The temperature uniformity of the high and low temperature test chamber refers to the maximum temperature difference at each point in the working space of the test chamber in a stable state. The temperature uniformity of the high and low temperature test chamber is generally ± 2 ℃. If the temperature uniformity difference is too large, it can lead to temperature deviation inside the high and low temperature test chamber, measurement errors, uneven distribution of thermal stress, unreliable test results, and other consequences, directly affecting the accuracy of the evaluation.

The reasons that generally affect the temperature uniformity of high and low temperature test chambers are:

Equipment structure

The structural design of the high and low temperature test chamber, including the position of the door and the fan room, has a direct impact on its temperature uniformity. The commonly used structure for high and low temperature test chambers includes a front door, an air conditioning room at the back of the chamber, and upper air supply and lower air return. This structure has good left-right symmetry and is easy to achieve uniform temperature on the left and right sides. However, the structure is asymmetric on the top and bottom, and the front and back are also different, which has an uneven impact on the temperature of the workspace. Moreover, traditional single-sided air supply can easily create temperature blind spots, leading to excessive local temperature differences.

Solution: 1. Adopt a "circular air duct+symmetrical layout of multiple air outlets", set up air supply outlets at the top, bottom, and both sides of the test chamber, and cooperate with the back return air channel to form circulating convection of the airflow and reduce local temperature differences.

2. Under the conditions allowed by the experimental method, increase the wind speed to enhance the flow of air inside the box, eliminate dead zones, and achieve uniform temperature inside the box.

Box wall heat conduction

The thermal conductivity of the box wall directly affects the uniformity of temperature. If the thermal conductivity of the box wall material is too high, it will cause heat leakage in the high-temperature box or cold leakage in the low-temperature box, thereby increasing the temperature difference of the air supply and reducing the temperature uniformity.

resolvent:

Reducing the temperature difference of the supply air can reduce the impact of airflow on the temperature field inside the working room, and can more effectively protect the temperature difference. Increasing the air supply volume can not only reduce the temperature difference of the air supply, but also ensure the elimination of dead zones in indoor air flow. Under the conditions allowed by the experimental method, increase the wind speed to enhance the flow of air inside the box, eliminate dead zones, and achieve uniform temperature inside the box.

Box sealing performance

The anti deformation, cracking, and aging properties of door seals and inner plastic can cause air leakage and disrupt the original temperature balance if they lose their elasticity. This not only reduces temperature uniformity, but also affects the operational efficiency of the equipment.

Solution: To prevent local air leakage, choose high-performance insulation materials with sufficient insulation layer thickness to reduce heat loss; The connection between the inner container and the outer shell of the box should have thermal isolation measures to reduce local heat leakage.

Sample volume and placement method

If the sample volume is too large or placed improperly, it will hinder air convection inside the box, resulting in uneven temperature distribution. Especially when testing large or complex samples, if the layout is not reasonable, it will seriously affect the uniformity of temperature.

Solution: Pay attention to the volume, weight, and placement of the sample. The relevant standards stipulate that the total volume of the sample should be less than 1/5 of the internal volume to leave sufficient ventilation space. The area of the sample on each windward side should be less than 1/3 of the windward cross-sectional area. The test sample should not be placed around the air duct, which will seriously affect the circulation of wind. The test sample should be placed steadily to ensure stability.

Temperature control system

The temperature control system is the core component of the high and low temperature test chamber, responsible for regulating and maintaining the temperature inside the chamber. If the control system is inaccurate or unstable, it can cause large temperature fluctuations, which in turn affect the uniformity of temperature. Especially when conducting high-precision testing, the stability and accuracy of the control system are particularly important.

Solution: PID control algorithm: High precision high and low temperature test chambers usually use PID (proportional integral derivative) control algorithm to monitor and adjust temperature in real time through high-precision sensors, ensuring the accuracy and consistency of temperature control.

Intelligent electrical system: equipped with PLC system and human-machine interface engineering, supporting upper computer control, making operation more convenient and flexible. The intelligent system also has data recording function, real-time monitoring and recording of key data, and provides data analysis support.