JP2013076491A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner which can perform stable starting that prevents cavitation from being generated upon pump starting when switched from a compressor cycle operation to a pump cycle operation.SOLUTION: The air conditioner includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, a decompression means that reduces the pressure of the refrigerant condensed by the condenser, an evaporator that evaporates the refrigerant pressure-reduced by the decompressor, a gas-liquid separator that separates the refrigerant flowing from the evaporator into a liquid refrigerant and a gas refrigerant. In addition, the air conditioner includes a heater that heats the refrigerant in the liquid-gas separator, a pump that circulates the liquid refrigerant flowing from the condenser while the compressor remains suspended where the refrigerant in the liquid-gas separator is heated by making the heater operate before the pump starts, and the pump is started afterwards to perform the pump cycle operation that makes the refrigerant circulate by the pump.

Description

  The present invention relates to an air conditioner.

  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. On the other hand, the server generates a large amount of heat during operation, and is operated with an air conditioner for stable operation.

  In data centers and the like having many server machine rooms, in recent years, there has been an increasing demand for reducing power consumption other than for servers, and air conditioners are also required to have low power consumption. As an air conditioner for the entire server machine room, in general, a compressor, an outdoor heat exchanger (condenser), an expansion valve, and an indoor heat exchanger (evaporator) are connected in order by refrigerant piping to form an air conditioner. A device 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 can be directly cooled by the outside air by simply circulating the refrigerant without using the compressor. Therefore, the cooling operation can be performed.

  Regarding this point, for example, Japanese Patent Laid-Open No. 10-82566 (Patent Document 1) states, “With a simple configuration, a small number of refrigerant pipes, and without being restricted by the installation conditions (height position) of the indoor / outdoor units, Air-cooled packaged air conditioner that can improve energy efficiency by enabling energy-saving operation while securing necessary and sufficient cooling capacity throughout the year without considering problems such as increased fan power and water quality management. For this purpose, in the vapor compression cooling circuit in which the refrigerant is circulated by connecting the compressor 21, the condenser 22, the expansion valve 13, and the evaporator 11 to each other, the space between the condenser 22 and the expansion valve 13 is provided. A refrigerant pump 23 is provided in the pipe, and either the cooling operation of the compression cycle by the operation of the compressor 21 or the cooling operation of the heat transport cycle by the operation of the refrigerant pump 23 is based on the outside air temperature. Has been described as automatically selected to run. "Te (see Abstract).

Japanese Patent Laid-Open No. 10-82566

  According to the technology described in Patent Document 1, when the outside air temperature is lower than the room temperature, the refrigerant is circulated by the pump, so that the cooling operation is performed with low power consumption compared to the circulation by the compressor. Is possible. However, Patent Document 1 does not take into consideration any stable refrigerant amount when switching from a compressor cycle operation by a compressor to a pump cycle operation by a pump.

  That is, in the air conditioner of Patent Document 1, when switching from the compressor cycle operation to the pump cycle operation, there is not enough liquid refrigerant on the pump inlet side, and a large amount of gas refrigerant is supplied to the pump when the pump is started. There is a possibility that so-called cavitation may occur due to the inflow. When this cavitation occurs, refrigerant cannot be circulated by the pump.

  Then, an object of this invention is to provide the air conditioning apparatus which can perform the starting stably so that the cavitation at the time of pump starting may not generate | occur | produce, when switching from a compressor cycle driving | operation to a pump cycle driving | operation.

  In order to solve the above problems, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above problems. To give an example, a compressor that compresses refrigerant in an air conditioner, a condenser that condenses the refrigerant compressed by the compressor, and a condenser Pressure reducing means for reducing the pressure of the refrigerant condensed by the evaporator, an evaporator for evaporating the pressure reduced by the pressure reducing means, and a gas-liquid separator for separating the refrigerant flowing from the evaporator into liquid refrigerant and gas refrigerant. Yes. Furthermore, a heater that heats the refrigerant in the gas-liquid separator and a pump that circulates the liquid refrigerant that flows from the condenser in a state where the compressor is stopped, and the gas-liquid by operating the heater before the pump is started. The refrigerant in the separator is heated, and thereafter, a pump is started to perform a pump cycle operation in which the refrigerant is circulated by the pump.

