JP2005188812A - Heat pump type refrigerating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the service life of a heat exchanger without causing an increase in a device cost by allowing the use of a heat exchanger of structure heretofore in use while reducing the temperature change in switching air-conditioning and heating operation in the load side heat exchanger and reducing shock applied to the heat exchanger following the temperature change even if switching of air-conditioning and heating operation is frequently performed. <P>SOLUTION: In this heat pump type refrigerating apparatus, a discharge refrigerant from a compressor is changed over by a selector valve 3 provided at an intermediate part of refrigerant piping, so as to be fed to a first heat exchanger 5 and a second heat exchanger 8 in this order and returned to the compressor in air-conditioning operation, and to be fed to the second heat exchanger 8 and the first heat exchanger 5 in this order and returned to the compressor in heating operation. In this case, a third heat exchanger 16 is provided between the second heat exchanger 8 and the selector valve 3 so that a cooling medium from the load side passes through the third heat exchanger and the second heat exchanger in this order. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat pump type refrigeration apparatus.

  In a heat pump type refrigeration system, the refrigerant is decompressed and supplied to a heat exchanger that performs heat exchange between a cooling medium such as water from the load side and the refrigerant during cooling (cooling) operation, and heating (heating) operation is performed. Sometimes, high-temperature discharged refrigerant gas from the compressor is supplied.

  Therefore, when switching between the cooling operation and the heating operation is frequently performed, the heat exchanger is supplied with a low-temperature refrigerant in the cooling operation and a high-temperature refrigerant in the heating operation, and the rapid temperature change is repeated. Sudden temperature changes can cause damage to the heat exchanger.

Specifically, there is a case where stress accompanying the dimensional change of each member due to temperature change concentrates on the joint part of the constituent members of the heat exchanger, and the joint part and its peripheral part are damaged.
Such damage to the joint causes leakage of the refrigerant and not only causes a problem that the operation of the apparatus is not stably performed, but also when using a toxic refrigerant such as ammonia, This causes serious problems such as mixing of toxic refrigerant into the cooling medium supplied to the load side and leakage of toxic gas around the apparatus.

  In particular, there is a concern about damage to the joints of heat exchanger components that are joined by brazing, for example, brazing type plate heat exchangers. This brazing type plate heat exchanger is small in size and heat exchange efficiency. Although it is excellent, it cannot be said to be suitable as a heat exchanger in a heat pump refrigeration system in a usage environment in which the cooling operation and the heating operation are frequently switched.

  Also, if the heat exchanger is made of a highly durable material or structure so that it can withstand rapid changes in temperature as described above, it will cause an increase in manufacturing costs and the size of the heat exchanger will increase. There is a risk of downsizing the device.

  Furthermore, in recent years, ammonia has been increasingly used as a refrigerant due to the review of natural refrigerants. Since ammonia has a higher discharge gas temperature than chlorofluorocarbon refrigerants, the temperature change of heat exchangers associated with operation switching Therefore, a higher degree of consideration is required to prevent damage to the heat exchanger.

  The present invention can suppress the temperature change during the cooling operation and the heating operation in the heat exchanger on the load side to be small, and to the heat exchanger even if the switching between the cooling operation and the heating operation is frequently performed. Heat pump refrigeration that can reduce the shock caused by temperature changes and can improve the life of the heat exchanger without increasing the cost of the equipment by using a heat exchanger with a conventional structure It is an object to provide an apparatus.

  In order to achieve the above object, an apparatus according to the present invention includes a refrigerant compressor that discharges a compressed refrigerant, a first heat exchanger that acts as a condenser during cooling operation and acts as an evaporator during heating operation, A second heat exchanger that acts as an evaporator during cooling operation, acts as a condenser during heating operation, and exchanges heat with a cooling medium such as water sent to the load side, and discharges from the compressor during cooling operation The refrigerant is sent in the order of the first heat exchanger and the second heat exchanger and returned to the compressor. During the heating operation, the refrigerant discharged from the compressor is supplied to the second heat exchanger and the first heat exchanger. In the heat pump refrigeration apparatus that is switched by a switching valve provided in the middle of the refrigerant pipe so as to be sent back in order and returned to the compressor, a third heat exchange is performed between the second heat exchanger and the switching valve. A cooling medium from the load side. There a heat exchanger and a second heat exchanger as configured as occupied spend flow in this order, and there as a configuration in which the refrigerant and ammonia.

