Hydrothermal analysis of hybrid nanofluid flow inside a shell and double coil heat exchanger; Numerical examination

Abstract

In a shell-and-coil heat exchanger, employing a double coil instead of a simple coil causes more heat transfer compared to a simple coil because the double coil improves heat exchange through enhanced fluid flow and turbulence, enabling a longer tube length in constrained locations.. In addition to reducing fouling and the requirement for maintenance, the helical shape may also provide the benefit of a self-cleaning action. Ensuring a more even flow distribution also maximizes the heat exchanger's surface area use and reduces low flow zones. Applications needing compact solutions without compromising performance especially benefit from this design's versatility, allowing customization to meet unique operational demands. In numerous industrial applications, helical coils offer substantial benefits in terms of effectiveness, upkeep, and design freedom.In the present work, heat transfer and fluid flow in a shell-and-coil tube heat exchanger equipped with a double helical coil are evaluated numerically. The employed heat transfer fluids are water-based hybrid nanofluids, including TiO2-Mgi/water and AG-HEG/Water. The obtained outcomes are compared with the results of pure water. The range of considered Reynolds numbers is 500 – 2000. This work consists of two sections. In the first part, the impact of the type of hybrid nanofluid on the hydrothermal behaviour of the proposed heat exchanger is analysed. The volume concentration of the nanoparticles here is ϕ1 = ϕ2 = 0.3. In the second section, the best hybrid nanofluid is selected according to the results of the first section; then, the impact of the nanoparticles' volume concentration on the thermal performance of the proposed heat exchanger is evaluated. Three various nanoparticle volume concentrations, including ϕ1 = ϕ2 = 0.1, ϕ1 = ϕ2 = 0.3, and ϕ1 = ϕ2 = 0.5, are considered, and the results are compared with those of the pure water case (ϕ1 = ϕ2 = 0).The obtained results show that amongst the different heat transfer fluids considered, the Water/MgO-TiO2 model shows the most outstanding value of thermal performance in all the studied Reynolds numbers. Also, the obtained numerical results show that the use of the proposed double coil tube leads to an increase in the heat transfer rate.

Keywords

• Heat transfer
• Shell-and-Coil tube heat exchanger (SCTHE)
• Numerical analysis, Hybrid nanofluid