Experimental study of carbon nano tube/oil nanofluid in dish concentrator using a cylindrical cavity receiver: Outdoor tests

The application of nanofluids is accounted as an effective way for improving the thermal performance of solar systems. In the current study, MWCNT/thermal oil nanofluid was experimentally tested as a solar heat transfer fluid. A dish collector, using a wounded cylindrical cavity receiver, was considered as the solar system. The main aim of this work was the experimental investigation of the cylindrical cavity's performance, using MWCNT/thermal oil nanofluid. Two experimental models were suggested for the prediction of the cavity's thermal efficiency, by considering MWCNT/thermal oil nanofluid and pure thermal oil in the steady-state period. It was indicated that the heat loss coefficient of the cylindrical cavity receiver decreased by the application of nanofluid. The results revealed the average thermal efficiencies of 63.9% and 56.44% for MWCNT/thermal oil nanofluid and pure thermal oil, respectively. The thermal efficiency was changed form 60.04% to 64.76%, by using the nanofluid, in the steady-state period. Also, it was observed that the thermal performance of the cavity receiver was improved by 13.12%, by using MWCNT/thermal oil nanofluid. Based on the obtained results, the application of MWCNT/oil nanofluid is recommended in the solar dish concentrators with cavity receiver.