JP2013167368A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve the efficiency of a pump cycle operation in an air conditioner which performs both a compressor cycle operation and the pump cycle operation.SOLUTION: An air conditioner includes: a compressor which performs a compressor cycle operation for circulating a refrigerant; a condenser which condenses the refrigerant compressed by the compressor; an expansion valve which expands the refrigerant compressed by the condenser; an evaporator which evaporates the refrigerant expanded by the expansion valve; and a pump which performs a pump cycle operation for circulating the refrigerant by feeding a liquid refrigerant flowing out of the condenser with the compressor stopped at the expansion valve. In the pump cycle operation, when the degree of superheat on the outlet side of the evaporator is a first set degree of superheat or higher, the opening of the expansion valve is increased, and when the degree of superheat on the outlet side still remains at the first set degree of superheat or higher even if the opening reaches an upper limit, the rotating speed of the pump is increased.

Description

  The present invention relates to an air conditioner, and particularly to an apparatus that performs both a compressor cycle operation by a compressor and a pump cycle operation by a pump.

  In order to construct a computer network, a server for communication, a database, a file management, etc. is required to receive and process a request from each computer. This type of server is installed in the server machine room for convenience of operation and management. A plurality of servers are stored in a server rack, and a plurality of server racks are installed in the server machine room. The server generates a large amount of heat during operation, and an air conditioner is installed in the server machine room for stable operation.

  Here, as an air conditioner for the entire server machine room, generally, a compressor, an outdoor heat exchanger (condenser), an expansion valve, and an indoor heat exchanger (evaporator) are sequentially connected by a refrigerant pipe to constitute a refrigeration cycle. An air conditioner is used.

  However, since the server machine room is operated at about 30 ° C, if the outside air temperature is lower than that, for example in the case of midwinter, the refrigerant is directly cooled by the outside air by simply circulating the refrigerant without using the compressor. Therefore, cooling operation can be performed. However, the method of directly taking outside air is not suitable in an environment such as a server machine room because humidity adjustment and removal of impurities such as dust are necessary. In view of this, a technique called an indirect outdoor air cooling system in which cold air from outside air is transported through a heat exchanger of an air conditioner has attracted attention. Cooling can be performed without using the compressor by cooling the refrigerant with outside air using an outdoor heat exchanger (condenser) and forcibly circulating the refrigerant. It is known that for forced circulation of the refrigerant, a cooling operation can be performed with lower power consumption than the power consumption when the compressor is driven by using a refrigerant pump.

  In this regard, Patent Document 1 discloses a compressor cycle operation in which a compressor, an outdoor heat exchanger (condenser), an expansion valve, and an indoor heat exchanger (evaporator) are sequentially connected by a refrigerant pipe, and the outside of the room air temperature is exceeded. Under conditions such as winter and nighttime when the temperature is low, the refrigerant pump, the outdoor heat exchanger (condenser), the expansion valve, and the indoor heat exchanger (evaporator) are connected to the refrigerant pipe in sequence, It is described that efficient operation is performed in an environment requiring annual cooling by switching the cycle according to the operation conditions.

Japanese Patent No. 4352604

  Patent Document 1 discloses a compression cycle in which the compressor, the outdoor heat exchanger (condenser), the expansion valve, and the indoor heat exchanger (evaporator) are sequentially connected by a refrigerant pipe, the refrigerant pump, and the outdoor An air conditioner having two types of cycle configurations of a refrigerant pump cycle in which a heat exchanger (condenser), the expansion valve, and the indoor heat exchanger (evaporator) are sequentially connected by refrigerant piping is used to open the expansion valve. The control of the temperature and the refrigerant pump frequency are controlled to adjust the circulation amount of the refrigerant.

  According to the pump cycle operation by the pump, significant power saving can be achieved as compared with the compressor cycle operation by the compressor.

  However, the power consumption of the pump in the pump cycle operation is not negligible, and further energy saving is required.

  In the air conditioning apparatus described in the above-mentioned patent document, further improvement in this respect is necessary.

  Therefore, an object of the present invention is to provide an air conditioner that can further improve the efficiency of the pump cycle operation in the air conditioner that performs both the compressor cycle operation and the pump cycle operation.

