Effect of coupled heat and mass transfers on the performance of adsorptive solar refrigerator using the pair activated carbon / methanol

Abstract

This paper presents a one-dimensional mathematical model which accounts for heat and mass transfer in a tubular adsorber as well as the effects of non-uniform temperature and uniform pressure distribution, using the pair activated carbon AC-35/ methanol as an adsorbent/adsorbate. The modelling and the analysing of the adsorber is the key point of such studies, because of the complex coupled heat and mass transfer phenomena that occur during the working cycle. This model consists of the energy equation in the adsorbent layers, the energy balance equation of the adsorber wall, and state equation of the bivariant solid- vapour equilibrium using the Dubinin-Astakhov model to describe the adsorption phenomena. The discretization of equations system is carried out using the finite differences method with a fully implicit scheme. The resolution of the discretized system is carried out using an iterative method. The validity of the model has been checked by using theoretical results of the thermodynamic cycle under the same numerical conditions. A good agreement between numerical simulation and theoretical results has been achieved. This comparison shows that the proposed model can describe the details of thermal behaviour in a tubular adsorber of the solar refrigerator. Several main factors affecting the solar performance and the cooling power system's are discussed according to the results of computer simulations, such as: equivalent conductivity of the solid adsorbent, heat transfer coefficient between the tube wall and the porous media and the emissivity of the metallic adsorber wall. The relationship between the performance system's and these factors is investigated.