Dhaka University Journal of Applied Science & Engineering

This paper presents the thermal efficiency and thermal performance of a newly designed and fabricated Concentrating Transpired Air Heating (CTAH) system, designed solar air heating collector comprised of an inverted perforated absorber and an asymmetric compound parabolic concentrator was applied to increase the intensity of solar radiation incident on the perforated absorber. Experimental thermal efficiency remained high at higher air flow rates. The average thermal efficiency was found to be approximately 55%-65% with average radiation above 400 W/m2 for flow rates in the range of 0.03 kg/s/m2 to 0.09 kg/s/m2. Experimental results at air flow rates of 0.03 kg/s/m2 and 0.09 kg/s/m2 showed temperature rise of 38oC and 19.6oC respectively at a solar radiation intensity of 1,000 W/m2.The black colour carbon fibre plain weave with inherent lower pitch and perforation diameter combination (porosity < 5%) was adopted in the CTAH design.Highly reflective reflector material (dimension 1250mm x 1000mm x 0.5mm) was used (95% total light reflection) from the company ‘Alanod’.The glazing material of the CTAH system is one 6 mm thick low iron glass cover.The air chamber was protected and insulated with thermawrap insulation from the inside and outside walls.A comparative performance study shows the thermal performance of CTAH at different flow rate. As the absorber of the CTAH facing downward, it avoids radiation loss and the perforated absorber with tertiary concentrator reduces thermal losses from the system.

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