Experimental Performance Analysis of Adsorption Modules with Sintered Aluminium Fiber Heat Exchangers and SAPO-34-Water Working Pair for Gas-Driven Heat Pumps: Influence of Evaporator Size, Temperatures, and Half Cycle Times

Abstract

A major challenge for gas-driven adsorption heat pumps is the production of compact, efficient, and cost-effective adsorption modules. We present the experimental data of a design based on sintered aluminum fiber heat exchangers, a technology currently under development. The adsorption module presented here is the result of the downsizing of a larger module. The downsized module has an adsorption heat exchanger that is 60% of the size of the larger-scale component, and an evaporator-condenser that is only 30% of the size of the larger-scale component. It is designed to fit the heating requirements of a wall-hung heat pump for a single-family home. For the first time, a comprehensive experimental study of the influence of half-cycle time, evaporator and adsorption temperature, and driving temperature on the efficiency and power of the module is presented. At temperature conditions relevant for the application of a gas-driven adsorption heat pump, i.e., evaporator temperature < 10 °C and adsorption temperature > 30 °C, we found that the downsizing has its price in terms of a higher thermal capacity of the components in relation to the adsorbent mass (9.6 kJ/(kg∙K) for ‘Size S’) vs. 5.6 kJ/(kg∙K) for ‘Size L’). We carried out an evaluation of heat and mass transfer resistances to compare the ‘Size L’ module directly with the ‘Size S’ module. Both modules have nearly the same volume-scaled heat and mass transfer resistances of 0.012 dm3 K/W (adsorption heat exchanger during adsorption) and 0.005 dm3 K/W (evaporator–condenser during evaporation), and consequently a very similar volumetric power density. This evaluation proves the applicability and the consistency of the concept of heat and mass transfer resistances, and the scalability of this adsorption module technology.