With the development of industry and information technology, environmental testing has become an important method for various scientific research institutes and companies to test product quality. As one of the most important supporting equipment for research and environmental research, temperature and humidity laboratories are used more and more.
1 Affect
Structure of the building
Since the temperature and humidity test room has different inner walls, the temperature and humidity of each part of the wall inside the test room are also different, which affects the convection temperature and studio, causing differences in temperature uniformity and differences.
Thermal load
Some of the heating and cooling loads placed in the test room or sample that affect the total internal temperature will affect the internal temperature and uniformity. According to the relevant standards, by default, the temperature and humidity of the climate testing room and space will be measured.
Heat transfer
Since the number of heat sources in the front, back, left, top and top six of the inner walls of the laboratory are different, but there is detection holes, cable lines and test holes in some parts of the house wall, there will be power. The heat dissipation and heat transfer in some parts of the test room, causing the wrong temperature in the room, because the heat transfer is not consistent convection heat radiated from the room wall, much to affect temperature uniformity.
Thermal radiation
The space design and internal structure of the test room, such as the location of the heating pipe, design, strength and location of the air duct, difficult to achieve the standard of ‘uniformity and symmetry, which will inevitably lead. So that the temperature and humidity are unreasonable in the room.
Mode and volume of test samples
The unreasonable position of the test sample or the size of the sample will prevent the heating of the air in the room, thus affecting the uniformity of temperature and humidity. For example, placing the sample against an interior wall or air vent on one side will affect the rate of thermal cycling in the room, causing the temperature and humidity to increase. According to the requirements of the test standard, for the test of heat-resistant materials, the number of heat-resistant materials is a maximum of 1/5 of the number of laboratories.
Sign
The seal of the house and the door is not strong. For example, when the sheet is damaged and the door is leaking, the temperature and humidity in the temperature and humidity laboratory will be affected.
Wind speed
Generally speaking, during the environmental test, the air speed in the room temperature and humidity should not exceed 1.7m / s. If the wind speed is too high, it will cause a temperature change between the surface of the test piece and the air circulating in the room, and cause the evaporation of water in the liquid gauze, which not suitable for testing and incorrect. Therefore, during the test, reduce the wind speed, better. However, to ensure the uniformity of temperature and humidity in the room, it is necessary to circulate the air in the laboratory. During the no-load test, the average wind speed in the room is 0.6~0.8m/s.
Fair management
When the laboratory reaches the place where the temperature and humidity are kept, there will be some changes in a short time because the different temperatures are not the same. By improving the control of the laboratory and reducing temperature fluctuations, temperature fluctuations can be reduced. For advanced test rooms, the temperature change can be reduced by continuous PID adjustment of the heating power; For the low test room, the temperature change is controlled by equalization, that is, when the test room reaches the set temperature, the refrigerator is still open and the heating power is controlled to correct the excess refrigeration power.
2 Size characteristics
The measurement characteristics of the temperature and humidity laboratory should include the range of temperature and humidity, the change in temperature and humidity, and the same temperature and humidity.
Deviation
The deviation of the laboratory of temperature and humidity refers to the difference between the average value of temperature and humidity shown when the environmental monitoring equipment reaches a stationary position and the average value of the real temperature and humidity considering the middle of the work.
Changes
The laboratory change of temperature and humidity refers to 1/2 of the difference between the maximum value and the minimum value of temperature (humidity) at the centre of its working area within 30 minutes after temperature (humidity) processing has reached stability.
Unity
The uniformity of the test room temperature and humidity is defined as the arithmetic mean of the difference between the highest and the lowest temperature values in each test in 30 minutes after the set temperature value (reach water) reached stability.
3.Connection test
According to the experimental data, when the temperature in the laboratory temperature and humidity are constant and the humidity is increased, the uniformity and the corresponding change in temperature and humidity will be improved. The main reason is that air is a poor thermal conductor. Generally speaking, when the content of water is low and the temperature is low, the temperature of the material is low, the temperature of the solid is higher than that of the liquid, and the temperature of the liquid is high more than that gas. This difference is largely due to different molecular spaces in different states. For air, the relative humidity is high, that is, the ratio between the amount of water and air humidity and the amount of water and air saturated at the same temperature and at the same pressure, air pressure higher and higher and thermal conductivity. When the wind speed is constant, the circulation and convection in the room is better, which makes the uniformity and change of temperature and humidity in the room.
Conclusion
In the daily maintenance work, it is found that the temperature and humidity changes and the uniformity of the same temperature and humidity laboratory under high humidity are better than those under low humidity. It is recommended that the higher the humidity, the higher the air temperature, which increases the temperature, to improve the temperature system in the room. Therefore, important research experiments are designed and conducted.
