Abstract
This paper investigates forced convection of nanofluids within helical tubes, where a constant wall temperature is maintained and thermal equilibrium is assumed between the nanoparticles and the base fluid. The nanofluid model accounts for the effects of nanoparticle volume fraction, diameter, and temperature on thermophysical properties. The governing equations are solved using the Forward-Time Central-Space Finite Volume method in conjunction with the SIMPLE algorithm. Numerical results are validated against experimental data, demonstrating high accuracy. The study explores the effects of pitch size, curvature ratio, nanoparticle volume fraction, nanoparticle diameter, and Reynolds number on velocity contours, temperature profiles, secondary flow, thermophysical properties, friction coefficient, and heat transfer rate. Additionally, the figure of merit is used to evaluate the impact of these parameters on the thermal performance of the system. The results indicate that increasing Reynolds number and nanoparticle diameter diminishes thermal performance, while higher nanoparticle volume fraction, curvature ratio, and pitch size enhance it. Furthermore, incorporating nanoparticles in straight tubes proves to be more advantageous compared to helical tubes.