  In order to achieve the above object, the present invention provides a compressor that performs a compressor cycle operation for circulating a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and an expansion of the refrigerant condensed by the condenser. An expansion valve for evaporating, an evaporator for evaporating the refrigerant expanded by the expansion valve, and a pump cycle operation for circulating the refrigerant by sending liquid refrigerant flowing from the condenser to the expansion valve with the compressor stopped When the pump cycle operation is performed, the opening degree of the expansion valve is increased when the outlet side superheat degree of the evaporator is equal to or higher than a first set superheat degree, and the opening degree is The air conditioner increases the number of revolutions of the pump when the outlet superheat degree of the evaporator is equal to or higher than the first set superheat degree even when the upper limit is reached.

  Further, when performing the pump cycle operation, when the outlet side superheat degree of the evaporator is equal to or lower than a second set superheat degree lower than the first set superheat degree, the rotation speed of the pump is reduced, Even when the rotational speed reaches the lower limit, it is desirable to reduce the opening of the expansion valve when the outlet side superheat degree of the evaporator is equal to or lower than the second set superheat degree.

  Furthermore, the evaporator is configured by arranging a plurality of heat exchangers in parallel, and an expansion valve is installed on each inlet side of the plurality of heat exchangers, and the evaporation is performed when the pump cycle operation is performed. When the outlet side superheat degree of the heat exchanger is equal to or higher than the first set superheat degree, among the plurality of expansion valves, the outlet side superheat degree of the heat exchanger becomes equal to or higher than the set superheat degree of the heat exchanger. And increasing the number of rotations of the pump if the degree of superheat on the outlet side of the evaporator is equal to or higher than the first set superheat degree even if the plurality of expansion valve openings reach an upper limit. Is desirable.

  Furthermore, the evaporator is configured by arranging a plurality of heat exchangers in parallel, and an expansion valve is installed on each inlet side of the plurality of heat exchangers, and the evaporation is performed when the pump cycle operation is performed. When the outlet superheat degree of the evaporator is equal to or lower than the second set superheat degree, the rotational speed of the pump is decreased, and even if the rotational speed reaches the lower limit, the outlet superheat degree of the evaporator is the second superheat degree. When the degree of superheat of the heat exchanger is equal to or less than the set superheat degree, it is desirable to reduce the opening degree of the plurality of expansion valves whose outlet side superheat degree is equal to or less than the set superheat degree of the heat exchanger.

  ADVANTAGE OF THE INVENTION According to this invention, in the air conditioning apparatus which performs both a compressor cycle driving | operation and a pump cycle driving | operation, the air conditioning apparatus which can aim at the further efficiency improvement of a pump cycle driving | operation can be provided.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

The refrigeration cycle block diagram of Example 1 is shown. It is an example of the flowchart explaining the refrigerant | coolant circulation amount control of Example 1. FIG. The refrigeration cycle block diagram of Example 2 is shown. It is an example of the flowchart explaining the refrigerant | coolant circulation amount control of Example 2. FIG. It is an example of the flowchart explaining the refrigerant | coolant circulation amount control of Example 2. FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a refrigeration cycle of the air conditioner for information communication according to the first embodiment. The air conditioner of the present embodiment includes an outdoor unit housing 6 and an indoor unit housing 7, and the liquid blocking valves 19 and the gas blocking valves 21 of each housing are connected by piping. Then, the compressor 1, the condenser 2, the expansion valve 4, and the evaporator 5 are sequentially connected by refrigerant piping to perform the cooling operation, the condenser 2, the forced refrigerant circulation pump 3, the expansion valve 4, and the evaporator 5 Are sequentially connected by refrigerant pipes, and both the pump cycle operation for cooling operation is performed. In both cycles, the condenser 2, the expansion valve 4, and the evaporator 5 are shared. A check valve 22 is connected to the compressor 1 outlet in order to prevent the liquid refrigerant from flowing backward. This check valve may be an open / close control according to the compressor operation.

  The forced refrigerant circulation pump 3 is installed alone in the outdoor unit housing 6 or in a separate unit, and an excess refrigerant adjusting device 9 is arranged between the condenser 2 and the inlet side of the forced refrigerant circulation pump 3 is A pressure sensor 10 and a temperature sensor 11 for monitoring the degree of supercooling of the refrigerant are arranged, and the frequency of the outdoor blower 8 is controlled according to the degree of supercooling. The indoor blower 18, the expansion valve 4, the evaporator 5, and the compressor 1 are mounted on the indoor unit 7 side. The expansion valve 4, the evaporator 5, and the compressor 1 are sequentially connected by piping. The outlet side piping of the evaporator 5 is connected to the inlet side piping of the compressor 1, and in the case of compressor cycle operation, the refrigerant flows through this piping to form a cycle. A pipe for bypassing the compressor 1 is connected between the outlet side pipe of the evaporator 5 and the inlet side pipe of the compressor 1, and in the case of pump cycle operation, the refrigerant flows through this pipe so that the pump flows. Cycle operation is performed. A check valve 13 is connected to the pipe bypassing the compressor 1 to prevent the refrigerant discharged from the compressor 1 during the compressor cycle operation from flowing to the outlet side pipe of the evaporator 5. .

