The following factors must be taken into account when selecting a radiator:
Module operating current size, in order to determine the required cooling area;
The use of the environment, according to which can determine what the cooling way - natural cooling, forced air cooling, or water cooling;
The shape, the volume of the device, the size of the space of the heat sink is determined, so as to determine the shape of the radiator.
Generally speaking, most users will choose aluminum radiator.
The calculation formula of the radiator length is given below:
Module required cooling area = (radiator perimeter) * (radiator length) + (sectional area) x 2
The heat dissipation area of the module is the reference value given in the module characteristic parameter table. The perimeter and section area of the radiator can be found in the sample of the radiator manufacturers. In the use of power devices, the most important is how to make the heat generated by the effective distribution to obtain high reliability.
The most common method of heat dissipation is to install the device on the radiator, the heat radiation board will heat radiation to the surrounding air, as well as through natural convection to distribute heat.
Generally, heat flow from the heat sink to ambient air (P) can be expressed by the following example.
P=hA ETA Delta T where h is the total heat radiator conductivity (W/cm2 C), A surface area of the radiator (cm2), ETA for radiator efficiency, Delta T is the highest temperature and the ambient temperature of the radiator difference (C). In the formula, h is composed of radiation and convection is determined by the shape of the radiator is determined. In short, the larger the surface area of the radiator, the greater the difference between the temperature and the environment temperature, the more effective the heat radiation of the heat sink.
(1) radiation heat dissipation
Approximate expression of radiation heat dissipation
Hr=2.3 * 10-11 * e (T/2+237) 3 (W/cm2 C)
Type E is surface emissivity, surface condition and change with the radiator. Surface grinding and polishing products e =0.05 ~ 0.1 is the radiation rate range. However, the radiator surface coated with paint, after oxidation can make e =1
(2) convection heat dissipation
When the power device is installed on the frame of the device, the convective heat radiation is more effective than the radiation heat radiation. In the air of a large air pressure, the transmission rate of the convection heat sink is approximated by a lower expression.
Hc=4.3 * 10-4 * (T/H) 1/4 (W/cm2 C)
In the formula, H is the height of the vertical direction of heat dissipation. The distance between the heat sink is set at H1/4 (CM). In short, the vertical direction of the radiator is longer than the horizontal direction is more effective.
(3) the radiator efficiency
If the heat sink is made of thin material, the farther away from the heat source, the lower the surface temperature, the worse the heat radiation effect is. The above formula is assumed that the temperature is evenly distributed, and in fact, the lower surface temperature of the edge of the heat sink.