REFRIGERATION CYCLE APPARATUS

A refrigeration cycle apparatus provided with: a compressor; a first heat exchanger; a second heat exchanger; a third heat exchanger; a first heat medium passage connecting a heat medium outlet of the third heat exchanger to a heat medium inlet of the second heat exchanger; a first bypass valve; a second heat medium passage to allow the heat medium flowing out of the second heat exchanger to flow into a second load device; a second bypass valve; a return passage; a flow path switching valve to switch between a first mode in which the heat medium flows into the first heat medium passage from the return passage without passing through the third heat exchanger and a second mode in which the heat medium flows into the third heat exchanger from the return passage.

FIELD

The present disclosure relates to a refrigeration cycle apparatus.

BACKGROUND

PTL 1 below discloses an air-conditioning operation method using free cooling. In this air-conditioning operation method, a low-temperature cold water tank and a high-temperature cold water tank are provided, and in an intermediate period, low-temperature cold water produced by a refrigerator is supplied to the low-temperature cold water tank for latent heat treatment, and high-temperature cold water produced by a cooling tower is supplied to the high-temperature cold water tank for sensible heat treatment. In summer or winter, high-temperature cold water in the high-temperature cold water tank is produced using low-temperature cold water produced by the refrigerator or low-temperature cold water produced by the cooling tower.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

The conventional technology described above requires two water tanks and requires two pumps for supplying water between each water tank and a load, which causes a problem of high cost.

An object of present disclosure, which has been made in order to solve the above problem, is to provide a refrigeration cycle apparatus that has a simple structure and is advantageous in increasing opportunities to utilize free cooling.

Solution to Problem

A refrigeration cycle apparatus according to the present invention includes: a compressor to compress refrigerant; a first heat exchanger to cool the refrigerant compressed by the compressor with outdoor air; a decompressor to reduce a pressure of the refrigerant; a second heat exchanger to cool a heat medium with the refrigerant decompressed by the decompressor; a third heat exchanger to cool the heat medium with the outdoor air; a first heat medium passage connecting a heat medium outlet of the third heat exchanger to a heat medium inlet of the second heat exchanger; a first bypass valve to allow the heat medium to flow from the first heat medium passage into a first load device; a second heat medium passage to allow the heat medium flowing out of the second heat exchanger to flow into a second load device; a second bypass valve to allow the heat medium flowing out of the second heat exchanger to flow into the first load device; a return passage through which the heat medium returning from the first load device and the heat medium returning from the second load device pass; and a flow path switching valve to switch between a first mode in which the heat medium flows into the first heat medium passage from the return passage without passing through the third heat exchanger and a second mode in which the heat medium flows into the third heat exchanger from the return passage.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide a refrigeration cycle apparatus that has a simple structure and is advantageous in increasing opportunities to utilize free cooling.

DESCRIPTION OF EMBODIMENTS

Embodiments will be described below with reference to the drawings. In the drawings, common or corresponding elements are denoted by the same reference numerals, and the description thereof is simplified or omitted. In the present disclosure, the outside of a building is referred to as “outdoor”, the inside of a room of the building is referred to as “indoor”, the air outside the building is referred to as “outdoor air”, and the air inside the room of the building is referred to as “indoor air”. The temperature of the outdoor air is referred to as an “outside air temperature”.

First Embodiment

FIG.1is a diagram illustrating a refrigeration cycle apparatus1according to a first embodiment. As illustrated inFIG.1, a refrigeration cycle apparatus1is provided with: a compressor2configured to compress refrigerant; a first heat exchanger3configured to cool the refrigerant compressed by the compressor2with outdoor air; a decompressor4configured to reduce a pressure of the refrigerant; a second heat exchanger5configured to cool a heat medium with the refrigerant decompressed by the decompressor4; a third heat exchanger6configured to cool the heat medium with the outdoor air; a first heat medium passage7connecting a heat medium outlet of the third heat exchanger6to a heat medium inlet of the second heat exchanger5; a first bypass valve8configured to allow the heat medium to flow from the first heat medium passage7into a first load device100; a second heat medium passage9configured to allow the heat medium flowing out of the second heat exchanger5to flow into a second load device200; a second bypass valve10configured to allow the heat medium flowing out of the second heat exchanger5to flow into the first load device100; a return passage11through which the heat medium returning from the first load device100and the heat medium returning from the second load device200pass; a flow path switching valve12configured to switch between a first mode in which the heat medium flows into the first heat medium passage7from the return passage11without passing through the third heat exchanger6and a second mode in which the heat medium flows into the third heat exchanger6from the return passage11.

