Studies on dynamics of two-stage air cooled water/silica gel adsorption system

The objective of this study is to develop a computational model of two-stage silica gel/water adsorption cooling system. Thermal compression is achieved by adsorption, with silica gel (RD type) as the adsorbent and water as the refrigerant. Three dimensional transient heat and mass transfer analysis of adsorption heat exchangers are carried out to derive salient design and performance features. Numerical studies are carried out to evaluate the performance of the beds with respect to key operating parameters. Two different geometric models are considered for the transient study, one having vapor flow only in axial direction through the cylinder, and the other having a thin mesh inserted between the shell and heat exchanger tubes, resulting in a much shorter vapor flow path through the packed bed. Bed temperature distribution, pressure dynamics and the effect of critical depth on uptake of the adsorber heat exchanger are studied numerically. In addition, a parametric study is carried out to determine the significance of silica gel particle diameter on the uptake of the bed. The optimum particle diameter in terms of uptake was found to be 0.8 mm. The effect of ambient temperature on the performance of single-stage and two-stage systems is also studied.