Abstract:

Adsorption system is a hot research subject recent years with the increasing problems of energy shortage and environmental pollution. In adsorption systems, heat transfer coefficient of the adsorber is the most important, since, with the same amount of uptake circulated in the system, the cycle time will decide the system cooling capacity. In this study, a specially designed, high efficient plate fin type adsorber is developed in a continuous silica gel adsorption refrigeration system to improve its performance. The two-dimension mathematical model for the adsorber is set up. As silica gel and water pair gives very quick adsorption and desorption process, the rate of heat transfer in desorption and adsorption process becomes very crucial for the system. Thus, only the heat transfer is considered in this model to seek the way to improve the process. The effect of the main dimensions of the adsorber is analyzed. The theoretical study demonstrates that the optimum design for this adsorber is: fin pitch 3—6 mm, fin height 6—12 mm and fin thickness 0.03—0.15 mm. Experimental results show that by using this design, the adsorption/desorption time can be as short as 420 s. The overall heat transfer coefficient of adsorber can be improved to 370.8 W·(m²·℃)^-1 though the heat conductivity of silica gel is only 0.175 W·(m²·℃)^-1.