Comparative Study of Heat Transfer Enhancement in Parabolic Trough Collector Based on Modified Absorber Geometry

Abstract

The parabolic trough collector (PTC) is one of the most deployed and cost-effective solar concentrating systems available. The PTC under study is modeled after the LS-2 collector with different geometrically modified absorber tubes. The proposed model is validated using the Sandia national laboratory, AZTRAK, platform results. The absorber tube is modeled for five different geometry configurations: plain tube (smooth tube), longitudinal finned tube, a tube with a porous insert, a tube with a twisted tape insert, and a wavy (converging-diverging) tube. An analysis was conducted to observe the effects of these modifications on the thermal efficiency, Nusselt number, heat transfer coefficient, receiver temperature, and pressure losses. The converging-diverging absorber tube provides the maximum thermal enhancement of 1.16% whereas the absorber tube with porous insert yielded a mean enhancement of 0.89%. The results prove that modifying the inner geometry of the absorber tube leads to increased heat transfer coefficient and a reduction in the circumferential temperature of the receiver. The thermal and exergetic enhancement factors along with the exergetic efficiency are among other parameters investigated.