JP2003130430A - Air conditioner and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner capable of performing a high sensible heat control in response to a load without excess dehumidification and suppressing a dehumidification amount to a minimum, by detecting a dew-point temperature of sucked air, and to provide its control method. SOLUTION: The air conditioner comprises a variable displacement compressor 1, a condensation side heat exchanger 2 for condensing and liquifying gas refrigerant delivered from the compressor, a throttle device 3 for decompressing the liquified refrigerant from the condensation side heat exchanger, and an evaporation side heat exchanger 4 for evaporating and liquifying the refrigerant decompressed by the throttle device. The air conditioner also comprises a dry bulb temperature detecting means 7 or 8 for detecting temperature on the suction side or the discharge side of the evaporation side heat exchanger, a humidity detecting means 10 for detecting a humidity on the suction side of the evaporation side heat exchanger, and controllers 11 and 12 for controlling the compressor and the throttle device based on the detection results of the dry bulb temperature detecting means and the humidity detecting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner and its control method, and more particularly to an air conditioner used as an air conditioner for a computer room and its control method.

[0002]

2. Description of the Related Art FIG. 5 is a refrigerant circuit diagram showing the structure of a conventional computer room air conditioner. In this figure, 1 is a variable capacity compressor, 2 is a condensation side heat exchanger that condenses and liquefies the gas refrigerant discharged from the compressor 1, and 3 is a flow rate that reduces the pressure of the liquefied refrigerant from the condensation side heat exchanger 2. Variable diaphragm device,
4 is an evaporation side heat exchanger for evaporating the depressurized refrigerant into gas
5 is a refrigerant pipe that connects the above-mentioned devices to form a refrigerant circuit,
6 is a blower provided in the evaporation side heat exchanger 4, which is indicated by an arrow 6A.
The air path shown by is formed. Reference numeral 7 indicates a suction side dry-bulb temperature detecting means which is provided on the suction side of the air passage of the evaporation side heat exchanger 4 and detects the temperature on the suction side. , 9 are evaporation temperature detecting means provided on the inflow side of the evaporation side heat exchanger 4 for detecting the evaporation temperature.

FIG. 6 is a schematic psychrometric chart showing changes in the sensible heat ratio (SHF) in a conventional air conditioner. Here, as an example, a design point A (suction air temperature 24
SHF = 45 ° C (dry bulb temperature) and humidity (RH)
1, air volume of 300 m ³ / min, suction at sensible heat capacity of 56 kW, heat exchanger designed with the state of blown air and dew point temperature), suction port when the set humidity condition is different from the blower specifications, The state of the air of a heat exchanger part and an outlet is shown. At 100% load at design point A (load 5
The blowout temperature of 6 kW) is obtained by calculating ΔT from the sensible heat ratio (SHF) = 1 by the following formula. Q = 60 × Va × Cp / v × ΔT / 860 (1) Q: Sensible heat capacity (kW) Va: Air volume (m ³ / min) Cp: Specific heat of air (kcal / kg · ° C.) v: Air ratio Volume (m ³ / kg) ΔT: Dry-bulb temperature difference between suction side and outlet side (° C)

Here, for the sake of simplicity, Δp is set as Cp = 0.24 and v = 0.85 in the equation (1).
When T is calculated and the outlet temperature is calculated, it becomes 14.5 ° C. as shown in FIG. The dew point temperature at this time is SHF.
= 1 and the moist air diagram, the intake air temperature is 24
It is determined as the intersection of the saturation curve and the same absolute humidity line B of SHF = 1 that passes through the design point A in ° C, and becomes 11 ° C.
If the dew point temperature is controlled as the target evaporation temperature, the sensible heat capacity can be satisfied without dehumidifying. In the past, it was general to set the dew point temperature + α at a certain design point as the target evaporation temperature, and then adjust the target evaporation temperature while checking the difference (load) between the suction temperature set value and the suction temperature, for example.

