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Time : 2015-01-16 09:45Source :analogtechnologies Author : Analog Click :

At present, there are many kinds of heat sinks, including natural convection, forced convection and liquid cooling. The natural convection radiator can be used in the small power condition, especially when the working current of small thermoelectric coolers is less than 2A. But for most application conditions, natural convection radiator cannot meet the requirement that all heat need to be exhausted, then we need to use forced convection radiators or liquid cooling radiators.
In general, radiator performance can be measured by using thermal resistance (Qs): Where,
Qs is thermal resistance, the unit is ℃/W
Tsis temperature of heat sinks, the unit is ℃
Ta is temperatureof the environment or cold end, the unit is℃
Q is input heat of heat sinks, the unit is W
Natural convection radiators: Generally speaking, the natural convection radiators can only be used in the small power condition of involving a small amount of heat flow. Although it is difficult to accurately summarize, most of resistances of the radiator should be more than 0.5 ℃ /W, and in most cases the resistancescan reach 10℃/W. The installation position of the natural convection radiators need to satisfy two conditions: (a). the direction of the heat sink length should be along the direction of air flow, and vertical operation can enhance the natural convection; (b). there cannot be obvious physical obstruction of air flow. In addition, we should also consider that around the heat sinks, some other devices can generate heat, which will improve the environment temperature. Thus that can impact on the whole performance.
Forced convection radiators: Forced convection cooling can be regarded as the most common cooling method in the application of thermoelectric coolers. Compared with natural convection radiator, its performance superiority can be found. Thermal resistance of qualified forced convection cooling system should be generally maintained in the range of 0.02~0.5℃/W.Cooperation between many standard extruded heat sinks and appropriate fans can be as the basis of the complete cooling system. In application, the cooling air can not onlybe obtained through fans or blowersalso can make the air through the radiator from the direction of length.Or by blowing air towards the center of the radiator and flowing out of both ends of the opening, cooling effect will be obtained. Generally speaking, if the air flows into heat sinks from its surface, it can strengthen the vortex and enhance heat transfer effect.  As shown in Figure 1, this air circulation patterncan provide the best performance of thermoelectric refrigeration. In addition, based on different application conditions, there are different layouts.

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