A Comprehensive Numerical Study on Nanofluid Flow and Heat Transfer of Helical, Spiral and Straight Tubes with Different Cross Sections

A numerical comparative analysis is carried out on heat transfer performance of laminar fluid flow of water/Al2O3 nanofluid in straight, spiral and helical tubes with various cross sections. Circular, triangular, rectangular and square cross-section in an identical length are considered as geometrical variables. Nanoparticles of Al2O3 added into the water (as base fluid) with volume fractions of 0.1-0.7 and it was flowed through different types of tubes, for different Reynolds number. Governing equations on fluid flow were solved based on finite element method. Results show, adding nanoparticles improves heat transfer as well as pressure drop. Among all types of tubes, helical-shaped tube has higher amount of heat transfer and pressure drop compared to spiral and straight. In a specific geometry at constant volume fraction and Re, highest heat transfer and pressure drop is related to the tube with rectangular cross-section. In all volume fractions and sections, average heat transfer coefficient in helical tube is higher than spiral and straight. Although helical tube has better heat transfer performance compared to spiral and straight, pressure drop between outlet and inlet in helical is higher than spiral and straight tubes. As a result, amount of FOM, the ratio of heat transfer to pressure drop, for helical geometry is lower than spiral and straight.