Numerical simulation of plate solar air heater considering gas radiation

In this paper, the thermal characteristics of solar gas heaters were analyzed to find the effect of using radiating gases rather than air on the efficiency of converting radiative heat flux into gas enthalpy. The set of governing equations including the gas energy equation with radiative term was solved by the finite difference method (FDM). The radiative term in this equation was calculated by numerical solution of the radtaive transfer equation (RTE) using the discrete ordinate method (DOM). Based on the numerical results, it was found that using the radiating gas in the solar gas heater can lead to a considerable efficiency increase. In the studied test case, about 7% increase in the gas outlet temperature was seen when the optical thickness increased from zero (non participating medium) to 2. Comparison between the present numerical results with experimental data published in literature shows good consistency with the error less than 3%.