A substance used as the refrigerant in the present disclosure is not particularly limited but may be, for example, any of CO2, HFC, HFO, and hydrocarbon.

A substance used as the heat medium in the present disclosure is typically liquid water. However, a liquid except for water, such as an aqueous solution of calcium chloride, an aqueous solution of ethylene glycol, an aqueous solution of propylene glycol, or alcohol, may be used as the heat medium. In the illustrated example, a heat medium pump13for circulating the heat medium is provided in the return passage11.

The first heat exchanger3is configured to cool the heat medium by heat exchange using outdoor air. For example, the first heat exchanger3may be configured to directly exchange heat between the outdoor air and the heat medium in a closed type cooling tower. Alternatively, the first heat exchanger3may be configured to exchange heat between cooling water cooled by outdoor air in an open type cooling tower and the heat medium.

The third heat exchanger6is configured to cool the heat medium by heat exchange using outdoor air. For example, the third heat exchanger6may be configured to directly exchange heat between the outdoor air and the heat medium in the closed type cooling tower. Alternatively, the third heat exchanger6may be configured to exchange heat between the cooling water cooled by outdoor air in the open type cooling tower and the heat medium.

In the illustrated example, the first heat exchanger3and the third heat exchanger6are disposed adjacent to each other. In the illustrated example, a blower14for feeding outdoor air to the first heat exchanger3and the third heat exchanger6is provided. The blower14may not be provided. In place of the illustrated example, the third heat exchanger6may be disposed at a position away from the first heat exchanger3. In this case, a blower for feeding outdoor air to the first heat exchanger3and a blower for feeding outdoor air to the third heat exchanger6may be provided separately.

In the present embodiment, an example will be mainly described where the first load device100and the second load device200are configured to perform air conditioning in a room by using a heat medium. However, the present disclosure is not limited to a system for performing air conditioning. For example, one or both of the first load device100and the second load device200may be configured to cool a production apparatus by using a heat medium.

The first load device100may include a heat exchanger for exchanging heat between the indoor air and the heat medium. The first load device100may be formed of, for example, a fan coil unit. The first load device100may be configured to mainly handle a sensible heat load in air conditioning. That is, the first load device100may be configured to mainly lower the temperature of the indoor air.

The air flowing into the room from outside is hereinafter referred to as “ventilation air”. The second load device200may include a heat exchanger for exchanging heat between the ventilation air and the heat medium. The second load device200may be formed of what is generally called an outside air processing air conditioner. The second load device200may be configured to mainly handle latent heat load in air conditioning. That is, in order to reduce humidity, the second load device200may be configured to mainly cool air to condense water vapor.

FIG.1illustrates a state in which the refrigeration cycle apparatus1is being operated in a chiller independent operation mode. In the chiller independent operation mode, the heat medium is cooled by operating the compressor2without performing free cooling by the third heat exchanger6. The refrigeration cycle apparatus1in the chiller independent operation mode operates as follows. The high-temperature and high-pressure refrigerant compressed by the compressor2flows into the first heat exchanger3. The refrigerant cooled by the outdoor air in the first heat exchanger3is decompressed when passing through the decompressor4. The first bypass valve8is closed. The second bypass valve10is open. The flow path switching valve12is in the first mode. In the second heat exchanger5, the heat medium is cooled by exchanging heat between the low-temperature and low-pressure refrigerant flowing out of the decompressor4and the heat medium. A part of the heat medium flowing out of the second heat exchanger5is supplied to the first load device100through the second bypass valve10. The remainder of the heat medium flowing out of the second heat exchanger5is supplied to the second load device200through the second heat medium passage9. The heat medium returned from the first load device100and the heat medium returned from the second load device200merge and flow through the return passage11. The heat medium flows from the return passage11into the first heat medium passage7without passing through the third heat exchanger6. The entire amount of the heat medium flowing into the first heat medium passage7flows into the second heat exchanger5.

