Entropy generation in a solar collector filled with a radiative participating gas

• Thermal losses in solar collectors are assessed using the 2nd law analysis method.
• Near-wall zones are identified as critical regions in solar collectors.
• Radiative entropy generation is found to be important in gas-filled solar collectors.
• Optimum optical thickness and tilt are determined for gas-filled collectors.

Heat losses in solar energy collectors are associated with thermodynamic irreversibility, which causes entropy generation. These losses can be reduced through EGM (entropy generation minimization) techniques. Using computational fluid dynamics, entropy generation associated with viscous dissipation, heat conduction and convection, and thermal radiation is studied for a solar collector filled with a radiative participating gas. The EGM methodology shows that gas filled solar collectors have an optimum optical thickness and an optimum tilt angle where the heat losses are minimized. These optimum conditions for gas filled collectors cannot accurately be determined using conventional performance parameters. Solar collectors filled with radiative participating gases are also found to be suitable for the tropics.