Heat Transfer and Thermal Efficiency Enhancement of Parabolic Trough Collectors Using Al2O3–Therminol VP-1 Nanofluids

A parabolic trough collector (PTC) is a linear concentrating system consisting of a parabolic-shaped reflector with a receiver tube positioned along the focal axis. In this study, the performance of a parabolic trough solar collector is evaluated, with aperture area, collector length, breadth, Rim angle, and inner and outer absorber diameters of 5.54 m2, 3.65 m, 1.52 m, 70°, 0.048 m, and 0.05 m, respectively. The experiment was conducted at Ranchi, India (23.35° N and 85.30° E). During this day, marked by a cloudless sky, the ambient temperature ranged from 27 °C to 39 °C. The global solar radiation ranged from (630 W/m2 to 975 W/m2), and the wind speed varied between (0.8 m/s and 1 m/s). Aluminium oxide (Al2O3) and Therminol VP-1-based nanofluid were employed as the working fluid. The different volume fractions of nanoparticles were taken, and the evacuated tube PTC performance was analysed. When Al2O3–Therminol VP-1 of varying concentration (0–4%) and mass flow rate of 0.041 kg/sec is used, it has been observed that the receiver’s heat transfer performance improved with an increment in nanoparticle volume fraction. Temperature-dependent properties were applied to the thermal efficiency, exhibiting a notable increase of approximately 7.2% when the volume fraction ascends from 0 to 4%. At elevated Reynolds numbers, the efficiency decreases compared to lower volume fractions. These results contribute to understanding the effect of nanoparticle concentration on PTC performance.