Parabolic trough solar collector for medium temperature applications: An experimental analysis of the efficiency and length optimization by using inserts

The present indoor experimental study is focused on performance enhancement of a parabolic trough collector (PTC) with twisted tape insert by incorporating an innovative Soltrace^VR -mathematical model-differential heating combination. This simulation-based methodology is very useful in analyzing the system behavior under defined environmental conditions. By the use of insert, the circumferential temperature difference has been dropped considerably in all cases compared to plain receiver. Hence, this gain is reflected in both instantaneous and thermo-hydraulic efficiency. As the role of inserts is justified in different thermal parameters, the system evaluation factors have been defined as H-W-B constants. Further, to take into account the influence of enhanced heat transfer on geometry, receiver length optimization has been performed which gave a maximum of 26% short in length of the receiver with best twist ratio under the transition flow regime. Hence, for moderate flow and medium temperature applications, inserts are useful. The range of Reynolds number considered in the experimental study is 2600-24,000 to analyze the flow regime based effect.