  The compressor cycle operation and the pump cycle operation are switched depending on the outside air temperature and the operation state. During the compressor cycle operation, when the outdoor temperature is sufficiently lower than the indoor temperature, if the cooling load continues to be less than the capacity that can be exhibited by the pump cycle operation, the operation is switched to the pump cycle operation. When the cooling load cannot be covered during the pump cycle operation or when the outdoor temperature continues to be high, the operation is switched to the compressor cycle operation.

  The refrigerant circulation amount during the pump cycle operation is adjusted by the frequency of the forced refrigerant circulation pump 3 or the opening degree of the expansion valve 4 so that the degree of superheat at the outlet of the evaporator 5 becomes a set value. The degree of superheat is calculated by calculating the saturation temperature of the refrigerant at that pressure from the pressure value obtained by the pressure sensor 15 disposed at the outlet of the evaporator 5 and calculating the difference from the temperature of the refrigerant obtained by the temperature sensor 14. To do. The inlet / outlet of the forced refrigerant circulation pump 3 is connected by a bypass pipe through a check valve 23 so as to bypass the forced refrigerant circulation pump 3 during the compressor cycle operation. In addition, the piping before and after the forced refrigerant circulation pump 3 has a structure that allows the forced refrigerant circulation pump 3 to be replaced in the compressor cycle operation state by stopping the forced refrigerant circulation pump 3 through the check valve 20. .

  FIG. 2 shows a flowchart for adjusting the refrigerant circulation amount during pump cycle operation. An upper limit value SH2 and a lower limit value SH1 are set for the outlet side superheat degree of the evaporator 5, and the refrigerant circulation amount is adjusted by comparing the set value with the calculated evaporator outlet side superheat degree SHe. . First, the case where the evaporator outlet side superheat degree SHe is lower than the lower limit value SH1 will be described. In this case, it is necessary to reduce the refrigerant circulation amount, but in this embodiment, the opening degree of the expansion valve 4 is reduced at this time. Instead, the frequency of the forced refrigerant circulation pump 3 is lowered stepwise. Thus, by reducing the rotational speed of the forced refrigerant circulation pump 3 before the expansion valve 4, while reducing the refrigerant circulation amount to the desired degree of superheat on the outlet side of the evaporator, the power consumption by the forced refrigerant circulation pump 3 is reduced. It is possible to reduce.

  Further, when the rotational speed of the forced refrigerant circulation pump 3 is decreased and the lower limit frequency is reached, if the evaporator outlet side superheating degree SHe is still lower than the lower limit value SH1, it is necessary to further reduce the refrigerant circulation amount. Therefore, the refrigerant circulation amount is reduced by gradually controlling the opening degree of the expansion valve 4 to be reduced. If the evaporator outlet side superheat degree SHe continues to be lower than the lower limit value SH1, the opening degree control is performed until the opening degree of the expansion valve 4 reaches the lower limit.

  Next, the case where the evaporator outlet side superheat degree SHe is higher than the upper limit value SH2 will be described. In this case, it is necessary to increase the amount of refrigerant circulation. Instead of increasing, first, the opening degree control for increasing the opening degree of the expansion valve 4 is performed. As a matter of course, the relationship is upper limit value SH2> lower limit value SH1. As a result, the amount of refrigerant circulating increases, so that it is not necessary to drive the pump 3 while maintaining the desired degree of superheat on the outlet side of the evaporator, and this can be done with low power consumption.

  If the evaporator outlet side superheat degree SHe continues to be higher than the upper limit value SH2 even when the opening degree of the expansion valve 4 reaches the upper limit, the frequency of the forced refrigerant circulation pump 3 is gradually increased from the lower limit frequency at this time. Increase the amount of refrigerant circulation. If the evaporator outlet side superheat degree SHe continues to be higher than the upper limit value SH2, control is performed until the frequency of the forced refrigerant circulation pump 3 reaches the upper limit.

  As described above, the control procedure as shown in FIG. 3 enables the pump cycle operation with low power consumption, and controls both the forced refrigerant circulation pump 3 and the expansion valve 4, so that the refrigerant can be optimized. The range of circulation amount can be expanded.