  ADVANTAGE OF THE INVENTION According to this invention, when switching from a compressor cycle driving | operation to a pump cycle driving | operation, the air conditioning apparatus which can perform stable starting so that the cavitation at the time of pump starting may not be generated can be provided.

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

The figure for demonstrating the structure of the air conditioning apparatus of Example 1. FIG. The Mollier diagram explaining the refrigerating cycle of the air conditioning apparatus of Example 1,2. The figure for demonstrating the structure of the air conditioning apparatus of Example 1. FIG.

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

  A first embodiment will be described with reference to FIGS.

  The air conditioner of the present embodiment has a particularly advantageous effect for cooling operation of a server machine room or the like, and the server machine room to be cooled is about 30 ° C. even when the outside air temperature is low such as in midwinter. It is operated by. Thus, if the outside air temperature is lower than the temperature in the server machine room, cooling can be performed by simply circulating the refrigerant, so that the cooling operation can be performed with low power consumption without using a compressor. Such a system that uses the cold heat of low-temperature outside air is called free cooling. In order to effectively perform free cooling, a system with a forced refrigerant circulation system is being developed. By using a pump for forced circulation, cooling operation with low power consumption can be achieved for a refrigeration cycle using a compressor. Is possible.

  In addition, as equipment attached to the air conditioner, the temperature difference between the air that passes through the air conditioner and the cooling coil is increased by providing a cooling coil that cools the air by passing the cooling water from the refrigerator. And there exists a method corresponding to the low power consumption of an air conditioning apparatus main body. However, this method has a problem in that the structure becomes complicated and the introduction cost increases when viewed as a whole air conditioning system.

  Therefore, in the present embodiment, a highly reliable air conditioner will be described in which the cooling coil is provided in series as described above and the power consumption is reduced by the air conditioner alone without increasing the cost.

  FIG. 1 is a diagram for explaining a configuration of an air conditioner for information communication according to the present embodiment. The air conditioner is composed of an outdoor unit 6 and an indoor unit 7, and includes a compressor cycle operation by a compressor that performs cooling operation by sequentially connecting a compressor 1, a condenser 2, an expansion valve 4, and an evaporator 5 with refrigerant pipes. , Both the condenser 2, the pump 3 (forced refrigerant circulation pump), the expansion valve 4, and the evaporator 5 are sequentially connected to each other through refrigerant pipes to perform both the cycle operation and the pump cycle operation by the pump that performs the cooling operation. In both cycles, the condenser 2, the expansion valve 4, and the evaporator 5 are shared. On the indoor unit 7 side, the expansion valve 4, the evaporator 5, the accumulator 16, and the compressor 1 are mounted and sequentially connected. On the outlet side of the evaporator 5, a temperature sensor 14 for detecting the refrigerant temperature and a pressure sensor 15 for detecting the refrigerant pressure are provided, and the superheat degree of the refrigerant is detected using the detection values of these sensors.

  The compressor cycle and the pump cycle are switched depending on the indoor heat load and the outside air condition. Basically, when the outside air temperature is lower than the room temperature, the compressor cycle operation is switched to the pump cycle operation. Thereby, since the power consumption of the pump is much lower than that of the compressor, the pump can be operated with lower power consumption than the compressor cycle operation.

  Here, it may be assumed that the refrigerant has accumulated in the accumulator 16 based on the operation history so far before the pump is started. In such a case, when the pump 3 is started, there is no sufficient liquid refrigerant on the inlet side of the pump 3, and there is a possibility that the gas refrigerant flows into the pump 3. When a large amount of gas refrigerant flows into the pump 3 in this way, the pump 3 may cause so-called cavitation, and refrigerant circulation cannot be performed.

