Performance evaluation of solar parabolic trough receiver using multiple twisted tapes with circular perforation and delta winglet

Abstract

A parabolic trough collector (PTC) is one of the concentrating types of a solar collector working in the medium range of temperature from 100–400 °C, for this reason, the efficiency of the solar parabolic trough is less than other types of concentrating solar collector (Point focusing types) in terms of solar to thermal energy conversion, the improvement in efficiency is achieved by various passive heat augmentation techniques in the receiver tube. One of the promising passive techniques is twisted tape inserts used in the receiver due to its simplicity in design and the various possibility of geometric modification. This paper deals with the performance evaluation of the solar parabolic trough receiver system by using passive techniques in the receiver. The testing of the receiver of PTC was done by using multiple perforated twisted tapes with winglets having different perforation ratios ( $d_p/w$ ) of 0.05, 0.15, 0.25, twist ratios ( $y/w$ ) of 3, 4, 5 and wing depth ratios ( $d/w$ ) of 0.1, 0.2 and 0.3. The number of twisted tapes was fixed at 4. The examination was conducted for Reynolds numbers ( $Re$ ) varying from 3000–21,000 using air as working fluid. The outcome shows that the use of perforation and winglet in twisted tapes augment the Nusselt number as compared to that of smooth twisted tapes. The maximum thermohydraulic performance ( ${\eta }_{TH(MPTTW)}$ ) of 2.40 is received by using multiple twisted tapes with perforation and winglet having $d/w$  = 0.3, $y/w$  = 3, and $d_p/w$  = 0.05 at the Re = 21,000. The correlations for Nusselt number ( $N{u}_{MPTTW}$ ) and friction factor ( $f{f}_{MPTTW}$ ) are also developed with ± 8.5% and ± 8.3% accuracy, respectively.