Test methods of moisture adsorption/desorption performance of humidity control materials

Establishing the coupled equations of heat and moisture transfer in the materials to describe the moisture adsorption/desorption processes, obtains the analytical solutions of temperature and humidity ratio in the materials by transforming the equations with the steady periodic convective boundary conditions. The analytical solutions are utilized to clarify the moisture adsorption/desorption characteristics of the humidity control plate that is free placed in a closed space, and it shows that the air humidity ratio amplitude is in direct proportion to the air temperature amplitude, the proportion coefficient can be used as a criterion to indicate the adsorption/desorption ability of a material, and the lag time between the humidity ratio and the temperature can be used as a criterion to indicate the adsorption/desorption response of the material. Thereby, a test method called the closed box and thermal effect method is introduced to investigate the moisture adsorption/desorption performance. The validity of this method is experimentally checked by testing the performance of three kind of materials including silica gel plate, concrete slab and puddle plate. The results show that the performance of the silica gel plate is the best and that of the concrete slab is the poorest, and that the moisture is desorbed from materials when the closed box is heated and absorbed from air when the closed box is cooled, and that the tested curve of absolute humidity can show the performance of the material.