Influence of geometrical and operational parameters on the performance of natural circulation looped parabolic trough collector

Natural circulation loop of a larger diameter is analysed analytically in the present study intending parabolic trough application. 1-D analytical model is developed and validated with 3-D numerical model. SolTrace® is used to find the heat flux distribution over the receiver. The validated analytical model is used to study the effect of geometric and operating parameters on the flow rate and bulk temperature of the heat transfer fluid under different solar irradiances and the optimised model is defined. To enhance the loop performance further, Al₂O₃ nanofluid at different volume fractions are incorporated, which resulted in 55% improvement in the loop flow rate compared to the model with base fluid. Finally, the use of single-phase natural circulation systems can be a replacement to the existing conventional systems and provide sustainability.