  Therefore, the air conditioner of this embodiment includes a compressor 1 that compresses the refrigerant, a condenser 2 that condenses the refrigerant compressed by the compressor 1, and a decompression unit (expansion) that decompresses the refrigerant condensed by the condenser 2. Valve 4), evaporator 5 for evaporating the refrigerant depressurized by the depressurizing means (expansion valve 4), and gas-liquid separator (accumulator 16) for separating the refrigerant flowing from evaporator 5 into liquid refrigerant and gas refrigerant And a heater 24 for heating the refrigerant in the gas-liquid separator (accumulator 16).

  Further, a pump 3 that circulates the liquid refrigerant flowing from the condenser 2 in a state where the compressor 1 is stopped is further provided, and the heater 24 is operated before the pump 3 is started to operate in the gas-liquid separator (accumulator 16). The refrigerant is heated, and after that, the pump 3 is started and the pump 3 is circulated by the pump 3 to perform the pump cycle operation.

  As described above, the refrigerant in the accumulator 16 is heated by the heater 24 (accumulator heater) before the pump is started, so that the dryness of the refrigerant increases or becomes an overheated region, and the refrigerant that has existed as the liquid refrigerant is vaporized refrigerant. As the refrigerant moves from the accumulator 16 to the outdoor unit 6 side, sufficient liquid refrigerant can be secured in the surplus refrigerant regulator 9 provided on the outlet side of the condenser 2. Therefore, since the liquid refrigerant flows into the pump 3 when the pump is started, it is possible to stably start the pump and perform subsequent pump cycle operation without performing cavitation.

  FIG. 2 shows a Mollier diagram for explaining compressor cycle operation and pump cycle operation. Since the contents shown in the Mollier diagram are well known, detailed description thereof is omitted. In FIG. 2, the right side of the saturated vapor line is the superheated region, which is in a gas phase only state. The degree of heating indicates the degree of heating, and can be obtained by the difference between the saturation temperature obtained for the pressure detected by the pressure detecting means 15 and the temperature detected by the temperature detecting means 14. For example, when the saturation temperature obtained with respect to the pressure detected by the pressure detection means 15 is 20 ° C. and the temperature detected by the temperature detection means 14 is 25 ° C., the temperature is higher than the saturation temperature and the superheat degree is 5 degrees.

  During the pump cycle operation, the degree of superheat on the outlet side of the evaporator 5 is controlled by the rotational speed / opening of any of the outdoor unit blower 8, the pump 3, and the expansion valve 4, or a combination thereof. However, even if the degree of superheat on the outlet side of the evaporator 5 cannot be ensured, that is, overheating from the saturation region in the lower line of the “refrigeration cycle by the pump” in FIG. 2 (liquid refrigerant evaporation process by the evaporator 5). If it does not reach the region, the refrigerant may accumulate in the gas-liquid separator 16 (accumulator) on the indoor unit 7 side. If such a state continues, a shortage of refrigerant on the inlet side of the pump 3 occurs, which may cause cavitation of the pump 3.

  Therefore, in the air conditioner of the present embodiment, when the pump cycle operation is performed in which the refrigerant is circulated by the pump 3 with the heater 24 stopped, the superheat degree on the outlet side of the evaporator 5 is less than the set value. In some cases, the heater 24 is operated to heat the refrigerant in the gas-liquid separator (accumulator heater). That is, a cavitation detection mechanism that determines that cavitation of the forced refrigerant circulation pump 3 occurs when the degree of superheat on the outlet side of the evaporator 5 cannot be secured. Thereby, since the refrigerant | coolant which accumulated in the accumulator 16 of the indoor unit 7 can be moved to the outdoor unit 6 side, lack of the refrigerant | coolant by the side of a pump inlet can be eliminated, and cavitation generation | occurrence | production can be prevented.

  In FIG. 1, the compressor 1 is connected to a pipe that bypasses the compressor 1 when the pump 3 is operated via an inlet pipe and a check valve or a check valve 13. A check valve is connected to the outlet side of the compressor 1 to prevent the liquid refrigerant from flowing backward. This check valve may be an open / close control according to the compressor operation. The pump 3 is installed independently with respect to the indoor unit and the outdoor unit, and incorporates a control device. A pressure sensor 10 and a temperature sensor 11 for monitoring the degree of supercooling of the refrigerant are arranged on the inlet side of the pump 3.

