Heatsink with forced circulation for electronics.

Knowing the thermal resistance in free air of an heatsink and the air velocity which flows the heatsink surface itself is possible to calculate the thermal resistance and the maximum dissipate power with forced air circulation.

Input dati

Maximum expected air temperature (ambient temperature).

°C

Maximum working temperature of the heatsink.

°C

Air velocity that flows the heatsink.

m/s

Help for the definition of the air flow.

Distance between the baffles or width of the surface for passage of air.

Distance between the baffles

mm

Height of the baffle or height of the surface for passage of air.

Fin height

mm

Number of slits for the air passage (n.1 in case of one only surface).

Quantity of slits

n.

Some examples of air flows

Fan type	W x H (mm)	m3/h
Axial	40 x 40	9.7
	60 x 60	21
	80 x 80	50
	92 x 92	80
	119 x 119	130
	127 x 127	250
	172 x 172	305
Centrifugal	15 x 51	9.6
	33 x 93	56
	127 x 117	80
	115 x 159	200
	253 x 83	115
	329 x 83	173
	395 x 83	200

Calculates and sets velocity.

Air flow

m³/h

Thermal resistance in free air of the heat sink

°C/W, K/W

This value can be obtained from the catalog of the producer or calculated with the available application in this section of the website.

Notes.
Important: give the thermal resistance of the heatsink in free air considering the only surfaces touched by the air circulation.

In the picture on the left you can see an example of a special heatsink normally functioning with natural air circulation, by necessity, a fan pressurize the internal of the case and a series of slit canalizing the air into the external baffle.
This solution allows the cooling of the inner components and the fins of power limiting accretion of dust and noisiness, the external fin is able to assolve its function without the fan for the 90% of the hours of functioning.
Only in summer or with sun exposition come into action the forced ventilation for keep the temperature into the project limits.