Recent updates on the adsorption capacities of adsorbent-adsorbate pairs for heat transformation applications

Adsorption cooling is getting huge attention from last few years due to environment-friendly and thermally-driven technology. Many systems designs based on various adsorbent-adsorbate pairs are investigated worldwide to develop a cost-effective and high-performance system. Until now, performance of the systems is lower as compared to conventional compressor-based systems. Performance of the adsorption systems mainly depends on adsorption equilibrium, adsorption kinetics, isosteric heat of adsorption, and thermo-physical/chemical properties of assorted adsorbent-refrigerant pairs. Thereby, the present study aims to review and compare the physical properties (surface area, pore volume/size etc.) of adsorbents and adsorption equilibrium (adsorption isotherm) by various types of adsorbent-adsorbate pairs available in the literature. Amount of adsorbate adsorbed per unit mass of adsorbent has been critically reviewed and compared accordingly. Highest adsorption uptake was attributed in case of R-32 adsorption onto phenol resin-based activated carbon i.e. 2.23 kg/kg (excess adsorption) and 2.34 kg/kg (absolute adsorption) at 30 degrees C and 1670 kPa. Activated carbon of type Maxsorb-III being highly microporous possesses high surface area and shows good adsorption uptakes for most of the adsorbates including ethanol, methanol R-134a, CO2, R-507A and n-butane. In addition, fundamentals, principle and features of adsorption cooling systems are discussed. Adsorption equilibrium models used to express the adsorption mechanics of adsorbent-adsorbate pairs are explored, and the models' parameters are collectively listed and discussed. The review is useful to prioritize available adsorbent-adsorbate pairs for adsorption based heat transformation applications. The study is useful for researchers working for the development of adsorbent materials for various applications and conditions.