# The Thermal Analysis and Heat Dissipation Structure Optimization of a Propeller Driver System
## 1 Introduction  
In recent years, the intensification of marine resource exploration and development has led to an increased use of submarine robots and underwater vehicles. Among them, the propeller driver is used as a driving component to control the submersible robots and underwater vehicles to dive, float, advance, and retreat. Therefore, the stability of the propeller drive is becoming more and more important. The rapid development of electronic information technology has resulted in the miniaturization and high power density of various electronic devices [1; 2; 3], which are now widely used in propeller drives. The dense arrangement of electronic devices on the driver increases the heat flux density and the temperature rises rapidly, the driver is prone to overheating, and high temperature is one of the main reasons for the failure of electronic devices, which seriously affects the stability of the driver. Statistics show that electronic equipment failure caused by high temperature accounts for up to 55% every year [4; 5; 6; 7]. Moreover, for every 10 \({}^{\circ}\)C increase in temperature, the reliability of the device is reduced by 50% [8]. When the device temperature is above 70 \({}^{\circ}\)C, reliability decreases by 5% for every 1 \({}^{\circ}\)C increase in temperature [9; 10]. Therefore, the heat dissipation of the propeller driver device has become one of the main problems restricting the working stability of underwater vehicles. Scholars have proposed many optimization methods for different electronic devices. These methods can mainly be classified into material optimization and structure optimization. For example, [PERSON] [11] and others studied the influence of substrate material, bonding layer material, and package shell material on chip temperature. [PERSON] et al. [12] studied the effect of silicon thickness, 3D interconnection, and packaging schemes on the temperature distribution of 3D chips. [PERSON] et al. [13] studied the heat dissipation performance of finned heat sinks made of thermally conductive polymer composites under forced convection conditions. The study found that carbon-filled polymer heat sinks have better heat dissipation capabilities than metal-filled polymer heat sinks. [PERSON] et al. [14] used a two-dimensional transient numerical simulation method to study the heat transferperformance of finned heat sinks based on phase change materials (PCMs) in the passive cooling of electronic devices. Transient numerical simulations were carried out using the finite volume method to investigate the coupled heat transfer and melting/solidification phenomena at different power levels. [PERSON] et al. [15] studied the effect of PCM type, PCM porosity, and PCM material on heat sink thermal performance. [PERSON] et al. [16] used numerical methods to study finned heat sinks embedded with single and multiple phase change materials and used the Nusselt number to characterize their heat transfer characteristics to compare their heat dissipation performance. The analysis compares the time to reach the transient average temperature for different cases. However, most of the material-optimizing methods are limited by their processing cost, material strength, high-temperature resistance, and other factors. Therefore, they are difficult to use in underwater equipment. Therefore, structural optimization becomes mainstream. [PERSON] et al. [17] optimized the design based on the number and distribution mode of the heat sink; [PERSON] et al. [18] studied the heat dissipation of the fin shape. [PERSON] et al. [19] and [PERSON] et al. [20] analyzed the structure of the microchannel heat sink. [PERSON] et al. [21] studied the influence of fin number and fin spacing on heat dissipation. [PERSON] et al. [22] analyzed the heat dissipation characteristics of the microchannel by using experimental analysis and established the relationship between cooling water flow and temperature. [PERSON] et al. [23] adopted the bionics method to optimize the structure of the heat sink shape. [PERSON] et al.