  The state located on the left side of the saturated liquid line in FIG. 2 is called supercooling, and is a state of only the liquid phase. The degree of supercooling indicates the degree of supercooling, which can be obtained from the difference in measured temperature with respect to the saturation temperature obtained for the pressure detected by the pressure sensor 10. For example, if the saturation temperature with respect to the detected pressure is 10 ° C. and the measured temperature is 5 ° C., the temperature is lower than the saturation temperature, the supercooling is performed, and the supercooling is 5 degrees.

  During the pump cycle operation, the degree of supercooling is controlled by controlling the number of rotations / openings of any one of the outdoor unit blower 8, the pump 3, and the expansion valve 4 or a combination thereof according to the degree of supercooling to suppress cavitation. That is, in FIG. 2, the supercooling region is reached from the saturation region. The pump inlet / outlet is connected by a bypass pipe through a check valve 23 so that the refrigerant bypasses the pump during compressor operation. In addition, the piping before and after the pump has a structure that allows the pump to be replaced when the pump is stopped and the compressor is in operation, via the blocking valve 20.

  In order to suppress driving noise, the silencer 12 is disposed on the inlet side piping or outlet side piping or both sides of the inlet and outlet to suppress pump driving noise. The silencer 12 may be any of a simple expansion type, an insertion tube type, a quinke tube, and a resonance tube. In addition, the pump 3 is fixed to the housing structure via a vibration insulator having a low natural frequency such as rubber or silicon in order to suppress the solid propagation sound caused by the pump drive.

  Moreover, since the pump 3 is installed in the vicinity of the outdoor unit 6, the pipe length between the condenser 2 and the pump 3 is shortened. The pressure drop and vaporization are suppressed, and the possibility of cavitation in the pump 3 can be reduced. Moreover, the pump 3 is installed on the bottom surface of the housing, and the bottom surface is installed at a position lower than the bottom surface of the housing of the outdoor unit 6, thereby reducing the risk of gas phase entering the pump when the pump is activated. That is, the liquid refrigerant moves downward due to gravity, while the gas refrigerant moves upward, thereby reducing the risk of cavitation by facilitating the flow of liquid refrigerant to the pump 3 installed at a low position. Can do.

  In addition, in order to avoid a cavitation driving | operation, when switching to a compressor driving | operation, the liquid refrigerant compression of the compressor 1 may occur. Therefore, when the degree of superheat on the outlet side of the evaporator 5 cannot be ensured by any of the indoor air volume, pump operating frequency, indoor unit expansion valve 4, or a combination thereof (when remaining in the saturation region in FIG. 2), the gas-liquid separator 16 (accumulator) is heated by the heater 24 to control the liquid refrigerant to be expelled.

  Hereinafter, Example 2 will be described with reference to FIG. About the same code | symbol, since it is the same as that of Example 1, description is abbreviate | omitted.

  FIG. 3 shows that the pump 3 is built in the outdoor unit 6 in order to shorten the pipe length between the condenser 2 and the pump 3. As a result, the refrigerant that has entered the supercooling region and has been liquefied by the condenser 2 is further suppressed from being reduced in pressure and vaporized due to pipe loss, and the pump cavitation risk can be reduced.

  Furthermore, it is desirable that the pump 3 is installed in the lower part in the outdoor unit 6. As a result, the gas refrigerant moves upward, so that it is possible to prevent the gas refrigerant from flowing into the pump 3. Further, by installing the pump 3 at a low position that is not more than one-third of the condenser height, it is possible to reduce the risk that the gas phase due to the gas refrigerant enters the pump 3 when the pump is activated. The same effect can be obtained by installing the pump 3 at a position lower than the condenser 2.

  In addition, the air conditioner of a present Example is comprised including the outdoor unit 6 installed outdoors, and the indoor unit 7 installed indoors, and the indoor unit 7 equips the compressor 1 inside. . That is, in this embodiment, since the pump 3 is built in the outdoor unit 6, further installation of the compressor in the outdoor unit 6 leads to an increase in size. Therefore, in the present embodiment, the compressor 1 is built in the indoor unit 7 to reduce the size of the outdoor unit.

