Combined Effects of Using a Nanofluid and Adding Fins to the Absorber Tube of a Double-Reflection Parabolic Trough Collector

This paper presents an analysis of the thermal performance of a parabolic trough collector (PTC) integrating a secondary reflector. The primary objective is to examine the impact of incorporating fins within the absorber tube, the introduction of nanoparticles to the base fluid, and the combination of fins and a nanofluid as a heat transfer fluid (HTF). The study is divided into two parts: The first part employs a ray-tracing method based on the Monte Carlo technique to determine the heat flux distribution on the lateral surface of the receiver tube. The second part involves simulating the conjugate heat transfer and fluid flow within the absorber tube. The heat transfer fluid used in this study is alumina (Al₂O₃) nanofluid, and the meteorological conditions are representative of Laghouat, a city in southern Algeria. The calculations revealed an average efficiency of approximately 47% for a secondary reflector. In addition, the results demonstrated that the optimal system configuration includes inserting three fins inside the tube, which leads to an efficiency improvement of 11% when using rectangular fins. Furthermore, the addition of 4% alumina nanoparticles (Al₂O₃) to the base fluid (water) increases the system’s efficiency by 12%. Finally, an optimal combination using a secondary reflector, the insertion of fins and the use of a nanofluid as a heat transfer fluid offer an efficiency gain of around 16%.