Parametric investigation of nanofluids utilization in parabolic trough collectors

The objective of this study is to investigate the use of nanofluids in parabolic trough collectors for various cases. The two most usual nanoparticles (Al2O3 and CuO) are examined in the usual thermal oil Syltherm 800. A detailed thermal model is developed in EES (Engineering Equator Solver) and its results are validated with experimental results from the literature. In the first part of the analysis, the Eurotrough ET-150 module is examined for various inlet temperature levels (25-325 °C) for the three examined working fluids. The results prove that both nanofluids are more efficient than the Syltherm 800, with Syltherm 800/CuO to be the best choice. The heat transfer enhancement with the use of nanofluids is proved to be approximately to 50% and this enhancement is greater at higher temperature levels. In the parametric analysis part, the mean thermal efficiency enhancement is determined for various combinations of flow rates and concentration ratios for both nanofluids. The use of CuO is able to increase the thermal efficiency up to 1.26% and the use of Al2O3 up to 1.13% when the concentration ratio is maximized and the flow rate is relative low.