Experimental Investigation and Thermodynamic Analysis of Coconut-Shell-Derived Activated Carbon for CO₂-Based Advanced Adsorption Cooling Systems

Abstract

The current investigation explores the CO 2 adsorption capacity of an indigenous coconut-shell-derived activated carbon, namely AC CARB 6X12 55, at an adsorption temperature and pressure of 5−70 °C and 0−42 bar, respectively, suitable for CO 2 -based adsorption cooling applications using an in-house developed high-pressure test facility. Additionally, experiments are conducted to measure thermal diffusivity, thermal conductivity, and specific heat of activated carbon using the hot-disk method on a TPS 2500 S analyzer. The activated carbon possesses the maximum CO 2 adsorption capacity of 0.70 kg/kg at 5 °C and 32 bar. Isotherm modeling is carried out based on experimental data employing Toth, D−A, and modified D−A isotherm models, followed by detailed thermodynamic investigation to estimate the heat of adsorption, adsorbed phase-specific heat, enthalpy, and entropy. Based on the adsorption isotherm data and thermophysical properties, study is extended to explore the performance of different advanced CO 2 -based adsorption cooling systems employing internal heat and mass recovery schemes, an ejector expansion, and a thermoelectric subcooler. The results confirm that the suggested cycle modifications are crucial for cooling applications, as a maximum COP and SCE of 0.341 and 44.88 kJ/kg, respectively, with an increment of 163% in system COP compared to the basic cycle, are achieved.