Investigation and optimization of the behavior of heat transfer and flow of MWCNT-CuO hybrid nanofluid in a brazed plate heat exchanger using response surface methodology

Abstract

In this work, a new stability method (a mixture of surfactants) was used to preparation 0.1 wt% of hybrid nanofluid including multi-walled carbon nanotubes‑copper oxide (MWCNT-CuO) as a cold fluid in the brazed plate heat exchanger. The four Non-ionic surfactants were used to evaluate the stability of nanofluids. Effects of water and hybrid nanofluid (as cold fluid) on thermal characteristics in the brazed plate heat exchanger were studied. The results display that the stability of hybrid nanofluid with a mixture of two surfactants, including GA and Tween-80, is suitable, and no sedimentation was observed. Also, when the hot fluid is at a consistent temperature of 35 °C and volume flow rate of 6 L/min, the highest increase in the convective heat transfer coefficient of hybrid nanofluid at a volume flow rate of 14.4, 18.9 and 24.4 L/min in comparison with water are 85.56%, 101.25%, and 139.19%, respectively. The significance of the factors and their interactions were verified by using the analysis of variance (ANOVA) with 95% of confidence level (p < 0.05). Finally, the response surface methodology was used to achieve an empirical relationship for the convective heat transfer coefficient and optimization.