Simulation of natural convection heat transfer in dielectric liquids for single-phase immersion cooling rack server

• First transient comparison of FC-40, EC-130, and mineral oil in natural convection. • EC-130 outperformed others, absorbing 7.9% more heat than mineral oil in 10 min. • FC-40 excelled in convection-dominated regions; EC-130 in conduction-dominated zones. • Mineral oil yielded 13–16% higher temperatures due to its elevated viscosity. • Study aids SPIC optimization by linking fluid properties to component-level performance. The growing energy demands of data centers necessitate innovative cooling solutions to reduce environmental impact. This study addresses the critical challenge of optimizing single-phase immersion cooling (SPIC) by evaluating three dielectric liquids (FC-40, EC-130, and mineral oil) under natural convection—a gap in existing literature, which predominantly focuses on steady-state, pump-driven systems. A time-dependent computational fluid dynamics (CFD) analysis was conducted using a 3D model of an Intel® Server System M50FCP1UR, simulating heat dissipation over 10 min under an 883 W thermal load. Results demonstrate mineral oil’s inferior performance, yielding component temperatures 13–16 % higher than FC-40/EC-130 due to its elevated viscosity. Both FC-40 and EC-130 maintained CPU temperatures below the 95 °C safety threshold, with FC-40 excelling in high-velocity regions (peak velocity: 0.062 m/s) dominated by convection, while EC-130 outperformed in low-velocity zones reliant on conduction. Quantitative analysis revealed that EC-130 absorbed 7.9 % more heat than mineral oil, and 0.2 % more than FC-40 over the 10-minute simulation, demonstrating superior overall heat dissipation. This work provides the first direct comparison of these fluids in transient natural convection, revealing that fluid selection hinges on component-level thermal profiles. These findings enable data center operators to tailor SPIC systems for energy efficiency without compromising safety.