Performance assessment of a parabolic trough solar collector using nanofluid and water based on direct absorption

In this investigation, a parabolic trough solar concentrating collector with an evacuated tube was fabricated with an aperture area, collector length, breadth, and rim angle, inner and outer diameter of absorber as 2.45 m2, 2.1 m, 1.2 m, 90 deg, 0.0286 m, and 0.03058 m, respectively. A copper oxide (CuO) and water-based nanofluid was employed as the working fluid. Different mass fractions (0.05%, 0.075%, and 0.1%) and volume flow rates (70 lit/hr and 140 lit/hr) of nanofluid were taken, and performance of an evacuated tube parabolic trough collector was analysed. When CuO–H2O nanofluid of varying concentrations (0.05%, 0.075%, and 0.1%) is used in place of H2O (DI), it has been observed that the solar collector's efficiency increases. The efficiency of the collector increases in direct proportion to the working fluid's volume flow rate increment. The maximum heat transfer coefficients for CuO–H2O based nanofluid were 280.68 W/m2-K and 466.8 W/m2-K while the maximum convective heat transfer coefficients for water as working fluid were 268.11 W/m2-K and 488.7 W/m2-K at 70 lit/h and 140 lit/h, respectively. An efficiency increase of 45.15%, 51.19% and 53.26% for 70 lit/h and 59.61%, 63.56% and 69.07% for 140 lit/h mass flow rate has been observed for different nanoparticle's concentrations, respectively. Economic studies showed that the cost of the experiment (for 0.05% CuO dispersion) has increased by 1.08% for 70 lit/h mass flow rate when compared to the water based direct cooling method.