Exergy analysis of roughened duct using multiple arcs with gaps used in solar air heaters

ABSTRACT

Energy from the sun can either be stored (as electricity, using solar panels) or used as a heat source to do some work (solar heating and dying applications). The absorber plate roughened with artificial ribs is found to have better thermal ability in comparison to smooth duct SAH. Exergy analysis is a useful tool for the design of SAH’s as it methodically calculates the quality of useful energy and its friction penalty. Exergetic efficiency of a SAH with multi-arc elements with discrete gaps is studied mathematically and the results obtained are found to be impressive as compared to smooth SAH. The results have also been validated experimentally and are found to be in accordance with the mathematical results. The study includes the effect of various roughness parameters on exergetic efficiency. Results indicated temperature rise parameter values between 0.003 and 0.012 as optimum. A relative roughness pitch of 8, relative roughness width of 5, relative gap position of 0.65, arc angle of 60°, relative gap width of 1.0 and relative roughness height of 0.045 are found to yield maximum exergetic efficiency values for the studied range of temperature rise parameter.

KEYWORDS:

• Exergetic efficiency
• Nusselt number
• friction factor
• artificial roughness
• viscous sub layer
• turbulent boundary layer

Disclosure statement

No potential conflict of interest was reported by the author(s).