Heat Transfer Studies on Solar Parabolic trough Collector Using Corrugated Tube Receiver with Conical Strip Inserts

The heat transfer characteristics of the working fluid passing through the absorber of a solar parabolic trough collector (SPTC) can be enhanced by the creation of a turbulence effect. Therefore, a novel idea was implemented by introducing a corrugated tube (CT) absorber instead of a plain tube absorber in a solar parabolic trough collector. The heat transfer enhancement was improved further through the use of conical strip inserts inside the corrugated tube absorber of the SPTC. A corrugated tube (CT) receiver with a pitch of 8 mm and corrugation height of 2 mm was used with three different pitches of conical strip inserts (pitch pi = 20 mm, 30 mm and 50 mm) for the analysis of the thermal performance of the SPTC. Initially, experiments were conducted in a plain tube and corrugated tube receiver at different mass flow rates. The convective heat transfer rate was increased for all the configurations of the conical strip inserts. The SPTC performance was good for the combination of the corrugated tube (pc = 8 mm and hc = 2 mm) and the conical strip insert I3 (pi= 20 mm). The experimental results showed that the maximum achieved Nu value, friction factor, instantaneous efficiency and thermal efficiency of the CT-I3 were 177%, 38%, 26.92% and 9% compared to the plain tube under the same working conditions.