Transient boiling enhanced thermal transport and magnetically driven circulation in a closed ferrofluid cooling loop

This study investigates the transient thermo-hydraulic behavior of a magnetically driven closed-loop cooling system utilizing a ferrofluid under both non-boiling and subcooled flow boiling conditions. A numerical model is employed to capture the complex dynamics of ferrofluid motion and phase change, incorporating a body force arising from the application of non-uniform magnetic field. The simulations are conducted for two working pressures: 100 kPa (non-boiling) and 3.17 kPa (boiling), across a range of heat fluxes (40,000–80,000 W/m 2 ) and magnetic field gradients (2 × 10 5 –4 × 10 5 A/m 2 ). Results reveal that magnetic actuation induces a circulating flow within the loop. This enhances heat removal without the need for mechanical pumping. As the magnetic field gradient increases, the ferrofluid velocity increases which contributes to enhancement of convective heat transfer. In the boiling condition, the formation of vapor bubbles significantly improves the heat transfer coefficient reaching values up to 16, 830 W/(m 2 ·K) under high heat flux showing over 200 % improvement in comparison with the non-boiling case. Moreover, in the boiling regime, the wall temperature is slightly above the saturation temperature. This prevents from thermal overshoot and causes efficient thermal management. The proposed magnetically driven ferrofluidic loop combined with controlled boiling can be an effective thermal management solution for high heat flux applications.