Analysis of the heat transfer and airflow in solar chimney drying system with porous absorber

Abstract

In this paper, the chimney is assembled with porous absorber for the indirect-mode solar dryer. Local thermal non-equilibrium (LTNE) exists in the porous absorber, so the double energy equations and Brinkman–Forchheimer extended Darcy model are employed to analyze the heat transfer and flow in the solar porous absorber, and the k-ε turbulent model coupled with the above equations are also used to investigate the influences of the porous absorber inclination and the height of drying system on the heat transfer in the solar dryer. The specific heat capacities (ρc) and thermal conductivity ks have remarkable effects on the average temperature of solar porous absorber in the drying system. The mean temperature of the higher (ρc) Aluminous solar absorber is lower and the top temperature of porous absorber delays due to lower thermal conductivity ks. The inclined angle of porous absorber influences the airflow and temperature field in the solar dryer greatly. With the height of solar dryer changing from 1.41 m to 1.81 m, the higher airflow velocity and the lower temperature at chimney exit can be achieved. The simulations agree with the published experimental data. All these results should be taken into account for the promotion and application of the solar chimney dryer with porous absorber.