Reversibility analysis of an experimental heat and mass recovery adsorption cycle with PCM thermal energy storage

Abstract

This study analyzed a reversibility scenario and state equilibrium of an experimental dual-stage dual-bed adsorption chiller silica gel-water pair with phase change material (PCM) thermal energy storage. Results showed that adsorptive cycle entropy decreased to 352.63 J/K with heat and mass recovery model, while exergy efficiency improved to 29% and Carnot performance coefficient reached 1.45. Specifically, adsorbent beds exhibited an optimal entropy of 344.8 J/K, while thermal energy storage increased the overall model entropy to 400.1 J/K. Comparison between experimental and simulation results revealed an absolute error of 3% and relative error of 9.3% in terms of exergy efficiency and Carnot coefficient of performance. The findings revealed that the overall entropy was 760.13 J/K and 715.03 J/K with and without thermal energy storage, while the entropy of the beds alone was 654.13 J/K. Yet, Carnot performance coefficient and exergy efficiency were found to be 1.92% and 32%, respectively. Notably, heat and mass recovery reduced the disorder within adsorptive cycle and enhanced its thermodynamic efficiency. Meantime, thermal energy storage influenced the system’s energy degradation and contributed to enhancing exergy performance. The state equilibrium of the regenerative cycle was also conducted and examined. Results revealed a lower enthalpy (3.74 kJ) compared to the heat transfer (7.7 kJ), with steam pressure reaching 2.088 kPa. The Gibbs free energy was negative (-1.17 × 10² kJ) and decreased with increasing temperature during the reversible isobaric process.