US20070028631A1

US20070028631A1 - Cooling System

Info

Publication number: US20070028631A1
Application number: US11/459,930
Authority: US
Inventors: Toshiyuki Fukuda; Makoto Kobayashi; Kazumasa Takada
Original assignee: Sanden Corp
Current assignee: Sanden Corp
Priority date: 2005-08-08
Filing date: 2006-07-25
Publication date: 2007-02-08
Also published as: CN1912512A; JP2007046810A

Abstract

A cooling system using brine includes: a refrigerant circuit that has a compressor, a condenser, and an expansion valve; a brine circuit that has a cooler and a pump for circulating the brine; a first heat exchanger that is shared by the refrigerant circuit and the brine circuit and performs heat exchange between a refrigerant flowing on a downstream side of the expansion valve of the refrigerant circuit and the brine flowing on a downstream side of the cooler of the brine circuit; and a second heat exchanger that is provided between the cooler and the first heat exchanger and performs heat exchange between the brine and the outdoor air.

Description

BACKGROUND OF THE INVENTION

(i) Field of the Invention
The present invention relates to a cooling system using brine.
(ii) Description of the Related Art
Conventionally, there is known a cooling system including a refrigerant circuit that has a compressor, a condenser, and an expansion valve, a brine circuit that has a pump and a cooler, and a first heat exchanger shared by the refrigerant circuit and the brine circuit.
The cooling system performs, in the first heat exchanger, heat exchange between a refrigerant flowing on a downstream side of the expansion valve of the refrigerant circuit and brine flowing on a downstream side of the cooler of the brine circuit to cool the brine. The cooling system supplies the brine cooled to the cooler to cool articles stored in an apparatus, for example, a showcase, in which the cooler is set.
The cooling system using brine is a cooling system proposed in response to the request for the post-Freon process or the Freon-saving in recent years. However, since it is necessary to circulate the brine in the brine circuit, energy consumption is large compared with the conventional direct expansion type cooling system. In other words, if a way of making it possible to reduce the energy consumption is found, it is possible to realize running cost equivalent to or lower than that of the direct expansion type cooling system and improve flexibility of the cooling system.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a cooling system that can realize running cost saving by reducing energy consumption at the time of system operation.
In order to attain the object, the cooling system of the invention includes: a refrigerant circuit that has a compressor, a condenser, and an expansion valve; a brine circuit that has a cooler and a pump for circulating brine; a first heat exchanger that is shared by the refrigerant circuit and the brine circuit and performs heat exchange between a refrigerant flowing on a downstream side of the expansion valve of the refrigerant circuit and the brine flowing on a downstream side of the cooler of the brine circuit; and a second heat exchanger that is provided between the cooler and the first heat exchanger and performs heat exchange between the brine and the outdoor air.
In this cooling system, for example, in winter when the outdoor air temperature is low, heat exchange is performed between the brine and the outdoor air by the second heat exchanger to cool the brine. The cooling system can lower operating ratios of the compressor and the like by cooling the brine using the outdoor air. Since the operating ratios of the compressor and the like are lowered, the cooling system can reduce energy consumption at the time of system operation. Since the energy consumption at the time of system operation is reduced, the cooling system can realize running cost saving.
The object, other objects, characteristics, and benefits of the invention will be made apparent from the following explanation and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall diagram of a cooling system of the invention;
FIG. 2 is a flowchart showing control of the cooling system shown in FIG. 1;
FIG. 3 is a diagram for explaining operations of the cooling system shown in FIG. 1;
FIG. 4 is a diagram for explaining operations of the cooling system shown in FIG. 1;
FIG. 5 is a diagram for explaining operations of the cooling system shown in FIG. 1;
FIG. 6 is an overall diagram according to another embodiment of the cooling system shown in FIG. 1;
FIG. 7 is an overall diagram according to still another embodiment of the cooling system shown in FIG. 1; and
FIG. 8 is a diagram for explaining operations of the cooling system shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 to FIG. 5 shows a preferred embodiment of the invention.
A structure of a cooling system using brine will be explained with reference to FIG. 1 and FIG. 2. The cooling system has a refrigerant circuit 10, a brine circuit 20, and a first heat exchanger 30.
The refrigerant circuit 10 has a compressor 11, a condenser 12, and an expansion valve 13. A refrigerant circulates to the compressor 11, the condenser 12, the expansion valve 13, the first heat exchanger 30, and the compressor 11 in this order. The condenser 12 has a first blower 12 a. The first blower 12 a forcibly brings the outdoor air into contact with the condenser 12. The refrigerant used in the refrigerant circuit 10 is Freon, non-Freon (e.g., ammonium), or the like.