  In the case of a normal air conditioner, since there is a user on the indoor unit side, noise becomes a big problem, and it is difficult to arrange a compressor in the indoor unit. However, since the air conditioner of the present embodiment is applied to the cooling of a machine room such as a server, the noise on the indoor unit side is not a big problem. Thus, the outdoor unit 6 includes the pump 3 and the indoor unit 7 as described above. It is effective to incorporate the compressor 1 in each. In addition, when the compressor is installed in the indoor unit, the phenomenon of refrigerant circulation decrease due to pipe loss during long piping is reduced compared to the case where a compressor is installed in the outdoor unit. Can be maintained, leading to higher efficiency of the system.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Pump 4 Expansion valve 5 Evaporator 6 Outdoor unit housing 7 Indoor unit housing 8 Outdoor fan 9 Excess refrigerant adjusting device 10 Pump inlet pressure sensor 11 Pump inlet temperature sensor 12 Silencer 13 Compressor bypass valve 14 Evaporator outlet temperature sensor 15 Pressure sensor 16 Accumulator 17 Compressor outlet pressure sensor 18 Indoor blower 19 Stop valve 20 Pump replacement stop valve 21 Pump bypass valve 22 Compressor bypass valve 23 Pump unit housing 24 Accumulator heater

Claims (9)

A compressor for compressing the refrigerant;
A condenser for condensing the refrigerant compressed by the compressor;
Decompression means for decompressing the refrigerant condensed by the condenser;
An evaporator for evaporating the refrigerant decompressed by the decompression means;
A gas-liquid separator that separates the refrigerant flowing from the evaporator into a liquid refrigerant and a gas refrigerant;
A heater for heating the refrigerant in the gas-liquid separator;
A pump for circulating liquid refrigerant flowing from the condenser in a state where the compressor is stopped,
Before the pump is started, the heater is operated to heat the refrigerant in the gas-liquid separator, and then the pump is started to perform a pump cycle operation in which the pump circulates the refrigerant. Air conditioner to do. In the air conditioner according to claim 1,
The air conditioner includes an outdoor unit installed outside and an indoor unit installed indoors,
The indoor unit includes the compressor inside, and an air conditioner. In the air conditioning apparatus according to claim 1,
When performing a pump cycle operation in which the refrigerant is circulated by the pump while the heater is stopped,
An air conditioner characterized in that when the degree of superheat on the outlet side of the evaporator is equal to or less than a set value, the heater is operated to heat the refrigerant of the gas-liquid separator. In the air conditioning apparatus according to claim 1,
The air conditioner includes an outdoor unit installed outside and an indoor unit installed indoors,
The outdoor unit includes the pump, the condenser, and a pipe connecting the pump, the air conditioner. In the air conditioning apparatus according to claim 4,
The air conditioner is characterized in that the pump is disposed below the condenser. In the air conditioning apparatus according to claim 4,
The air conditioner is characterized in that the pump is disposed in a lower part of the outdoor unit. In the air conditioning apparatus according to claim 4,
The air conditioner characterized in that the outdoor unit has a built-in cavitation detection mechanism of a forced refrigerant circulation pump. In the air conditioning apparatus according to claim 1,
When switching from the pump cycle operation for circulating the refrigerant by the pump to the compressor cycle operation for circulating the refrigerant by operating only the compressor,
An air conditioner characterized in that when the degree of superheat on the outlet side of the evaporator is equal to or less than a set value, the heater is operated to heat the refrigerant of the gas-liquid separator. The air conditioner according to claim 7,
Pressure detecting means for detecting the pressure of the refrigerant on the inlet side of the compressor;
Temperature detecting means for detecting the temperature of the refrigerant on the outlet side of the evaporator,
The air conditioner characterized in that the degree of superheat on the outlet side of the evaporator is calculated using the pressure detected by the pressure detecting means and the temperature detected by the temperature detecting means.