Screening versatile water/adsorbent working pairs for wide operating conditions of adsorption heat pumps

Abstract

Adsorption heat pumps (AHPs) for space cooling and heating using environment-friendly water as a working fluid have attracted growing research interest. In order to explore high-performance adsorbent/water working pairs, many efforts have been devoted to the cooling or heating performance evaluation of adsorbent/water working pairs under typical operating conditions. However, theoretical assessment of the performance limits of each working pair is essential to identify versatile working pairs for wide operating conditions. In this work, two evaluation criteria, i.e. the effective COP (COP^eff) and the effective ΔT_lift (ΔT^eff_lift), are introduced in order to reach a compromise between the coefficient of performance (COP) and temperature lift (ΔT_lift) of each working pair. The adsorption cooling and heating potential of 231 adsorbents/water working pairs under varying operating conditions were estimated by mathematical modeling. The versatile working pairs exhibiting both high ΔT^eff_lift (>20 K for cooling and >30 K for heating) and high COP^eff (>0.6 for cooling and >1.6 for heating) are selected, in which working pairs with a high specific cooling/heating effect (SCE/SHE) and lower desorption temperature are favorable candidates. Besides, the potential of COP enhancement of each working pair by tuning operating conditions is also estimated. The computational strategy reported in this work provides unique insights to select versatile working pairs for a wide range of operating conditions of adsorption cooling and heating.