JP7416604B2 - air conditioner - Google Patents

Description

The present invention relates to an air conditioner, and more particularly to an air conditioner installed in a constant temperature and humidity room to perform constant temperature and humidity control.

BACKGROUND ART Conventionally, an air conditioner is known that is installed in a constant temperature and humidity room and performs constant temperature and humidity control to maintain indoor air at a set temperature and humidity with high precision (for example, ±0.1° C.). This type of air conditioner cools and dehumidifies indoor air using a cooling coil, heats the cooled and dehumidified air with a heater, and humidifies the heated air with a humidifier to maintain constant temperature and humidity. Take control.

As the cooling coil, a heat exchanger is used which acts as an evaporator of the refrigeration system. The cooling coil cools the air by evaporating the refrigerant passing through the heat exchanger. Dehumidification by the cooling coil is performed by condensing moisture in the indoor air on the cooling coil and removing the condensed moisture.

For example, Patent Document 1 discloses an air conditioner that performs constant temperature and humidity control by setting the evaporation temperature of a refrigerant in a cooling coil. In such an air conditioner, a temperature obtained by subtracting a predetermined value from the set temperature is set as the evaporation temperature. The predetermined value varies depending on the set temperature.

JP 2017-122573 Publication

Problems with conventional constant temperature and humidity control will be explained using FIGS. 6A and 6B. 6A and 6B are psychrometric diagrams showing cooling and dehumidification states in constant temperature and humidity control of a conventional air conditioner. In FIGS. 6A and 6B, state A is the set temperature SP and set humidity, and state B is the dry bulb temperature and relative humidity at the outlet of the cooling coil. Dp is the dew point temperature at the set temperature SP and set humidity, Tf is the surface temperature of the cooling coil (hereinafter referred to as coil surface temperature), and Et is the evaporation temperature of the refrigerant passing through the cooling coil.

In addition, below, temperature shall be dry bulb temperature, Comprising: Humidity shall be relative humidity. Similarly, the set temperature is the set dry bulb temperature, and the set humidity is the set relative humidity. Further, below, as an example of constant temperature and constant humidity control in a steady state, consideration will be given on the assumption that the set temperature SP and the set humidity are substantially the same as the temperature and humidity of the air sucked into the air conditioner.

With reference to FIG. 6A, a case where the set humidity is low (eg, set humidity 20%) as in state A4 will be considered. The evaporation temperature Et is set as the predetermined value γ subtracted from the set temperature. When the set humidity is low, the evaporation temperature Et is not set sufficiently low with respect to the dew point temperature Dp4, so the coil surface temperature Tf4 may become higher than the dew point temperature Dp4. In this case, unlike state B, the cooling coil does not dehumidify, but only cools.

With reference to FIG. 6B, a case where the set humidity is high (eg, set humidity 80%) as in state A5 will be considered. Note that the set temperature SP in state A5 in FIG. 6B is the same as the set temperature SP in FIG. 6A. Further, the evaporation temperature Et is the same as in FIG. 6A, and is set as the predetermined value γ subtracted from the set temperature SP. When the set humidity is high, the evaporation temperature Et is set significantly lower than the dew point temperature Dp5, the coil surface temperature Tf5 decreases significantly, and the amount of dehumidification by the cooling coil increases significantly as in state B5. In this case, it is necessary to increase the amount of subsequent humidification by the humidifier. Therefore, the air conditioner consumes wasteful energy.

In other words, when the evaporation temperature is set by subtracting a predetermined value from the set temperature as in the past, dehumidification may not be performed if the set humidity is low. Furthermore, when the set humidity is high, the amount of dehumidification increases significantly.

An object of the present invention is to provide an air conditioner that can perform dehumidification even when the set humidity is low, and can reduce the amount of dehumidification when the set humidity is high.

