An experimental study on adsorption characteristics of R134a and R404a onto granular and pellet-type activated carbon

Abstract

Relatively low-temperature renewable energy and industrial waste heat resources can be used to configure a solid adsorption refrigeration or cooling system that has no destructive or harmful effects on the environment. Therefore, such a system has attracted much interest for researchers across the world. The physical adsorption phenomenon is a reversible process realized mainly within the cavities and pore surfaces of the solid adsorbent. It is known that the adsorption characteristics of an adsorbent-adsorbate pair are strongly related to variations in temperature and pressure. The objective of the current study was to investigate experimentally the adsorption characteristics of the refrigerants R134a and R404a onto activated carbon. An experimental setup working with a constant-volume variable pressure method was used in the experimental measurements. During the adsorption processes, data from experimental isotherms were obtained at different constant temperatures ranging from 293K to 323K while pressure varied from 0 to about 500. kPa. These data are useful for designing adsorption cooling and refrigeration systems. Commercially available granular and pellet-type activated carbon (AC) samples were considered in this work. Experimental measurements were performed for four different adsorbent-adsorbate pairs obtained by combining the adsorbents (granulated AC and pellet AC) and adsorbates (R134a and R404a). Adsorption parameters were evaluated from the measured isotherms to obtain correlations in the form of the Dubinin-Astakhov equation. The pressure and temperature dependence of the isosteric enthalpies of adsorption were computed by evaluating the measured data and the derived equations. Furthermore, the parameters of the correlations are provided for each adsorbent-adsorbate pair. Results are compared and discussed in detail.