An investigation of the ammonia adsorption performance on different adsorbents for cooling applications

Abstract

Ammonia (NH3) is a common gas and has been widely investigated on adsorption for numerous purposes. Ammonia is commonly employed as a refrigerant in the refrigeration systems to obtain temperatures below 263 K. Adsorption systems powered by low-temperature heat sources that utilize ammonia as working fluid work at positive pressures, therefore, their manufacturing and usage are much easier, and they require less maintenance, comparing with vacuum systems. In this study, ammonia adsorption performance of various adsorbents is investigated numerically for cooling applications. The adsorbents considered in this study are zeolite, alumina, silica gel and activated carbon. The adsorption performance of each adsorbent-adsorbate pair under various operating conditions is compared. Among the adsorbate-adsorbent pairs investigated in this study, ammonia and activated carbon gave the best performance values in all cases. According to the results of the study, most important parameters that effects COP, Qr and SCP of an adsorption cooling system are the adsorbent type, cooling source temperature, heating source temperature and evaporation temperature at the evaporator, respectively. It is shown that increasing evaporator temperature and heating source temperature results an increase in COP, Qr and SCP values of the adsorption system, whereas, for the case of cooling source temperature, highest values of COP, SCP and Qr are obtained at the lowest cooling fluid inlet temperature.