Influence of glass cover inclination angle on radiation heat transfer rate within stepped solar still

In the present work, a new theoretical analysis of the radiation heat transfer rate inside a stepped solar still is presented. Radiation shape factor between hot saline water and glass cover for a stepped solar still is computed. The effect of taking the radiation shape factor into consideration is qualitatively and quantitatively determined. The effect of glass cover inclination angle (from 10° to 70°) and solar insolation (from 200 to 1200 W/m2) on stepped solar still productivity; taking into account the radiation shape factor is investigated. It is found that the influence of the radiation shape factor on the thermal performance predictions is significant. Moreover, the productivity of the solar still is found to be sensitive to the radiation shape particularly at low solar insolation and/or high glass cover inclination angle (i.e. latitude angle of the site) and vice versa. At low solar insolation of 200 W/m2 and glass cover inclination angle of 70°, the percentage increase in the still productivity, when considering the radiation shape factor, is up to 18.8%. Finally, fair agreement between the present theoretical work and the previous experimental result has been accomplished.