# Numerical Simulation on Thermoelectric Cooling of Core Power Devices in Air Conditioning
## 2 Simulations  
**Geometric modeling:** The heat dissipation structure of the power device after adding the TEC is shown in Figure 2. To ensure the reliability of the power device in application, it is usually packaged with the upper part connected to the protective case through thermal interface material and the lower part connected to the PCB board through welding. The TEC is positioned at the lower end of the PCB to directly cool the chip, and the heat is dissipated through the air duct via the cooling fins under the TEC. An optical photo of the air conditioner circuit board is shown in Figure S1. This paper establishes geometric models for the two heat dissipation models of the chip, cooling through the cooling fins and the TEC combined with air-cooling, to study the effect of the TEC on the temperature control of the chip in this structure. The TEC simulation model, as depicted in Figure 3, comprises a sandwich structure consisting of an upper ceramic substrate, upper electrodes, thermoelectric units, lower electrodes, and a lower ceramic substrate in a top-to-bottom configuration. The planar dimensions of the TEC measured 35 \(\times\) 57 mm\({}^{2}\), with a total vertical thickness of 3.8 mm, containing 416 thermoelectric legs measuring 1.4 \(\times\) 1.4 \(\times\) 1.6 mm\({}^{3}\) each, and the thicknesses of the ceramic substrate and the electrode were 0.8 mm and 0.3 mm, respectively. The CAD model and the geometric model of TEC forced cooling combined with fin air-cooling are shown in Figure S2 and Figure 4, and the model consists of power devices, TECs, heat-sink fins, and air ducts. The dimensions of the three core power devices were 35 \(\times\) 57 \(\times\) 3 mm\({}^{3}\), 20 \(\times\) 30 \(\times\) 3 mm\({}^{3}\), and 20 \(\times\) 30 \(\times\) 3 mm\({}^{3}\), corresponding to a power consumption of 173.81 W, 27.5 W, and 27.5 W, respectively, and an effective heat dissipation area of 1995 mm\({}^{2}\), 587 mm\({}^{2}\), and 587 mm\({}^{2}\), respectively. The TEC featured the same planar dimensions as mentioned earlier, along with a flat fin size of 196 \(\times\) 210 mm\({}^{2}\), comprising 30 fins, and a center fin size of 52 \(\times\) 210 \(\times\) 1.5 mm\({}^{3}\). The air duct size was 430 \(\times\) 230 \(\times\) 86 mm\({}^{3}\). The contact interface between the TEC, the power device, and the fin was connected by a thermally conductive silicone grease with a thickness of 0.15 mm to ensure good contact heat conduction. Figure 2: Heat dissipation structure for temperature control of power devices. **Material property parameter setting:** \"FR4\" from the material library of COMSOL Multiphysics 5.6 was used as the material of the circuit board, \"6063 [solid]\" alloy was used as the material of the heat-sink fin, and \"air\" was used as the material of the fluid heat transfer medium. The other materials in the model were custom materials and the specific material properties [55] are shown in Table 1. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Parameter** & **Value** \\ \hline N-type Bi\({}_{2}\)Se\({}_{0,3}\)Te\({}_{2.7}\) & Resistivity (10\({}^{4}\) S m\({}^{-1}\)) & 7.640 \\  & Thermal conductivity & 1.275 (at room temperature) \\  & (W m\({}^{-1}\) K\({}^{-1}\)) & 9.535 \\ P-type Bi\({}_{0,5}\)Sb\({}_{1.5}\)Te\({}_{3}\) & Resistivity (10\({}^{4}\) S m\({}^{-1}\)) & 1.362 (at room temperature) \\  & Thermal conductivity & 5.998 \\ Copper electrode & Resistivity (10\({}^{7}\) S m\({}^{-1}\)) & 400 \\  & Thermal conductivity & 170 \\ AlN substrate & Thermal conductivity & 10 \\  & (W m\({}^{-1}\) K\({}^{-1}\)) & 10 \\ Thermal grease & Thermal conductivity & 10 \\  & (W m\({}^{-1}\) K\({}^{-1}\)) & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The main material property parameters of the simulation model. Figure 4: Fluid heat transfer simulation model of the TEC forced cooling combined with finned air-cooling. Figure 3: Simulation model of the TEC.