  The apparatus according to the present invention controls the opening degree of the expansion valve that decompresses the refrigerant during cooling operation at the refrigerant inlet of the second heat exchanger based on the refrigerant outlet temperature of the third heat exchanger. The configuration is as follows.

  Furthermore, the apparatus according to the present invention is configured such that the switching valve is switched to the cooling operation state at a required time interval during the heating operation, and the defrosting operation by the reverse cycle in the first heat exchanger is performed. It is as.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the apparatus according to the present invention will be described below in detail based on specific examples shown in the accompanying drawings.
The other end of the discharge pipe 2 whose one end is connected to the discharge port of the compressor 1 is connected to the first port 3a of the four-way valve 3 serving as a switching valve, and one end is connected to the second port 3b of the four-way valve 3. The other end of the refrigerant pipe 4 is connected to the water heat exchanger 8 serving as the second heat exchanger via the air heat exchanger 5 serving as the first heat exchanger, the first check valve 6 and the first expansion valve 7. It is connected to the first refrigerant pipe connection port 8a.
The water heat exchanger 8 is a small heat exchanger having a high heat exchange efficiency, for example, a brazing type plate heat exchanger.

  The other end of the second refrigerant pipe 9 having one end connected to the second refrigerant pipe connection port 8b of the water heat exchanger 8 is connected to the third port 3c of the four-way valve 3, and the fourth port of the four-way valve 3 is connected. The other end of the suction pipe 10 having one end connected to 3d is connected to the suction port of the compressor via the accumulator 11.

  A second expansion valve 13 is provided in the first bypass pipe 12 straddling the first check valve 6, and a second check valve 15 is provided in the second bypass pipe 14 straddling the first expansion valve 7. Is provided.

  Accordingly, a sub heat exchanger 16 as a third heat exchanger is provided in the middle of the second refrigerant pipe 9 so that, for example, water as a cooling medium from the load side such as the air conditioner 17a of the air-conditioned room 17 is sub. The heat exchanger 16 and the water heat exchanger 8 are allowed to flow in this order, and the sub heat exchanger 16 is preferably a heat exchanger that has a high strength against temperature changes. A multi-tube type heat exchanger is used.

Specifically, the cold / hot water return pipe 18 from the air conditioner 17a is connected to the water inlet 16c of the sub heat exchanger 16, and the other end of the cold / hot water pipe 19 having one end connected to the outlet 16d is hydrothermal. The other end of the cold / hot water feed pipe 20 connected to the water inlet 8c of the exchanger 8 and having one end connected to the outlet 8d is connected to the air conditioner 17a.
In addition, the code | symbols 16a and 16b in a figure have shown the refrigerant pipe connection port.

  In the apparatus having the above-described configuration, the air heat exchanger 5 serving as the first heat exchanger functions as a condenser during the cooling operation of the apparatus, and serves as an evaporator during the heating operation, and the water heat serving as the second heat exchanger. The exchanger 8 and the sub heat exchanger 16 as the third heat exchanger function as an evaporator during the cooling operation of the apparatus and as a condenser during the heating operation, and the operation of the apparatus during the cooling operation and the heating operation will be described below. .

  FIG. 1 is a configuration diagram showing the flow of refrigerant during cooling operation (during cold water supply operation). The refrigerant (ammonia in this embodiment) from the compressor 1 flows from the first port 3a of the four-way valve 3 to the second port. 3 b is passed through and sent to the air heat exchanger 5, condensed by heat exchange with air in the air heat exchanger, becomes liquid refrigerant, passes through the first check valve 6, and passes through the first expansion valve 7. The pressure is reduced, and vaporization is performed by heat exchange (water cooling) with water from the load side in the water heat exchanger 8.