[0005]

Since the conventional air conditioner is constructed as described above, the suction state is slightly higher than the design point A in FIG. 6 such as humidity (RH).
At 50%, the outlet temperature at 100% load (56 kW load) is calculated as 14.5 ° C from equation (1) as in the case of 45% humidity (RH), but the dew point at this time is The temperature is the intersection C between the intake air temperature 24 ° C and 50% RH in Fig. 6.
It is determined as the intersection of the saturation curve and the same absolute humidity line D of SHF = 1 passing through, and becomes 13 ° C., and the difference between the outlet temperature and the dew point temperature becomes small. That is, the target evaporating temperature is set without knowing the humidity state of the suction air, and the target evaporating temperature is set to 11 ° C. and is controlled by only the suction side dry-bulb temperature information as in the above 45% RH. Then, the portion corresponding to the humidity of 5% is dehumidified. Especially when pulling down (at 50% RH or more), dehumidification becomes remarkable, and excessive dehumidification is performed transiently, resulting in a design condition of 45%.
There is a problem that it is much lower than RH, and there is a possibility that adverse effects may be exerted on computer devices such as computers due to static electricity generation in a low humidity environment.

Further, as a conventional high sensible heat control method, for example, as shown in Japanese Patent Publication No. 7-92259, a dew condensation water detecting means is provided, and this means detects dew condensation water (dehumidified drain water). There is also a method to raise the target evaporation temperature when the temperature is detected), but this method is an evaporation temperature control that does not generate dew condensation water under high load and high humidity conditions. There was a problem that the heat capacity could not be achieved. Conventionally, as a backup in case of falling into such a low humidity condition, a low humidity condition is detected and humidification is performed by a humidifier, but in this case, the amount of humidification and the humidification capacity increase. was there. There is also a problem that when the air condition around a computer or other computer is unmatched with the evaporation temperature control of the evaporation side heat exchanger, the operation becomes inefficient and power consumption increases.

The present invention has been made in order to solve the above-mentioned problems, and the humidity detecting means is provided in the heat exchanger on the evaporation side to detect the humidity on the suction side, and at the same time, the dew point temperature with respect to the suction air is measured. An object of the present invention is to provide an air conditioner and a control method thereof that can perform high sensible heat control according to a load without excessive dehumidification by detecting and can suppress the dehumidification amount to a minimum.

[0008]

An air conditioner according to the present invention comprises a variable capacity compressor, a condensing side heat exchanger for condensing and liquefying a gas refrigerant discharged from the compressor, and a condensing side heat exchanger. A throttle device for reducing the pressure of the liquefied refrigerant from the exchanger,
An evaporation side heat exchanger for evaporating and gasifying the refrigerant decompressed by this expansion device, a dry-bulb temperature detecting means for detecting the temperature of the suction side or the outlet side of this evaporation side heat exchanger, and an evaporation side heat exchanger It is provided with a humidity detecting means for detecting the humidity on the suction side and a control device for controlling the compressor and the throttle device based on the detection results of the dry bulb temperature detecting means and the humidity detecting means.

The air conditioner according to the present invention also includes
A variable capacity compressor, a condensing side heat exchanger that condenses and liquefies the gas refrigerant discharged from this compressor, a throttle device that depressurizes the liquefied refrigerant from this condensing side heat exchanger, and a depressurizing device Evaporation side heat exchanger for evaporating the generated refrigerant, dry bulb temperature detecting means for detecting the temperature of the suction side or blow side of this evaporation side heat exchanger, and the humidity of the suction side of the evaporation side heat exchanger. A humidity detecting means for detecting, an evaporation temperature detecting means for detecting the evaporation temperature of the evaporation side heat exchanger, and a control device for controlling the evaporation temperature to be equal to or higher than the dew point temperature are provided.

The air conditioner according to the present invention also includes
A dew-point temperature matrix is provided that associates the suction-side dry-bulb temperature and humidity with the intersections of the same absolute humidity line and the saturation curve in the moist air diagram, and the dew-point temperature is obtained from this dew-point temperature matrix. .

The air conditioner according to the present invention also includes
Cooling air blown out from the heat exchanger on the evaporation side is supplied to a rack containing a load such as a computer via the inside of the double floor of the room where the heat exchanger on the evaporation side is installed. Is.

In the air conditioner control method according to the present invention, in the air conditioner described above, the target evaporation temperature is set to the dew point temperature, and the evaporation temperature during operation is within a predetermined range including the target evaporation temperature. When the evaporation temperature during operation exceeds the upper limit of the predetermined range, the capacity of the compressor is increased and the throttle flow rate of the expansion device is increased to a predetermined value. When the lower limit of the range is exceeded, the capacity of the compressor is reduced and the throttle flow rate of the throttle device is reduced.

