Heat Dissipation Design Heat dissipation design is to t …
Heat Dissipation Design
Heat dissipation design is to take various mechanical design measures to control the working temperature of electronic products according to the thermal characteristics and heat transfer principles of electronic components so that it is within the allowable range to provide good performance for chip level, component level, component level, and system level and work normally and reliably according to the predetermined scheme under the specified thermal environment. The design also needs to ensure that accessible parts will not be scalded due to excessive temperature; insulating materials used for electric shock protection will not be degraded due to overheating; flammable materials and components will not spontaneously ignite; Reduced electrical distance does not cause some materials and components to emit toxic or flammable gases.
The basic theory of heat transfer is the basis for heat dissipation design, and different heat transfer methods have different mechanisms. Therefore, only by mastering the basic theory, design method and experimental method of the heat transfer process can we effectively solve various practical problems in the heat dissipation design of electronic products.
Heat Dissipation Design of Electronic Products
The heat dissipation design of the casing is very important. The working heat of the equipment can be dissipated out of the machine through the conduction and radiation of the casing. Through reasonable openings, convection ventilation and heat dissipation can be formed to accelerate the dissipation of the working heat of the equipment.
Since the electric shock resistance and fireproof performance of the casing should be considered in the design of the casing, there is not much room for the selection of materials and thickness. Therefore, the heat dissipation design of the casing mainly considers the following points:
(1) Reasonably choose the color of the casing
The use of black paint coating can increase the heat dissipation effect. Black paint on the inner surface can reduce the temperature rise in the machine and promote the heat dissipation of the heating elements in the machine. Black paint on the outer surface can reduce the temperature rise of the inner surface of the machine and accelerate the heat conduction and heat radiation of the casing.
(2) Reasonably open ventilation holes to form a natural convection heat dissipation
The air inlet and outlet of the ventilation holes should be located at the two places with the largest temperature difference of the whole machine, the air inlet should be as low as possible, the air outlet should be as high as possible, and the position of the hole should be close to the heating element.
Treatment of heating elements
Try to place it in a place that is easy to ventilate and dissipate heat;
Increase the heat dissipation area of the heating element, for example, add heat sinks to high-power transistors; use appropriate derating design to reduce power consumption.
Reasonable selection of thermal protection device
In order to prevent excessive temperature rise caused by fault conditions, an over-temperature protection device can be appropriately installed to cut off the power supply in time.
Thermal protection devices are divided into two types, one is the non-recoverable type, such as thermal fuse link; the other type is the recoverable type, that is, after disconnection, it can automatically resume work when the temperature rises down, such components have PTC components, bimetal thermal protector, etc.
Select an appropriate heat dissipation method
Commonly used cooling methods
(1) Air-cooled cooling fan + heat sink
(2) Water-cooled radiator + water pipe + water pump
(3) Semiconductor refrigeration method uses semiconductor refrigerators
(4) Heat pipe heat dissipation method Fill the heat pipe with a special liquid heat transfer medium so that the heat is evenly distributed to all parts of the radiator
On the thermal fins, the thermal conductivity of the heat sink is greatly improved.
(5) Liquid nitrogen heat dissipation method
(6) Software cooling method can allow the CPU to rest when there is no work or when the work is relatively leisurely, thereby reducing the temperature, resulting in less CPU power consumption and lower temperature.
(7) Heat sink for heat dissipation
(8) Fan cooling
The installation of the radiator
The radiator transfers heat energy to the environment by convection and radiation. The thermal resistance RθS-a of the radiator is related to the material, structure, surface color, cooling method, and installation position of the radiator.
Surface of the radiator:
Paint black or passivated. The purpose is to increase the emissivity coefficient, which can reduce the thermal resistance by 10%-15%.
Installation of radiator:
Should be placed vertically. Because the thermal airflow is light in density, it naturally flows upwards to form a “chimney effect” and facilitate heat dissipation. Thermal resistance can be reduced by 15%-20%.
3.4 Cooling method of radiator
Natural cooling – relies on natural convection and radiation of the air. Simple structure, no noise, but low heat dissipation efficiency.
Air cooling – forced ventilation and enhanced convection heat dissipation. It is 2-4 times of the self-cooling heat dissipation efficiency, and the noise is large.
Water cooling – The heat dissipation efficiency is extremely high, 150 times that of natural heat dissipation. The cooling medium includes water and transformer oil, and the investment is high.
3.5 The material of the radiator
Mainly made of aluminum plate or aluminum material (low price), in addition to copper, magnesium and steel, and other materials.