circulated; and a heat medium circuit in which a heat medium for exchanging heat between the first refrigerant of the first heat exchanger and the second refrigerant of the second heat exchanger is circulated, wherein the first freezing circuit is arranged on the exterior side and the second freezing circuit is arranged in the machinery room of a thermal system on the interior side.
This cooling system has its first freezing circuit in which the high-pressure first refrigerant circulates installed on the exterior side. The cooling system has its second freezing circuit in which the high-pressure second refrigerant circulates installed in the machinery room of a thermal system arranged on the interior side. The arrangement of the first freezing circuit on the exterior side and of the second freezing circuit in the machinery room means the interior arrangement of no piping in which the high-pressure first refrigerant or the high-pressure second refrigerant flows (except the piping in the machinery room of the thermal system). This means enhanced safety because there is no fear of leaking of the high-pressure first refrigerant or the high-pressure second refrigerant into the room. Furthermore, this cooling system has a heat medium circuit intervening between the first freezing circuit and the second freezing circuit. This heat medium circuit enables heat to be exchanged between the first refrigerant of the first freezing circuit and the second refrigerant of the second freezing circuit. The intervening presence of the heat medium circuit makes it unnecessary to elongate the piping of the first freezing circuit or of the second freezing circuit even if the machinery room of the thermal system is installed rather far from the exterior side. Therefore, the required quantity of the first refrigerant or the second refrigerant can be minimized and accordingly the safety of operation can be enhanced.
The above-stated objects and other objects, features and advantages of the invention will become more apparent from the following description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic configuration of a cooling system of a first preferred embodiment of the present invention;
FIG. 2 shows a schematic configuration of a cooling system of a second preferred embodiment of the invention;
FIG. 3 shows a schematic configuration of a conventional cooling system; and
FIG. 4 shows a schematic configuration of another conventional cooling system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a first preferred embodiment of the invention.
This cooling system comprises a first freezing circuit 10, a second freezing circuit 20 and a heat medium circuit 30.
The first freezing circuit 10 is provided with a first compressor 11, a first condenser 12, a first expansion valve 13, which is a first expansion mechanism, and a first heat exchanger 14. This first freezing circuit 10 circulates a first refrigerant in the sequence of the first compressor 11→the first condenser 12→the first expansion valve 13→the first heat exchanger 14→the first compressor 11. The first refrigerant used in the first freezing circuit 10 is a natural refrigerant (e.g., ammonia).
The second freezing circuit 20 is provided with a second compressor 21, a second heat exchanger 22, a second expansion valve 23, which is a second expansion mechanism, and an evaporator 24. This second freezing circuit 20 circulates a second refrigerant in the sequence of the second compressor 21→the second heat exchanger 22→the second expansion valve 23→the evaporator 24→the second compressor 21. The second refrigerant used in the second freezing circuit 20 is the natural refrigerant (e.g., carbon dioxide).
The heat medium circuit 30 is provided with the first heat exchanger 14, the second heat exchanger 22 and a circulating pump 31. The first heat exchanger 14 is shared by the first freezing circuit 10 and the heat medium circuit 30. The second heat exchanger 22 is shared by the second freezing circuit 20 and the heat medium circuit 30. The heat medium circuit 30 circulates a heat medium in the sequence of the first heat exchanger 14→the circulating pump 31→the second heat exchanger 22→the first heat exchanger 14. The heat medium used in this heat medium circuit 30 is brine (e.g., a calcium chloride solution) or water.
The cooling system configured as described has the first freezing circuit 10 and the first heat exchanger 14 installed on an exterior B side. Further, the cooling system has the second freezing circuit 20 and the second heat exchanger 22 installed in a machinery room of a refrigerated showcase C, which is a thermal system arranged on an interior A (indicated by double-dot chain lines in FIG. 1) side.
Next, the operation of the cooling system shown in FIG. 1 will be described.
The first refrigerant of the first freezing circuit 10 circulates in the sequence of the first compressor 11→the first condenser 12→the first expansion valve 13→the first heat exchanger 14→the first compressor 11 (see the broken arrow in FIG. 1). The second refrigerant of the second freezing circuit 20 circulates in the sequence of the second compressor 21→the second heat exchanger 22→the second expansion valve 23→the evaporator 24→the second compressor 21 (see the solid arrow in FIG. 1). Further, the heat medium of the heat medium circuit 30 circulates in the sequence of the first heat exchanger 14→the circulating pump 31→the second heat exchanger 22→the first heat exchanger 14 (see the bold arrow in FIG. 1). The circulation of the first refrigerant, the second refrigerant or the heat medium in the circuit 10, 20 or 30, respectively causes heat to be exchanged in the first heat exchanger 14 between the first refrigerant flowing in the first freezing circuit 10 and the heat medium flowing in the heat medium circuit 30 or, in the second heat exchanger 22, between the second refrigerant flowing in the second freezing circuit 20 and the heat medium flowing in the heat medium circuit 30. These heat exchanges cause the refrigerated showcase C arranged on the interior A side to be refrigerated by the cooled second refrigerant.
