Air conditioning system

Abstract

The present invention provides an air conditioning system that can perform sensible heat treatment while suppressing latent heat treatment of indoor air, with cooling capacity corresponding to the airflow. To this end, the air conditioning system comprises a refrigeration cycle having a compressor, a condenser, an expansion valve, and an evaporator; an airflow acquisition unit that acquires the airflow of a fan that generates an airflow for passing indoor air through the evaporator; a temperature and humidity sensor that detects the temperature and humidity of the indoor air; a pressure sensor that detects the suction pressure of the compressor; a heat quantity calculation unit that calculates the amount of sensible heat that can be treated per unit time, which is the amount of sensible heat of indoor air that can be treated per unit time, based on the airflow of the fan and the temperature and humidity of the indoor air; a frequency determination unit that determines the upper limit frequency of the compressor so that the amount of heat exchange between indoor air and refrigerant in the evaporator is equal to the amount of sensible heat that can be treated, according to the amount of sensible heat that can be treated and the suction pressure of the compressor; and a control unit that controls the compressor so that the frequency of the compressor is less than or equal to the upper limit frequency.

Description

Technical Field

[0001] The present disclosure relates to an air conditioner.

Background Art

[0002] In an air conditioner that performs heat exchange on the inhaled air in a heat exchanger and discharges the air into the room, there are a first acquisition means for acquiring the temperature and relative humidity of the air, a second acquisition means for acquiring the evaporation temperature of the refrigerant that evaporates in the heat exchanger, an arithmetic means for calculating the dew point temperature of the air based on the acquisition value of the first acquisition means, and a control means for controlling the operation so that the evaporation temperature of the refrigerant acquired by the second acquisition means is equal to or higher than the dew point temperature (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the air conditioner as shown in Patent Document 1, the operation of a compressor or the like is controlled only based on the dew point temperature of the air, and the amount of air (air volume) passing through the heat exchanger (evaporator) is not taken into consideration. For this reason, it is not possible to exhibit an appropriate cooling capacity according to the air volume passing through the evaporator, and there is a possibility of causing an excess or deficiency of the cooling capacity and wasteful power consumption.

[0005] The present disclosure has been made to solve such problems. The object is to provide an air conditioner that can process the sensible heat of indoor air while suppressing the treatment of the latent heat of indoor air and dehumidifying with a cooling capacity according to the air volume.

Means for Solving the Problems

[0006] The air conditioning system according to this disclosure comprises a refrigeration cycle having a compressor, a condenser, an expansion valve, and an evaporator; an airflow acquisition unit that acquires the airflow of a fan that generates an airflow for passing indoor air through the evaporator; a temperature sensor that detects the temperature of the indoor air; a humidity sensor that detects the humidity of the indoor air; a pressure sensor that detects the suction pressure of the compressor; a heat quantity calculation unit that calculates a processable sensible heat quantity, which is the amount of sensible heat of the indoor air that can be processed per unit time, based on the airflow of the fan, the temperature, and the humidity of the indoor air; a frequency determination unit that determines the upper limit frequency of the compressor so that the amount of heat exchange between the indoor air and the refrigerant in the evaporator is equal to the processable sensible heat quantity, based on the processable sensible heat quantity and the suction pressure; and a control unit that controls the compressor so that the frequency of the compressor is less than or equal to the upper limit frequency. [Effects of the Invention]

[0007] The air conditioning system described herein has the effect of being able to process the sensible heat of the indoor air while suppressing dehumidification by processing the latent heat of the indoor air, with a cooling capacity corresponding to the airflow. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram shows a schematic configuration of the refrigerant circuit provided in the air conditioning system according to Embodiment 1. [Figure 2] This is a block diagram showing the configuration of the control system of the air conditioning system according to Embodiment 1. [Figure 3] This figure shows an example of a configuration that realizes the functions of the control device for the air conditioning system according to Embodiment 1. [Modes for carrying out the invention]

[0009] The embodiments for implementing the air conditioning system described herein will be explained with reference to the attached drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are simplified or omitted as appropriate. For convenience, the positional relationships of each structure may be expressed based on the illustrated state in the following explanation. This disclosure is not limited to the embodiments described below, and any combination of embodiments, any modification of any component of each embodiment, or any omission of any component of each embodiment is possible without departing from the spirit of this disclosure.