FIG.2is a diagram illustrating a state in which the refrigeration cycle apparatus1is being operated in the free-cooling combined operation mode. In the free-cooling combined operation mode, free cooling by the third heat exchanger6and the operation of the compressor2are used in combination to cool the heat medium. The refrigeration cycle apparatus1in the free-cooling combined operation mode operates as follows. The refrigerant circulates through the same path as in the chiller independent operation mode. The first bypass valve8is open. The second bypass valve10is closed. The flow path switching valve12is in the second mode. The heat medium returned from the first load device100and the heat medium returned from the second load device200merge and flow through the return passage11. The heat medium having passed through the return passage11flows into the third heat exchanger6. The heat medium cooled by the outdoor air in the third heat exchanger6flows into the first heat medium passage7. A part of the heat medium flowing through the first heat medium passage7is supplied to the first load device100through the first bypass valve8. The remainder of the heat medium flowing through the first heat medium passage7flows into the second heat exchanger5. The heat medium cooled by the refrigerant in the second heat exchanger5is supplied to the second load device200through the second heat medium passage9.

In order to treat the latent heat by the second load device200, the temperature of the heat medium flowing from the second heat exchanger5into the second load device200needs to be made lower than the dew point temperature. The greater the flow rate of the heat medium flowing through the second heat exchanger5, the greater the power consumption of the compressor2when the heat medium is cooled to an isothermal temperature. The flow rate of the heat medium flowing through the second heat exchanger5in the free-cooling combined operation mode is smaller than that in the chiller independent operation mode. Therefore, in the free-cooling combined operation mode, the power consumption of the compressor2can be reduced as compared with the chiller independent operation mode, and energy saving can be achieved.

In the free-cooling combined operation mode, the heat medium cooled by the free cooling of the third heat exchanger6flows into the first load device100. The temperature of the heat medium cooled by free cooling varies in accordance with the outside air temperature. The temperature of the heat medium flowing into the first load device100, which treats sensible heat, can be higher than the dew point temperature. In the free-cooling combined operation mode, the heat medium cooled by free cooling can be supplied to the first load device100, and the heat medium further cooled by the second heat exchanger5to a temperature lower than the dew point temperature can be supplied to the second load device200. Therefore, in the refrigeration cycle apparatus1of the present embodiment, free cooling can be utilized even when the temperature of the heat medium cooled by free cooling is higher than the dew point temperature. As a result, opportunities to utilize free cooling can be increased, and energy saving can thus be achieved. Further, according to the present embodiment, since the above effect can be achieved by the refrigeration cycle apparatus1having a simple configuration, the product cost can be reduced. For example, the simple configuration can be achieved by not requiring a tank that separately stores the heat medium cooled by free cooling and the heat medium further cooled by the second heat exchanger5. Moreover, the simple configuration can be achieved by the common heat medium pump13circulating both the heat medium cooled by free cooling and the heat medium further cooled by the second heat exchanger5.

In the free-cooling combined operation mode, the second bypass valve10may be slightly opened. Thereby, the heat medium having passed through the second bypass valve10mixes with the heat medium passing through the first bypass valve8, so that the temperature of the heat medium flowing into the first load device100can be lowered.

The refrigeration cycle apparatus1may further include control circuitry50configured to control the operation of the first bypass valve8, the operation of the second bypass valve10, and the operation of the flow path switching valve12. The addition of the control circuitry50has an advantage that these operations can be automated.

The control circuitry50may be configured to close the first bypass valve8and open the second bypass valve10when the flow path switching valve12is in the first mode. This can automate the operation of the chiller independent operation mode.

The control circuitry50may be configured to perform a process of opening the first bypass valve8and a process of closing the second bypass valve10when the flow path switching valve12is in the second mode. The control circuitry50may be configured to perform, when the flow path switching valve12is in the second mode, a process of opening the first bypass valve8and a process of making the opening degree of the second bypass valve10smaller than the opening degree when the flow path switching valve12is in the first mode. These can automate the operation of the free-cooling combined operation mode.

