Two-Phase Immersion Cooling System under Atmospheric Pressure for Lv4 and 5 Autonomous Driving Computers

"Heat generation in Lv4 and 5 autonomous driving computer chips will be much higher than the current market level of Lv3. In order to solve this cooling issue, we have developed two-phase immersion cooling system under atmospheric pressure. In water cooling, the heating chips and heat exchanger are contacted with each other through heat spreader and thermal conductive material. Thermal resistance of the thermal conductive material is relatively large, thus the thickness control of that is quite important. Additionally, a plurality of heating chips on a board needs to be cooled simultaneously with the accurate thickness control.On the other hand, the proposed two-phase immersion cooling system enables high performance cooling simply by mounting a boiling accelerator plate on heating chips and immersing them in dielectric fluid. Moreover, the atmospheric pressure system realizes easy installation in vehicle and cost reduction. In this study, a performance prediction equation was developed focusing on the number of boiling points, and a boiling accelerator structure was developed with the equation to meet Lv4 and 5 cooling requirements. First the average cooling performance of one boiling point was obtained from the visualization results, then the relationship between the superheating and the number of boiling points on the surface was deduced to compose the equation. It was verified that the performace predicted with the developed equation is in good agreement with the measured one. It was confirmed that the cooling performance of the boiling accelerator designed from the developed equation achieved 474 kW/m2 @ ?T=10K. This shows our designed cooling system can be used for Lv 4 and 5 autonomous driving computers. "