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 concentrated evacuated tube single-sided coated heat pipe absorber for medium temperature applications. The aperture areas of the solar collectors were 0.107 m(2) and 0.2004 m(2) for the evacuated tube heat pipe and the concentrated evacuated tube single-sided coated heat pipe absorber, respectively. Experiments were conducted at five different transverse angles (0-40 degrees) with a collector title angle of 60 degrees to the horizontal. These solar collectors were tested over a range of operating temperatures and the mean fluid and ambient air temperature differential increase and outlet and inlet fluid temperature differential, energy collection rates and efficiency and the heat loss coefficients of each solar collector was experimentally measured, calculated and compared to each other. The concentrated evacuated tube heat pipe solar collector showed an improvement of 30% and 25.42% in overall average outlet and inlet fluid temperature differential and total daily energy collection, respectively compared to the non-concentrated evacuated tube heat pipe collectors. (C) 2012 Elsevier B.V. All rights reserved.