Although not illustrated, the refrigeration cycle apparatus1may be operated in a free-cooling independent operation mode in which the heat medium is cooled only by free cooling without operating the compressor2. In the free-cooling independent operation mode, the compressor2is stopped, the flow path switching valve12is set to the second mode, the first bypass valve8is opened, and the second bypass valve10is fully closed.

The control circuitry50may be configured to vary the operating speed of the compressor2by, for example, inverter control to adjust the capability of cooling the heat medium. The control circuitry50may be configured to further control at least one of the operation of the decompressor4, the operation of the heat medium pump13, and the operation of the blower14. The decompressor4may be an expansion valve with an adjustable opening degree. The control circuitry50may be configured to vary the operating speed of the heat medium pump13by, for example, inverter control, thus adjusting the circulating flow rate of the heat medium. The control circuitry50may be configured to vary the operating speed of the blower14by, for example, inverter control, thus adjusting the air flow rate. The control circuitry50may control at least one of the operating speed of the compressor2, the circulating flow rate of the heat medium, the opening degree of the decompressor4, and the operating speed of the blower14so that each of the first load device100and the second load device200satisfies the required capability.

In the following description, the temperature of the heat medium passing through the return passage11is referred to as a “return temperature”. The refrigeration cycle apparatus1may further include an outside air temperature sensor15for detecting the outside air temperature and a return temperature sensor16for detecting the return temperature. The control circuitry50may switch the flow path switching valve12from the first mode to the second mode when the outside air temperature is lower than the return temperature, and the difference between the return temperature and the outside air temperature is larger than a reference. That is, the control circuitry50may be configured to shift from the chiller independent operation mode to the free-cooling combined operation mode when the outside air temperature is lower than the return temperature, and the difference between the return temperature and the outside air temperature is larger than the above reference. This increases the opportunity to use the free-cooling combined operation mode instead of the chiller independent operation mode, thereby saving energy.

In the following description, the cooling capability of the heat medium supplied by the refrigeration cycle apparatus1to the first load device100and the second load device200is referred to as a “supplied cooling capability”. The refrigeration cycle apparatus1may further include a capability shortage detector for detecting the shortage of the supplied cooling capability. The control circuitry50may have the function of the capability shortage detector. For example, the capability shortage detector may determine whether the supplied cooling capability is sufficient for the sensible heat capability, which is the cooling capability required by the first load device100, and the latent heat capability, which is the cooling capability required by the second load device200. The capability shortage detector may detect the shortage of the supplied cooling capability based on information obtained from an indoor sensor (not illustrated) that detects the temperature and humidity of the indoor air. For example, the capability shortage detector may detect the shortage of the supplied cooling capability based on the difference between an actual indoor temperature and a target value and the difference between an actual indoor humidity and a target value.

When the supplied cooling capability becomes insufficient while with the flow path switching valve12is in the second mode, the control circuitry50may reduce the opening degree of the first bypass valve8and increase the opening degree of the second bypass valve10. That is, the control circuitry50may be configured to lower the opening degree of the first bypass valve8and to increase the opening degree of the second bypass valve10when the supplied cooling capability becomes insufficient during the execution of the free-cooling combined operation mode. When the opening degree of the first bypass valve8decreases and that of the second bypass valve10increases, the flow rate of the heat medium flowing into the second heat exchanger5and cooled by the refrigerant increases, so that the supplied cooling capability increases. As a result, the shortage of supplied cooling capability is solved.

Further, during the execution of the free-cooling combined operation mode, the control circuitry50may shift to the free-cooling independent operation mode in response to the difference between the return temperature and the outside air temperature. Alternatively, during the execution of the free-cooling combined operation mode, the control circuitry50may shift to the free-cooling independent operation mode in response to the fact that the supplied cooling capability is sufficient.

The refrigeration cycle apparatus1of the present embodiment will be further described below. The inlet of the first bypass valve8is connected to a branch portion17provided in the first heat medium passage7. The outlet of the first bypass valve8is connected to the heat medium inlet of the first load device100by a heat medium passage18. The second heat medium passage9connects the heat medium outlet of the second heat exchanger5to the heat medium inlet of the second load device200. The inlet of the second bypass valve10is connected to a branch portion19provided in the second heat medium passage9. The outlet of the second bypass valve10is connected to a branch portion20provided in the heat medium passage18.