  FIG. 3 is a diagram illustrating a refrigeration cycle configuration diagram of the air conditioner for information communication according to the second embodiment. The air conditioner according to the present embodiment is controlled by switching between the compressor cycle operation and the pump cycle operation. If the circulation amount of the refrigerant amount is excessive in the evaporator 5 during the pump cycle operation, the air conditioner is located near the compressor 1. Liquid refrigerant accumulates, and necessary and sufficient refrigerant does not flow to the forced refrigerant circulation pump 3, which may deteriorate the refrigeration cycle efficiency.

  For example, if the refrigerant flow rate control is performed by controlling the opening degree of only one expansion valve 4 as in the first embodiment, when the opening degree of the expansion valve 4 is narrowed, the evaporator 5 Since the amount of refrigerant entering the inlet path pipe is not necessarily uniform, there is a possibility that a flow rate distribution that is biased toward the refrigerant flowing in the evaporator 5 may be formed. If an uneven flow distribution is generated in the refrigerant passing through the evaporator 5, an appropriate heat exchange capacity may not be obtained, and reliability in the order of the superheat degree is lost. Further, if liquid refrigerant accumulates in the compressor 1, when switching to the compressor cycle operation, the liquid refrigerant flows to the compressor suction side, and liquid compression occurs, which may cause a failure of the compressor.

  Therefore, in FIG. 3, unlike FIG. 1, the evaporator 5 is constituted by a plurality of indoor heat exchangers (5-1, 5-2, 5-3) so that the refrigerant circulation amount can be adjusted with higher accuracy. Is. Each indoor heat exchanger (5-1, 5-2, 5-3) is provided with an expansion valve (4-1, 4-2, 4-3) for controlling the refrigerant circulation amount. Further, a temperature sensor 16 and a pressure sensor 17 for calculating the degree of refrigerant superheating on the outlet side are provided for each indoor heat exchanger for each indoor heat exchanger.

  Further, a temperature sensor 14 and a pressure sensor 15 are provided on the outlet side in the same manner as in FIG. 1 in order to calculate the outlet side superheat degree as the entire evaporator 5. A target outlet side superheat degree is set for each indoor heat exchanger (5-1, 5-2, 5-3), and this target outlet side superheat degree is a target outlet side as a whole of the evaporator. It is determined to be the degree of superheat. The target outlet superheat degree is set in a certain range determined from the upper limit value and the lower limit value as in the first embodiment, and control is performed so that the outlet side superheat degree falls within the range.

  Next, the refrigerant | coolant circulation amount control of each specific indoor heat exchanger (5-1, 5-2, 5-3) is demonstrated.

  FIG. 4 is a diagram for explaining the control when the outlet-side superheat degree of the evaporator 5 as a whole, that is, the outlet-side superheat degree She calculated by the temperature sensor 14 and the pressure sensor 15 is lower than the set lower limit value SH1. It is. In this case, it is necessary to reduce the refrigerant circulation amount, but in this embodiment, control is first performed so as to lower the rotational speed of the forced refrigerant circulation pump 3 as in the first embodiment. If the outlet side superheat degree SHe is lower than the set lower limit value SH1 even when the rotational speed of the forced refrigerant circulation pump 3 reaches the lower limit, each expansion valve (4-1, 4-2, 4- 3) is controlled.

  Here, the target outlet side superheat degree is set in each indoor heat exchanger (5-1, 5-2, 5-3) as described above, and the temperature sensor 16 and the pressure installed in each are set. Since the outlet-side superheat degree can be calculated from the sensor 17, control is performed to throttle the expansion valve (4-1) of the indoor heat exchanger (for example, 5-1) where the outlet-side superheat degree is lower than the set lower limit value. . Thus, the evaporator 5 is comprised by several indoor heat exchangers (5-1, 5-2, 5-3), and control is carried out by each expansion valve (4-1, 4-2, 4-3). Therefore, it is possible to suppress the uneven performance in the evaporator and adjust the refrigerant circulation amount with higher accuracy.

  FIG. 5 is a diagram for explaining control when the outlet-side superheat degree of the evaporator 5 as a whole, that is, the outlet-side superheat degree She calculated by the temperature sensor 14 and the pressure sensor 15 is higher than a set upper limit value SH2. It is. In this case, it is necessary to increase the refrigerant circulation amount, but in this embodiment, before increasing the rotational speed of the forced refrigerant circulation pump 3, each expansion valve (4-1, 4-2, 4- Opening control for increasing the opening in 3) is performed. In this configuration, the forced refrigerant circulation pump 3 can be replaced in the stopped and compression cycle operation state.