[0010] Embodiment 1. Embodiment 1 of this disclosure will be described with reference to Figures 1 to 3. Figure 1 is a schematic diagram of the configuration of the refrigerant circuit of an air conditioning system. Figure 2 is a block diagram showing the configuration of the control system of an air conditioning system. Figure 3 is a diagram showing an example of a configuration that realizes the functions of the control device of an air conditioning system.

[0011] As shown in Figure 1, the air conditioning system according to this embodiment comprises an indoor unit 1 and an outdoor unit 2. The indoor unit 1 is installed inside the room to be air-conditioned, i.e., indoors. The outdoor unit 2 is installed outside the room, i.e., outdoors. The indoor unit 1 comprises an evaporator 10, an indoor unit fan 61, a compressor 30, and an expansion valve 40. The outdoor unit 2 comprises a condenser 20 and an outdoor unit fan 62.

[0012] The indoor unit 1 and the outdoor unit 2 are connected by refrigerant piping 50. The refrigerant piping 50 connects the compressor 30, condenser 20, expansion valve 40, and evaporator 10 in a ring shape. Refrigerant is sealed inside the refrigerant piping 50. This forms a refrigerant circuit in which the refrigerant circulates between the evaporator 10 and the condenser 20. From the standpoint of protecting the global environment, it is desirable to use a refrigerant with a low global warming potential (GWP) in the refrigerant circuit.

[0013] As such refrigerants, for example, a (mixed) refrigerant consisting of one or more refrigerants selected from tetrafluoropropene (CF3CF=CH2:HFO-1234yf), difluoromethane (CH2F2:R32), propane (R290), propylene (R1270), ethane (R170), butane (R600), isobutane (R600a), 1,3,3,3-tetrafluoro-1-propene (CF3-CH=CHF:HFO-1234ze), etc., can be used. Specific examples of mixed refrigerants include R516A, R445A, R444A, R454C, R444B, R454A, R455A, R457A, R459B, R452B, R454B, R447B, R447A, R446A, R459A, R474A, R479A, and others.

[0014] The compressor 30 is a device that compresses the supplied refrigerant to increase its pressure and temperature. For example, the compressor 30 can be a rotary compressor or a scroll compressor.

[0015] The expansion valve 40 expands the incoming refrigerant, thereby reducing its pressure. In other words, the expansion valve 40 is a pressure reducing device that reduces the pressure of the refrigerant. For example, a linear electric expansion valve (LEV) can be used as the expansion valve 40.

[0016] The condenser 20 exchanges heat between the refrigerant flowing into the condenser 20 and the air surrounding the condenser 20. The outdoor unit fan 62 blows outside air so that it passes around the condenser 20. In the condenser 20, the incoming refrigerant condenses, and heat exchange occurs between the refrigerant and the outside air sent by the outdoor unit fan 62, heating the air. The air heated in the condenser 20 is then sent outside again by the outdoor unit fan 62.

[0017] The evaporator 10 exchanges heat between the refrigerant flowing into the evaporator 10 and the air surrounding the evaporator 10. The indoor unit fan 61 blows air from the room so that it passes around the evaporator 10. In the evaporator 10, the incoming refrigerant evaporates, and heat exchange takes place between the refrigerant and the indoor air supplied by the indoor unit fan 61, cooling the air. The air cooled in the evaporator 10 is then sent back into the room by the indoor unit fan 61.

[0018] The refrigerant circuit configured in this way forms a refrigeration cycle that acts as a heat pump, transferring heat from the indoor unit 1 to the outdoor unit 2 by performing heat exchange between the refrigerant and air in the evaporator 10 and the condenser 20, respectively. In other words, the air conditioning system according to this embodiment is equipped with a refrigeration cycle having a compressor 30, a condenser 20, a first expansion valve 40, and an evaporator 10, and is capable of cooling operation. The air conditioning system may also be capable of heating operation by further providing a four-way valve that reverses the circulation direction of the refrigerant in the refrigerant circuit. In heating operation, the roles of the condenser 20 and the evaporator 10 are reversed compared to cooling operation. That is, in heating operation, the heat exchanger (evaporator 10) provided in the indoor unit 1 acts as a condenser, and the heat exchanger (condenser 20) provided in the outdoor unit 2 acts as an evaporator.

