Numerical analysis of flow boiling around different microfin structure

The high heat flux generated in electronic devices manufactured in smaller sizes than traditional ones can lead to decreased system performance and various malfunctions. Design changes to microchannel heat exchangers used in cooling electronic devices can increase cooling efficiency. One such application is improving the heat exchangers by modifying the design of the microfins used in microchannel heat exchangers. Furthermore, the use of dielectric working fluids can provide safer and more effective cooling.Among the heat transfer methods used to achieve thermal management, phase change cooling systems are considered a successful application. Phase change cooling systems utilize the latent heat of the vapor to enable optimal heat dissipation. This characteristic makes two-phase flow more advantageous in terms of heat transfer than single-phase flow. While attempts to solve the cooling problem with two-phase flow have been made, the lack of a complete understanding of the mechanisms involved in heat transfer and fluid boiling characteristics has increased the focus on research in this area. Experimental and numerical studies are being conducted to interpret the heat transfer mechanism resulting from the boiling of the fluid within the channel in microchannel heat exchanger cooling systems. Due to the difficulty and increasing costs of experimental studies, numerical studies have become increasingly popular to investigate these transfer mechanisms in more detail. This study investigates the effects of shape changes in microfin structures, which allow for increased heat transfer in microchannel heat exchangers, on the heat transfer coefficient. In addition to the microfin shapes previously studied in the literature, a time-dependent numerical analysis was conducted using elliptical microfins with equal hydraulic diameters and varying height and width values within the microchannel heat exchanger.Three different constant heat fluxes were defined for the fin walls: 50, 100, and 150 kW/m2. The Novec649 dielectric working fluid enters the flow field at constant speeds at 0.5 m/s and 1 m/s. In this study, the bubble dynamics formed around elliptical microfins of different shapes placed within the channel were investigated, as a result of the boiling of Novec649 fluid heated by heat fluxes defined around the microfin. The aim of the numerical analysis was to determine the heat transfer coefficient generated by the microfins and, consequently, to determine the microfin shape that improves heat transfer performance. In the simulation created using the ANSYS Fluent 2023 R1 module, numerical analysis was performed using the VOF method with six different boundary conditions. The conditions affecting heat transfer performance were evaluated, and it was found that the microfin with the highest heat transfer coefficient was an elliptical shape with a height of 3.88 mm and a width of 3.88 mm.