Enhancing the performance of a parabolic trough collector with combined thermal and optical techniques

Abstract

The objective of this work is the investigation of different thermal enhancements methods in the LS-2 parabolic trough collector. The use of internal longitudinal fins and of a reflector shield are the examined enhancement techniques. The shield has a reflecting inner surface and acts as a secondary reflector for the absorber tube. The novelty of this work is mainly based on the combination of the two enhancement methods in order to achieve higher overall enhancements in the collector. The investigation is performed with Syltherm 800 as the working fluid, for inlet temperatures from 350 K up to 650 K and for volumetric flow rates from 50 L/min up to 200 L/min. According to the final results, it is found that the use of internal fins leads always in thermal enhancement, while the use of the radiation shield is beneficial in high temperatures. The combination of both techniques is the best choice compared to the separate techniques. For inlet temperature at 650 K and flow rate at 150 L/min, the thermal enhancement with internal fins is 0.90%, with the shilled is 1.66% and with both fins and shield is 2.41%.