Composite Materials
Hamid Zalnezhad; N. Kordani
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 a numerical investigation of ...
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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 a numerical investigation of nanofluids flows in spiral tubes with an injection of base fluid in different Reynolds numbers. 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 nanofluid flow in order to investigate the changes in 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 the use of nanoparticles, the rotational effects of the tube and the injection process increase the heat transfer performance. It is 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. The 90-degree injection has the best effect. Cu2O3 –water nanofluid mixture is also used. The results and the comparison with the Al2O3 nanofluid model indicate that the increase in heat transfer rate in Cu nanofluid is higher than aluminum nano fluid due to higher heat transfer capacity of copper.