The air conditioner according to the present invention is an air conditioner that maintains the indoor air of a constant temperature and humidity room at a set temperature and set humidity, and is a heat exchanger that acts as an evaporator of a refrigeration system, and is a heat exchanger that uses evaporation of a refrigerant. A cooling coil that cools and dehumidifies the air in a constant temperature and humidity room, a heater that heats the air that has been cooled and dehumidified by the cooling coil, a humidifier that humidifies the air heated by the heater, and air that passes through the cooling coil. A control device that sets the evaporation temperature of the refrigerant, and the control device sets the evaporation temperature based on the difference between the set temperature and the dew point temperature at the set temperature and the set humidity.

In the air conditioner according to the present invention, it is preferable that the control device sets the lower of the evaporation temperatures calculated by Equation 1 or Equation 2 below as the evaporation temperature.
(Formula 1) Et=SP-α (5≦α≦10)
(Formula 2) Et=SP-β×(SP-Dp) β>1
Here, Et is the evaporation temperature of the cooling coil, SP is the set temperature, and Dp is the dew point temperature at the set temperature and set humidity.

According to the air conditioner according to the present invention, dehumidification can be performed even when the set humidity is low, and the amount of dehumidification can be reduced when the set humidity is high.

FIG. 1 is a schematic diagram showing the configuration of an air conditioner that is an example of an embodiment. FIG. 1 is a schematic diagram showing the configuration of a refrigeration system including a cooling coil, which is an example of an embodiment. FIG. 2 is a psychrometric diagram showing changes in the state of air due to constant temperature and humidity control, which is an example of an embodiment. It is a flow which shows the flow of evaporation temperature setting control in constant temperature and constant humidity control of this embodiment. It is a psychrometric diagram showing an example of constant temperature and humidity control. It is a psychrometric diagram showing another example of constant temperature and constant humidity control. It is a psychrometric diagram showing another example of constant temperature and constant humidity control. It is a psychrometric diagram for explaining the problems of conventional constant temperature and constant humidity control. It is a psychrometric diagram for explaining the problems of conventional constant temperature and constant humidity control.

Hereinafter, an example of an embodiment of the present invention will be described in detail. In the following description, specific shapes, materials, directions, numerical values, etc. are illustrative to facilitate understanding of the present disclosure, and can be changed as appropriate according to usage, purpose, specifications, etc.

In the following, temperature is assumed to be dry bulb temperature, and humidity is assumed to be relative humidity. Similarly, the set temperature is the set dry bulb temperature, and the set humidity is the set relative humidity.

An air conditioner 10, which is an example of an embodiment, will be described using FIG. 1. FIG. 1 is a schematic diagram showing the configuration of an air conditioner 10.

The air conditioner 10 is installed in a constant temperature and humidity room. The air conditioner 10 maintains indoor air in a constant temperature and humidity room at a set temperature and humidity. The constant temperature and humidity room is used, for example, as a clean room or a product testing room.

The air conditioner 10 includes a cooling coil 25 that cools and dehumidifies air, a heater 30 that heats the air cooled and dehumidified by the cooling coil 25, and a humidifier 40 that humidifies the air heated by the heater 30. , and a blower 50 that sends air humidified by the humidifier 40 to a constant temperature and humidity room. The air conditioner 10 also includes a control device 60, the details of which will be described later.

The cooling coil 25 cools and dehumidifies the air. As the cooling coil 25, a heat exchanger functioning as an evaporator of the refrigeration system 20 described later is used, and the air is cooled by evaporation of a refrigerant passing through the heat exchanger. The cooling coil 25 is arranged downstream of the suction section 10A in the air flow of the air conditioner 10.

The heater 30 heats the intake air that has been cooled and dehumidified by the cooling coil 25. As the heater 30, for example, an electric heater is used. An electric heater generates heat by passing electricity through a resistance wire to convert electrical energy into thermal energy. The heater 30 is arranged downstream of the cooling coil 25.

The humidifier 40 humidifies the suction air heated by the heater 30. As the humidifier 40, for example, an electric steam humidifier is used. An electric steam humidifier heats water using heat generated by a heater to generate humidifying steam. Humidifier 40 is arranged downstream of heater 30.

