Since, the objective of this research is to find out the adsorption/regeneration performance of longan dryer with tray-type desiccant unit. Therefore, this work can be divided into two parts. For the first part, the performance of desiccant tray with different tray thickness is investigated and the models for predicting the adsorption/regeneration processes are also developed. The second part studies the performance of longan dryer with tray-type desiccant unit by using computer simulation. The research method and instrumentation of each part is as follows: