Heat transfer of alumina-deionized water nanofluids in concentric tube heat exchanger

Abstract

This research studied the characteristics of nanofluids in a concentric tube heat exchanger. The objectives of this research are to prepare the stable nanofluids with addition of surfactant and to investigate the stability, properties, and heat transfer of nanofluids in concentric tube heat exchanger. Aluminium oxide (Al2O3) was added to base fluid deionized water (DW) with addition of polyvinylpyrrolidone (PVP) as surfactant by two-step method. First, the best stability ratio of nanofluids to surfactant PVP was determined by preparing several samples of 0.50 wt% nanofluids with addition of different weight fraction of surfactant. Thus, each sample has different ratio and being observed for one week by visual observation. Then, nanofluids samples (0.25, 0.50, 0.75 and 1.00 wt%) were prepared based on the best stability ratio. The properties and heat transfer of nanofluids were analyzed at different concentration of nanofluids and at different temperatures (room temperature, 40 °C, 50 °C, 60 °C and 70 °C). From the observation, the alumina nanofluids was stable with the addition of surfactant at ratio 1:2. The thermal conductivity of nanofluids are higher than base fluid and increased as the temperature and concentration increased. Viscosity of nanofluids was highest at 1.00 wt% and at room temperature. The heat transfer performance of heat exchanger increased by using nanofluids. Nanofluids absorbed more heat than base fluid and the highest percentage drop of hot stream is 120% at 70 °C by using 1.00 wt% nanofluids.