Exergy based performance evaluation of solar air heater with arc-shaped wire roughened absorber plate

Highlights

Analytical model is used to evaluate exergetic efficiency (ηII) of arc shaped wire rib roughened solar air heater using developed correlations.

Exergetic efficiency (ηII) enhances up to 56% at e/D = 0.0422 over the smooth plate solar air heater.

At higher Reynolds number (Re) Re > 35,000 the exergetic efficiency becomes negative and it is not desirable to run the system beyond this value.

Various design plots have been obtained based on the results. These design plots can be used to design arc shaped wire rib roughened solar air heater.

Abstract

Exergy efficiency analysis is an useful method to evaluate overall performance of solar thermal systems as it takes into consideration of useful energy output and consequent pumping power requirement. In present work, an investigation on exergetic performance evaluation of solar air heater with arc-shaped wire rib roughened absorber plates has been made analytically by employing mathematical model and the results have been compared with a plane absorber plate solar air heater for similar operating conditions. The exergetic efficiency curves as a function of Reynolds number (Re) and temperature rise parameter (ΔT/I) for different roughness parameters have been plotted. The maximum enhancement in exergetic efficiency of roughened solar air heater as compared to smooth absorber plate solar air heater has been found as 56% corresponding to relative roughness height (e/D) = 0.0422. The design plots, exhibiting the optimum combination of roughness parameters, can be used to design arc shaped wire rib roughened solar air heater.

Keywords

  • Entropy generation rate;
  • Exergy efficiency;
  • Artificial roughness;
  • Solar air heater

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