The brine circuit 20 has a pump 21, a cooler 22, and a second heat exchanger 23 for performing heat exchange between the brine and the outdoor air. In the brine circuit 20, the brine circulates to the pump 21, the cooler 22, the second heat exchanger 23, the first heat exchanger 30, and the pump 21 in this order. The brine used in the brine circuit 20 is, for example, a calcium chloride solution.
The pump 21 is provided between the first heat exchanger 30 and the cooler 22 and circulates the brine to the brine circuit 20. A first electromagnetic valve 21 a is provided between the pump 21 and the cooler 22.
The cooler 22 cools the inside of a showcase 22 b in which articles and the like are stored. The cooler 22 is provided between the pump 21 and the second heat exchanger 23 and set in the showcase 22 b. The cooler 22 has a second blower 22 a for facilitating cooling in the showcase 22 b.
The second heat exchanger 23 is provided between the cooler 22 and the first heat exchanger 30. The second heat exchanger 23 has a third blower 23 b. The third blower 23 b forcibly brings the outdoor air into contact with the second heat exchanger 23. A by-pass path 24 is provided in parallel with the second heat exchanger 23. Moreover, a second electromagnetic valve 23 a serving as means for switching the circulation of the brine is provided upstream the second heat exchanger 23. A third electromagnetic valve 24 a serving as means for switching the circulation of the brine is provided on the by-pass path 24. The second electromagnetic valve 23 a and the third electromagnetic valve 24 a switch a circulation path of the brine to one of the second heat exchanger 23 and the by-pass paths 24.
The first heat exchanger 30 is shared by the refrigerant circuit 10 and the brine circuit 20. The first heat exchanger 30 performs heat exchange between the refrigerant flowing on a downstream side of the expansion valve 13 of the refrigerant circuit 10 and the brine flowing on a downstream side of the cooler 22 of the brine circuit 20. The first heat exchanger 30 is provided between the expansion valve 13 and the compressor 11 in the refrigerant circuit 10 and is provided between the second heat exchanger 23 and the cooler 22 in the brine circuit 20.
In the cooling system constituted as described above, the refrigerant circuit 10, the first heat exchanger 30, the pump 21, the second heat exchanger 23, the electromagnetic valves 23 a and 24 a, and the third blower 23 b are set outside a room (see a square indicated by an alternate long and two dashes line shown in FIG. 1). In the cooling system, the showcase 22 b that has the cooler 22 and the second blower 22 a and the first electromagnetic valve 21 a are set inside the room.
A control system structure of the cooling system shown in FIG. 1 will be explained.
A controller 40 includes a microcomputer, various drivers, and the like. Two predetermined outdoor temperatures T1 and T2 (T1>T2), which are temperatures for judgment in switching of operation, and the like are stored in the controller 40. The controller 40 controls, on the basis of an outdoor temperature T detected by a not-shown temperature sensor, the compressor 11, the first blower 12 a, the expansion valve 13, the pump 21, the second blower 22 a, the third blower 23 b, and the electromagnetic valves 21 a, 23 a, and 24 a.
Control by the cooling system will be explained with reference to a flowchart in FIG. 2.
First, the cooling system judges whether the outdoor temperature T is equal to or higher than the predetermined outdoor temperature T1, for example, 5° C. (step S1). The predetermined outdoor temperature T1 is, for example, temperature set according to temperature in the showcase 22 b when it is desired to maintain the temperature in the showcase 22 b at 5° C.
When the outdoor temperature T is equal to or higher than the predetermined outdoor temperature T1 in step S1, the cooling system performs a normal operation (step S2).
The normal operation in step 2 will be explained with reference to FIG. 3. The cooling system in the normal operation opens the first electromagnetic valve 21 a and the third electromagnetic valve 24 a and closes the second electromagnetic valve 23 a to circulate the brine to the by-pass path 24 (see a solid line arrow in FIG. 3). The refrigerant circuit 10 circulates the refrigerant in a state in which a capacity of the compressor 11 is controlled to a maximum by the controller 40 (see a broken line arrow in FIG. 3). The brine circuit 20 circulates the brine in a state in which the operation of the third blower 23 b is stopped by the controller 40 and an amount of circulation by the pump 21 is controlled to be a maximum. In the first heat exchanger 30, heat exchange is performed between the brine after circulating through the by-pass path 24 and the refrigerant circulating through the refrigerant circuit 10. When the brine subjected to the heat exchange in the first heat exchanger 30 is supplied to the cooler 22 in the showcase 22 b, articles stored in the showcase 22 b are cooled.
When the outdoor temperature T is not equal to or higher than the predetermined outdoor temperature T1 in step S1, the cooling system judges whether the outdoor temperature T is equal to or higher than the predetermined outdoor temperature T2 and lower than the predetermined outdoor temperature T1, for example, equal to or higher than 0° C. and lower than 5° C. (step S3).
