Numerical analysis of heat transfer in helical tube with the aluminum oxide (Al2O3) nano fluid injection in water

Abstract

The most important reason for the design of curved tubes is increasing the heat transfer between the fluid and the wall which has provided many applications in various industries such as air conditioning, micro-electric, heat exchangers and etc. The aim of this study is numerical investigation of nano fluids flow in spiral tubes with injection of base fluid in different Reynolds numbers. According to, the effects of volume fraction, nanoparticle diameter, fluid injection, Reynolds number and spin effects on heat transfer and flow in the spiral tube are discussed. In this study, a mixture of water-Al2O3 is selected to model nano fluid flow in order to investigate the changes of the heat transfer rate by the injection of nanofluid to the base fluid in the spiral tube at different angles. The results show that by use of nanoparticles, the rotational effects of tube and the injection process increase the heat transfer performance. It was found that increasing the volume fraction has a direct effect on increasing the heat transfer coefficient. As the volume fraction increases from 2% to 8%, the heat transfer coefficient increases by 2%. In fact, the effect of nanoparticles on the thermal conductivity of the fluid causes this increase. Also, injection of fluid into the stream due to disturbance in the thickness of the boundary layer and the further mixing of the fluid layers which increases the heat transfer. 90-degree injection has the best effect. Cu2O3 –water nano fluid mixture has also been used. The results are presented in this paper and compared with the Al2O3 nano fluid model which indicates that the increase of heat transfer rate in Cu nano fluid was higher than aluminum nano fluid due to higher heat transfer capacity of Copper.