Performance investigations of carbon based consolidated composite adsorbents effective for adsorption cooling systems

Abstract

• Composite adsorbent with activated carbon has been developed and characterized. • Presence of metal organic framework improves surface properties of composites. • Expanded graphite powder in the composites improves thermal conductivity. • Volumetric uptake of newly composite is 24.38% more than activated carbon. This paper proposes a new composite adsorbent synthesized by employing activated carbon as the parent element with expanded natural graphite and metal organic framework as secondary elements. The binder used in the composite is polyvinylpyrrolidone. The parameters such as surface area, pore volume, thermal conductivity, and adsorption/desorption of adsorbate are studied in depth for the proposed combinations. The characteristic study suggests Composite B, having a material composition of activated carbon 70 % in weight, expanded graphite powder 10 % and metal organic framework 10 % and binder 10 % as the favourable choice for adsorption cooling system. The surface area and pore volume of the composite B is determined to be 1597 ± 26 m 2 /g and 0.93 cm 3 g −1 , respectively. The thermal conductivity of the composite B is determined to be 0.29 Wm -1 K −1 , which is 55.17 % greater than the parent material activated carbon at atmospheric temperature. The Dubinin-Radushkevich equation has been used to fit adsorption uptake measurement, and it is found that the maximum adsorption of the composite B as 0.983. A performance study of a single bed adsorption cooling system with a cooling capacity of 600 W has been conducted with activated carbon/composite B as adsorbent and ethanol as the refrigerant. The performance parameters such as the coefficient of performance and specific cooling power of the adsorption cooling system using consolidated adsorbent is obtained as 0.61 and 198 Wkg −1 , respectively. The coefficient of performance obtained by using the consolidated adsorbent/ethanol is 21.31 % higher than the system using activated carbon/ethanol as the working pair. The results shows that the suggested composite material's enhanced surface area, pore volume, and thermal conductivity can improve the performance of the adsorption cooling system and can be employed as a viable alternative for conventional adsorbents.