In the method for controlling an air conditioner according to the present invention, the target temperature of the intake temperature or the outlet temperature is set, and the intake temperature or the outlet temperature during operation is within a predetermined range including the target temperature. When the intake or blowout temperature during operation exceeds the upper limit of the specified range, the control device is operated every predetermined time, and the target evaporation temperature is lowered within the range not falling below the dew point temperature. When the lower limit is exceeded, the target evaporation temperature is increased.

In the method for controlling an air conditioner according to the present invention, the target humidity is set, and the controller is set so that the suction side humidity of the evaporation side heat exchanger is within a predetermined range including the target humidity. When the suction side humidity exceeds the upper limit of the specified range, the target evaporation temperature is lowered within the range that does not fall below the dew point temperature, and when the lower limit of the specified range is exceeded, the target evaporation temperature is decreased. Is designed to be higher.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a refrigerant circuit diagram showing the configuration of the first embodiment. In this figure, 1 is a variable capacity compressor, 2 is a condensation side heat exchanger that condenses and liquefies the gas refrigerant discharged from the compressor 1, and 3 is a flow rate that reduces the pressure of the liquefied refrigerant from the condensation side heat exchanger 2. A variable expansion device, 4 is an evaporative heat exchanger for evaporating the decompressed refrigerant into evaporative gas, 5 is a refrigerant pipe that connects the above-mentioned devices to form a refrigerant circuit, and 6 is provided in the evaporative heat exchanger 4. With a blower
The air path shown by arrow 6A is formed. 7 is the evaporation side heat exchanger 4
Suction side dry-bulb temperature detecting means for detecting the temperature on the suction side, 8 for blowing-side dry-bulb temperature detecting means for detecting the temperature on the blowing side, and 9 for evaporating side heat exchanger. 4, evaporating temperature detecting means for detecting the evaporating temperature, 10 is temperature detecting means provided on the suction side of the evaporating side heat exchanger 4, and 11 is suction side dry-bulb temperature detecting means 7 or blowing side. A capacity control means for controlling the capacity of the compressor based on the detection values of the dry-bulb temperature detection means 8, the evaporation temperature detection means 9 and the humidity detection means 10, and 12 of the expansion device 3 based on the detection values of the evaporation temperature detection means 9. It is a flow rate control means for controlling the flow rate of the refrigerant.

FIG. 2 is a schematic diagram showing a state in which the air conditioner of the first embodiment is installed in a computer room. In this figure, 20 is a computer room, 21 is a double floor forming a free access floor, and the inside is a passage for cooling air blown out from an indoor unit described later. An indoor unit 22 of the air conditioner accommodates the evaporation side heat exchanger 4, the expansion device 3, the blower 6, the suction side and blowout side dry bulb temperature detecting means 7 and 8, the humidity detecting means 10, the flow rate controlling means 12 and the like. In addition, the air in the computer room is sucked in through the upper suction port 23, and the cooling air is blown out through the lower air outlet 24 into the floor surface 21. In this embodiment, the upper portion is the suction port 23 and the lower portion is the air outlet 24. However, the configuration may be reversed to use the lower air outlet 24 as the air inlet and the upper air inlet 23 as the air outlet. it can.

Further, in this embodiment, in order to reduce the installation area of the indoor unit, a split system in which refrigerant circuit components such as a compressor and an accumulator are housed in an outdoor unit (not shown) is shown. But,
It is also possible to adopt a remote system in which each of the above refrigerant circuit components is housed in an indoor unit. Further, reference numeral 25 is a rack accommodating computer equipment, the lower surface of which communicates with the inside of the double floor 21.

In such a structure, the indoor unit 2
The cooling air blown from the outlet 24 of 2 passes through the inside of the floor surface 21 of the free access as shown by the arrow 6A,
The air that has been sucked into the rack 25 in which the load computer is stored and has finished cooling the computer is discharged upward from the rack 25 into the computer room 20, and is sucked into the suction port 23 of the indoor unit 22. Be done. In the indoor unit 22, the evaporation temperature detecting means 9 detects the evaporation temperature of the evaporation side heat exchanger 4, and the compressor capacity and the refrigerant flow rate of the expansion device are controlled so that this temperature becomes equal to or higher than the dew point temperature.

