One of the standards for evaluating the performance of high and low temperature test chambers is uniformity, but most of the manufacturers of high and low temperature test chambers have shortcomings in uniformity control and cannot meet the needs of users for high precision, so today I will analyze the high and low temperature The reasons for the poor uniformity of the test chamber, and how the excellent high and low temperature test chamber manufacturers control the uniformity.
The structure of the high and low temperature test box affects the temperature uniformity in the middle of the work to a large extent. Because the structure is difficult to be completely symmetrical, it will adversely affect the temperature uniformity. The door is at the front, the air-conditioning room is at the back of the box, and the upper air is supplied and the lower is returned. Obviously, this structure has good left-right symmetry, and it is easier to achieve uniform temperature on the left and right sides, but the structure is asymmetrical from top to bottom and completely different from front to back, which has an uneven effect on the temperature of the working space. Nevertheless, if this single air duct structure is properly designed and handled, practice has proved that the studio can be used from 0.1 to 300m³, and its temperature deviation can meet the standard requirements.
Due to the heat conduction of the box wall, heat loss such as heat leakage (high temperature box) or cold leakage (low temperature box) is generated. In order to compensate for the heat loss, there must be a temperature difference in the supply air. The supply air temperature of the high temperature box is higher than the working temperature in the box, and the low temperature The supply air temperature of the box is lower than the working temperature inside the box. Due to the inevitable temperature difference in the supply air, temperature unevenness occurs in the working room.
Due to the different heat transfer coefficients on the six sides of the high and low temperature test box walls, and some have local heat transfer such as threading holes, the temperature of the box wall is not uniform, so that the radiative convection heat transfer of the box wall is not uniform, which affects the uniformity of the temperature field.
The sealing performance of the box is not good, such as air leakage from the door, which affects the uniformity of the temperature field in the working space.
If the detection of temperature deviation requires placing the test sample in the studio, when the volume of the test product is too large, or the way or position of placement is inappropriate, the air convection is blocked, and a large temperature deviation will occur.
In terms of the precision control of the high and low temperature test box, we have always been the leader. In order to accurately control the uniformity of the test box, the test adopts the working method of hot air flow. The method of bypassing the high temperature gaseous refrigerant to the low pressure side of the system, so as to ensure that the system always operates at a given minimum return gas pressure. Coupled with efficient control methods, the overall operation of the equipment achieves high stability and uniformity.