  The opening degree control of the first expansion valve 7 is performed based on the refrigerant outlet temperature of the sub heat exchanger 16.

  The vaporized refrigerant further exchanges heat with the water from the load side in the sub heat exchanger 16, and takes away the latent heat of vaporization of the liquid refrigerant and the sensible heat of the refrigerant gas that could not be vaporized in the water heat exchanger 8, and then the four-way valve 3 From the third port 3c through the fourth port 3d, the air enters the suction pipe 10 and is separated into gas and liquid by the accumulator and returned to the compressor.

That is, the return cold water from the load side is first cooled to some extent by the sub heat exchanger 16 and further cooled to a required temperature by the water heat exchanger 8.
In addition, the example of the value of the temperature of the refrigerant | coolant and water in each site | part was attached | subjected to the refrigerant | coolant inlet / outlet of the water heat exchanger 8 and the sub heat exchanger 16 in FIG.

  In the heating operation (during hot water supply operation), as shown in FIG. 2, the refrigerant from the compressor 1 flows through the third port 3 c from the first port 3 a of the four-way valve 3 to the sub heat exchanger 16. In this sub heat exchanger, the water from the load side is heated to some extent and sent to the water heat exchanger 8, and by heat exchange with the water from the load side in the water heat exchanger (heating water) The liquid is condensed, becomes a liquid refrigerant, is depressurized by the second expansion valve 13 through the second check valve 15, and is vaporized by heat exchange with air in the air heat exchanger 5.

  The vaporized refrigerant enters the suction pipe 10 from the second port 3b of the four-way valve 3 through the fourth port 3d, and is separated into gas and liquid by the accumulator and returned to the compressor.

  Thus, the temperature of the water heat exchanger 8 is not different from the temperature of the water heat exchanger in the conventional apparatus during the cooling operation, but the hot discharge gas from the compressor 1 is sub-heat exchanger during the heating operation. The temperature drops due to heat exchange with water from the load side at 16, so the temperature difference of the water heat exchanger during cooling operation and heating operation is smaller than that of the conventional one.

  In addition, the example of the value of the temperature of the refrigerant | coolant and water in each site | part was attached | subjected to the refrigerant | coolant inlet / outlet and water inlet / outlet of the water heat exchanger 8 and the sub heat exchanger 16 in FIG.

  Accordingly, since the temperature change during the cooling operation and the heating operation is small in the water heat exchanger 8, damage due to a rapid temperature change can be suppressed even when the cooling operation and the heating operation are frequently switched. The life of the water heat exchanger can be extended.

  By the way, in the apparatus of the Example mentioned above, although the frost formation by the condensation of the water | moisture content in air is carried out to the air heat exchanger 5 which is a 1st heat exchanger at the time of heating operation, removal of the frost adhering to an air heat exchanger is carried out. In the frost operation, the four-way valve 3 as a switching valve is automatically switched from the heating operation state to the cooling operation state at a required time interval, and the high-temperature discharged refrigerant from the compressor 1 is supplied to the air heat exchanger 5. This is performed by so-called reverse cycle operation.

  In the defrosting operation by the reverse cycle described above, the temperature change accompanying the reverse cycle operation also occurs in the water heat exchanger 8 as the second heat exchanger, but even in this case, the sub heat exchanger is interposed. Similarly to the suppression of the temperature change accompanying the switching between the cooling operation and the heating operation described above, the rapid temperature change is prevented. Since this defrosting operation is frequently performed, for example, once per hour, the effect of preventing damage due to temperature change of the water heat exchanger 8 is remarkable.

  In the above-described embodiments, the ammonia refrigerant refrigeration apparatus has been described. However, the present invention can be applied to an apparatus using other refrigerants, and is particularly suitable for an apparatus using a refrigerant whose discharge gas temperature is high. It is.

  Since the apparatus according to the present invention has the above-described configuration, the temperature of the second heat exchanger, which is a heat exchanger on the load side, is lowered to some extent by the third heat exchanger during heating operation. Discharged refrigerant gas is supplied.

