Steady state simulation on combination of glazed and unglazed flat plate solar collectors for air heating

Abstract

Unglazed flat plate solar collectors usually have lower costs and can have an advantage in situations where heat loss is low. In this study a steady state simulation of the combination of glazed and unglazed flat plate solar collectors for air heating was performed for various conditions of heat transfer coefficient (3, 12 and 21 W/m2-°C), inlet temperature (30, 45, 60 and 75°C) and solar irradiation (350, 600 and 850 W/m2). The efficiency of combined system of the glazed and unglazed solar collector area was better compared to the system which consists entirely of glazed at a low coefficient of heat transfer (3 W/m2-°C), except for high inlet temperature (more than 60°C) and low solar irradiation (350 W/m2-°C). For the combination of 6m2 unglazed and 9m2 glazed solar collector, the higher percentage of flow rate through unglazed collector slightly increases efficiency except at high inlet temperatures (> 60°C) for high heat transfer coefficient (12 and 21 W/m2-°C) and at low solar irradiation (350 W/m2). For air heating operations which are maintained in equilibrium conditions the temperatures of the air produced were slightly higher than that of the collector inlet.