When the outdoor temperature T is equal to or higher than the predetermined outdoor temperature T2 and is lower than the predetermined outdoor temperature T1 in step S3, the cooling system performs a light-load operation (step S4).
The light-load operation instep S4 will be explained with reference to FIG. 4. The cooling system in the light-load operation opens the first electromagnetic valve 21 a and the second electromagnetic valve 23 a and closes the third electromagnetic valve 24 a. The refrigerant circuit 10 circulates the refrigerant in a state in which a capacity of the compressor 11 is controlled to about half compared with that in the normal operation by the controller 40 (see a broken line arrow in FIG. 4). The brine circuit 20 circulates the brine in a state in which an amount of circulation by the pump 21 is controlled to about two third compared with that in the normal operation and an air quantity of the third blower 23 b is controlled to a maximum by the controller 40 (see a solid line arrow in FIG. 4). In the second heat exchanger 23, heat exchange is performed between the brine and the outdoor air. In the first heat exchanger 30, heat exchange is performed between the brine and the refrigerant circulating through the refrigerant circuit 10. The brine subjected to the heat exchange in the second heat exchanger 23 and the first heat exchanger 30 is supplied to the cooler 22 in the showcase 22 b. Consequently, the articles stored in the showcase 22 b are cooled.
When the outdoor temperature T is not equal to or higher than the predetermined outdoor temperature T2 and is not lower than the predetermined outdoor temperature T1 in step S3, the cooling system judges whether the outdoor temperature T is lower than the predetermined outdoor temperature T2, for example, 0° C. (step S5).
When the outdoor temperature T is lower than the predetermined outdoor temperature T2 in step S5, the cooling system performs an individual operation of only the brine circuit 20 (step S6).
The individual operation in step S6 will be explained with reference to FIG. 5. The cooling system in the individual operation opens the first electromagnetic valve 21 a and the second electromagnetic valve 23 a and closes the third electromagnetic valve 24 a. The refrigerant circuit 10 stops the operation of the compressor 11 with the controller 40 to stop the circulation of the refrigerant. The brine circuit 20 circulates the brine in a state in which an amount of circulation by the pump 21 is controlled to about half compared with that in the normal operation and an air quantity of the third blower 23 b is controlled to about half compared with that in the normal operation by the controller 40 (see a solid line arrow in FIG. 5). In the second heat exchanger 23, heat exchange is performed between the brine and the outdoor air. The brine subjected to the heat exchange in the second heat exchanger 23 is supplied to the cooler 22 in the showcase 22 b. Consequently, the articles stored in the showcase 22 b are cooled. Further, the cooling system controls an air quantity of the third blower 23 b to about half compared with that in the normal operation to prevent the second heat exchanger 23 from being excessively cooled.
When the outdoor temperature T is temperature considerably lower than the predetermined outdoor temperature T2, for example, −5° C. or −10° C., it is possible to perform sufficient heat exchange in the second heat exchanger 23 even in a state in which the third blower 23 b is stopped.
According to the cooling system, heat exchange is performed between the brine and the outdoor air by the second heat exchanger 23 to cool the brine. The cooling system can lower operating ratios of the compressor 11 and the like by cooling the brine using the outdoor air. Since the operating ratios of the compressor 11 and the like are lowered, the cooling system can reduce energy consumption at the time of system operation. Since the energy consumption at the time of system operation is reduced, the cooling system can realize running cost saving.
At the time of light-load operation, the cooling system controls the compressor 11 to reduce a capacity thereof and controls the pump 21 with the controller 40 to reduce an amount of circulation by the pump 21. The cooling system can reduce energy consumption of the brine circuit 20 at the time of system operation by controlling the compressor 11 and the pump 21.
At the time of the individual operation, the cooling system completely stops the operation of the compressor 11. The cooling system can reduce energy consumption of the refrigerant circuit 10 to zero by completely stopping the operation of the compressor 11. The cooling system controls the pump 21 with the controller 40 to reduce an amount of circulation by the pump 21. The cooling system can reduce energy consumption of the brine circuit 20 at the time of system operation by controlling the pump 21. Moreover, the cooling system controls the third blower 23 b with the controller 40 to reduce an air quantity. The cooling system can further reduce energy consumption of the brine circuit 20 at the time of system operation and prevent the second heat exchanger 23 from being excessively cooled by controlling the third blower 23 b. The cooling system can control the fall in viscosity of the brine circulating through the second heat exchanger 23 and prevent the fall in circulation speed of the brine in the brine circuit 20 by preventing excessive cooling of the second heat exchanger 23.
