Performance analysis of bare steel and evacuated tube receivers using water and Al₂O₃ nanofluid in Al Seeb region of Oman

In the current study, a concentrating parabolic trough solar collector was fabricated and experimented to measure its performance. The performances of the Stainless Steel Receiver (SSR) tube and the Evacuated Tube Receiver (ETR) were investigated for water and Al₂O₃-water nanofluid in terms of fluid temperature rise and thermal efficiency in the Al-Seeb region in Oman. The Al₂O₃-water nanofluid was tested at 0.1 %, 0.2 %, 0.3 %, and 0.4 % mass concentrations at different flow rates ranging from 46 l/h to 138 l/h, and performance was compared with water as a working fluid. The experiments with the SSR tube using water as the heat transfer fluid produced a maximum efficiency of 27 % at a flow rate of 138 l/h. However, the experiments with the ETR produced a maximum efficiency of 30.1 % at the same flow rate under similar solar flux and ambient conditions. The nanofluid produces higher efficiency for all concentrations investigated in this study. The maximum thermal efficiency of 39.1 % was achieved using the ETR with a 0.4 % mass fraction of nanofluids at a flow rate of 138 l/h whereas, it was 30.1 % for water as a working fluid.