Investigation of Gas Radiation Effect on Thermal Behavior of Solar Gas Heaters under High Irradiation

Abstract

Based on the global consensus on mitigation of greenhouse gas and human footprint as well as improvement of engineering application sustainability, the mission of this study dedicated to the numerical simulation of plane solar gas heaters under different solar irradiation for both radiating and non radiating working gases. In numerical simulation, the continuity and momentum equations for the gas flow were solved by the finite volume method (FVM) using the SIMPLE algorithm, and the energy equation for the forced convection gas flow coupled with the conduction equation for solid parts have been solved by the finite difference method (FDM). The intensity of radiation in participating gas flow was computed by numerical solution of the radiative transfer equation (RTE) with the discrete ordinate method (DOM). It is seen thatl that increasing in gas optical thickness causes significant reduction in temperature difference between the absorber plate and flowing gas, especially at high solar irradiation. In the cases of using radiative gas with optical thickness of 0.2, instead the non participating gas, numerical results show 55%, 64% and 77% improvement in the gas temperature increase along the heater under the incidence of 900 W/m^2, 1100 W/m^2 and 1400 W/m^2, respectively. This makes the heat transfer more reversible that leads to high performance. Comparison between the present numerical results with experimental data shows good consistency.