Since the second heat exchanger 23 has the third blower 23 b, heat exchange between the brine and the outdoor air is facilitated in the second heat exchanger 23. Since the heat exchange between the brine and the outdoor air is facilitated in the second heat exchanger 23, the cooling system can efficiently perform heat exchange of the brine circulating through the second heat exchanger 23.
Since the second heat exchanger 23 is provided outside the room, the cooling system can surely perform heat exchange between the brine and the outdoor air.
Moreover, since the refrigerant circuit 10 is provided outside the room, it is unlikely that the refrigerant circulating through the refrigerant circuit 10 leaks to the inside of the room. Consequently, even when the refrigerant has inflammability, toxicity, or a pungent smell, the cooling system can prevent the refrigerant from adversely affecting a person or the like present in the room.
Since the cooling system has the electromagnetic valves 23 a and 24 a, the cooling system can circulate the brine to one of the second heat exchanger 23 and the by-pass path 24. Consequently, the cooling system can select, according to the outdoor temperature T, whether the second heat exchanger 23 should be used.
FIG. 6 shows another preferred embodiment of the invention. Components identical with those of the cooling system shown in FIG. 1 to FIG. 5 are denoted by the identical reference numerals and signs. Explanations of the components are omitted.
A cooling system using brine shown in FIG. 6 is different from the cooling system shown in FIG. 1 to FIG. 5 in that the cooling system has a three-way valve 33 a in order to switch a path, through which the brine circulates, to one of the second heat exchanger 23 and the by-pass path 24. Other actions and effects of this cooling system are the same as those of the cooling system shown in FIG. 1 to FIG. 5.
FIG. 7 shows still another preferred embodiment of the invention. Components identical with those of the cooling system shown in FIG. 1 to FIG. 5 are denoted by the identical reference numerals and signs. Explanations of the components are omitted.
A cooling system shown in FIG. 7 is different from the cooling system shown in FIG. 1 to FIG. 5 in that only the second heat exchanger 23 is provided outside the room (see a square indicated by an alternate long and two dashes line shown in FIG. 7). Other actions and effects of this cooling system are the same as those of the cooling system shown in FIG. 1 to FIG. 5.
In the embodiment explained above, temperature for judging switching of operation by the controller 40 may be temperature of the brine that has passed through the cooler 22. For example, when the temperature of the brine that has passed through the cooler 22 is higher than the outdoor temperature T, the cooling system opens the first electromagnetic valve 21 a and the second electromagnetic valve 23 a and closes the third electromagnetic valve 24 a. Consequently, after the brine circulates to the second heat exchanger 23, heat exchange is performed between the outdoor air and the brine in the second heat exchanger 23. The brine subjected to the heat exchange in the second heat exchanger 23 is fed into the cooler 22. Further, for example, when the temperature of the brine after passing through the cooler 22 is lower than the outdoor temperature T, the cooling system opens the first electromagnetic valve 21 a and the third electromagnetic valve 24 a and closes the second electromagnetic valve 23 a. Consequently, after the brine circulates to the by-pass path 24, the brine not subjected to the heat exchange in the second heat exchanger 23 is fed into the cooler 22.
In the embodiment explained above, the method of switching the circulation path of the brine to one of the second heat exchanger 23 and the by-pass path 24 is explained as an example. However, the invention is not limited to this. For example, as shown in FIG. 8, the cooling system may open both the second electromagnetic valve 23 a and the third electromagnetic valve 24 a and divide the brine to both the second heat exchanger 23 and the by-pass path 24. This cooling system can control the cooling of the brine by the second heat exchanger 23 by adjusting respective flow rates of the brines circulating to the second heat exchanger 23 and the by-pass path 24. In this cooling system, the brine circulating to the second heat exchanger 23 and the brine circulating to the by-pass path 24 merge on an upstream side of the first heat exchanger 30. When the brines merge, the brines having a temperature difference are mixed. Since the brines having a temperature difference are mixed, the cooling system can control the fall in the viscosity of the brine and prevent the fall in circulation speed of the brine in the brine circuit 20.
The preferred embodiment of the invention hitherto described in this specification is only illustrative but not restrictive. The scope of the invention is stated in the appended claims, and every modification that can be encompassed by those claims is to be included in the invention.

