A single passive system is larger in size, but more reliable and efficient, and the fan can play a role in situations where passive cooling cannot be used alone. Which system to choose for cooling is often a difficult decision? At this time, it is necessary to determine how much cooling air is needed and how to achieve cooling through modeling and simulation, which is essential for efficient thermal management strategies.
For the miniature model, the heat source and its heat flow path are characterized by their thermal resistance, and the thermal resistance is determined by the material, quality and size used. Modeling shows how heat flows from the heat source and is also the first step in evaluating components that cause thermal accidents due to their own heat dissipation. For example, device suppliers such as high heat dissipation ICs, MOSFETs, and IGBTs usually provide thermal models that can provide details of the thermal path from the heat source to the surface of the device.
Once the thermal load of each component is known, the next step is to model at a macro level, which is both simple and complex: through adjust the size of the airflow through various heat sources to keep its temperature below the allowable limit; Use air temperature, unforced air flow available flow, fan air flow and other factors to perform basic calculations to get a rough idea of temperature conditions.
The next step is to use the model and location of each heat source, PC board, shell surface and other factors to perform more complex modeling of the entire product and its packaging.
Finally, modeling has to solve two problems:
The problem of peak and average dissipation. For example, a steady-state component with a continuous thermal dissipation of 1W and a device with a thermal dissipation of 10W but with a 10% intermittent duty cycle have different thermal effects. That is to say, the average heat dissipation is the same, and the related heat mass and heat flow will produce different heat distribution. Most CFD applications can combine static and dynamic analysis.
The imperfect physical connection between the components and the surface of the miniature model. For example, the physical connection between the top of the IC package and the heat sink. If the connection has a small distance, the thermal resistance of this path will increase, and it is necessary to fill the contact surface with a thermal pad to enhance the thermal conductivity of the path.
Thermal management can reduce the temperature of the components in the power supply and the internal environment, which can extend the service life of the product and improve reliability. But thermal management is an integrated concept, if broken down to the minutiae, it is a huge subject. It involves the trade-offs of size, power, efficiency, weight, reliability, and cost. The priority and constraints of the project must be evaluated.
