Performance analysis of a novel direct absorption parabolic trough solar collector with combined absorption using MCRT and FVM coupled method

Direct absorption parabolic trough solar collector (DAPTSC) using nanofluid absorber has been demonstrated as an efficient technology for exploiting solar energy at high temperature. However, most mono nanofluids are unable to achieve broadband absorption and hybrid nanofluids are unstable at high temperature. In this work, the mono nanofluid and optical glass combined absorption is proposed for the DAPTSC. In which the absorption glass (HB850) and an outer glass tubes form an annular space for indium-tin-oxide (ITO)/Therminol VP-1 nanofluid flowing. Monte Carlo Ray-Tracing and Finite Volume Method (MCRT-FVM) coupled model is developed and validated for system investigation. The results show that the novel collector with the combined absorber exhibits obvious enhancement in thermal performance compared to Therminol VP-1 or ITO/Therminol VP-1 nanofluid. The DAPTSC with concentric annular tube (CAT) has a significantly superior thermal performance to that of the single tube collector, with 45.91 % higher achievable temperature gain and 1.15 % more achievable exergy efficiency. Finally, an eccentric annular tube (EAT) is proposed for further improvement. To quantify the performance improvement of the DAPTSC with EAT, a comparison has been made to that of a DAPTSC with CAT. The results indicate that EAT configuration shows 1.96 % enhancement in the exergy efficiency.