Performance evaluation of solar air heater having expanded metal mesh as artificial roughness on absorber plate

A parametric study of artificial roughness geometry of expanded metal mesh type in the absorber plate of solar air heater duct has been carried out and compared with smooth duct. The performance evaluation in terms of energy augmentation ratio (EAR), effective energy augmentation ratio (EEAR) and exergy augmentation ratio (EXAR) has been carried out for various values of Reynolds number (Re) and roughness parameters of expanded metal mesh roughness geometry in the absorber plate of solar air heater duct. It is found that the augmentation ratios decrease at faster rate with Re in the order of EAR, EEAR and EXAR. It is also found that augmentation ratios increase with increase in duct depth and intensity of solar radiation. The artificially roughened solar air heater duct performs better as per EAR or heat energy gain criteria for any values of Re and roughness parameters of expanded metal mesh. The EAR is high for the parameters of expanded metal mesh type roughness geometry which create more turbulence, however the pump work required for flow of air will also increase. The FAAR is a more suitable criterion to incorporate the quality of heat collected and pump work required. The EXAR is more for higher duct depth and low Re range. Based on EXAR the suitable design parameters of expanded metal mesh roughness geometry are determined. (C) 2008 Elsevier Masson SAS. All rights reserved.