The upstream portion of the return passage11is connected to both the heat medium outlet of the first load device100and the heat medium outlet of the second load device200. The flow path switching valve12corresponds to a three-way valve having an inlet12a, a first outlet12b, and a second outlet12c. The inlet12ais connected to the downstream portion of the return passage11. The first outlet12bis connected to a branch portion21provided in the first heat medium passage7. The second outlet12cis connected to the heat medium inlet of the third heat exchanger6by a heat medium passage22. In the first mode, the flow path switching valve12communicates the inlet12awith the first outlet12band closes the second outlet12c. In the second mode, the flow path switching valve12communicates the inlet12awith the second outlet12cand closes the first outlet12b.

The refrigeration cycle apparatus1of the illustrated example further includes a refrigerant circuit switching valve23for switching between a normal cycle circuit and a reverse cycle circuit. As illustrated inFIGS.1and2, the normal cycle circuit is a circuit in which high-temperature and high-pressure refrigerant discharged from the compressor2flows into the first heat exchanger3through the refrigerant circuit switching valve23. Although not illustrated, the reverse cycle circuit is a circuit in which high-temperature and high-pressure refrigerant discharged from the compressor2flows into the second heat exchanger5through the refrigerant circuit switching valve23. By adding the refrigerant circuit switching valve23, the refrigeration cycle apparatus1can perform a heating operation using the reverse cycle circuit. In the heating operation, the heat medium is heated by the high-temperature and high-pressure refrigerant in the second heat exchanger5. For example, by supplying the heat medium heated by the heating operation to the first load device100and the second load device200, the inside of the room can be heated. In the heating operation, the high-pressure refrigerant that has passed through the second heat exchanger5is decompressed by the decompressor4. The decompressed refrigerant absorbs the heat of the outdoor air in the first heat exchanger3and is evaporated. The evaporated refrigerant is sucked into the compressor2. However, the refrigeration cycle apparatus1of the present disclosure may not include the refrigerant circuit switching valve23, that is, may not perform the heating operation using the reverse cycle circuit.

Each function of the control circuitry50may be achieved by a processing circuit. The processing circuit of the control circuitry50may include at least one processor and at least one memory. At least one processor may read and execute a program stored in at least one memory to implement each function of the control circuitry50. The processing circuit of the control circuitry50may include at least one dedicated hardware.

Second Embodiment

Next, a second embodiment will be described with reference toFIG.3, focusing on the differences from the first embodiment described above, and elements common to or corresponding to the elements described above are denoted by the same reference numerals to simplify or omit the common description.

FIG.3is a diagram illustrating a refrigeration cycle apparatus24according to the second embodiment. As illustrated inFIG.3, the refrigeration cycle apparatus24according to the second embodiment further includes a forward header31, a return header32, and an inter-header bypass valve33. The forward header31has a predetermined volume. The return header32has a predetermined volume.FIG.3illustrates a state in the free-cooling combined operation mode.

The forward header31includes an inlet31aand a plurality of outlets31b. The inlet31ais connected to the heat medium outlet of the second heat exchanger5by a heat medium passage25. The second heat medium passage9connects one of the plurality of outlets31bto the heat medium inlet of the second load device200. The inlet of the second bypass valve10is connected to another one of the plurality of outlets31b.

The return header32includes an outlet32aand a plurality of inlets32b. The upstream portion of the return passage11is connected to the outlet32a. One of the plurality of inlets32bis connected to the heat medium outlet of the first load device100by a heat medium passage26. Another one of the plurality of inlets32bis connected to the heat medium outlet of the second load device200by a heat medium passage27.

The inter-header bypass passage28connects the forward header31to the return header32. The inter-header bypass passage28is provided with an inter-header bypass valve33. When the inter-header bypass valve33is opened, the heat medium can move between the forward header31and the return header32through the inter-header bypass passage28.

In the following description, the difference between the pressure of the heat medium in the forward header31and that in the return header32will be referred to as an “inter-header pressure difference”. According to the present embodiment, the inter-header pressure difference can be adjusted by changing the opening degree of the inter-header bypass valve33. By adjusting the inter-header pressure difference, it can be more reliably ensured that the flow rate of the heat medium supplied to the first load device100and the flow rate of the heat medium supplied to the second load device200are appropriate values. In particular, even when the distance to the first load device100or the distance to the second load device200is long, it is possible to reliably supply the heat medium at an appropriate flow rate.

