Effect of flow regime on the boiling characteristics of discrete pin-fin surfaces in immersion cooling applications

Immersion cooling systems have the potential to find wide applications in data centers and battery thermal management systems due to their high cooling capacity. In this study, a boiling immersion cooling system using Novec 7100 dielectric liquid was constructed and tested. Four electric cartridge heaters with circular and square cross-sections were positioned vertically in a rectangular arrangement. Pool boiling and flow boiling mechanisms were investigated at two different flow rates, and the effects of varying distances between the heaters were examined.For different spacing values, the maximum heat transfer coefficient ranged from 6.57 kW/m2K to 9.28 kW/m2K for circular heaters, and 10.15 kW/m2K to 16 kW/m2K for square heaters. Introducing flow into the pool boiling significantly reduced the surface temperatures. Increasing the distance between the heaters led to even lower surface temperatures under flow boiling conditions. Owing to their 1.15 times larger surface area, the square heaters exhibited up to a 30–40% increase in heat transfer coefficients compared to the circular heaters, particularly under high heat flux conditions.