JP2001311567A - Freezer device and environmental test device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a cooling capability to be adjusted within a range of about 0 to 100% in respect to the maximum cooling capability and realize an energy saving. SOLUTION: A bypass passage 9 having a specific pressure expansion valve 8 is connected at its one end with an outlet side passage of a condenser 3 and at the other end with a suction side passage of a compressor 2. When a refrigerant pressure at the suction side passage of the compressor 2 become a negative pressure, the specific pressure expansion valve 8 is opened. A downstream side passage of the specific pressure expansion valve 8 in the bypass passage 9 is provided with a heat exchanger 7 for performing a heat exchanging operation between refrigerant flowing at the downstream side passage and refrigerant flowing at a discharging passage of the compressor 2. When a degree of opening of an electronic expansion valve 4 becomes 0% and a pressure within the suction side passage of the compressor 2 is apt to become a negative pressure, the specific pressure expansion valve 8 is opened, the refrigerant flows through the bypass passage 9 and it may be adjusted to prevent the pressure in the suction side passage of the compressor 2 from becoming a negative pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus and an environmental test apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in order to accurately realize a desired test environment, an environmental test apparatus cools a refrigerator by constantly operating it, while heating it with a responsive heater, and cooling and heating them. There is known an apparatus in which the temperature is controlled so as to keep the internal temperature of the apparatus substantially constant in balance with the above.

[0003] In such an environmental test apparatus, since the range of controlling the temperature in the refrigerator is wide, a refrigerator having the ability to maintain the minimum temperature in the refrigerator becomes excessively burdensome when the temperature in the refrigerator is high. The output of the heater that balances with the power also increases, and energy is wasted.

[0004] Therefore, a control system that makes the cooling capacity variable by adjusting the refrigerant flow rate by an electronic expansion valve or an inverter and reduces the cooling capacity when the cooling capacity is unnecessary is being adopted.

[0005]

However, the above-mentioned environmental test apparatus uses an ON-OF compressor for a refrigerator.
Due to the restriction from the specification range of the compressor that the temperature inside the refrigerator is disturbed when the F control is performed, it is necessary to keep the refrigerator operating at all times. Therefore, the variable range of the cooling capacity of the refrigerator is smaller than the maximum cooling capacity. Only about 40% to 100%, 40
At present, it cannot be made smaller than%. Therefore, the output of the heater can be reduced only to a certain value in order to balance the cooling capacity of the refrigerator.
Therefore, if the cooling capacity of the refrigerator is larger than necessary, the output of the heater that balances it becomes larger than necessary, which is not sufficient in terms of energy saving.

Therefore, the inventor of the present invention has proposed that when the cooling capacity of the refrigerator is unnecessary, the operation state of the compressor is maintained by bypassing the flow of the refrigerant to the evaporator, but the inside of the refrigerator is not cooled. Therefore, the inventors have focused on the fact that the output of the heater can be reduced, and have come up with the present invention.

Incidentally, as described in, for example, JP-A-8-5163, an excessive pressure increase in the refrigeration cycle due to an operation in which liquid return occurs is avoided while suppressing a decrease in operation efficiency. A bypass passage that bypasses the outlet side of the condenser and the outlet side of the evaporator via a heat exchanger, and a throttling device is provided in the bypass passage portion on the inlet side of the bypass passage toward the outlet side of the condenser. It is known that a valve device (poppet type valve) for opening the bypass passage when the refrigerant pressure becomes equal to or higher than a predetermined pressure is provided upstream of the expansion device. When the high pressure is increased, the bypass passage is opened, and energy is not saved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has a refrigeration apparatus capable of adjusting the cooling capacity within a range of 0% to 100% with respect to the maximum cooling capacity and realizing energy saving, and a refrigeration apparatus using the same. The purpose of the present invention is to provide an environmental test device that has been used.

[0009]

A refrigeration apparatus according to the present invention comprises a refrigeration cycle in which a compressor, a condenser, an electronic expansion valve, and an evaporator are sequentially connected to form a refrigeration cycle. One end is connected to the outlet side passage of the condenser, the other end is connected to the suction side passage of the compressor, and the refrigerant pressure of the suction side passage of the compressor provided in the bypass passage is negative. A heat exchange is performed between a constant pressure expansion valve that opens when pressure is reached, and a refrigerant that is provided in a downstream passage of the constant pressure expansion valve of the bypass passage and flows through the downstream passage and refrigerant that flows through a discharge passage of the compressor. And a heat exchanger.

