Performance analysis and comparison of glazed and unglazed solar air collector

Abstract

Glazed and unglazed solar collectors are now well-recognized solar collectors. Analysis of glazed glass tube solar air collector (GGTSAC) and unglazed glass tube solar air collector (UGGTSAC) is presented by developing a mathematical model in JAVA script language. The effect of five parameters (wind speed, mass flow rate of air, absorber tube diameter, length of glass tube and ambient temperature) is investigated by considering outlet air temperature and thermal efficiency as performance indicators. The agreement between theoretical and experimental data is good. Results show that out of five parameters, mass flow rate of air and length of glass tube are most critical parameters for GGTSAC and UGGTSAC. Outlet air temperature difference decreases from 49.7 to 38 and 28 to 24.1 °C and thermal efficiency increases from 0.67 to 0.71 and 0.33 to 0.42, when mass flow rate of air increases from 0.0074 to 0.0118 kg/s for GGTSAC and UGGTSAC. Outlet air temperature difference increases from 4.3 to 43.6 and 3.2 to 26.5 °C and thermal efficiency decreases from 0.74 to 0.71 and 0.52 to 0.38 when length of glass tube increases from 0.3 to 1.2 m for GGTSAC and UGGTSAC. The present work reflects the importance of transparent glazing in the design of solar air collector.