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Blog posts : "Heat Transfer"

Modes Of Heat Transfer

Heat Transfer takes place from hot body to cold body. There are basically three modes of heat transfer by which heat can be transferred from hot body to cold body: Conduction, Convection & radiation. Any type of heat transfer from one body to another occurs by the combination of these three heat transfer modes. Heat transfer is one of very important aspect of product design.

Heat Transfer Figure 1

Conductive heat Transfer

Conduction heat transfer is the transfer of heat between two or more bodies that are in direct contact with each other. In figure-1, transfer of heat from Face A to Face B is conductive heat transfer considering T2<T1.

Rate of conductive heat transfer is directly proportional to contact area, thermal conductivity of the material & temperature differenc…

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Effects of Anodising on radiant heat transfer in heat sink

Heat sinks cooled by natural convection may benefit from an anodized finish, but the added cost of the finish may not be justified when the part is used in forced convection cooling.

Surface emissivity limits the amount of heat transfer due to radiation cooling. With 1.0 being perfect (black body) emissivity anodized aluminum is 0.85 and unfinished is 0.05.

Heat transfer due to radiation is proportional to the heat sink surface area exposed to its surroundings and to the temperature rise above ambient (in absolute °K) raised to the 4th power (T Heat-sink Tambient)4. In natural convection on small heat sinks with open fins, and a high benefit from anodizing by up to 45%.

Relatively large extrusions and those used at low temperature rise, as in many high power applications, wil…

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