With this arrangement, when the refrigerant pressure in the suction side passage of the compressor becomes negative pressure, the constant pressure expansion valve provided in the bypass passage is opened, and the outlet side passage of the condenser communicates with the outlet passage through the bypass passage. The suction side passage of the compressor communicates with the suction side passage. Therefore, the refrigerant flows from the outlet side passage of the condenser to the suction side passage of the compressor through the bypass passage, and the pressure of the suction side passage of the compressor is controlled so as not to be a negative pressure, and the operating state of the compressor is maintained. Liquid back operation is avoided. Here, before flowing into the suction side passage of the compressor, heat is exchanged with the refrigerant discharged from the compressor in the heat exchanger. With respect to the amount of heat of condensation of the refrigerant, the amount of heat of condensation always becomes larger by the amount of heat input from the compressor, so that there is no heat exchange failure in the heat exchanger.

Therefore, the opening of the electronic expansion valve is reduced to 0%, and the low pressure side pressure of the compressor (the refrigerant pressure in the suction side passage).
Even if the pressure becomes negative pressure, the constant pressure expansion valve is opened and the low pressure side pressure of the compressor is adjusted so as not to become negative pressure, so that the liquid back operation is avoided. Therefore, the opening of the electronic expansion valve can be adjusted in the range of 0% to 100%, and the cooling capacity can be adjusted in the range of 0 to 100% with respect to the maximum cooling capacity. .

Also, one end of the bypass passage may be connected to the inlet passage of the evaporator instead of the suction passage of the compressor.

[0013] In this case, in addition to the above-described operation, an oil return defect due to a low flow velocity does not occur.

[0014] Further, an internal temperature detecting sensor for detecting the internal temperature, a signal received from the internal temperature detecting sensor, and an internal temperature detected by the internal temperature detecting sensor and a set temperature. A temperature controller that adjusts an opening degree of the electronic expansion valve based on the temperature difference.

With this configuration, the opening degree of the electronic expansion valve is set to 0 by the temperature controller on the basis of the temperature difference between the inside temperature detected by the inside temperature detection sensor and the set temperature.
It is adjusted in the range of% to 100%.

Further, the refrigerating apparatus may be cooled by a refrigerating machine while being heated by a heater, and may be used as a refrigerating machine of an environmental test apparatus in which the temperature in a refrigerator is maintained at a set temperature. That is, as the refrigerator, a compressor,
A condenser, an electronic expansion valve, and an evaporator are sequentially connected to form a refrigeration cycle, and a refrigeration apparatus that cools the inside of the refrigerator.
A bypass passage having one end connected to the outlet side passage of the condenser and the other end connected to the suction side passage of the compressor;
A constant pressure expansion valve that is provided in the bypass passage and opens when the refrigerant pressure in the suction side passage of the compressor becomes a negative pressure; and a refrigerant that is provided in the bypass passage downstream of the constant pressure expansion valve and flows through the downstream passage. A heat exchanger that exchanges heat with a refrigerant flowing through a discharge side passage of the compressor, or an end of the bypass passage, wherein the suction passage of the compressor is replaced with an inlet of an evaporator. What is connected to the side passage is used.

With this configuration, the opening degree of the electronic expansion valve becomes zero.
%, And when the low pressure side pressure of the compressor becomes negative pressure, the constant pressure expansion valve opens, the refrigerant flows through the bypass passage, and the low pressure side pressure of the compressor (the refrigerant pressure in the suction side passage) becomes negative pressure. The liquid back operation is avoided so as not to occur, so that the opening degree of the electronic expansion valve can be adjusted in the range of 0% to 100%.

When the opening degree of the electronic expansion valve is reduced, the flow of the refrigerant is restricted, and the cooling capacity in the refrigerator is reduced. The output of the heater can be reduced. As a result, the output of the heater can be reduced to 0%.

Further, it is desirable that the output of the heater is controlled so as to balance the amount of heat taken from the refrigerator by the amount of heat load entering the refrigerator and the amount of internal heat load from the amount of heat taken from the refrigerator. .

With this configuration, it is possible to avoid excessive heating due to the heat load entering the refrigerator and the internal heat load of the fan and the like, which is further advantageous in saving energy.

Further, a temperature controller is provided for monitoring the output of the heater and adjusting the opening of the electronic expansion valve so that the output of the heater maintains a set value. It can also be a few percent of the maximum output of the vessel.

In this way, the cooling by the refrigerator and the heating by the heater are balanced without increasing the output of the heater, and energy saving can be achieved.

The temperature controller decreases the opening of the electronic expansion valve when the output of the heater becomes larger than a set value, and decreases the opening of the electronic expansion valve when the output of the heater becomes smaller than the set value. Can be increased.

With this arrangement, when the output of the heater becomes larger than the set value, the temperature in the refrigerator becomes low.
The opening degree of the electronic expansion valve is reduced by the temperature controller, and the cooling capacity is reduced.On the other hand, when the output of the heater becomes smaller than the set value, the temperature in the refrigerator increases, so that the electronic temperature is controlled by the temperature controller. The degree of opening of the expansion valve is increased, and the cooling capacity is increased.

The temperature controller adjusts the temperature based on the dead zone including the set value. If the output of the heater is within the dead zone, the opening degree of the electronic expansion valve is maintained and the temperature exceeds the dead zone. In such a case, the opening degree of the electronic expansion valve may be reduced while the opening degree of the electronic expansion valve may be increased when the opening degree is smaller than the dead zone.

In this way, the opening of the electronic expansion valve is maintained if the temperature in the refrigerator is within the dead zone including the set value, and if the temperature exceeds the dead zone, the opening of the electronic expansion valve is maintained. It is reduced, the supply of low-temperature refrigerant is reduced, the rise in output of the heater is suppressed, while if it is smaller than the range of the dead zone,
The opening degree of the electronic expansion valve is increased, the supply of the low-temperature refrigerant is promoted, and the increase in the output of the heater is promoted.

[0027]

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

FIG. 1 is an explanatory view showing a schematic configuration of a refrigerating apparatus used in an environmental test apparatus according to the present invention.

In the environmental test apparatus according to the present invention, in order to accurately realize a desired test environment, the refrigeration apparatus is always operated, and is heated by a heater (not shown) which has a good reaction and excellent responsiveness. Thus, the cooling by the refrigerating apparatus and the heating by the heater are balanced so that the temperature is controlled so as to keep the temperature in the refrigerator substantially constant.

As shown in FIG. 1, in the refrigerating apparatus 1, a compressor 2, a condenser 3, an electronic expansion valve 4, and an evaporator 5 are connected in order to constitute a refrigerating cycle. The evaporator 5
Is designed to cool the inside of the storage, which serves as a test room of the environmental test device 6, and reduce the temperature in the storage.

The electronic expansion valve 4 is not linked to the heater, and the heater tries to maintain a constant temperature based on another control program. The output of the heater is controlled so as to balance the amount of heat taken by the refrigerating apparatus 1 from the inside of the refrigerator with the amount of heat load intruding into the refrigerator or heat load of internal heat generated by a fan or the like. Heating is avoided.

A heat exchanger 7 is provided between the compressor 2 and the condenser 3. As is well known, the heat exchanger 7 has a first heat exchange pipe formed inside a casing.
And a second passage 7b using the internal space of the casing around the first passage 7a.
The first passage 7 a is provided in the middle of a passage connecting the discharge side passage of the compressor 2 and the inlet side of the condenser 3, and is configured so that the high-temperature refrigerant discharged from the compressor 2 flows. .

The inlet side of the second passage 7b is connected to a refrigerant passage between the condenser 3 and the electronic expansion valve 4 via an upstream bypass 9A provided with a constant-pressure expansion valve 8 in the middle. It is connected so that the refrigerant flowing out of the condenser 3 flows in. The constant pressure expansion valve 8 opens and closes based on the pressure (low pressure side pressure) of the suction side passage of the compressor 2, and functions to keep the low pressure side pressure of the compressor 2 constant.

On the other hand, the outlet side of the second passage 7b is connected to a refrigerant passage between the evaporator 5 and the compressor 2 via a downstream bypass passage 9B. The refrigerant is returned to the suction side passage of the compressor 2. The upstream and downstream bypass paths 9A, 9
B forms a bypass passage 9 having one end connected to the outlet side passage of the condenser 3 and the other end connected to the suction side passage of the compressor 2.

The constant pressure expansion valve 8 is set so as to open when the pressure in the suction side passage of the compressor 2 becomes negative pressure, so that the pressure in the suction side passage of the compressor 2 does not become negative pressure. Controlled. That is, when the pressure in the suction side passage of the compressor 2 is going to be a negative pressure, the constant pressure expansion valve 8 is opened, and the refrigerant from the condenser 3 flows into the bypass passage 9.
Through the compressor 2 to the suction side of the compressor 2.

The degree of opening of the electronic expansion valve 4 is controlled by a temperature controller 11 based on a signal from an internal temperature detection sensor 10 for detecting the temperature in the internal chamber (test chamber) of the environmental test apparatus 6. The amount of the refrigerant for cooling the inside is adjusted, and the temperature in the refrigerator is adjusted to be maintained at a substantially constant temperature.
That is, the electronic expansion valve 4 has an actuator 4a for controlling the opening thereof, and based on the temperature difference between the inside temperature (test room temperature) detected by the inside temperature detection sensor 10 and the set temperature, The actuator 4a is controlled by the temperature controller 11 to adjust the opening. Therefore, for example, when the temperature in the refrigerator is lower than the set temperature, the opening degree of the electronic expansion valve 4 is reduced. Alternatively, control may be performed such that if the inside temperature detected by the inside temperature detection sensor 10 is equal to or higher than the set temperature, the opening is opened by a certain opening degree, and if the inside temperature does not reach the set temperature, the opening is closed.

On the other hand, when the opening of the electronic expansion valve 4 is controlled and the low-pressure side pressure in the suction side passage of the compressor 2 becomes negative,
The constant pressure expansion valve 8 opens, the bypass passage 9 communicates, the refrigerant from the condenser 3 flows through the bypass passage 9 to the suction side passage of the compressor 2, and the pressure of the suction side passage of the compressor 2 becomes negative pressure. Is avoided.

According to the above apparatus, when the compressor 2 operates, the refrigerant discharged from the compressor 2 normally passes through the heat exchanger 7, the condenser 3, the electronic expansion valve 4, and the evaporator 5,
The temperature is circulated back to the compressor 2, and the temperature in the chamber of the environmental test device 6 becomes a substantially constant set temperature due to the balance between cooling by evaporation in the evaporator 5 and heating by a heater (not shown). Is controlled as follows.

In this case, for example, if the temperature in the refrigerator is substantially equal to the set temperature, there is no need to cool down. Therefore, under the control of the temperature controller 11, the opening of the electronic expansion valve 4 becomes 0%. As a result, no refrigerant flows into the inlet side passage of the evaporator 5, and the cooling capacity for the inside of the refrigerator becomes zero.

Usually, the control standard for the low pressure side of the compressor 2 is 0 MPa or more. However, if the control set value of the constant pressure expansion valve 8 is set to 0 MPa, a cooling capacity is required. At the time of normal operation, since the opening degree of the electronic expansion valve 4 is large, the low-pressure side pressure of the compressor 2 is not more than 0 MPa and is not in a negative pressure state. Therefore, the constant pressure expansion valve 8 is in a fully closed state.
The refrigerant does not flow through the bypass passage 9 (the bypass passages 9A and 9B). On the other hand, when the temperature condition in the refrigerator becomes stable and the cooling capacity becomes unnecessary, the opening of the electronic expansion valve 4 gradually decreases, and the low-pressure side pressure of the compressor 2 decreases.

In the conventional case, if the opening degree of the electronic expansion valve 4 is reduced until the low-pressure side pressure of the compressor 2 decreases to 0 MPa, the opening degree of the electronic expansion valve 4 cannot be reduced further. In this embodiment, it is possible to further narrow down the cooling capacity. This is because, when the low pressure side pressure (pressure in the suction side passage) of the compressor 2 becomes negative pressure, the constant pressure expansion valve 8 is automatically opened, the amount of the refrigerant flowing through the bypass passage 9 is adjusted, and the constant pressure The opening of the expansion valve 8 is controlled so that the pressure in the suction side passage of the compressor 2 is set to 0 MPa.

Thus, the refrigerant discharged from the compressor 2 passes through the heat exchanger 7 (first passage 7a), the condenser 3, the constant pressure expansion valve 8, and the heat exchanger 7 (second passage 7b). ,
Circulation is performed so as to return to the compressor 2, and a failure of the compressor 2 due to a liquid back operation or the like is avoided.

Here, before returning to the suction side passage of the compressor 2, the heat is exchanged with the refrigerant discharged from the compressor 2 in the heat exchanger 7. With respect to the heat of condensation of the discharged refrigerant, the heat of condensation always increases by the amount of heat input from the compressor 2, so that the heat exchanger 7 does not fail in heat exchange.

More specifically, in a conventional apparatus,
The bypass passage 9 having the constant pressure expansion valve 8 as described above.
Therefore, the electronic expansion valve 4 is
It cannot be throttled until its opening reaches 0%.
, It was necessary to supply the refrigerant at a constant rate, so that the output of the heater could only be reduced to a constant value. However, according to the device of the present invention, the opening degree of the electronic expansion valve 4 was reduced. 0%, so the output of the heater is also 0%
And energy savings can be achieved.

In the above embodiment, the condenser 2
The bypass passage 9 having the constant pressure expansion valve 8
Is connected to the suction-side passage of the compressor 2 through the above, but the present invention is not limited to this.
For example, as shown in an environmental test apparatus 6 ′ shown in FIG. 2, a downstream side bypass passage 9 ′ of a bypass passage 9 ′ having a constant pressure expansion valve 8 is provided.
The refrigerating apparatus 1 ′ may be configured such that the downstream end (one end) of B ′ is connected to the inlet side passage of the evaporator 5 instead of the suction side passage of the compressor 2. With this configuration, in addition to the above-described functions and effects, there is an effect that the oil return failure due to the low flow velocity does not occur.

In the above-described embodiment, the temperature controller 11 adjusts the opening of the electronic expansion valve 4 based on the temperature in the chamber serving as a test room. It is also possible to monitor and adjust its output to be a few percent of the maximum output.

In this case, the temperature controller 8 includes the electronic expansion valve 4
The actuator 4a is controlled to increase the opening of the electronic expansion valve 4 when the output of the heater becomes smaller than the set value, while increasing the opening of the electronic expansion valve 4 when the output of the heater becomes larger than the set value. Can be adjusted to be smaller.

The actuator 4a of the electronic expansion valve 4 is controlled based on the dead zone including the set value. If the output of the heater is within the dead zone, the opening of the electronic expansion valve 4 is maintained. The opening of the electronic expansion valve 4 may be adjusted so as to be smaller when the temperature exceeds the dead zone, while the opening of the electronic expansion valve 4 is increased when the temperature is smaller than the dead zone. In this way, for example, when the set opening is 3%, the upper limit of the dead zone is set to 5% and the lower limit is set to 2%, so that the output of the heater becomes 5%.
%, The opening degree of the electronic expansion valve 4 is reduced, if it is less than 2%, the opening degree is increased, and if it is in the range of 2% to 5%,
Since the opening degree is controlled so as not to be changed, the opening degree of the electronic expansion valve 4 is not frequently changed, and stable temperature control is realized.

[0049]

The present invention is embodied in the form described above, and has the following effects.

In the refrigeration apparatus according to the present invention, the constant-pressure expansion valve provided in the bypass passage is provided even if the opening of the electronic expansion valve is reduced to 0% and the pressure in the suction side passage of the compressor becomes negative. Is opened, the refrigerant flows from the outlet side passage of the condenser to the suction side passage of the compressor through the bypass passage, and the pressure of the suction side passage of the compressor is controlled so as not to be a negative pressure,
Since the liquid back operation is avoided, the opening degree of the electronic expansion valve is adjusted in the range of 0% to 100%, and the cooling capacity is set in the range of 0 to 100% with respect to the maximum cooling capacity. Adjustment is possible, and energy saving can be realized.

If one end of the bypass passage is connected to the inlet side passage of the evaporator instead of the suction side passage of the compressor, oil return failure due to a low flow rate can be prevented.

Further, if the opening degree of the electronic expansion valve is adjusted by the temperature controller based on the temperature difference between the inside temperature and the set temperature, the temperature difference between the inside temperature and the set temperature changes. The degree of opening of the electronic expansion valve can be adjusted efficiently.

According to the environmental test apparatus of the present invention, since the above-described refrigeration apparatus is used as a chiller, when the cooling is not required, the opening of the electronic expansion valve is set to 0%.
As a result, heating by a heater for temperature balance can be eliminated. Therefore, the output of the heater is 0%
It is possible to reduce energy consumption.

