On the linear driving force approximation for adsorption cooling applications

This paper aims to address the effect of using classical Linear Driving Force (LDF) model on the performance of adsorption chillers. A comparative study between the well known LDF equation and the Fickian diffusion (FD) model has been conducted. Two adsorbent/refrigerant pairs namely, RD silica gel/water and “CaCl2 confined to KSK silica gel”/water pairs have been used. Relative and absolute errors between adsorption uptakes estimated by both models have been estimated. It is found that the LDF model has numerous errors at relatively shorter adsorption times which imply that using LDF equation may lead to incorrect evaluation of the performance of adsorption chiller especially at short cycle times. This study also presents an improved form of LDF model considering the dependency of the particle mass transfer coefficient on the dimensionless time. Theoretical calculations show good agreement between the improved LDF approximation and the FD model.