The effect of tray thickness on the performance of desiccant tray is shown in figures 5-6. In case of adsorption process (figure 5), it is found that the mass ratio in case of the tray thickness equals to 2.5 cm is higher than those of 5.0 and 7.5 cm. This result comes from the effect of air entering into the desiccant bed. Lower thickness of the tray, easier the air penetrates into the desiccant bed. Hence, the mass transfer rate of moisture to the desiccant is increased. This phenomenon also occurs with the regeneration process shown in figure 6 that the 2.5 cm tray thickness gives the highest performance.