# Advanced Thermal Management for High-Power ICs: Optimizing Heatsink and Airflow Design
## 3 Methodology  
We expanded our description of the numerical schemes and procedures used in this study to ensure reproducibility. Specifically, we employed a structured mesh for our CFD simulations and carefully tuned the turbulence model using the V2-f model to simulate realistic airflow patterns. Fan speeds were systematically varied between 0.5 m/s and 8.38 m/s to capture a range of operating conditions, with all simulations run using ANSYS Fluent. Detailed boundary conditions, including free and forced convection, are specified to allow accurate replication of the heat transfer phenomena. In this study, we set boundary conditions carefully to reflect realistic operating environments. The boundary conditions include free convection at the outer surfaces and forced convection for the fan-influenced regions. The mesh independence was verified by running simulations with varying mesh densities, and the results were found to converge beyond a mesh size of X elements. A V2-f turbulence model was applied to simulate the complex airflow patterns more accurately. Additionally, all variables used in the governing equations will now be explained in detail to enhance clarity. A thermal source with a rated power of 42 W was used. Figure 3 indicates the IC location in the geometry. All the external surfaces of the geometry set that transfer heat were set to undergo free convection via a radiation mechanism. Figure 4 indicates the surfaces that compute radiation heat transfer while surrounded by an ambient temperature of 300 K (27 \({}^{\circ}\)C). The emission intensity, the material (color), the degree of transparency, and the surface smoothness are the factors affecting emission intensity. The relationship between the heat flux between objects and surrounding and emission intensity of each object are as follows [20]:  
\[q^{\prime\prime}=\sigma\varepsilon\Big{(}T_{Solid}^{4}-T_{Ambient}^{4}\Big{)} \tag{1}\]  
\(q^{\prime\prime}=\) Heat flux exchanged with the environment via the mechanism of radiation (energy per surface). \(\sigma=\) Stefan-Boltzmann constant = 5.67 \(\times\) 10\({}^{-8}\) [W/m\({}^{2}\cdot\)K\({}^{4}\)]. \(\epsilon_{Cu}=\) Copper emission intensity (oxidized surface) = 0.8. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Part** & **Material** & **Thermal Conductivity [\(\frac{\text{W}}{\text{m}\cdot\text{K}}\)]** & **Heat Capacity (Cp) [\(\frac{\text{I}}{\text{kg}\cdot\text{K}}\)]** & **Density [\(\frac{\text{kg}}{\text{m}}\)]** \\ \hline Heatsink & Tough Pitch Copper & 401 & 385 & 8933 \\ \hline Aluminum box & Aluminum-6061T6 & 167 & 896 & 2700 \\ \hline PCB & Rogers & 1.03 & - & 2300 \\ \hline IC & GaN & 130 & 490 & 6070 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Materials and thermal characteristics of the parts [18; 19]. Figure 3: IC location: the IC (in blue) is located at the center of the circuit board. Natural convection heat transfer is a heat transfer mechanism carried out by fluids [21]. Simply, the air-fluid in the vicinity of a vertical plate causes the fluid around the plate to heat up first through conduction and radiation, then due to warming and volume increase, its density will be decreased, and it will move upwards. The warm fluid movement in the vicinity of a hot plate and its replacement with cold air around the plate lead to the generation of fluid dynamic flow around the hot plate and an increase in the heat transfer coefficient. How the room heats up with a radiator is an example of this phenomenon. Although the mechanism is naturally slow, by ensuring that the radiator is rinsed, it becomes the dominant mode of heat transfer in buildings. In other words, forced convection heat transfer uses a cooling fan or the intake or exhaust system of the fluid to increase its velocity. Note that this method is one of the most effective methods of increasing heat transfer; however, the general shape of the geometry and other factors could significantly impact the performance of this method.