[0019] The outdoor unit 2 is equipped with an outdoor unit housing (not shown). Inside the outdoor unit housing are a condenser 20, an outdoor unit fan 62, and part of the refrigerant piping 50. The outdoor unit housing has an intake port and an outlet port. Each of these intake port and outlet port is an opening that connects the inside and outside of the outdoor unit housing. Inside the outdoor unit housing, there is an air passage that leads from the intake port to the outlet port. The condenser 20 and the outdoor unit fan 62 are located in the air passage of the outdoor unit housing. This air passage is for taking in air from outside the outdoor unit housing through the intake port, exchanging heat in the condenser 20, and then releasing it to the outside of the outdoor unit housing through the outlet port.

[0020] Similarly, the indoor unit 1 includes an indoor unit housing (not shown). The indoor unit housing is installed indoors, that is, in the space to be cooled (air-conditioned). Inside the indoor unit housing, an evaporator 10, an indoor unit fan 61, a compressor 30, an expansion valve 40, and a part of the refrigerant piping 50 are accommodated. The indoor unit housing has a suction port and a blowout port. Each of these suction port and blowout port is an opening that communicates the inside and the outside of the indoor unit housing. Inside the indoor unit housing, an air passage that leads from the suction port to the blowout port is formed. The evaporator 10 and the indoor unit fan 61 are arranged in the air passage of the indoor unit housing. This air passage is for heat-exchanging the air taken in from the outside of the indoor unit housing through the suction port with the evaporator 10 and then discharging it from the blowout port to the outside of the indoor unit housing.

[0021] In the above, a configuration example in which the compressor 30 and the expansion valve 40 are provided in the indoor unit 1 has been described. However, the configuration of the air conditioner according to this embodiment is not limited to this. The air conditioner may be such that the compressor 30 and the expansion valve 40 are provided in the outdoor unit 2.

[0022] The air conditioner includes a pressure sensor 71 and a temperature and humidity sensor 72. The pressure sensor 71 is a sensor that detects the suction pressure of the compressor 30, that is, the pressure of the refrigerant flowing into the compressor 30. The temperature and humidity sensor 72 is a sensor that detects the temperature and humidity of the air in the room where the indoor unit 1 is installed. Note that the indoor air may be described as the air taken into the indoor unit housing and passing through the evaporator 10. The temperature and humidity sensor 72 is installed, for example, near the suction port in the air passage of the indoor unit housing. Instead of the temperature and humidity sensor 72, a temperature sensor that detects the temperature of the indoor air and a humidity sensor that detects the humidity of the indoor air may be provided separately.

[0023] The air conditioning system is equipped with a control device 100. The control device 100 controls the operation of the air conditioning system. Figure 2 shows the configuration of the control system of the air conditioning system according to this embodiment. The detection results from the pressure sensor 71 and the temperature and humidity sensor 72 are input to the control device 100. Based on the detection results from these sensors, the control device 100 controls the operation of the air conditioning system by controlling the operation of the compressor 30, indoor unit fan 61, outdoor unit fan 62, etc.

[0024] As shown in Figure 2, the control device 100 includes an airflow acquisition unit 110, a heat quantity calculation unit 120, a frequency determination unit 130, and a control unit 140. The airflow acquisition unit 110 acquires the airflow of the indoor unit fan 61. As mentioned above, the indoor unit fan 61 is a fan that generates an airflow that passes indoor air through the evaporator 10. The airflow acquisition unit 110 acquires the airflow of the indoor unit fan 61, for example, by acquiring the rotation speed of the indoor unit fan 61. The rotation speed of the indoor unit fan 61 may be acquired by detecting the rotation speed of the motor of the indoor unit fan 61 using a sensor such as an encoder, or it may be acquired from the control signal of the indoor unit fan 61 by the control unit 140.

[0025] The heat quantity calculation unit 120 calculates the amount of sensible heat that can be processed. The amount of sensible heat that can be processed is the amount of sensible heat from the indoor air that can be processed per unit time. The heat quantity calculation unit 120 calculates the amount of sensible heat that can be processed based on the airflow rate of the indoor unit fan 61 and the temperature and humidity of the indoor air. The heat quantity calculation unit 120 obtains the airflow rate of the indoor unit fan 61 from the airflow rate acquisition unit 110. The heat quantity calculation unit 120 also obtains the temperature and humidity of the indoor air from the temperature and humidity sensor 72. Then, the heat quantity calculation unit 120 calculates the amount of sensible heat that can be processed using this acquired information.