  In this case, the upper limit value of the outlet side superheat degree is set in each indoor heat exchanger (5-1, 5-2, 5-3), and the outlet from the temperature sensor 16 and the pressure sensor 17 is set. Since the side superheat degree can be calculated, control is performed to increase the opening degree of the expansion valve (4-1) of the indoor heat exchanger (for example, 5-1) in which the outlet side superheat degree is higher than the set upper limit value. . And even if the opening degree of all the expansion valves (4-1, 4-2, 4-3) reaches the upper limit, the state where the outlet side superheat degree SHe is still higher than the set upper limit value SH2 continues. Controls to increase the rotational speed of the forced refrigerant circulation pump 3.

  As described above, in the refrigerant circulation amount control according to the present embodiment, the evaporator 5 is configured by a plurality of indoor heat exchangers (5-1, 5-2, 5-3), and each expansion valve ( By performing the opening control of (4-1, 4-2, 4-3), it is possible to suppress unevenness in performance and adjust the refrigerant circulation amount with higher accuracy. As a result, liquid refrigerant can be prevented from accumulating near the compressor 1 during pump cycle operation, and necessary and sufficient refrigerant can flow to the forced refrigerant circulation pump 3, thereby preventing deterioration in refrigeration cycle efficiency. it can. Further, the liquid refrigerant does not accumulate due to the liquid refrigerant accumulating in the compressor 1, and the reliability of the compressor can be improved.

1 Compressor 2 Outdoor heat exchanger (condenser)
3 Forced refrigerant circulation pump 4, 4-1, 4-2, 4-3 Expansion valve 5 Indoor heat exchange air (evaporator)
5-1, 5-2, 5-3 Indoor heat exchanger (evaporator)
6 Outdoor unit housing 7 Indoor unit housing 8 Outdoor blower 9 Excess refrigerant device 10, 15, 17 Pressure sensor 11, 14, 16 Temperature sensor 12 Silencer
13, 22, 23 Check valve 18 Indoor blower 19 Liquid blocking valve 20 Check valve 21 Gas blocking valve

Claims (4)

A compressor that performs a compressor cycle operation for circulating the refrigerant;
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve for expanding the refrigerant condensed by the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
A pump that performs a pump cycle operation to circulate the refrigerant by sending liquid refrigerant flowing from the condenser to the expansion valve while the compressor is stopped, and
When performing the pump cycle operation, if the degree of superheat on the outlet side of the evaporator is greater than or equal to a first set superheat degree, the opening of the expansion valve is increased, and the evaporator is not affected even when the opening reaches the upper limit. An air conditioner that increases the number of revolutions of the pump when the outlet side superheat degree is equal to or greater than the first set superheat degree. In the air conditioning apparatus according to claim 1,
When performing the pump cycle operation, when the outlet side superheat degree of the evaporator is equal to or lower than a second set superheat degree lower than the first set superheat degree, the rotation speed of the pump is reduced, and the rotation speed Even if the temperature reaches the lower limit, the opening degree of the expansion valve is reduced when the outlet side superheat degree of the evaporator is not more than the second set superheat degree. In the air conditioning apparatus according to claim 1 or 2,
The evaporator is configured by arranging a plurality of heat exchangers in parallel,
Expansion valves are respectively installed on the inlet sides of the plurality of heat exchangers,
When performing the pump cycle operation, if the outlet side superheat degree of the evaporator is equal to or higher than the first set superheat degree, the outlet side superheat degree of the heat exchanger among the plurality of expansion valves is Although the opening degree of the heat exchanger that is equal to or higher than the set superheat degree of the heat exchanger is increased, the superheat degree on the outlet side of the evaporator is equal to or higher than the first set superheat degree even if the plurality of expansion valve openings reach the upper limit. In this case, the air conditioner increases the rotational speed of the pump. In the air conditioning apparatus according to claim 2,
The evaporator is configured by arranging a plurality of heat exchangers in parallel,
Expansion valves are respectively installed on the inlet sides of the plurality of heat exchangers,
When performing the pump cycle operation, if the superheat degree on the outlet side of the evaporator is equal to or lower than the second set superheat degree, the rotational speed of the pump is decreased, and even if the rotational speed reaches the lower limit, When the outlet side superheat degree of the evaporator is less than or equal to the second set superheat degree, among the plurality of expansion valves, the outlet side superheat degree of the heat exchanger becomes less than or equal to the set superheat degree of the heat exchanger. An air conditioner characterized in that the opening degree of what is present is reduced.