Thermal-hydraulic performance of coolants flowing in channels with varied cross-sections and flow path geometries: A numerical study

Abstract

Heat transfer and hydrodynamic characteristics are compared numerically for the straight, stepped, zigzag spiral and Archimedean helical tubes of various cross-sectional shapes under laminar flow conditions ranging between 1300 - 2500 of water and CuO-water nanofluid. The channel geometries considered are circular, square, rectangular, elliptic (oval), T-section, and I-section, with a total length of 1830 mm. The simulations are conducted with Ansys Fluent R2021. Heat transfer characteristics are examined for the inlet fluid temperature and the external tube surface heat flux system. Best cross-sections are chosen, and a fluid path is designed that leads to the maximum heat transfer efficiency and ease of frictional losses, using water as the working fluid. After optimizing the structure, CuO-water nanofluids with volume fractions of 1% and 2% are employed to assess enhancements in heat transfer and pressure drop relative to pure water. With the presence of spirally directed flow using a helical twisted channel, the I-shaped model exhibits much-enhanced thermal characteristics compared to those in linear channels, with further enhancement in maximum temperature at the outlet to (312.7 K) from the conventional round tube value of (305.7 K). On the other hand, as imposed with Archimedean helical flow pattern in conjunction with the I-shaped scenario, there is an increase in heat transfer improvement leading to outlet temperatures with values of (315.0 K) as opposed to straight channel results (312.7 K). Furthermore, promisingly higher levels of heat transfer are found for CuO for output temperatures ranging from (316.1 K) to (317.0 K), corresponding to nanoparticle concentrations of 1% and 2% respectively. It is also ascertained that an I-section together with an Archimedean helical trajectory showed higher thermal efficiency, although this leads to increased energy consumption arising from the dynamic resistance of the fluid flow. The results provide insights into a favorable approach to I-shaped channels for enhanced designs in advanced thermal systems.