Application of Cu-water and Cu-ethanol nanofluids in a small flat capillary pumped loop

An experimental study was carried out to investigate the thermal performance of a flat capillary pumped loop (CPL) using the water based and the ethanol based Cu nanofluids as the working fluids under several steady sub-atmospheric operating pressures. The evaporator of the CPL was placed horizontally and heated from the bottom. The experimental results show that adding Cu nanoparticles into both base fluids can significantly enhance the evaporating heat transfer coefficient and the maximum heat removal capacity. There is an optimal mass concentration of Cu nanoparticles corresponding to the maximum heat transfer enhancement. The operating temperature or the operating temperature has an apparent effect on the heat transfer enhancement. The heat transfer enhancement effects increase distinctly with increasing the operating temperature. The heat transfer coefficient and the maximum heat removal capacity can be increased up to 45% and 16% after substituting Cu-ethanol nanofluids for the base fluids, respectively. The present investigation discovered that the thermal performance of a CPL can be evidently strengthened by using Cu nanofluids.