Claims

1. A cooling system comprising:

a refrigerant circuit that has a compressor, a condenser, and an expansion valve;

a brine circuit that has a cooler and a pump for circulating brine;

a first heat exchanger that is shared by the refrigerant circuit and the brine circuit and performs heat exchange between a refrigerant flowing on a downstream side of the expansion valve of the refrigerant circuit and the brine flowing on a downstream side of the cooler of the brine circuit; and

a second heat exchanger that is provided between the cooler and the first heat exchanger and performs heat exchange between the brine and outdoor air.

2. The cooling system according to claim 1, further comprising:

a blower for forcibly bringing the outdoor air into contact with the second heat exchanger.

3. The cooling system according to claim 1, wherein:

at least the second heat exchanger out of the refrigerant circuit and the second heat exchanger is provided outside a room.

4. The cooling system according to claim 1, wherein:

the brine circuit includes a by-pass path provided in parallel to the second heat exchanger and switching means for switching a circulation path of the brine to at least one of the second heat exchanger and the by-pass path.

5. The cooling system according to claim 1, further comprising:

a first controlling means for controlling a capacity of the compressor of the refrigerant circuit to fall when outdoor temperature is lower than a predetermined temperature.

6. The cooling system according to claim 1, further comprising:

a second controlling means for controlling an amount of circulation by the pump to fall when outdoor temperature is lower than a predetermined temperature.

7. The cooling system according to claim 2, further comprising:

a third controlling means for controlling an air quantity of the blower to fall when outdoor temperature is lower than a predetermined temperature.

8. The cooling system according to claim 4, further comprising:

9. The cooling system according to claim 4, further comprising:

10. The cooling system according to claim 4, further comprising:

11. The cooling system according to claim 5, further comprising:

a second controlling means for controlling an amount of circulation by the pump to fall when the outdoor temperature is lower than the predetermined temperature.

12. The cooling system according to claim 5, further comprising:

13. The cooling system according to claim 6, further comprising:

14. The cooling system according to claim 10, further comprising:

a third controlling means for controlling an air quantity of the blower to fall when outdoor temperature is lower than a predetermined temperature

15. The cooling system according to claim 12, further comprising:

a third controlling means for controlling an air quantity of the blower to fall when the outdoor temperature is lower than the predetermined temperature.

16. The cooling system according to claim 13, further comprising: