JPH087128B2 - Thermal shock test equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for performing a thermal shock test by alternately changing the temperature of a test chamber to a low temperature exposure temperature and a high temperature exposure temperature.

2. Description of the Related Art A conventional thermal shock test device is disclosed in, for example, Japanese Patent Laid-Open No.
274035. In such a thermal shock test apparatus, a heat shock cycle in which the temperature of the test chamber is rapidly and alternately changed between a low temperature exposure temperature and a high temperature exposure temperature can be repeated. By storing the test object in the test chamber and repeating the heat shock, that is, the thermal shock, the durability and reliability of the test object can be accelerated and tested.

In the thermal shock tester, a precooling chamber and a preheating chamber are provided separately from the test chamber in order to rapidly change the temperature inside the test chamber. The pre-cooling chamber is pre-cooled to a temperature lower than the low temperature exposure temperature, and when cooling the test chamber to the low temperature exposure temperature, cold air in the pre-cooling chamber is circulated in the test chamber. The preheating chamber is preheated to a temperature higher than the high temperature exposure temperature,
When the test chamber is exposed to high temperature, hot air in the preheating chamber is circulated in the test chamber. In this way, the temperature inside the test chamber is rapidly cooled or heated.

The precooling chamber is cooled to 0 ° C or lower. Therefore, an evaporator or the like that absorbs ambient heat and cools by evaporating the refrigerant is provided. Frost tends to adhere to the evaporator and the like. When frost adheres, the circulation of cold air and the absorption of heat from the surroundings are hindered, and the cooling capacity is reduced. for that reason,
The defrosting operation, that is, the defrosting operation is performed each time the predetermined number of thermal shocks is reached. In the defrosting operation, the frost of the evaporator is melted by the hot gas defrosting method or the like, and is dropped and removed as a drain.

One thermal shock test consists of multiple thermal shock cycles. Therefore, the defrost operation is performed every fixed number of times.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the thermal shock test equipment, the precooling temperature is −40 to −50.
Reaches about ℃. At such a low temperature, the amount of water that can be contained in air is extremely small. Compared to the amount, in the air at room temperature, a large amount of water is contained even if the relative humidity is small. Since it is difficult to make the test chamber completely airtight, it is not possible to completely prevent water from entering the test chamber from the periphery of the test chamber. In addition, there is a test standard in which the test chamber is opened so that the temperature is kept at room temperature for a certain time in the middle of thermal shock. The water thus introduced into the test chamber adheres to the evaporator or the like in the precooling chamber as frost when the test chamber is cooled.

A defrosting operation, that is, a defrost operation is performed in order to remove the water attached to the precooling chamber. As the defrosting operation, the evaporator is heated by a hot gas defrosting method or the like to melt the attached frost and drop it as a drain. The dropped drain is stored in the lower part of the precooling chamber. In the prior art disclosed in Japanese Patent Laid-Open No. 1-274035,
Introduce air around the equipment for defrosting. Therefore, the amount of frost that adheres to the evaporator and the like during the precooling operation increases, and the amount of water that is stored as drainage during defrosting also increases.

The precooling chamber is provided with a drain pipe for draining the drain to the outside. The drain pipe is water-sealed to prevent air and heat from entering the precooling chamber from the outside through the drain pipe. That is, the drain pipe is always filled with water.
However, since the temperature of the precooling chamber becomes low, the water in the drain pipe freezes. If the water in the drain pipe is frozen, the drain cannot be drained during defrost operation. Therefore, in order to prevent the drain pipe from freezing, a heater for heating the drain pipe is provided. If the heater is constantly heated, the drain pipe will not freeze and drainage will be possible during the defrost operation of the precooling chamber.

However, constantly heating the drain pipe provided in the pre-cooling chamber to be pre-cooled to a low temperature increases the load for cooling the pre-cooling chamber.

An object of the present invention is to provide a thermal shock test apparatus capable of effectively draining drainage and reducing an increase in load of a precooling chamber due to heating of a heater.

Means for Solving the Problems In the present invention, the test chamber 3 includes cold air from a precooling chamber 4 and a preheating chamber 5.
The hot and cold air is alternately supplied to perform a thermal shock test, and the precooling chamber 4 is provided with a cooling means 10 for cooling the precooling chamber to a precooling temperature lower than the low temperature exposure temperature of the test chamber 3 and a precooling chamber. A drain pipe 12 for sealing water and draining the drain is provided, and the drain pipe is used in the cold heat shock test device for performing the defrosting operation of the cooling means 10 every time the number of cold heat shocks reaches a predetermined number N. A heater 13 provided in 12 and a detection for detecting that the number of times of thermal shock until reaching the number N of times of performing the defrosting operation is m or less, which is set to be larger as the low temperature exposure temperature or the precooling temperature is lower. Means 35 and the heater 13 in response to the output from the detection means 35.
And a control means (14) for controlling the heating of the cooling and thermal shock test device.

In the present invention, cold air from the precooling chamber 4 and hot air from the preheating chamber 5 are alternately supplied to the test chamber 3 to perform a thermal shock test, and the precooling chamber 4 is lower than the low temperature exposure temperature of the test chamber 3. Cooling means 10 for cooling the precooling chamber to the precooling temperature, and a drain pipe 12 for sealing the precooling chamber with water and draining the drain
Is provided, and the number of thermal shocks is a predetermined number N
In the cold heat shock test apparatus that performs the defrosting operation of the cooling means 10 every time when the temperature reaches, the heater 13 provided in the drain pipe 12 and the cold heat shock time until reaching the number N of the defrosting operations are the low temperature exposure temperature. Alternatively, in response to the output from the detection unit 35, the heater 13 detects that the pre-cooling temperature is set to be less than or equal to the set time w, which is set larger as the pre-cooling temperature becomes lower.
And a control means (14) for controlling the heating of the cooling and thermal shock test device.

Action According to the present invention, the cooling means of the precooling chamber is defrosted every predetermined number N of thermal shocks. The detection means detects that the number of thermal shock shocks before reaching the number of defrosting operations is a preset number m or less. The control means controls the heating of the heater provided in the drain pipe in response to the output from the control means. That is, the drain pipe is heated by the thermal shock that precedes the defrosting operation by the predetermined number of times m. Therefore, when the defrosting operation is started, the water in the drain pipe is sufficiently melted, and the drainage generated in the precooling chamber due to the defrosting operation can be sufficiently drained.
In addition, since the heating of the heater is performed only during the period of the thermal shock of m or less times from the defrosting operation, the load on the cooling unit of the precooling chamber is not increased.

The heating of the heater is started from the number of times of thermal shock as the low temperature exposure temperature of the test chamber or the precooling temperature of the precooling chamber decreases. Therefore, the ice in the drain pipe can be completely melted immediately before starting the defrosting operation.

Further, according to the present invention, the heater for heating the drain pipe is controlled to be heated within a time period that is equal to or shorter than a predetermined time w from the number of thermal shocks during which the defrosting operation is performed. Therefore, the ice in the drain pipe can be sufficiently melted, and the cooling load on the refrigerating device in the precooling chamber does not increase much.

Further, the time w for heating the drain tube heater is set to be larger as the low temperature exposure temperature of the test chamber or the precooling temperature of the precooling chamber becomes lower. Therefore, the ice in the drain pipe can be completely melted immediately before starting the defrosting operation.

Example FIG. 1 is a schematic sectional view for explaining the configuration of a thermal shock test apparatus according to an example of the present invention. In the housing 1 of the thermal shock testing apparatus, a test chamber 3 is provided, the periphery of which is thermally insulated by a heat insulating wall 2. Below the test chamber 3, a precooling chamber 4 which is also thermally insulated by the heat insulating wall 2 is provided. A preheating chamber 5 that is also thermally insulated by the heat insulating wall 2 is provided above the test chamber 3.

An evaporator 6 for cooling the surroundings by evaporating the refrigerant and a cooling fan 7 for circulating the air in the precooling chamber 4 are provided in the precooling chamber 4. The cooling fan 7 is driven by a motor 8 provided outside the precooling chamber. A regenerator 9 is also provided in the precooling chamber 4. The regenerator 9 has a metal fin such as copper, aluminum or stainless steel, and is cooled by the air circulating in the precooling chamber 4, and absorbs heat when cooling the test chamber 3. In this way, the evaporator 6, the cooling fan 7 and the regenerator 9 constitute a cooling means 10 for cooling the inside of the precooling chamber 4.

Since the evaporator 6 and the regenerator 9 are cooled to a low temperature,
Frost tends to adhere. In order to remove this frost, the evaporator 6
When degassing operation is performed by introducing hot gas into the
Frost is melted and stored as drain in the drain pan 11 below the precooling chamber 4. The drain stored in the drain pan 11 also includes the amount of frost attached to the wall surface of the precooling chamber 4 and the like. When the water level of such a drain rises, the volume of the precooling chamber 4 decreases, and the water level may reach the evaporator 6 and the regenerator 9. Therefore, the precooling chamber 4 is provided with a drain pipe 12 for draining the drain. Drain tube 12
Are drawn out almost horizontally to the heat insulating wall 2. The drain pipe 12 is made of synthetic resin and has a heater 13 provided therein. The heating state of the heater 13 is controlled by the control means 14. The end of the drain pipe 12 is guided below the water surface of the drain trap 15 provided outside the heat insulating wall 2. The water surface of the drain trap 15 is defined by a drain pipe 16 for draining the drain trap 15 to the outside of the housing 1. In this way, ambient air and heat are prevented from directly entering the drain pipe 12.

Cool air circulates in the pre-cooling chamber 4 by the cooling fan 7. The direction of this cold air is indicated by reference numeral 17. A cold air outlet 18 is provided between the precooling chamber 4 and the test chamber 3. The cold air outlet 18 is opened and closed by a low temperature damper 19. The state where the low temperature damper 19 is angularly displaced and the cold air outlet 18 is opened is shown by an imaginary line. In this state, the cold air in the pre-cooling chamber 4 is indicated by reference numeral 17
It is blown into the test chamber 3 without circulating in the direction indicated by. The air in the test chamber 3 is cooled by the regenerator 9 and the evaporator 6. By opening the low temperature damper 19 in this way,
The inside of the test chamber 3 can be cooled rapidly.

A heating heater 20 and a heating fan 21 are provided in the preheating chamber 5. The heating fan 21 is driven by a motor 22,
Hot air circulates in the preheating chamber 5. A hot air outlet 23 is provided between the preheating chamber 5 and the test chamber 3 and is opened and closed by a high temperature damper 24. When the high temperature damper 24 is opened, the hot air in the preheating chamber 5 circulates in the test chamber 3 and rapidly heats the test chamber 3.

A door 25 that can be opened and closed is provided at the opening of the test chamber 3. The door 25 is opened, the test object is brought into the test chamber 3, and the test object after the test is discharged. Door like this
The space between 25 and the heat insulating wall 2 is hermetically sealed. However, since the temperature inside the test chamber 3 rapidly rises or falls, it is difficult to completely prevent ambient moisture or the like from entering the test chamber 3 through the sealing portion of the door 25.

According to the specifications of the thermal shock test, a process of maintaining the room temperature between the low temperature and the high temperature is also required. Therefore, the housing 1 is provided with an intake duct 26 and an exhaust duct 27. An intake port 28 is provided to introduce air at room temperature from the intake duct 26 into the test chamber 3. Inlet port 28
Is opened and closed by an intake damper 29. An intake fan 30 is provided in the intake duct 26. Reference numeral 31 indicates an air inflow direction into the intake duct 26. An exhaust port 32 is provided between the exhaust duct 27 and the test chamber 3 and is opened and closed by an exhaust damper 33. Reference numeral 34 indicates the air discharge direction in the exhaust duct 27.

In the housing 1, there is further provided a detection means 35 for detecting the time point when the heating of the heater 13 of the drain pipe 12 is started, from the number of times of thermal shock.

FIG. 2 is a schematic block diagram showing the electrical configuration of the thermal shock test apparatus shown in FIG. First illustrated detecting means
The reference numeral 35 includes a central processing unit (hereinafter abbreviated as "CPU") 36 realized by a microcomputer or the like. Further, a read-only memory (hereinafter abbreviated as “ROM”) 37 and C in which programs for operating the CPU 36 are stored.
A writable memory (hereinafter abbreviated as “RAM”) 38 as a work memory necessary for the operation of the PU 36 is provided. Further, the detection circuit 35 is also provided with a counter 39 controlled by the CPU 36.

The low temperature exposure temperature T1 for the thermal shock test is set by the low temperature exposure temperature setting means 40. This temperature is, for example, −40 ° C. The precooling temperature setting means 41 responds to the output from the low temperature exposure temperature setting means 40 and sets the precooling temperature T2 shown by the first equation.

T2 = T1−ΔT1 (1) When the low temperature exposure temperature T1 is −40 ° C, the precooling temperature T2 is
For example, it is set to -50 ° C.

The high temperature exposure temperature T3 for the thermal shock test is set by the high temperature exposure temperature setting means 42. The high temperature exposure temperature T3 is, for example, 150 ° C. . Preheating temperature setting means 4
3 responds to the output from the high temperature exposure temperature setting means 42,
The preheating temperature T4 is set as in the second equation.

T4 = T3 + ΔT3 (2) Low temperature and high temperature exposure temperature set in this way
The time of exposure to T1 and T3 is set to 30 minutes, for example. The time of exposure to normal temperature between the high temperature and the low temperature is set to, for example, 5 minutes. The number of times the cycle of low temperature and high temperature thermal shock is repeated is set to 670 times, for example. In such a thermal shock test, the number of defrost times N, which is the interval of the number of cold shock for performing the defrosting operation, is, for example, 45, and the defrost frequency setting means
Set by 44.

The CPU 36 controls the cooling means 10 according to the program set in the ROM 37 to cool the precooling chamber 4 to the precooling temperature T2.
The CPU 36 controls the heater 20 to heat the preheating chamber 5 to the preheating temperature T4. Further, the low temperature damper 19, the high temperature damper 24, the intake damper 29, the intake fan 30, and the exhaust damper 33 are controlled to perform a cycle of thermal shock. The number of times of this cycle is counted by the counter 39, and every time the number of defrost times N is reached, the cooling means 10 is defrosted. From this defrosting operation, heating of the heater 13 is started m times before the scheduled start number of times. This pre-scheduled start number m is set by the pre-scheduled start number setting means 45. When the CPU 36 detects from the count value of the counter 39 that counts the number of thermal shock cycles that the number of times until the start of the defrosting operation is m or less, the CPU 36 energizes the heater 13 through the control means 14 and the drain pipe 12
Heating.

FIG. 3 is a diagram for explaining a process of performing the thermal shock of a preset number of times by the thermal shock test apparatus of the embodiment shown in FIG. FIG. 3 (1) shows a state in which each cycle of thermal shock is carried out. FIG. 3 (2) shows the state of the defrosting operation. For convenience of description, it is assumed that the defrosting operation is performed every five thermal shocks. After the fifth thermal shock, the cooling means 10 starts the first defrosting operation. After the defrosting operation is completed, the cooling means 10 is cooled again. Precooling room 4
When the internal temperature reaches the pre-cooling temperature, the thermal shock of the sixth and subsequent times is performed in total. In this way, the thermal shock test is performed a set number of times while performing the fifth defrosting operation.

FIG. 3 (3) shows a state in which the heater 13 is energized and heated. The energization heating of the heater 13 is performed m times before the defrosting operation is started. In FIG. 3 (3), the case of m = 1 ... (3) is shown, and the heating of the heater 13 is started at the 4th, 9th, 14th, ... And the heating is also ended at the end of the defrosting operation.

FIG. 4 shows a third example of the thermal shock testing apparatus shown in FIG.
9 is a flowchart for explaining the illustrated operation. From step s1 to step s2 and step s3,
Both the total number k of thermal shocks and the number n between defrosting operations are initialized to 1. Cooling heat shock is K times in total, defrosting operation is N times
It should be done every time.

After the initialization, the process proceeds to step s4, and it is determined whether or not n has reached the number N of defrosting operation starts, which is a defrosting operation. If n has not reached the number N of defrost operation starts, the process proceeds to step s5. In step s5, if the number n of thermal shocks does not reach the number N-m of precooling of the heater 13, the process proceeds to step s6.

In step s4, when the number n of thermal shocks reaches the number N of times to perform the defrost operation, step s7
In, the defrosting operation which is the defrosting operation of the cooling means 10 is performed. Next, at step s8, it is judged if the defrost operation should be ended. When it should not be ended, the process returns to step s7. In step s8, when the defrost operation should be ended, the process proceeds to steps s9 and s10. In step s9, the energization of the heater 13 of the drain pipe 12 is stopped. At step s10, the number of times n for determining whether or not the defrost operation should be performed is set to 1 again.

When it is determined in step s5 that the number n of cold and thermal shocks is N-m or more, the process proceeds to step s11, the heater 13 of the drain pipe 12 is energized, and the drain pipe 12 is heated. Since the drain pipe 12 is heated m times before the defrost operation is performed, it is possible to dissolve the frozen water in the drain pipe 12 before the defrost operation.

When each of the above processes is completed, one cycle of thermal shock is performed in step s6. Next, at step s12, it is determined whether or not the total number of times k has reached the set number of times K, and the thermal shock test should be ended. If it should not end, move to step s13 and step s14, k
And m are each incremented by 1 and the process returns to step s4. If it is determined in step s12 that the thermal shock test should be ended, the process moves to step s15 and ends.

FIG. 5 is a diagram for explaining the operation of another embodiment of the thermal shock testing apparatus according to the present invention. In the present embodiment, the number m of pre-planned start times is set to be larger as the precooling temperature T2 becomes lower, as shown in FIG. 5 (1). The setting of the value m of the preceding scheduled start number is performed according to the flow chart shown in FIG. 5 (2). When it is determined that T2 is -20 or more in steps p1 to p2, m is set to 0 in step p3. When it is determined that T2 is less than −20 and −30 or more at step p4, 1 is set to m at step p5. In the same manner, the value of m is set corresponding to the value of T2 in steps p6 to p12. In this way, at step p13, the value of the pre-scheduled start number m having a correspondence relationship with the precooling temperature T2 as shown in FIG. 5 (1) is set. Such a precooling temperature T2 is set according to the first equation based on the value of the low temperature exposure temperature T1. Therefore,
Of course, the number of times m of the preceding scheduled start may be set according to the low temperature exposure temperature T1. The value of ΔT1 in the first expression is preset in the ROM 37, and the calculation of the first expression is performed by the CPU.
By 36. Also, the correspondence relationship in Fig. 5 (1) is RO
It is set as data in M37. The correspondence relationship and the value of ΔT1 and the like are determined in advance by experiments.

FIG. 6 is a diagram for explaining the operation when the value of m is 2 in each of the above embodiments. Fig. 6 (1)
Indicates the temperature in the test chamber 3 with a solid line, the temperature in the precooling chamber 4 with a broken line, and the temperature in the preheating chamber 5 with a two-dot chain line. Temperature T0 indicates normal temperature, T1 indicates low temperature exposure temperature, T2 indicates precooling temperature, T3 indicates high temperature exposure temperature, and T4 indicates preheating temperature. FIG. 6 (2) shows the energized state of the heater 13.

When the number of thermal shock tests reaches the N-2th cycle after the completion of the defrosting operation every N times, the heater 13 is turned on.
When the Nth thermal shock cycle is completed, the defrost operation of the cooling means 10 is started. The temperature in the precooling room rises during the defrost operation. Therefore, even after the defrost operation is completed, the pre-cooling chamber 4 is kept until the next thermal shock cycle.
A preparation period for cooling the inside is required. The power supply to the heater 13 is turned off when the defrost operation ends.
In this way, the heater 13 is heated prior to the defrost operation, so that the ice in the drain pipe is sufficiently melted during the defrost operation. Therefore, the drain generated in the defrost operation can be sufficiently discharged.

FIG. 7 is a moist air ix diagram for explaining the reason why a large amount of drain is generated in the precooling chamber 4. A is 25 ℃
Indicates the indoor condition point where the relative humidity is 50%. At this time, 0.01 kg of water is contained per 1 kg of dry air. When the precooling temperature is −50 ° C., even in the state point B on the saturation line 1, the air can contain only 1/100 the water content of the state point A. The remaining water adheres to the precooling chamber 4 as frost. According to each of the above-described embodiments, the drain generated by defrosting the frost thus attached can be sufficiently discharged.

In each of the above embodiments, the heating of the heater 13 is performed from the number m of preceding scheduled start times of the thermal shock cycle. Since each thermal shock cycle is performed for a fixed time, it goes without saying that the heater 13 may be heated prior to the defrost operation for a time w corresponding to the number of times m. Further, if the heating of the heater 13 is started according to the time w, the heating of the heater 13 can be started even in the middle of one thermal shock cycle as shown in FIG. 6 (3). . Therefore, the drain pipe 12 can be sufficiently heated, and the cooling load of the cooling means 10 can be reduced.

EFFECTS OF THE INVENTION According to the present invention as described above, the heater in the drain pipe is heated by a preset number of times from the number of thermal shocks for performing the defrosting operation. This allows drainage to be drained through the drain pipe during the defrosting operation. Since the heater of the drain pipe is heated only during the period preceding the defrosting operation by a preset number of times, it is possible to reduce an increase in the cooling load on the cooling means of the precooling chamber. Further, the number of times preceding this is set to be larger as the low temperature exposure temperature or precooling temperature of the test chamber becomes lower, and the drain tube can be heated as necessary and sufficient corresponding to the exposure temperature and precooling temperature. .

Further, according to the present invention, the heater of the drain pipe can be heated prior to the defrosting operation for a predetermined time.
As a result, the drain generated in the precooling chamber due to the defrosting operation can be sufficiently drained, and an increase in the cooling load on the cooling means in the precooling chamber can be reduced. The predetermined time is set to be larger as the low temperature exposure temperature or the precooling temperature becomes lower, and the drain pipe can be heated as necessary and sufficient corresponding to the exposure temperature or the precooling temperature.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the construction of an embodiment of the present invention, FIG. 2 is a block diagram showing the electrical construction of the embodiment shown in FIG. 1, and FIG. 3 is a view of the embodiment shown in FIG. FIG. 4 is a flowchart for explaining the operation, FIG. 4 is a flow chart for explaining the operation in the embodiment shown in FIG. 1, and FIG. 5 is an operation for setting the preceding scheduled start number m in another embodiment of the present invention. FIG. 6 is a diagram for explaining the temperature change and energization of the heater 13 in the embodiment shown in FIG. 1 or 5, and FIG. 7 is a diagram for the embodiment shown in FIG. 1 or 5 It is a moist air diagram for explaining that frost adheres in the precooling chamber 4. DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Heat insulation wall, 3 ... Test chamber, 4 ... Pre-cooling chamber, 5 ... Pre-heating chamber, 6 ... Evaporator, 7 ... Cooling fan, 9 ... Regenerator, 10 Cooling means, 11 ... Drain pan, 12 ... Drain Tube, 13
... heater, 14 ... control means, 18 ... cold air outlet, 19 ... low temperature damper, 20 ... heating heater, 21 ... heating fan, 23 ... hot air outlet, 24 ... high temperature damper, 25 ... door, 35 ... detecting means, 36 … CP
U, 37 ... ROM, 38 ... RAM, 39 ... Counter, 40 ... Low temperature exposure temperature setting means, 41 ... Precooling temperature setting means, 42 ... High temperature exposure temperature setting means, 43 ... Preheating temperature setting means, 44 ... Defrosting frequency setting means , 45… Advance scheduled start count setting means

Claims (2)

[Claims] 1. A cold air from a precooling chamber 4 and a preheating chamber 5 in a test chamber 3.
The hot and cold air is alternately supplied to perform a thermal shock test, and the precooling chamber 4 is provided with a cooling means 10 for cooling the precooling chamber to a precooling temperature lower than the low temperature exposure temperature of the test chamber 3 and a precooling chamber. A drain pipe 12 for sealing water and draining the drain is provided, and the drain pipe is used in the cold heat shock test device for performing the defrosting operation of the cooling means 10 every time the number of cold heat shocks reaches a predetermined number N. A heater 13 provided in 12 and a detection for detecting that the number of times of thermal shock until reaching the number N of times of performing the defrosting operation is m or less, which is set to be larger as the low temperature exposure temperature or the precooling temperature is lower. A thermal shock test apparatus comprising: a means (35) and a control means (14) for controlling the heating of the heater (13) in response to the output from the detection means (35). 2. A cold air from a precooling chamber 4 and a preheating chamber 5 in a test chamber 3.
The cold shock test is performed by alternately supplying the hot air from the precooling chamber 4 to the precooling chamber 4, and the cooling means 10 for cooling the precooling chamber to a precooling temperature lower than the low temperature exposure temperature of the test chamber 3 and the precooling chamber. The drain pipe 12 is provided with the drain pipe 12 for sealing and draining the drain, and the drain pipe 12 is provided in the cold thermal shock test device for performing the defrosting operation of the cooling means 10 every time the number of cold thermal shock reaches a predetermined number N. The heater 13 provided and the detection means 35 for detecting that the thermal shock time to reach the number N of times of the defrosting operation is equal to or less than the time w that is set larger as the low temperature exposure temperature or the precooling temperature becomes lower. And a control means (14) for controlling the heating of the heater (13) in response to the output from the detection means (35).