An Experimental Study on Energy and Exergy for Glazed and Unglazed Solar System with Perforated Absorber Plate and Wire Mesh Layers

Abstract

The purpose of this experimental study is to construct and evaluation three solar heaters (glassed heater 90^o bed angle, unglazed heaters 90^o bed angle and glassed heater 47^o bed angle), these heaters device 50 mm height of the bed with a perforated absorber plate and wire mesh layers. The perforated plate and six steel wire mesh layers were painted black then placed parallel to each other in heater bed; the mesh layers had a cross-sectional area of 2.2 mm× 2.2 mm and an internal diameter of 4.11 mm, perforated plate had an internal hole diameter of 2 mm, pitch 4 mm. In this search, the outlet temperature and thermal efficiency were studied in a geographical zone, located in the Baghdad city, Iraq. The experimental results showed that the thermal efficiency increases as the air velocity increases in the range of 2 m/Sec to 7.5 m/Sec. The maximum efficiency obtained using the glazed solar heater 90^o bed slope was η= 63%, but for unglazed solar heater same bed slops the maximum thermal efficiency decreased to η= 43.3%. The maximum thermal efficiency increased to η= 65.6% as decrease the bed slop to the 47^o for the glazed heater at a flowing air velocity of 7.5 m/Sec. Additionally, the temperature differences, ∆T, (T_out – T_in) and exergy efficiency for three beds of solar heater indicated an inverse association with flowing air velocity: Temperature differences, ∆T, and exergy efficiency, η_Ex, increased as the air velocity decreased. The maximum temperature differences and exergy efficiency for glazed solar heater bed slope 90^o are ∆T = 37.9 °C and η_EX= 4.8 %, for unglazed solar heater bed slope 90^o, ∆T =16.8 ^oC and η_EX=2.23 %, for glazed solar heater bed slope 47^o are ∆T= 48 C^o and η_EX= 5.24 %, which were recorded for the duration 12:00 am at maximum solar intensity, I. The results validated an improvement in the outlet air temperature T_out, thermal efficiency, η and exergy efficiency, η_EX.