In-door experimental analysis of concentrated and non-concentrated evacuated tube heat pipe collectors for medium temperature applications

The paper presents the performance of an evacuated tube heat pipe solar collector compared to a concentratedevacuated tube single-sided coated heat pipe absorber for medium temperature applications.The aperture areas of the solar collectors were 0.107 m2 and 0.2004 m2 for the evacuated tube heat pipeand the concentrated evacuated tube single-sided coated heat pipe absorber, respectively. Experimentswere conducted at five different transverse angles (0–40◦) with a collector title angle of 60◦ to the horizontal.These solar collectors were tested over a range of operating temperatures and the mean fluid andambient air temperature differential increase and outlet and inlet fluid temperature differential, energycollection rates and efficiency and the heat loss coefficients of each solar collector was experimentallymeasured, calculated and compared to each other. The concentrated evacuated tube heat pipe solar collectorshowed an improvement of 30% and 25.42% in overall average outlet and inlet fluid temperaturedifferential and total daily energy collection, respectively compared to the non-concentrated evacuatedtube heat pipe collectors.