FIG. 3 is a block diagram showing a procedure of dew point temperature detection in the first embodiment. As shown in FIG. 3 (A), the suction side dry-bulb temperature detected by the suction-side dry-bulb temperature detecting means 7 and the humidity detected by the humidity detecting means 10 (here, the relative humidity is explained, but the absolute humidity may be used). From the above, the intersection point between the dry-bulb temperature and the humidity curve on the wet air diagram illustrated in FIG. 6 is obtained, and the sensible heat ratio (SHF) = 1 passing through this intersection point, that is, the intersection point between the same absolute humidity line and the saturation curve. Calculate the dew point temperature from In this case, as shown in FIG. 3 (B), the vertical axis is the suction side dry-bulb temperature, the horizontal axis is the humidity, and the dew point temperature matrix in which the dew point temperature obtained as described above is displayed at the intersection point is set in advance. By preparing, the dew point temperature can be easily obtained if the dry bulb temperature and the humidity are known.
The dry-bulb temperature of this dew-point temperature matrix is at intervals of 1 ° C., and the humidity is at intervals of 1%. Interpolation approximation is performed for intermediate values and extrapolation approximation is performed outside the matrix range.

Embodiment 2. Next, a second embodiment of the present invention will be described with reference to the drawings. Since the refrigerant circuit diagram and the temperature and humidity detecting means of this embodiment are the same as those in FIG. 1, description thereof will be omitted by diverting FIG. 1, and the control method of the second embodiment will be described based on the flowchart of FIG. Will be described.

First, in step S1, the target humidity RH
m and the target suction temperature or blowout temperature TLm are set. Next, in step S2, the dew point temperature TR is obtained from the target humidity RHm and the suction temperature Tin detected by the suction side dry-bulb temperature detecting means 7 by the procedure described in the first embodiment.
Next, in step S3, the initial set value Te of the target evaporation temperature Te
m0 is set to Tem0 = TR, and in step S4, the evaporation temperature Te is set to a certain value such that Tem0−ΔTe ≦ Te ≦ Tem0 + ΔTe at the temperature difference ΔTe set in advance with respect to the evaporation temperature Te. It controls every elapsed time. If the evaporation temperature Te exceeds the above range, a check is made in step S5. If Tem0 + ΔTe <Te, the compressor capacity F is increased by the capacity control means 11 of the compressor in step S6 and the expansion device 3 The flow rate control means 12 increases the throttle flow rate L. On the other hand, Te
If m0-ΔTe> Te, the compressor capacity F is reduced by the compressor capacity controller 11 and the throttle flow rate L is controlled by the flow controller 12 of the expansion device 3 in step S7.
Down.

Then, in step S8, it is determined whether or not the current intake temperature or blowout temperature TL has approached the target set temperature TLm at every set elapsed time, and if not, the target evaporation temperature Tem is changed. To do. That is, if they are not close to each other, it is checked in step S9, and if TLm0 + ΔTL <TL with a temperature difference ΔTL set in advance with respect to the intake temperature or the outlet temperature TL, the target evaporation temperature Tem is set in step S10. Bring it down. However, at this time, Te ≧ TR. On the other hand, TLm0
-If ΔTL> TL, the target evaporation temperature Tem is increased in step S11. When the suction temperature or the outlet temperature TL approaches the target set temperature TLm, it is determined in step S12 whether or not the current humidity RH approaches the target humidity RHm.
At 16, the target evaporation temperature Tem, the compressor capacity F, and the flow rate L of the expansion device are kept as they are. If they are not close to each other, the target evaporation temperature Tem is changed. That is, if they are not close to each other, a check is made in step S13, and a humidity difference ΔRH preset with respect to the humidity RH is calculated as RHm + ΔRH.
<RH, the target evaporation temperature Te in step S14
Down m. However, at this time, Te ≧ TR.
On the other hand, if RHm-ΔRH> RH, step S1
At 5, the target evaporation temperature Tem is increased.