In the cooling system of this embodiment, the first freezing circuit 10 in which the high-pressure first refrigerant circulates is arranged outside the room, and the second freezing circuit 20 in which the high-pressure second refrigerant circulates is arranged inside the refrigerated showcase C. This arrangement prevents the piping in which the high-pressure first refrigerant or the second refrigerant flows from being placed on the interior A side (except the piping in the machinery room of the refrigerated showcase C). Therefore, the cooling system of this embodiment can be enhanced in safety because there is no fear of leaking of the high-pressure first refrigerant or second refrigerant into the room.
Further in the cooling system of this embodiment, the heat medium circuit 30 intervenes between the first freezing circuit 10 and the second freezing circuit 20. This makes it unnecessary to elongate the piping of the first freezing circuit 10 or of the second freezing circuit 20 even if the refrigerated showcase C is installed rather far from the exterior B. Therefore, the cooling system of this embodiment can serve to minimize the required quantity of the first refrigerant or the second refrigerant and accordingly to enhance the safety of operation.
FIG. 2 shows a second embodiment of the invention. The same constituent parts as those in the cooling system 1 shown in FIG. 1 are represented by respectively the sane reference numerals and their description will be dispensed with.
The cooling system shown in FIG. 2 differs from the cooling system shown in FIG. 1 in that a heat medium circuit 40 is a known thermo-siphon type circuit using natural convection.
The cooling system shown in FIG. 2 also differs from the cooling system shown in FIG. 1 in that a low-pressure working fluid is used as the heat medium for the heat medium circuit 40.
The heat medium circuit 40 comprises the first heat exchanger 14 and the second heat exchanger 22. Thus, the first heat exchanger 14 is shared by the first freezing circuit 10 and the heat medium circuit 40, and the second heat exchanger 22 is shared by the second freezing circuit 20 and the heat medium circuit 40. Further, since a thermo-siphon type circuit is used as the heat medium circuit 40, the heat medium circuit 40 circulates the low-pressure working fluid in the sequence of the first heat exchanger 14→the second heat exchanger 22→the first heat exchanger 14 by utilizing natural convection. The working fluid used in this heat medium circuit 30 is a low-pressure refrigerant (e.g., water or alcohol).
The cooling system configured as described above has the first freezing circuit 10 and the first heat exchanger 14 installed on the exterior B side. Further, the cooling system has the second freezing circuit 20 and the second heat exchanger 22 installed in the machinery room of the refrigerated showcase C, which is the thermal system arranged on the interior A (indicated by double-dot chain lines in FIG. 2) side.
Next, the operation of the cooling system shown in FIG. 2 will be described.
As the circulation of the first refrigerant in the first freezing circuit 10 and that of the second refrigerant in the second freezing circuit 20 are the same as in the first embodiment described above, their description will be dispensed with. The working fluid of the heat medium circuit 40 circulates in the sequence of the first heat exchanger 14→the second heat exchanger 22→the first heat exchanger 14 (see the bold arrow in FIG. 2). The circulation of the first refrigerant, the second refrigerant or the working fluid in the circuit 10, 20 or 40 respectively causes heat to be exchanged in the first heat exchanger 14 between the first refrigerant flowing in the first freezing circuit 10 and the low-pressure working fluid flowing in the heat medium circuit 40 and in the second heat exchanger 22 between the second refrigerant flowing in the second freezing circuit 20 and the low-pressure working fluid flowing in the heat medium circuit 40. These heat exchanges cause the refrigerated showcase C arranged on the interior A side to be refrigerated by the cooled second refrigerant.
In the cooling system of this embodiment, the working fluid flowing in the heat medium circuit 40 arranged on the interior A side is low in pressure. The low pressure of the working fluid means that the cooling system of this embodiment has no high-pressure piping on the interior A side, resulting in enhanced safety. The other effects and advantages of the cooling system shown in FIG. 2 are the same as those of the cooling system shown in FIG. 1.
In the first and second embodiments described above, the second freezing circuit 20 and the second heat exchanger 22 are arranged in the refrigerated showcase C, which is a machinery room, but this is not the only possible arrangement. For instance, the second freezing circuit 20 and the second heat exchanger 22 may as well be arranged within an air conditioning system, a freezer or a refrigerator, which is a thermal system.
The preferred embodiments described in this specification are only illustrative but not limiting. The scope of the invention is stated in the appended claims, and all the variations that can be covered by the meanings of those claims are included in the present invention.

Claims

1. A cooling system comprising:

a first freezing circuit which comprises a first compressor, a first condenser, a first expansion mechanism and a first heat exchanger and in which a first refrigerant is circulated;

a second freezing circuit which comprises a second compressor, a second heat exchanger, a second expansion mechanism and an evaporator and in which a second refrigerant is circulated; and

a heat medium circuit in which a heat medium for exchanging heat between the first refrigerant of the first heat exchanger and the second refrigerant of the second heat exchanger is circulated, wherein:

the first freezing circuit is arranged on a exterior side and the second freezing circuit is arranged in a machinery room of a thermal system on a interior side.

2. The cooling system according to claim 1, wherein

the heat medium circuit is so configured that the heat medium is circulated between the first heat exchanger and the second heat exchanger with a pump.

3. The cooling system according to claim 1, wherein

the heat medium circuit is so configured that the heat medium is circulated between the first heat exchanger and the second heat exchanger with a thermo-siphon.

4. The cooling system according to claim 1, wherein

the first refrigerant is ammonia.

5. The cooling system according to claim 1, wherein

the second refrigerant is carbon dioxide.