Adsorption of difluoromethane onto activated carbon based composites: Thermophysical properties and adsorption characterization

• Published in: International journal of heat and mass transfer Vol. 171; p. 121112
• Main Authors: Yagnamurthy, Sai, Rakshit, Dibakar, Jain, Sanjeev, Rocky, Kaiser Ahmed, Islam, Md. Amirul, Saha, Bidyut Baran
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.2021; Elsevier BV
• Subjects: Activated carbon; Adsorbents; Adsorption; Adsorption cooling; Composite materials; Cooling; Cooling systems; Graphene; Graphene nanoplatelets; Gravimetry; Heat conductivity; Heat transfer; HFC 32; Hydrofluorocarbons; Ionic liquid; Ionic liquids; Polyvinyl alcohol; Surface area; Surface chemistry; Thermal conductivity; Thermophysical properties; Thermal conductivity; Adsorption cooling; Graphene nanoplatelets; HFC 32; Activated carbon; Ionic liquid
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2021.121112

•Synthesis of activated carbon based composites employing GNP and ionic liquid•Anisotropic thermal conductivities evaluated for the first time for GNP composites•Over 3 times higher thermal conductivities observed in perpendicular planes•Experimental study of R32 adsorption on composites and isotherm model fitting•Impact analysis of the thermal enhancement measures on uptake characteristics•Enhancement of cyclic volumetric uptake capacity by over 78% is observed In an attempt to promote research on adsorption cooling systems, novel activated carbon-based composite adsorbents have been studied for thermophysical properties and adsorption characterization with difluoromethane (HFC 32) refrigerant. High surface area activated carbon of type Maxsorb III has been selected as the primary constituent of adsorbent composites, with H25 graphene nanoplatelets (GNPs), 1-Hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide ([HMIM][Tf2N]) ionic liquid, and Polyvinyl alcohol (PVA) binder in varying fractions. The various thermophysical properties such as surface area and porosity, specific heat capacity, and thermal conductivity have been experimentally evaluated. The thermal diffusivities have been measured in two different planes of the composites: parallel and perpendicular to the direction of the compression. It has been observed that the perpendicular plane has significantly higher thermal diffusivities (up to 2.32 times) over the parallel plane of the composites. Besides, a considerable improvement in thermal conductivity of up to 65.6 times is observed over powdered activated carbon. Adsorption uptake characteristics are studied gravimetrically for the composite samples in the temperature range of 30–70°C. Dubinin-Astakhov (D-A) and Tóth models are fitted successfully for the adsorption isotherms, with the D-A model seen to offer better fits. Further, the specific and volumetric cooling energies are estimated for the consolidated carbon composites based on the respective D-A adsorption equilibrium parameters and thermophysical properties of the working pairs. Significant enhancements in volumetric cooling energy up to 78% over that of powdered activated carbon are seen for the consolidated composites. [Display omitted]