A dimensionless analysis of heat and mass transport in an adsorber with thin fins; uniform pressure approach

Abstract

A numerical study on heat and mass transfer in an annular adsorbent bed assisted with radial fins for an isobaric adsorption process is performed. A uniform pressure approach is employed to determine the changes of temperature and adsorbate concentration profiles in the adsorbent bed. The governing equations which are heat transfer equation for the adsorbent bed, mass balance equation for the adsorbent particle, and conduction heat transfer equation for the thin fin are non-dimensionalized in order to reduce number of governing parameters. The number of governing parameters is reduced to four as Kutateladze number, thermal diffusivity ratio, dimensionless fin coefficient and dimensionless parameter of Γ which compares mass diffusion in the adsorbent particle to heat transfer through the adsorbent bed. Temperature and adsorbate concentration contours are plotted for different values of defined dimensionless parameters to discuss heat and mass transfer rate in the bed. The average dimensionless temperature and average adsorbate concentration throughout the adsorption process are also presented to compare heat and mass transfer rate of different cases. The values of dimensionless fin coefficient, Γ number and thermal diffusivity ratio are changed from 0.01 to 100, 1 to 10 − 5 and 0.01 to 100, respectively; while the values of Kutateladze number are 1 and 100. The obtained results revealed that heat transfer rate in an adsorbent bed can be enhanced by the fin when the values of thermal diffusivity ratio and fin coefficient are low (i.e., α ⁎ = 0.01, Λ = 0.01). Furthermore, the use of fin in an adsorbent bed with low values of Γ number (i.e. Γ = 10 − 5) does not increase heat transfer rate, significantly.

Comparison of Uniform and Non-uniform Pressure Approaches Used to Analyze an Adsorption Process in a Closed Type Adsorbent Bed

“…It enables combination of heat storage and heat pumping functions in the same system. Although studies on coating type adsorbent bed continues (e.g., Marletta et al 2002;Restuccia et al 2004), granular-type adsorbent bed is still used in many investigations (e.g., Demir et al 2009;Ilis et al 2011). Two types of mass transfer occur in a closed type granular adsorbent bed as mass transfer within the adsorbent particle (intraparticle mass transfer) and mass transfer in the voids between adsorbent particles (interparticle mass transfer).…”

“…The employed approach (uniform or non-uniform pressure approach), the coordinate system, bed porosity, bed thickness, and isotherm model are also presented in the table. As can be seen from Table 1, both the uniform pressure approach (Ilis et al 2010(Ilis et al , 2011Chua et al 2004;Wang and Chua 2007;Saha et al 2009;Chahbani et al 2002;Leong and Liu 2004a) and non-uniform pressure approach (Marletta et al 2002;Demir et al 2009;Leong and Liu 2004a,b, 2006Liu and Leong 2005;Sun et al 1995;Ben Amar et al 1996;Restruccia et al 2002;Maggio et al 2009;Li Yong and Sumathy 2004) were preferred by many researchers to simulate heat and mass transfer in an adsorbent bed. Radial adsorbent bed was considered in the most of the studies except the study of Sun et al (1995) in which a rectangular bed was analyzed.…”

“…Most of the researchers performed one-dimensional study, and the changes of temperature and adsorbate concentration with time were obtained only in radial direction. The two-dimensional studies were performed by Saha et al (2009);Ben Amar et al (1996); Marletta et al (2002); Maggio et al (2009), andIlis et al (2011). A wide range of adsorbent bed thickness was analyzed.…”