Adsorption refrigeration cycle with mass and heat recovery

Abstract

A non-uniform temperature/uniform pressure mathematical model of a combined mass and heat recovery adsorption cooling cycle based on activated carbon/methanol working pair is examined and numerically solved under certain assumptions and operating conditions in this thesis study. The one dimensional model describes the transient heat and mass transfer phenomena within an external-heated generator containing a porous medium in detail by utilizing Dubinin-Astakhov adsorption equilibrium. Mathematical model was programmed with an algorithm in MATLAB software by using forward time centered space finite difference explicit method. Stability and convergence analysis are performed by changing grid size of the domain in order to ensure utilized numerical method reliability. Dynamic sorption amount and temperature development within adsorbent bed are obtained, and consequently system performance is calculated for several working pairs such as activated carbon/ammonia, activated carbon/methanol, silica gel/water, and zeolite/water in terms of coefficient of performance and specific cooling power. Then parametric analysis is carried out by searching heat source temperature, condenser temperature, evaporator temperature, adsorbent porosity, and adsorbent bed geometry effect on system performance. As an outcome of the analysis done, activated carbon/methanol is selected as an appropriate working pair for the combined mass and heat recovery adsorption refrigeration cycle. Mass recovery and heat recovery’s performance enhancement effect are analyzed and 25% improvement is obtained on both coefficient of performance and specific cooling power. By performing a cycle time optimization analysis, it is showed that total cycle time can be reduced 77.8% for basic adsorption cooling cycle utilizing activated carbon/methanol and consequently the performance enhancement can be promoted for the combined mass and heat recovery adsorption cooling cycle.