Heat transfer enhancement of a radiator with mass-producing nanofluids (EG/water-based Al2O3 nanofluids) for cooling a 100 kW high power system

Abstract

In this paper, the heat transfer performance of a radiator with ethylene glycol/water-based Al2O3 nanofluids used to cool a 100 kW high power system is investigated. The nanofluids are prepared by a modified two-step method including both a nanodisperser and centrifugal decanting processes, which can continuously facilitate the mass production of homogeneous nanofluids. The suspension stability of the manufactured nanofluids is quantitatively measured using a Turbiscan for seven months. Three thermophysical characteristics – the thermal conductivity, the viscosity, and the convective heat transfer coefficient of the nanofluids – are systematically measured. With these results, the theoretical enhancement on the heat transfer rate of the radiator for a high power system is evaluated using the effectiveness-NTU (Number of Transfer Units) method. Moreover, the heat transfer rate of the radiator with the nanofluids is experimentally measured under the fixed Reynolds number and the fixed pumping power. It is shown that the heat transfer rate of the radiator with nanofluids is improved by up to 6.9% and 2.8% under the fixed Reynolds number and the fixed pumping power, respectively. We present the experimental enhancement on the heat transfer rate of the radiator with nanofluids can be estimated by the effectiveness-NTU method with the thermophysical properties and the convective heat transfer coefficient. Finally, the present results clearly demonstrate that the heat transfer rate of the radiator for the 100 kW high power system can be improved by using ethylene glycol/water-based Al2O3 nanofluids as a working fluid.