The blower 50 sucks the indoor air of the constant temperature and humidity room into the air conditioner 10 from the suction part 10A, and blows out the air conditioned by the air conditioner 10 from the blowing part 10B to the constant temperature and humidity room. be. The blower 50 is arranged downstream of the humidifier 40 and upstream of the blowing section 10B of the air conditioner 10.

As constant temperature and humidity control, the control device 60 controls the compression of the refrigeration device 20, which will be described later, so that the temperature and humidity detected by the temperature and humidity sensor 65 become the set temperature and humidity set in a setting device (not shown). It has a function of adjusting the frequency of the machine 21 and the opening degree of the expansion valve 23, and controlling the output of the heater 30 or the humidifier 40. Further, the control device 60 has a function of setting the evaporation temperature of the refrigerant passing through the cooling coil 25 as evaporation temperature setting control S10 described later in constant temperature and humidity control.

The temperature and humidity sensor 65 detects the temperature and humidity of the air sucked into the air conditioner 10, that is, the temperature and humidity of the indoor air in the constant temperature and humidity room. The temperature and humidity sensor 65 is provided near the suction section 10A of the air conditioner 10. Note that a plurality of temperature and humidity sensors 65 may be provided in other parts of the constant temperature and humidity chamber.

The refrigeration system 20 that constitutes the cooling coil 25 will be explained using FIG. 2. FIG. 2 is a schematic diagram showing the configuration of the refrigeration device 20.

The refrigeration device 20 is a device that implements a vapor compression refrigeration cycle including the cooling coil 25 described above. The refrigeration system 20 includes a compressor 21 that compresses and raises the temperature of refrigerant gas, a condenser 22 that heats and condenses high-temperature and high-pressure refrigerant gas into a refrigerant liquid, and a condenser 22 that depressurizes and expands the refrigerant liquid to remove some of the liquid. It includes an expansion valve 23 that evaporates, and a cooling coil 25 that serves as an evaporator that evaporates the remaining liquid and removes heat from the surroundings.

The expansion valve 23 has a function of reducing the pressure of the refrigerant liquid. As described above, the frequency of the compressor 21 and the opening degree of the expansion valve 23 are adjusted by the control device 60 so that the evaporation temperature of the cooling coil 25 becomes the set evaporation temperature. The evaporation temperature of the cooling coil 25 may be detected by a temperature sensor, or may be calculated from the evaporation pressure detected by a pressure sensor.

In the refrigeration system 20, the cooling coil 25 is provided in the air conditioner 10 installed inside the constant temperature and humidity chamber, as described above. Further, in the refrigeration system 20, a compressor 21, a condenser 22, a blower for blowing air to the condenser 22, and an expansion valve 23 are provided in an outdoor unit 26 installed outside the constant temperature and constant humidity room.

Constant temperature and humidity control will be explained using FIG. 3. FIG. 3 is a psychrometric diagram showing changes in the state of air due to constant temperature and humidity control.

The air conditioner 10 maintains the temperature and humidity of a constant temperature and humidity room at a set temperature and humidity by constant temperature and humidity control. In FIG. 3, as an example of constant temperature and constant humidity control in a transient state, control to slightly lower the relative humidity of the intake air is illustrated.

Specifically, first, the intake air is cooled and dehumidified from state A to state B by the cooling coil 25. At this time, the dry bulb temperature and absolute humidity decrease on the psychrometric diagram. The suction air is then heated from state B to state C by heater 30. At this time, only the dry bulb temperature increases on the psychrometric diagram. Next, the sucked air is humidified from state C to state D by the humidifier 40. At this time, although it differs depending on the humidification method, when an electric humidifier is used, there is almost no change in the dry bulb temperature on the psychrometric diagram, and the absolute humidity mainly increases.

Evaporation temperature setting control S10 in constant temperature and humidity control will be explained using FIG. 4. FIG. 4 is a flowchart showing the flow of the evaporation temperature setting control S10.

