The integration of CPU chips has resulted in an increase in heat generation, leading to heightened performance requirements for the corresponding liquid cooling radiators. Due to the complex fluid dynamics within the CPU liquid cooling radiator and the restricted flow space, conducting performance analysis and structural optimization through experimental methods poses significant challenges. By utilizing ANSYS FLUENT for numerical simulations of the CPU liquid cooling radiator, the following conclusions were drawn: to optimize radiator performance while considering manufacturing and operational costs, the refrigerant temperature should be set at 20°C, and the inlet flow rate should be maintained at 5 m/s. Additionally, the heat dissipation efficiency of a diagonal structure radiator surpasses that of a side-by-side structure. Incorporating a guide plate into the radiator can enhance heat dissipation and significantly lower the local maximum temperature of the CPU.
introduction
The integration of CPU chips continues to advance, resulting in an increase in heat generation per unit area. When temperatures rise excessively, the performance of the CPU chip can significantly decline, directly impacting the safe and stable operation of the entire computer system. Liquid cooling radiators are commonly employed in CPU cooling solutions due to their high cooling efficiency. Therefore, it is crucial to evaluate the performance of CPU liquid cooling radiators and optimize their design further.
Shi Yujia et al. investigated the selection of coolants in liquid cooling radiators and compared the advantages of three liquid cooling devices along with three different coolants. Zou Ziwen et al. examined three distinct liquid cooling radiator structures: cavity type, fin column type, and baffle fin column mixed type, and evaluated the cooling performance of these three configurations. This paper employs ANSYS FLUENT software to numerically simulate the operation of two different liquid cooling radiator structures under various working conditions and optimizes their designs.
01 Numerical Calculation Method 1.1 Model Establishment and Mesh Division
As illustrated in Figure 1, the bottom surface of the radiator model under investigation is a square with a side length of 21.1 mm and a height of 6 mm. For a CPU liquid cooling radiator of this specification, the side lengths of the inlet and outlet pipes are typically set at approximately 3 mm , with a pipe length of 28.4 mm. The bottom of the radiator is heated by the CPU’s thermal output, and it is assumed that the heat flux density across the bottom plate of the entire radiator is uniformly distributed. The model was created using GAMBIT, where the mesh was generated and mesh independence was verified. The boundary conditions are specified in Table.
Figure 1 Model structure
Table 1 Boundary conditions
02 Result Analysis 2.1 Effect of Fluid Inlet Temperature on Heat Transfer Performance
Keeping other conditions constant, the inlet temperature of the CPU water cooling radiator is typically set around 20°C [4]. In investigating the effect of fluid inlet temperature on heat transfer performance, the cold fluid inlet temperatures are set to 283.15 K, 288.15 K, 293.15 K, and 298.15 K, respectively. The resulting temperature distribution maps are presented in Figures 2 to 5. From these maps, it is evident that as the temperature increases from low to high, the positions of the high-temperature and low-temperature zones remain relatively unchanged. The high-temperature zone is primarily concentrated near the outlet pipe, while the low-temperature zone is predominantly located near the inlet pipe.
Figure 2 283.15 K bottom surface temperature cloud map
Figure 3 288.15 K bottom surface temperature cloud map
Figure 4 293.15 K bottom surface temperature cloud map
Figure 5 298.15 K bottom surface temperature cloud map
Use Fluent to calculate and record the area-weighted average, maximum, and minimum values of the bottom surface temperature.
It can be seen from the curve that as the temperature increases, the area-weighted average, maximum and minimum values of the corresponding bottom surface temperature all increase. The maximum CPU temperatures corresponding to inlet fluid temperatures of 10°C, 15°C, 20°C and 25°C are 51.17°C, 56.17°C, 56.64°C and 66.17°C, respectively, all of which are within the acceptable range of CPU temperature. However, considering the heat dissipation effect and economic factors, it is more reasonable to set the fluid inlet temperature to 20°C.
Changing the structure of the CPU water cooling radiator, setting the inlet and outlet pipes on the same side, the temperature cloud map at 20°C is shown in Figure 6. Compared with the distribution diagram 5 when the inlet and outlet are diagonal, the high temperature area is larger. The area weighted average, maximum and minimum values of the temperature of the two planes are calculated as shown in Table 2. When the inlet and outlet are on the same side, the maximum temperature is 0.05°C lower than when they are diagonal, but the area weighted average temperature is 1°C higher. Based on the cloud map and data comparison results, the diagonal structure has a better heat dissipation effect.
Figure 6 Temperature cloud diagram of the bottom surface on the same side of the inlet and outlet
Table 2 Comparison of bottom surface temperature parameters of the two structures
03 Conclusion
This paper uses ANSYS FLUENT to perform numerical simulation on the CPU chip liquid cooling radiator, and draws the following conclusions:Lowering the refrigerant temperature and increasing the refrigerant flow rate can improve the heat dissipation effect of the radiator, but considering factors such as economy and service life, the most economical configuration of the refrigerant is 20℃ and 5m/s; The heat dissipation effect of the diagonal structure radiator is better than that of the same side structure; After adding a guide plate in the radiator, increasing the refrigerant flow rate to 7m/s can achieve better heat dissipation effect and significantly reduce the local maximum temperature of the CPU.