[0026] Specifically, for example, the heat quantity calculation unit 120 calculates the amount of sensible heat that can be processed qs [W] from the airflow rate Q [m^3 / s] of the indoor unit fan 61, air density ρ [kg / m^3], specific heat of air c [J / kg·K], indoor air temperature T [°C], and indoor air dew point temperature Td [°C] using the following equation (1). The dew point temperature Td can be determined from the indoor air temperature T and indoor air humidity. In addition, preset constants can be used for air density ρ and specific heat of air c.

[0027] qs = Q·ρ·c·(T-Td) ··· (1)

[0028] The frequency determination unit 130 determines the upper limit frequency of the compressor 30 during cooling operation. More specifically, the frequency determination unit 130 determines the upper limit frequency of the operating frequency of the compressor 30 such that the amount of heat exchange between the indoor air and the refrigerant in the evaporator 10 is equivalent to the amount of sensible heat that can be processed, as calculated by the heat quantity calculation unit 120. Here, the amount of heat exchange in the evaporator 10, i.e., the cooling capacity, can be calculated from the pressure of the low-pressure gas refrigerant flowing out of the evaporator 10 and the operating frequency of the compressor 30. Furthermore, the pressure of the refrigerant flowing out of the evaporator 10 can be rephrased as the pressure of the refrigerant flowing into the compressor 30. Therefore, the frequency determination unit 130 calculates the operating frequency of the compressor 30 necessary to achieve a cooling capacity equivalent to the amount of sensible heat that can be processed, based on the suction pressure of the compressor 30 detected by the pressure sensor 71, and determines this calculated operating frequency as the upper limit frequency.

[0029] The control unit 140 controls the operation of the air conditioning system by controlling the operation of the compressor 30, indoor unit fan 61, outdoor unit fan 62, etc., based on the detection results of each sensor and various control parameters. For example, in cooling operation, the control unit 140 controls the frequency of the compressor 30, etc., so that the indoor air temperature detected by the temperature and humidity sensor 72 reaches a set target temperature. The target temperature for cooling operation may be set by the user using a remote control, for example, or it may be automatically determined by the control unit 140, etc.

[0030] In particular, in this embodiment, the control unit 140 controls the operation of the compressor 30 so that the frequency of the compressor 30 is less than or equal to the upper limit frequency determined by the frequency determination unit 130 during cooling operation. That is, as described above, the control unit 140 controls the frequency of the compressor 30 so that the temperature of the indoor air reaches the target temperature, but in doing so, it ensures that the frequency of the compressor 30 does not exceed the upper limit frequency. If it is not possible to bring the temperature of the indoor air to the target temperature without exceeding the upper limit frequency, for example, the control unit 140 may operate the compressor 30 at the upper limit frequency to bring the temperature of the indoor air as close to the target temperature as possible.

[0031] With the air conditioning system configured as described above, by suppressing the operating frequency of the compressor during cooling operation so that the cooling capacity is within the range necessary for processing the sensible heat of the indoor air, it is possible to process the sensible heat of the indoor air while suppressing dehumidification by processing the latent heat of the indoor air with cooling capacity commensurate with the airflow, even when the room temperature is low or the humidity is high. Therefore, it is possible to achieve both the ability to exert cooling capacity commensurate with the airflow and the suppression of either or both of the scattering of drain water into the room and the generation of static electricity due to the decrease in humidity of the indoor air. Furthermore, since it is possible to avoid processing unnecessary latent heat, it is possible to reduce energy consumption and suppress the occurrence of excess or insufficient cooling capacity and wasted power consumption.

[0032] In particular, air conditioning systems installed in data centers are required to process the heat exhausted from servers, that is, to process the sensible heat of the indoor air to the extent that it is heated by the heat exhausted from the servers. On the other hand, if the latent heat of the indoor air is also processed and dehumidified, condensate water may be scattered from the indoor unit and splash onto the servers, or static electricity may be generated due to the decrease in humidity of the indoor air, potentially causing server failure. For this reason, air conditioning systems for data centers are strongly required to process only the sensible heat of the indoor air with minimal dehumidification during cooling operation, that is, to achieve a cooling operation with a sensible heat factor (SHF) of 1. As described above, the air conditioning system according to this embodiment can, during cooling operation, exert cooling capacity according to the airflow even when the room temperature is low or the humidity is high, and process sensible heat while suppressing dehumidification. For this reason, it is particularly suitable for use in data centers.

