Adsorption heat pump modeling: the thermal wave process with local equilibrium

This paper describes a model for a thermal-wave adsorption heat pump cycle. Local equilibrium is assumed, providing the asymptotic best-case performan ce. The model is utilized to examine the performance of adsorption refriger ation cycles powered by low temperature waste heat sources of 373-393 K. Th e impact of varying system temperatures, bed cycling frequency, valve posit ioning, and sectioning of the bed are examined. Cycle coefficients of perfo rmance (COPs) were greater than 1.2 for the base case of a 393 K heat sourc e, 303 K condenser temperature, and 278 K evaporator temperature for a cycl e utilizing a water/NaX zeolite adsorbate/adsorbent pair. As an effect of t he small temperature changes during the cycle, for some regions of the bed, the loading change was opposite of that expected; i.e., from the start to the end of the entire heating process some portions of the bed experienced loading increases. The location of the inlet/outlet valves in the bed was f ound to have an impact on the shape of the temperature and loading fronts. The introduction of partitions within the bed was found to have only a smal l impact on the performance of the cycle for the temperatures examined, wit h sections of the bed undergoing pressurization in a non-sequential order. (C) 2000 Elsevier Science Ltd. All rights reserved.