Assessment of Perforated Double-Pass Solar Air Heater Using Parametric Interaction Analysis for Performance Enhancement in Solar Thermal Systems

Abstract

The low performance of solar air heaters (SAHs) has been considered a drawback in commercializing solar thermal systems. The SAH performance is influenced directly by changing the level of the influential parameters. This work experimentally determines the optimum parameters for enhancing a perforated double-pass SAH performance. The interaction of factors related to the performance of circular staggered perforated double pass SAH was discussed based on the design of experiments (DOE) approach. Reynolds number values from 10000 to 30000 and perforation ratios from 3 to 7 were considered model design parameters, while temperature difference, useful heat gain, and thermal efficiency were adopted as responses for the correlating model. Three correlations corresponding to each response with two forms each (actual and coded) were obtained from the DOE analysis. The results revealed that the interaction percentage was 193% for efficiency and 148% for useful heat gain; however, it did not exceed 18% for the temperature difference. The optimum parameters obtained were 30000 for the Reynolds number and 3 for the perforation ratio. At high Reynolds numbers, the thermal efficiency enhancement of perforated SAH was 12.36% higher than the unperforated. The Reynolds number impact on thermal efficiency changed significantly as the perforation ratio varied.

Keywords

• Correlation
• Design of experiment
• Double pass
• Interaction of factors
• Perforated absorber
• Solar air heater