By performing such control, the temperature does not fall below the dew point temperature while satisfying the required load capacity with respect to the set temperature TLm of the suction or blowout temperature,
The amount of dehumidification can be suppressed.

[0024]

The air conditioner according to the present invention includes a variable capacity compressor, a condensing side heat exchanger for condensing and liquefying the gas refrigerant discharged from the compressor, and a condensing side heat exchanger. A throttling device that depressurizes the liquefied refrigerant, an evaporation side heat exchanger that evaporates and gasifies the refrigerant depressurized by this throttling device, and a dry-bulb temperature detection that detects the temperature of the suction side or the blowing side of this evaporation side heat exchanger. Means, a humidity detecting means for detecting the humidity of the suction side of the evaporation side heat exchanger, and a control device for controlling the compressor and the throttling device based on the detection results of the dry bulb temperature detecting means and the humidity detecting means. Because it is
As a result of being able to know the dew point temperature, it is possible to suppress excessive dehumidification, achieve high efficiency, and perform high sensible heat operation with a small dehumidification amount.

The air conditioner according to the present invention also includes
A variable capacity compressor, a condensing side heat exchanger that condenses and liquefies the gas refrigerant discharged from this compressor, a throttle device that depressurizes the liquefied refrigerant from this condensing side heat exchanger, and a depressurizing device Evaporation side heat exchanger for evaporating the generated refrigerant, dry bulb temperature detecting means for detecting the temperature of the suction side or blow side of this evaporation side heat exchanger, and the humidity of the suction side of the evaporation side heat exchanger. Since it is provided with a humidity detecting means for detecting, an evaporation temperature detecting means for detecting the evaporation temperature of the evaporation side heat exchanger, and a control device for controlling the evaporation temperature above the dew point temperature, such as when pulling down High sensible heat operation is possible even when the actual use environment conditions deviate from the design point.

The air conditioner according to the present invention also includes
A dew point temperature matrix is created that associates the suction-side dry-bulb temperature and humidity with the intersection of the same absolute humidity line and the saturation curve in the wet air diagram, and the dew-point temperature is obtained from this dew-point temperature matrix. Can be easily obtained and accurate control can be performed.

The air conditioner according to the present invention also includes
Cooling air blown out from the heat exchanger on the evaporation side is supplied to a rack containing a load such as a computer via the inside of the double floor of the room where the heat exchanger on the evaporation side is installed. Therefore, air conditioning in the computer room can be easily and accurately performed.

In the control method of the air conditioner according to the present invention, the target evaporation temperature is set to the dew point temperature, and the controller is set to a predetermined value so that the evaporation temperature during operation falls within a predetermined range including the target evaporation temperature. If the evaporation temperature during operation exceeds the upper limit of the prescribed range, the capacity of the compressor is increased and the throttle flow rate of the expansion device is increased to exceed the lower limit of the prescribed range. Is designed to reduce the compressor capacity and the throttle flow rate of the expansion device, so that the evaporation temperature does not fall below the dew point temperature while the required load capacity is satisfied, and the dehumidification amount is suppressed. You can

In the air conditioner control method according to the present invention, the target temperature of the intake temperature or the outlet temperature is set, and the intake temperature or the outlet temperature during operation is within a predetermined range including the target temperature. When the intake or blowout temperature during operation exceeds the upper limit of the specified range, the control device is operated every predetermined time, and the target evaporation temperature is lowered within the range not falling below the dew point temperature. When the temperature exceeds the lower limit, the target evaporation temperature is increased, so that highly efficient operation with high efficiency and small dehumidification amount can be performed.

In the air conditioner control method according to the present invention, the target humidity is set, and the controller is set so that the suction side humidity of the evaporation side heat exchanger is within a predetermined range including the target humidity. When the suction side humidity exceeds the upper limit of the specified range, the target evaporation temperature is lowered within the range that does not fall below the dew point temperature, and when the lower limit of the specified range is exceeded, the target evaporation temperature is decreased. Therefore, the amount of dehumidification can be suppressed without lowering the evaporation temperature below the dew point temperature while satisfying the required load capacity.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a state in which the air conditioner of the first embodiment is installed in a computer room.

FIG. 3 is a block diagram showing a procedure of dew point temperature detection in the first embodiment.

