Geometrical variation in receiver tube of SEGS LS-2 parabolic trough collector (PTC) based on heat flux distribution to improve the thermal performance

Heat flux (HF) distribution around the receiver tube of parabolic trough collectors (PTC) has a crucial effect on their outlet temperature (To) and thermal efficiency (ηth). Since its receiver tube is as a heat exchanger, the higher amounts of ηthcan be achieved by changing the geometry of the receiver tube. In previous researches, the geometrical variations were made in the internal geometry of the receiving tube, such as the use of corrugated paths, the installation of fins, using porous media, using twisted tape, etc. In this work, changes are simultaneously made in the internal and external geometry of the receiving tube, which is for the first time based on the model of HF distribution around the receiver tube. These changes include usVηing and moving the receiver's central plug, and creating concavities on the receiver tube to augment the contact surface of the wall with the internal working fluid. These concavities are created in regions of the tube that have a higher heat transfer to increase the heat transfer rate as a fin. In order to generate various HFs around the receiver tube and consequently create different arrangements of fins, two types of PTCs have been used in this research. To compare the improvement of each case-studies rather than smooth case, two indices of efficiency-based (VfNu) and two-objective evaluation () are defined. Finally the results show that, in view point of Vη index, PTC with three-piece reflector and also with the central plug as well as the big fins can give the optimum results than the other case-studies. On the other hand, considering the index of VfNu, the conventional PTC with E.F = 2/3 and the big fins can give the optimum results.