The control circuitry50may be configured to control the operation of the inter-header bypass valve33so that the inter-header pressure difference detected by a sensor (not illustrated) matches a target.

Third Embodiment

Next, a third embodiment will be described with reference toFIG.4, focusing on the differences from the first embodiment and the second embodiment described above, and elements common to or corresponding to the elements described above are denoted by the same reference numerals to simplify or omit the common description.

FIG.4illustrates a refrigeration cycle apparatus30according to the third embodiment. As illustrated inFIG.4, the refrigeration cycle apparatus30according to the third embodiment further includes a forward header31, a return header32, and an inter-header bypass valve33. Further, a plurality of first load devices100and a plurality of second load devices200are connected to the forward header31and the return header32. The refrigeration cycle apparatus30is provided with a plurality of second bypass valves10corresponding to the plurality of first load devices100.FIG.4illustrates a state in the free-cooling combined operation mode.

The heat medium inlet of each second load device200is connected by the second heat medium passage9to one outlet31bcorresponding to the second load device200among the plurality of outlets31bof the forward header31. The inlet of each second bypass valve10is connected by a heat medium passage34to one outlet31bcorresponding to the second bypass valve10among the plurality of outlets31bof the forward header31.

An upstream portion of a heat medium passage35is connected to the outlet of the first bypass valve8. The downstream portion of the heat medium passage35has a plurality of branch pipes36corresponding to the plurality of first load devices100. Each branch pipe36is connected to the heat medium inlet of one first load device100corresponding to the branch pipe36among the plurality of first load devices100. Each branch pipe36is provided with a check valve37and a branch portion38. The branch portion38is provided in the branch pipe36between the check valve37and the first load device100. The outlet of each second bypass valve10is connected by a heat medium passage39to the branch portion38of the branch pipe36connected to one first load device100corresponding to the second bypass valve10among the plurality of first load devices100.

When one of the second bypass valves10is opened, the heat medium flowing out of the second heat exchanger5to the forward header31flows into one first load device100corresponding to the second bypass valve10among the plurality of first load devices100. At this time, the check valve37prevents the heat medium from flowing into the other first load device100.

The system may be configured such that the number of first load devices100to be operated among the plurality of first load devices100can be changed. For example, the number of first load devices100to be operated may be changed by closing a valve (not illustrated) provided in each heat medium passage26or each branch pipe36and stopping the supply of the heat medium to the first load device100the operation of which is to be stopped. Alternatively, the number of first load devices100to be operated may be changed by providing a bypass passage (not illustrated) that bypasses each of the first load devices100and allowing the heat medium to flow so as to bypass the first load device100the operation of which is to be stopped.

The system may be configured such that the number of second load devices200to be operated among the plurality of second load devices200can be changed. For example, the number of second load devices200to be operated may be changed by closing a valve (not illustrated) provided in each second heat medium passage9or each heat medium passage27and stopping the supply of the heat medium to the second load device200the operation of which is to be stopped. Alternatively, the number of second load devices200to be operated may be changed by providing a bypass passage (not illustrated) that bypasses each of the second load devices200and allowing the heat medium to flow so as to bypass the second load device200the operation of which is to be stopped.

According to the present embodiment, by using the inter-header bypass valve33to adjust the inter-header pressure difference, it can be more reliably ensured that the flow rate of the heat medium supplied to each of the first load devices100and the flow rate of the heat medium supplied to each of the second load devices200become appropriate values. In particular, even when the number of first load devices100to be operated or the number of second load devices200to be operated changes, it is possible to reliably supply the heat medium at an appropriate flow rate.

In the present embodiment, since the plurality of second bypass valves10corresponding to the plurality of first load devices100are provided, the amount of heat medium flowing into the first load device100from the second heat exchanger5can be individually adjusted in the free-cooling combined operation mode. For example, by opening only the second bypass valve10corresponding to the first load device100having insufficient cooling capability among the plurality of second bypass valves10, it is possible to supply the heat medium from the second heat exchanger5only to the first load device100having an insufficient cooling capability.

REFERENCE SIGNS LIST