FIG. 4 is a high sensible heat control flowchart showing a control method according to a second embodiment of the present invention.

FIG. 5 is a refrigerant circuit diagram showing a configuration of a conventional air conditioner.

FIG. 6 is a schematic psychrometric chart showing SHF changes in a conventional air conditioner.

[Explanation of symbols]

1 compressor, 2 condensation side heat exchanger, 3 throttling device,
4 evaporation side heat exchanger, 5 refrigerant piping, 6 blower, 6A air passage, 7 suction side dry bulb temperature detecting means,
8 blow-out side dry bulb temperature detection means, 9 evaporation temperature detection means, 10 humidity detection means, 11 capacity control means,
12 flow rate control means, 20 computer room, 21 double floor, 22 indoor unit, 23 suction port, 24
Outlet, 25 racks.

Claims (7)

[Claims] 1. A variable capacity compressor; a condensing side heat exchanger for condensing and liquefying a gas refrigerant discharged from the compressor;
A throttle device for decompressing the liquefied refrigerant from the condensation side heat exchanger, an evaporation side heat exchanger for evaporating and gasifying the refrigerant decompressed by the expansion device, and a suction side or a blowing side of the evaporation side heat exchanger. Dry-bulb temperature detecting means for detecting the temperature, humidity detecting means for detecting the humidity of the suction side of the evaporation side heat exchanger, the compressor based on the detection results of the dry-bulb temperature detecting means and the humidity detecting means and An air conditioner comprising: a control device that controls a diaphragm device. 2. A variable capacity compressor, and a condensation side heat exchanger for condensing and liquefying a gas refrigerant discharged from the compressor.
A throttle device for decompressing the liquefied refrigerant from the condensation side heat exchanger, an evaporation side heat exchanger for evaporating and gasifying the refrigerant decompressed by the expansion device, and a suction side or a blowing side of the evaporation side heat exchanger. Dry-bulb temperature detecting means for detecting a temperature, humidity detecting means for detecting the humidity on the suction side of the evaporation side heat exchanger, evaporation temperature detecting means for detecting the evaporation temperature of the evaporation side heat exchanger, and the evaporation An air conditioner comprising: a controller for controlling the temperature to be equal to or higher than the dew point temperature. 3. A dew point temperature matrix is provided in which the suction-side dry-bulb temperature and humidity correspond to the intersections of the same absolute humidity line and the saturation curve in the moist air diagram, and the dew-point temperature is obtained from this dew-point temperature matrix. The air conditioner according to claim 1, wherein the air conditioner is configured as described above. 4. The rack in which a load such as a computer is stored in the cooling air blown out from the evaporation side heat exchanger via the inside of the double floor of the chamber in which the evaporation side heat exchanger is installed. The air conditioner according to any one of claims 1 to 3, wherein the air conditioner is supplied to the air conditioner. 5. The air conditioner according to any one of claims 1 to 4, wherein the target evaporation temperature is set to a dew point temperature, and the evaporation temperature during operation is within a predetermined range including the target evaporation temperature. When the evaporation temperature during operation exceeds the upper limit of the predetermined range, the capacity of the compressor is increased and
When the throttle flow rate of the throttle device is increased and exceeds the lower limit of the predetermined range, the capacity of the compressor is reduced and the throttle flow amount of the throttle device is reduced. Control method. 6. A target temperature of a suction temperature or an outlet temperature is set, and the control device is operated every predetermined time so that the intake temperature or the outlet temperature during operation falls within a predetermined range including the target temperature. When the suction or blowout temperature during operation exceeds the upper limit of the above specified range, the target evaporation temperature is lowered within the range not falling below the dew point temperature, and when the lower limit of the above specified range is exceeded, the target The method for controlling an air conditioner according to claim 5, wherein the evaporation temperature is increased. 7. The target humidity is set, and at the same time, the control device is operated at a predetermined time so that the suction side humidity of the evaporation side heat exchanger falls within a predetermined range including the target humidity. When the value exceeds the upper limit of the above-mentioned predetermined range, the target evaporation temperature is lowered within a range that does not fall below the dew point temperature, and when it exceeds the lower limit of the above-mentioned predetermined range, the target evaporation temperature is increased. The method for controlling an air conditioner according to claim 6, which is characterized in that.