Studying NanofluidHeat Transfer in Helical Tubes with Two-phase Numerical Methods

In recent decade, many studies have been empirically conducted on heat transfer of several nanofluids. To transfer convection heat, Lee and Choi studied heat transfer in parallel ducts using unknown nano-fluid and found that thermal resistance has decreased twofold. Xuan and Li were the first persons who reported considerable increase of Heat transfer coefficient of turbulent flow. They found that Heat transfer coefficient in an equal speed for water-copper nano-fluid with 2 volume percents of nano-particles is about 40% higher than that for wmpty water. Results of their study show considerable increase of Nusselt number of fluid compared with water so that the common theoretic models are not responsible for perdicting Nusselt number of water and the model has been proposed based on dispersion model which has been proposed by the same researchers can be used for comparison with empirical results.