  Therefore, the temperature of the second heat exchanger in the heating operation can be kept low, and even if the cooling operation and the heating operation are frequently switched, the temperature change of the second heat exchanger can be reduced, Even if heat exchangers with conventional materials and structures are used, there is no risk of damage to the heat exchanger, and it is possible to prevent refrigerant leakage and extend the life of the heat exchanger. It is suitable for an apparatus using an ammonia refrigerant having a high gas temperature.

  In addition, since the cold source that lowers the temperature of the discharge gas supplied to the second heat exchanger in the heating operation in the third heat exchanger is a cold medium such as water returned from the load side, the heat of the discharge gas Is reliably transmitted to the cooling medium, and there is no waste in the use of the cooling heat, and the third heat exchanger is provided for both the cooling operation and the heating operation, so that there is no difference between the refrigerant and the cooling medium from the load side. The heat exchange area becomes large, and the heat exchange efficiency can be improved.

  Note that, during the cooling operation, the opening degree of the expansion valve at the refrigerant inlet in the second heat exchanger is controlled based on the refrigerant outlet temperature of the third heat exchanger, so that the evaporation area in the second heat exchanger is widened. Therefore, efficient heat exchange can be performed.

  In addition, the apparatus of the present invention has a simple configuration in which a third heat exchanger is simply disposed between the second heat exchanger and the switching valve, and is generally used for the third heat exchanger. Since the used heat exchanger can be adopted, it can be easily manufactured, and there is an extremely great merit in practical use that it can be applied to an existing apparatus.

  Furthermore, the apparatus of the present invention not only prevents a sudden temperature change to the second heat exchanger due to switching between normal cooling operation and heating operation, but also reverses the first heat exchanger during heating by reverse cycle operation. Similarly, when the defrosting operation is performed, a sudden temperature change can be prevented.

The block diagram which attached | subjected the flow of the refrigerant | coolant at the time of air_conditionaing | cooling operation in the Example of the apparatus which concerns on this invention. The block diagram which attached | subjected the flow of the refrigerant | coolant at the time of heating operation in the Example of the apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Discharge pipe 3 Four-way valve 4 1st refrigerant pipe 5 Air heat exchanger 6 1st non-return valve 7 1st expansion valve 8 Water heat exchanger 9 2nd refrigerant pipe 10 Intake pipe 11 Accumulator 12 1st bypass pipe 13 Second expansion valve 14 Second bypass pipe 15 Second check valve 16 Sub heat exchanger 18 Cold / hot water return pipe 19 Cold / hot water pipe 20 Cold / hot water feed pipe

Claims (4)

  A refrigerant compressor that discharges the compressed refrigerant; a first heat exchanger that acts as an evaporator during cooling operation; and an evaporator during cooling operation; an evaporator during cooling operation; and a condenser during heating operation And a second heat exchanger that exchanges heat with a cooling medium such as water sent to the load side, and the refrigerant discharged from the compressor is the first heat exchanger and the second heat exchanger during cooling operation. Of the refrigerant pipe so that the refrigerant discharged from the compressor is sent in the order of the second heat exchanger and the first heat exchanger and returned to the compressor during heating operation. In the heat pump refrigeration apparatus that is switched by a switching valve provided in the middle, a third heat exchanger is provided between the second heat exchanger and the switching valve, and the cooling medium from the load side is the third heat. Let the exchanger and second heat exchanger flow in this order Heat pump type refrigerating apparatus which is configured to so that.   The heat pump refrigeration apparatus according to claim 1, wherein the refrigerant is ammonia.   The configuration is such that the opening degree of an expansion valve for depressurizing the refrigerant during cooling operation is controlled based on the refrigerant outlet temperature of the third heat exchanger at the refrigerant inlet of the second heat exchanger. 2. A heat pump refrigeration apparatus according to 1.   The said switching valve is switched to the state at the time of air_conditionaing | cooling operation at a required time interval at the time of heating operation, The defrosting operation by the reverse cycle in a said 1st heat exchanger is comprised. Heat pump refrigeration equipment.

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