Performance augmentation of a solar air heater using herringbone metal foam fins: An experimental work

Abstract

The transformation of massive solar irradiation into applicable energy forms like thermal energy plays an essential role in sustainable energy. Solar air heaters (SAH) are a way to transform solar irradiance into heat energy appropriate for human utilization. In the present study, experimental work was implemented to assess the thermo-hydraulic efficiency of a single duct single glazed SAH with herringbone metal foam fins attached beneath the absorber plate. Three corrugation angle values (30, 60, 90°) for the herringbone fins were examined. Metal foam fins porosity assists the air flows across the fin structure to exploit more heat from the absorber plate. Air flows were circulated by a centrifugal fan, their speeds varying between 0.01 to 0.05 m3/s. The experiments were implemented under realistic outdoor weather conditions in Baghdad, Iraq, from January to March 2020. The results showed that when the corrugation angle increases, the useful energy decreases. At an air flowrate of 0.05 m3/s, maximum useful energy at noon is 709, 588, and 442 W/m2 for corrugation angles of 30, 60, and 90°, respectively. The maximum outlet air temperature for a finned SAH with a corrugation angle of 30° is 60.4°C against 42.1°C for an unfinned SAH, at 0.01 m3/s air flowrate. Maximum thermal efficiency obtained by a finned SAH with a corrugation angle of 30° was 87.7% at an air flowrate of 0.04 m3/s, against 29.4% for an unfinned SAH at an air flowrate of 0.05 m3/s.