Steady-state investigation of carbon-based adsorbent-adsorbate pairs for heat transformation application

Abstract

In this study, the ideal adsorption cycle behavior of eight activated carbon and refrigerant pairs is evaluated. The selected pairs are KOH6-PR/ethanol, WPT-AC/ethanol, Maxsorb-III/methanol, Maxsorb-III/CO2, Maxsorb-III/n-butane, Maxsorb-III/R-134a, SAC-2/R32 and Maxsorb-III/R507a. The following cooling performance parameters are evaluated for all pairs: specific cooling energy (SCE), concentration difference (DW) and coefficient of performance (COP) of ideal adsorption cooling and refrigeration cycles. The evaporator temperatures for the applications of adsorption cooling and refrigeration are selected as 7 and-5 °C, respectively. It is found that the Maxsorb-III/methanol pair has shown the highest specific cooling energy and coefficient of performance in a wide range of desorption temperatures; i.e., for the adsorption cooling cycle it has SCE and COP of 639.83 kJ/kg and 0.803, respectively, with desorption temperatures of 80 °C. The KOH6-PR/ethanol and the WPT-AC/ethanol pairs also give good performances comparable to that of the Maxsorb-III/methanol pair. However, the SAC-2/R32 pair possesses a higher concentration difference than the Maxsorb-III/methanol, KOH6-PR/ethanol and WPT-AC/ethanol pairs but shows a lower performance. This is due to the lower isosteric heat of adsorption of SAC-2/R32 compared to these pairs. It is found that Maxsorb-III/methanol, KOH6-PR/ethanol and WPT-AC/ethanol are the most promising pairs for application in designing adsorption cooling and refrigeration systems.