Activated Carbon-Graphene Composite/Ethanol-Based Adsorption Refrigeration System: Minimum Regeneration Temperature, Uptake Efficiency, and Cooling Performance

Abstract

This article presents the thermodynamic cooling assessment of single stage vapour adsorption refrigeration system. The two composites with varying mass fractions of MaxsorbIII, PVA, and H25 are taken as adsorbents; however, ethanol is selected as refrigerant. Dubinin-Astakhov (D-A) isotherm model is used for the analysis of heat of adsorption, and the thermophysical characteristic of ethanol is determined by Antoine equation. The impacts of various operating parameters such as evaporator, condenser, and regeneration temperature are numerically explored. The steady state cooling assessment is computed in terms of specific cooling energy (SCE), volumetric cooling energy (VCE), uptake efficiency, and minimum regeneration temperature using MATLAB R2021b. It is observed that SCE, VCE, and uptake efficiency are found to be increasing with increase in regeneration temperature; however, at a finite value of regeneration temperature, SCE decreases whereas VCE and uptake efficiency improve towards higher evaporator temperature. At regeneration temperature of 90 °C, the SCE value is evaluated as 353.92 kJ/kg at Tevap = 0 °C and 575.96 kJ/kg at Tevap = 10 °C for composite 1; however, it is 285.04 kJ/kg at Tevap = 0 °C and 526.5 kJ/kg at Tevap = 10 °C, respectively for composite 2. The actual value of minimum regeneration temperature is found to be slightly higher than that of the theoretical one. Furthermore, on the basis of isosteric heat of adsorption, composite 2 is found to be better for cooling application whereas composite 1 is more suitable for heat pumping application.