Thermal performance of nanofluids in elliptical zigzag tube: a numerical approach

Abstract

This work was aimed at evaluating the thermal performance of nanofluids in an elliptical zigzag tube. The particle diameter and volume fraction of nanofluids were quantitatively investigated using two passive heat transfer configurations. The governing equations of mass, momentum, and energy of nanofluids containing ZnO and SiO2 in water at volume fractions of 1–4%, nanoparticle diameters of 15, 35, and 55 nm, and Reynolds number ranging from 400 to 2000 were solved using ANSYS. The results generally indicate that the Nusselt number and heat transfer coefficient increased with increasing volume fraction as Reynolds number increases. SiO2 exhibits a better thermal performance than ZnO, wherein a 4% volume fraction of 15 nm nanoparticle renders a greater heat transfer coefficient of 1149 W/m2·K at Reynolds number = 2000. The heat transfer is essentially improved at smaller particle diameter and higher volume fraction. The zigzag curvature displays an important attribute to enhance the heat transfer over the straight tube, although the skin friction coefficient increases with an increasing angle at 45°.