# Heat Transfer Optimization of an Electronic Control Unit Immersed in Forced Liquid Coolant
## 4 Conclusions  
In this study, a cooling concept for future centralized platforms of automotive electronic modules, which involves grouping multiple electronic devices into a single system and cooling them with recirculated dielectric coolant, is investigated. Measurements and explicit model predictive control based on the statistics method for the proposed immersion liquid cooling system have made some significant achievements, as listed below:  
Figure 8: Temperature comparison between reference modules, cooled by thermal paste and a dielectric coolant system.  
Figure 7: Cube plot for Buck1 temperatures.  
* The smallest temperatures on the hotspots were achieved with the highest coolant flow (1.54 L/min), the highest airflow (3.2 L/s), and the smallest quantity of liquid in the housing (300 mL);
* According to this statistical method, the fan airflow value has the greatest influence on the temperatures of electronic components. It also has the greatest influence on the slope from the lowest to the highest flow rate;
* Cooling is also affected by pump flow. The best results were obtained when the flow rate was increased to 1.54 L/min. The pump, of course, requires power to operate, and unfortunately, most of this energy is expanded in the coolant as heat. As a result, the power consumed by the pump raises the total heat rejected. However, the benefits of forced liquid cooling's small temperature gradients and increased cooling rates easily outweigh the disadvantages of increased system complexity;
* Temperatures were least affected by the volume of liquid in the casing. The results, however, revealed that the lowest temperatures were recorded with the least amount of liquid in the casing because of the advantage of faster recirculation of the liquid, cooled by the radiator and fan. Due to design constraints, a smaller amount of liquid could not be tested in these experiments;
* These measurements show that the single-phase liquid cooling system with forced convection achieved up to 57% lower temperatures on Buck1, 73% lower temperatures on \(\upmu\)C, 60% lower temperatures on Boost, and 55% lower temperatures on the PCB overall temperature when compared to thermal paste cooling solutions for the used boundary conditions.  
OEMs typically request automotive-grade components to ensure dependable and safe operation over the vehicle's long lifespan in harsh environmental conditions. While the technology shows promise with technically excellent performance, the increased weight and cost compared to currently used methods will make immersion cooling difficult to enter the mass-production automotive market. However, regulations concerning the thermal safety of electric vehicles are changing, and this emerging technology may begin to take a larger market share. Furthermore, the flame-retardant properties of the fluids serve as a safety feature, preventing thermal runaway events from spreading between electronics or battery cells. The choice of coolant fluid is obviously critical in this case. As a new cooling technology proposed for automotive, there is still a lack of research addressing the lifetime, fluid stability, material compatibility, and understanding of sustainability. Hermetical sealing of the ECU and expansion of the coolant should also be considered. This conclusion is encouraging for discussions about module weight, a critical topic in the automotive industry.  
Conceptualization, C.G.L. and C.G.D.; methodology, C.G.D.; software, C.G.L.; validation, C.G.L., C.G.D. and P.V.; formal analysis, C.G.L.; investigation, C.G.L.; resources, C.G.L.; data curation, C.G.D.; writing--original draft preparation, C.G.L.; writing--review and editing, P.V.; visualization, A.V.S.; supervision, P.V.; project administration, A.V.S.; funding acquisition, P.V. All authors have read and agreed to the published version of the manuscript.  
This research was also supported by TUIASI from the University Scientific Research Fund (FCSU).  
Not applicable.  
The authors declare no conflict of interest.