Heat transfer enhancement of a parabolic trough solar collector using a semicircular multitube absorber

This experimental work investigates the thermal performance of a parabolic trough solar collector (PTC) with a semicircular absorber tube of 7 mm diameter with a double inlet and outlets. The double inlets are provided to absorb more heat due to the increased length of the absorber tube with minimal heat loss. The tested water mass flow rates are 0.1, 0.15, and 0.2 kg/s. The thermal and exergy efficiencies, the heat transfer coefficient, the Nusselt number, and the friction factor of the modified absorber are compared with that of the conventional single-tube circular absorber of 25 mm diameter. The modified absorber's thermal and exergy efficiencies are 43.9% and 33.6% higher than conventional ones. The heat transfer coefficient of the modified absorber is 541 W/m(2)K which is 28.5% higher than the conventional absorber. The increased pressure drop results in more pump power, and it increases with an increase in mass flow rate. Thus, the proposed solar absorber improves the heat transfer rate through its semicircular arrangement with reduced hydraulic mean diameter. The outcomes are beneficial to designing line-focus solar absorbers for line-focus solar collectors. (c) 2022 Elsevier Ltd. All rights reserved.