Thermodynamic analysis and impact of thermal masses on adsorption cycles using MaxsorbIII/R245fa and SAC-2/R245fa pairs

Adsorption cycles have been gaining significant interest in waste-heat recovery and renewable energy utilization. Adsorption isotherm data and the equilibrium cycle analysis are crucial steps in evaluating a typical adsorbent + adsorbate pair. In this paper, the performance of Maxsorb III + R245fa and spherical activated carbon, SAC-2 + R245fa were studied for adsorption cooling and adsorption heat transformer (AHT) cycles. Adsorption isotherms of these pairs were measured using the constant-volume-variable-pressure apparatus for temperatures ranging from 30 degrees C to 60 degrees C, and fitted with the Dubinin-Astakhov (D-A) and the Toth isotherm model. An improved equilibrium model was developed, accounting the effects of thermal masses. The specific cooling energy (SCE) and the coefficient of performance (COP) of the adsorption cooling cycle were evaluated for various thermal mass to adsorbent mass ratios. It is observed that SAC-2 + R245fa pair offers better SCEs (20 kJ kg(-1) and 160 kJ kg(-1) at 60 degrees C and 90 degrees C, respectively) when compared to that of Maxsorb III + R245fa. The impact of thermal mass is found to be significant for all regeneration temperatures for Maxsorb III + R245fa while the deterioration of COP in SAC-2 + R245fa is notable for high regeneration temperatures (> 75 degrees C). When employed in the AHT cycle, Maxsorb III offers a slightly higher useful heat while SAC-2 provides a better Q uh/Q QR albeit by a small margin. The Q uh/Q QR values for both studied pairs are more than 0.6 for all regeneration temperatures for the heat extraction at 120 degrees C. (C) 2020 Elsevier Ltd and IIR. All rights reserved.

Automated summary

Adsorption cycles using different adsorbent-adsorbate pairs were studied for adsorption cooling and heat transformer applications. The study evaluated the specific cooling energy, coefficient of performance, and the impact of thermal mass ratios on the performance of the cycles. Results showed that the thermal mass had a significant impact on the cycles, with some pairs offering better performance at higher regeneration temperatures.