An analytical investigations on thermal and thermohydraulic performance of offset finned absorber solar air heater

In this study, an analytical investigation on thermal and thermohydraulic performance of offset finned solar air heater have been evaluated. A parametric study was done to investigate the effect of variation of system and operating parameters i.e. fin spacing, fin height, air mass flow rate and insolation on the thermal and thermohydraulic (effective) efficiencies. Results indicate that the thermal efficiency increases continuously with increase in mass flow rate, whereas thermohydraulic efficiency increases upto an inception value of air mass flow rate (0.028 kg/s), attains a maximum and then decreases sharply for a given fin spacing and fin height. For higher value of the fluid temperature rise parameter, the effective efficiency values closely follow the thermal efficiency values. It is found that attaching offset fins below the absorber plate at lower mass flow rate can lead to appreciable enhancement of 106.9% and 67.38% respectively for the thermal and thermohydraulic efficiencies. It is also found that the maximum percentage enhancement in thermal and thermohydraulic efficiencies increases to 114.1% and 112.65% respectively with decrease in fin spacing and increase in fin height.