# Heat Transfer Optimization of an Electronic Control Unit Immersed in Forced Liquid Coolant
## 1 Introduction
While most major OEMs in the passenger car market use air or indirect liquid cooling methods, new methods to meet the increasing thermal demand on high-performance computers are required. This is especially true when it comes to more specialized markets like electric construction vehicles. In this scenario, a large amount of power is required, which generates a significant amount of heat. Liquid cooling could be one of these emerging technologies for automotive electronics thermal management. It could be direct or indirect liquid cooling. Currently, liquid cooling solutions are used in automotive for the cooling of battery systems. The market for novel energy vehicles has grown rapidly in recent years. Power batteries are one of the most important components in electric vehicles (EVs) and hybrid electric vehicles (HEVs). Thermal Management systems are equally important as battery cell chemistry because the battery cell's life depends on them. During the charge and discharge process, a large number of battery cells generate a lot of heat and cause temperatures to rise [10; 11]. The operating temperature of a cell has a significant impact on its voltage, energy, efficiency, and life cycle [12]. Further thermal runaway and safety issues can occur if heat is not effectively dissipated [13; 14]. Because liquid has a higher specific heat and thermal conductivity than air, it can effectively mitigate battery temperature rise and prevent battery overheating at the expense of a more complex system. Currently, there are vehicles in production that use mainly indirect liquid cooling. Tesla has developed a novel method for cooling the thousands of cylindrical cells housed in the chassis. Tesla uses a metallic cooling tube that snakes through the EV battery pack,according to the patent [15]. By maintaining contact with the surface of each cell, this flexible tube provides direct cooling. To manage battery heat, GM's Chevy Volt [16] has a liquid cooling system with glycol. A plastic frame surrounds each battery cell. The coolant plate frames are then stacked longitudinally to form the entire pack. Both Tesla's and GM's systems have one big drawback, and the heat transfer coefficient of glycol could be improved. Additional research showed the advantages of indirect coolant performance, such as new liquid cold plate concepts that are well suited for single-sided cooled packages as well as double sided cooling of stacked press-pack-type modules [17]. Direct immersion cooling is classified into two types: single-phase immersion cooling (SLIC) and two-phase liquid immersion cooling (TLIC) (2 PIC). This method takes advantage of dielectric fluids, which, because of their high dielectric strength, have very little electrical conductivity. This makes it possible for the cooling liquid to come into direct contact with the electronic components, increasing the cooling capacity of the method and addressing the drawbacks of indirect liquid cooling. Immersion cooling, which is based on immersing the electronic components with dielectric fluid to increase cooling efficiency, is the most popular cooling approach for this method. Immersion cooling has previously been demonstrated mainly in electronics for data centers [18; 19], high-power electronic device systems [20; 21], and grid power systems but is now seeing interest in the electric and conventional vehicle markets. The operational complexity, the problem of hysteresis of the boiling curve and evaporation, and the high cost of 2 PIC [22] make this option less feasible to implement on the electronic modules on the vehicle, and for this reason they are not the purpose of this experiment. However, the SLIC solution appears to be more promising. Several studies have demonstrated the advantages of using single-phase fluids. It demonstrated that the given technology reduces heat flow barriers while maintaining the mechanical properties of the package. [PERSON] et al.