How to humidify and dehumidify the hottest constan

2022-09-23
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How is the constant temperature and humidity test chamber humidified and dehumidified

how is the constant temperature and humidity test chamber humidified and dehumidified

constant temperature and humidity test chamber in order to realize the test conditions, it is inevitable to humidify and dehumidify the test chamber. This paper analyzes various methods that are widely used in the constant temperature and humidity test chamber at present, and points out their respective advantages and disadvantages and recommended conditions for use

There are many ways to express humidity, which do not only refer to technology and product innovation. As for test equipment, the concept of relative humidity is usually used to describe humidity. The definition of relative humidity refers to the ratio of the partial pressure of water vapor in the air to the saturated vapor pressure of water at this temperature, which is expressed as a percentage. From the properties of water vapor saturation pressure, it can be seen that the saturation pressure of water vapor is only a function of temperature, and has nothing to do with the air pressure where water vapor can be located. People have sought to express the relationship between water vapor saturation pressure and temperature through a large number of experiments and collation, among which the formula that has been widely used in engineering and Metrology should be govglidge's formula. It is currently used by the meteorological department to compile the experimental table usually required for the completion of humidity calculation

the humidification process is actually to increase the partial pressure of water vapor. The initial humidification method is to spray water on the wall of the test chamber, and the saturation pressure on the water surface is controlled by controlling the water temperature. The water on the surface of the chamber wall forms a large surface, on which water vapor pressure is added to the chamber by diffusion to increase the relative humidity in the test chamber. On this side, Finland developed the low-cost polylactic acid foaming material method, which appeared in the 1950s. At that time, the humidity control was mainly based on the simple on-off value adjustment of the mercury electric contact conductivity meter, which was not adaptable to the control of the water temperature of the hot water tank with a large lag. Therefore, the transition process of the control was long, which could not meet the needs of alternating damp heat for more humidification. More importantly, when spraying the tank wall, it was inevitable that water dripping on the test object would form varying degrees of pollution to the test object. At the same time, there are certain requirements for the drainage in the box. This method was soon replaced by steam humidification and shallow water dish humidification, although the use of springs was large. But this method still has some advantages. Although its control transition process is long, the humidity fluctuation is small after the system is stable, which is more suitable for constant damp heat test. In addition, in the humidification process, the water vapor will not overheat and will not increase the additional heat in the system. In addition, when the spray water temperature is controlled to be lower than the key temperature required by the test, the spray water has a dehumidification effect

with the development of damp heat test from constant damp heat to alternating damp heat, it is required to have a faster humidification reaction capacity. When spray humidification can no longer meet the requirements, steam humidification and shallow water dish humidification methods began to be widely used and developed

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