Further, if the output of the heater is controlled so as to balance the amount of heat taken from the refrigerator by the amount of heat taken into the refrigerator and the amount of the internal heat load, the heater enters the refrigerator. As a result, it is possible to save energy without excessive heating due to the invasive heat load and the internal heat load.

In this case, if the temperature controller monitors the output of the heater and controls the opening of the electronic expansion valve so that the output of the heater maintains several percent of the maximum output, the output of the heater is controlled. Without increasing the temperature, the temperature in the refrigerator can be kept constant by balancing the cooling by the refrigerator and the heating by the heater.

The temperature controller reduces the opening of the electronic expansion valve when the output of the heater is larger than a set value, and increases the opening of the electronic expansion valve when the output is smaller than the set value. , The degree of opening of the electronic expansion can be easily controlled according to the temperature in the refrigerator.

Further, if the temperature controller adjusts based on the dead zone including the set value, the opening of the electronic expansion valve does not change frequently, and stable temperature control can be realized. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a part of a circuit configuration of a refrigeration apparatus used for an environmental test apparatus according to the present invention.

FIG. 2 is an explanatory view showing a part of another embodiment of the circuit configuration of the refrigeration apparatus used in the environmental test apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigeration apparatus 1 'Refrigeration apparatus 2 Compressor 3 Condenser 4 Electronic expansion valve 5 Evaporator 6 Environmental test apparatus 6' Environmental test apparatus 7 Heat exchanger 8 Constant-pressure expansion valve 9 Bypass passage 9 'Bypass passage 9A Upstream bypass passage 9B Downstream bypass 9B 'Downstream bypass 10 Internal temperature detection sensor 11 Temperature controller

Claims (8)

[Claims] 1. A refrigeration system comprising: a compressor, a condenser, an electronic expansion valve, and an evaporator connected in order to form a refrigeration cycle, and cools the interior of the refrigerator. A bypass passage having the other end connected to the suction-side passage of the compressor; a constant-pressure expansion valve provided in the bypass passage, which opens when the refrigerant pressure in the suction-side passage of the compressor becomes a negative pressure; And a heat exchanger provided in a downstream passage of the constant-pressure expansion valve and performing heat exchange between a refrigerant flowing through the downstream passage and a refrigerant flowing through a discharge-side passage of the compressor. apparatus. 2. The refrigerating apparatus according to claim 1, wherein the bypass portion has one end connected to an inlet-side passage of the evaporator instead of the suction-side passage of the compressor. 3. An internal temperature detecting sensor for detecting the internal temperature, a signal from the internal temperature detecting sensor, and an internal temperature and a set temperature detected by the internal temperature detecting sensor. 3. The refrigerating apparatus according to claim 1, further comprising: a temperature controller that adjusts an opening degree of the electronic expansion valve based on a temperature difference between the refrigerating apparatus and the temperature controller. 4. An environmental test apparatus in which a refrigerator is cooled by a refrigerator while being heated by a heater, and the temperature in the refrigerator is maintained at a set temperature, wherein the refrigerator is any one of claims 1 to 3. An environmental test apparatus, which is the refrigeration apparatus according to claim 1. 5. The output of the heater is controlled so as to balance the amount of heat taken from the refrigerator by the amount excluding the heat load entering the refrigerator and the internal heat load from the amount of heat taken from the refrigerator. The environmental test apparatus according to claim 4. 6. A temperature controller that monitors an output of the heater and adjusts an opening degree of the electronic expansion valve so that the output of the heater maintains a set value, wherein the set value is: The environmental test apparatus according to claim 5, wherein the output is several percent of the maximum output of the heater. 7. The temperature controller decreases the opening of the electronic expansion valve when the output of the heater becomes larger than a set value, and decreases the opening of the electronic expansion valve when the output of the heater becomes smaller than the set value. An opening is increased.
Environmental test equipment as described. 8. The temperature controller adjusts the temperature based on a dead zone including the set value, and maintains an opening of the electronic expansion valve when an output of the heater is within a dead zone. 7. The environmental test apparatus according to claim 6, wherein the opening degree of the electronic expansion valve is decreased when the value exceeds the threshold, and the opening degree of the electronic expansion valve is increased when the value is smaller than the dead zone.