[0033] The heat quantity calculation unit 120 may calculate the amount of sensible heat that needs to be processed in order to bring the temperature of the indoor air to the target temperature for cooling operation, that is, the amount of sensible heat from the indoor air that needs to be removed in order to lower the room temperature to the target temperature, and this calculated amount of sensible heat may be used as the amount of sensible heat that can be processed as described above. In this case, the heat quantity calculation unit 120 obtains the target temperature for cooling operation from the control unit 140, for example. By doing so, the system can be operated with a cooling capacity that is necessary and sufficient to bring the room temperature to the target temperature. Therefore, it is possible to further suppress the processing of latent heat and dehumidification of the indoor air due to excessive heat exchange in the evaporator 10. Furthermore, since it is possible to avoid not only the processing of unnecessary latent heat but also the processing of sensible heat that is not necessary to achieve the target temperature, it is possible to further reduce the amount of energy consumed.

[0034] Figure 3 shows an example of a configuration that realizes the functions of the control device 100 in this embodiment. The functions of the control device 100 are realized, for example, by a processing circuit. The processing circuit may include a processor 101 and a memory 102. The processing circuit may also include dedicated hardware 103. A part of the processing circuit may be formed as dedicated hardware 103, and the processing circuit may further include a processor 101 and a memory 102. In the example shown in the figure, a part of the processing circuit is formed as dedicated hardware 103. Also, in the example shown in the figure, the processing circuit further includes a processor 101 and a memory 102.

[0035] A processing circuit that is partly a dedicated hardware component 103 may include, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. If the processing circuit includes at least one processor 101 and at least one memory 102, the functions of the control device 100 are realized by software, firmware, or a combination of software and firmware.

[0036] The software and firmware are written as programs and stored in memory 102. The processor 101 reads and executes the programs stored in memory 102 to realize the functions of each part. The processor 101 is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. Examples of memory 102 include non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, and EEPROM, or magnetic disks, flexible disks, optical disks, compact disks, minidiscs, and DVDs.

[0037] In this way, the processing circuit of the control device 100 can realize each function of the control device 100 through hardware, software, firmware, or a combination thereof. If the processing circuit of the control device 100 includes at least a processor 101 and a memory 102, the processor 101 executes a program stored in the memory 102 of the control device 100, and the functions of each part of the control device 100 are realized through the cooperation of the hardware and software of the control device 100. It should be noted that the air conditioning system is not limited to a configuration in which the operation is controlled by a single control device 100. The air conditioning system may be controlled by the operation of multiple devices working together. [Industrial applicability]

[0038] This disclosure can be used in an air conditioning system that performs cooling operation and includes a refrigeration cycle having a compressor, condenser, expansion valve, and evaporator. [Explanation of Symbols]

[0039] 1 Indoor unit 2 Outdoor unit 10 Evaporator 20 Condenser 30 Compressors 40 Expansion valve 50 Refrigerant piping 61 Indoor unit fan 62 Outdoor unit fan 71 Pressure Sensor 72 Temperature and Humidity Sensor 100 Control device 101 Processors 102 memory 103 Dedicated Hardware 110 Air volume acquisition section 120 Calorie calculation part 130 Frequency Determination Unit 140 Control Unit

Claims

1. A refrigeration cycle having a compressor, condenser, expansion valve and evaporator, An airflow acquisition unit that acquires the airflow of a fan that generates an airflow that passes indoor air through the evaporator, A temperature sensor for detecting the temperature of the indoor air, A humidity sensor for detecting the humidity of the indoor air, A pressure sensor for detecting the suction pressure of the compressor, A heat quantity calculation unit calculates the amount of sensible heat that can be processed per unit time, which is the amount of sensible heat of the indoor air that can be processed per unit time, based on the airflow of the fan and the temperature and humidity of the indoor air. A frequency determination unit determines the upper limit frequency of the compressor such that the amount of heat exchange between the room air and the refrigerant in the evaporator is equal to the amount of heat that can be processed, in accordance with the amount of heat that can be processed and the suction pressure. An air conditioning system comprising: a control unit that controls the compressor so that the frequency of the compressor is less than or equal to the upper limit frequency;

2. The air conditioning device according to claim 1, wherein the heat quantity calculation unit calculates the amount of sensible heat that needs to be processed to bring the temperature of the indoor air to the target temperature, based on the target temperature for cooling operation, as the amount of sensible heat that can be processed.

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