Evaporation temperature setting control S10 is an example of constant temperature and humidity control by the control device 60 of the air conditioner 10, and is control for setting the evaporation temperature of the cooling coil 25. In the constant temperature and humidity control, the control device 60 adjusts the frequency of the compressor 21 and the opening degree of the expansion valve 23 of the refrigeration device 20 so that the evaporation temperature reaches the evaporation temperature set by the evaporation temperature setting control S10. In addition, below, as an example of constant temperature and constant humidity control in a steady state, consideration will be given on the assumption that the set temperature and set humidity are substantially the same as the temperature and humidity of the intake air.

In step S11, the control device 60 calculates the evaporation temperature using Equation 1 below.
[Formula 1] Et=SP-α (5≦α≦10)
Here, Et is the evaporation temperature of the cooling coil 25, and SP is the set temperature of the air conditioner 10. α is a predetermined value determined by the specifications of the cooling coil 25.

In step S11, the value obtained by subtracting a predetermined value from the set temperature is set as the evaporation temperature. In other words, by setting the evaporation temperature to be at least 5° C. lower than the set temperature, a state is realized in which heat is removed from the cooling coil 25 from the intake air. In other words, in step S11, the evaporation temperature at which the intake air is at least cooled is set.

In step S12, the control device 60 calculates the evaporation temperature using Equation 2 below.
[Formula 2] Et=SP-β×(SP-Dp) (β>1)
Here, Et is the evaporation temperature of the cooling coil 25, SP is the set temperature of the air conditioner 10, and Dp is the dew point temperature at the set temperature and set humidity of the air conditioner 10. β is a coefficient determined by the specifications of the cooling coil 25, etc.

In step S12, the evaporation temperature is set based on the difference between the set temperature and the dew point temperature at the set temperature and set humidity. More specifically, the evaporation temperature is set by subtracting the difference between the dew point temperature at the set temperature and the set humidity multiplied by a predetermined coefficient from the set temperature.

Here, (SP-Dp) in Equation 2 becomes lower as the set humidity is higher, and becomes higher as the set humidity is lower. In other words, in step S12, if the set humidity is high, the evaporation temperature is set to be high, and if the set humidity is low, the evaporation temperature is set to be low.

In step S13, the control device 60 selects and sets the lower of the evaporation temperatures calculated in step S11 and step S12 as the evaporation temperature. Actually, in step S13, the evaporation temperature calculated in step S12 is selected and set as the evaporation temperature, except when the set humidity is extremely high (for example, relative humidity is 90% or more). .

For example, when the set humidity is relatively high, in the method of calculating the evaporation temperature in step S12, the value obtained by subtracting 2 to 4° C. from the set temperature is set as the evaporation temperature. At such an evaporation temperature, a state in which heat is removed from the cooling coil 25 from the intake air cannot be realized. Therefore, when the set humidity is relatively high, the evaporation temperature is set to be at least 5° C. lower than the set temperature using the evaporation temperature calculation method in step S11. This ensures that the intake air is at least cooled.

An example of constant temperature and humidity control using the evaporation temperature set by the evaporation temperature setting control S10 will be described using FIGS. 5A, 5B, and 5C.

FIGS. 5A, 5B, and 5C are psychrometric diagrams showing cooling and dehumidification states of constant temperature and humidity control. 5A, 5B, and 5C, state A is the set temperature SP and set humidity, and state B is the dry bulb temperature and relative humidity at the outlet of the cooling coil 25. Dp is the dew point temperature of the set temperature SP and set humidity, Tf is the surface temperature of the cooling coil 25 (hereinafter referred to as coil surface temperature), and Et is the evaporation temperature of the refrigerant passing through the cooling coil 25. In addition, below, as an example of constant temperature and humidity control in a steady state, it will be considered that the set temperature SP and the set humidity are substantially the same as the dry bulb temperature and relative humidity of the air sucked into the air conditioner 10.

