Innovative Adsorbent Heat Exchangers: Design and Evaluation

Adsorption cycles can be used for thermally driven heat transformation applications such as heat pumps or chillers. A major challenge in building such devices is the design of the adsorbent heat exchanger (Ad-HX). Two main design criteria are discussed here: the coefficient of performance (COP), relating the useful heat or cold with the energetic expenses, and the (volume or mass) specific cooling or heating power (SCP/SHP). Addressing the aim of designing an adsorbent heat exchanger, the article proposes a two-step procedure. The first step is the analysis of the COP, which is determined by the thermophysical properties of the adsorbent material and the working fluid, the temperature levels of the process, and the mass ratio between active adsorbent and heat exchanger material. Promising configurations reach a required COP and can be specified more detailed in a second step by estimating the power density. A simplified design approach taking the chain of heat and mass transfer resistances into account is presented, and examples of recently developed innovative adsorbent heat exchangers are shown.