With reference to FIG. 5A, a case where the set humidity is low (eg, set humidity 20%) as in state A1 will be considered. In a state where the set humidity is low as in state A1, (SP-Dp) in Equation 2 becomes large, and the evaporation temperature calculated by Equation 2 becomes lower than the evaporation temperature calculated by Equation 1. evaporation temperature is set. At this time, the evaporation temperature Et1 is set sufficiently lower than the dew point temperature Dp1 in state A1.

This prevents the coil surface temperature Tf1 of the cooling coil 25 from becoming higher than the dew point temperature Dp1. Therefore, unlike the conventional constant temperature and humidity control described above, there is no possibility that dehumidification is not performed in the cooling coil 25 (see FIG. 6A). In the constant temperature and constant humidity control of this embodiment, dehumidification and cooling are performed by the cooling coil 25.

With reference to FIG. 5B, a case where the set humidity is high (eg, set humidity 80%) as in state A2 will be considered. Note that the set temperature SP in state A2 in FIG. 5B is the same as the set temperature SP in FIG. 5A. In a state where the set humidity is high as in state A2, although (SP-Dp) in Equation 2 becomes small, the evaporation temperature calculated by Equation 2 is lower than the evaporation temperature calculated by Equation 1. The calculated evaporation temperature Et2 is set. At this time, the evaporation temperature Et2 is set sufficiently higher than the dew point temperature Dp2.

Thereby, as in state B2, the amount of dehumidification by the cooling coil 25 is significantly reduced, and the amount of humidification by the humidifier 40 in subsequent constant temperature and humidity control can also be significantly reduced. Therefore, the air conditioner 10 does not waste energy. In other words, the air conditioner 10 can realize constant temperature and humidity control with the minimum necessary amount of dehumidification.

With reference to FIG. 5C, a case where the set humidity is very high (for example, set humidity 95%) as in state A3 will be considered. Note that the set temperature SP in state A3 in FIG. 5C is the same as the set temperature SP in FIGS. 5A and 5B. In a state where the set humidity is very high as in state A3, (SP-Dp) in Equation 2 becomes very small, and the evaporation temperature calculated by Equation 1 becomes lower than the evaporation temperature calculated by Equation 2. The evaporation temperature Et3 calculated using Equation 1 is set.

According to the air conditioner 10, the amount of dehumidification can be reduced when the set humidity is high, and dehumidification can be performed even when the set humidity is low.

Specifically, by setting the evaporation temperature of the refrigerant in the cooling coil 25 based on the difference between the set temperature and the dew point temperature at the set temperature and set humidity, the evaporation temperature can be set according to the set humidity. . Thereby, when the set humidity is low, the evaporation temperature is set lower than before, and it is possible to avoid dehumidification in the cooling coil 25 from not being performed. Furthermore, when the set humidity is high, the evaporation temperature is set higher than before, and constant temperature and humidity control can be achieved with the minimum necessary amount of dehumidification.

It should be noted that the present invention is not limited to the above-described embodiments and modifications thereof, and it goes without saying that various changes and improvements can be made within the scope of the claims of the present application. .

10 air conditioner, 10A suction section, 10B blowout section, 20 refrigeration device, 21 compressor, 22 condenser, 23 expansion valve, 25 cooling coil, 26 outdoor unit, 30 heater, 40 humidifier, 50 blower, 60 control device, 65 temperature and humidity sensor, Dp dew point temperature, Et evaporation temperature, Tf surface temperature.

Claims (1)

An air conditioner that maintains indoor air in a constant temperature and humidity room at a set temperature and humidity,
a cooling coil that is a heat exchanger that acts as an evaporator of a refrigeration device and that cools and dehumidifies the air in the constant temperature and humidity room by evaporating a refrigerant;
a heater that heats the air cooled and dehumidified by the cooling coil;
a humidifier that humidifies the air heated by the heater;
a control device that sets the evaporation temperature of the refrigerant passing through the cooling coil;
Equipped with
The control device has a first evaporation temperature set based on the set temperature , or a second evaporation temperature set based on a difference between the set temperature and a dew point temperature at the set temperature and the set humidity. Set the lower one as the evaporation temperature,
Air conditioner.

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