Heat Sink Requirements for MECA CTN-250

The following parameters are a function of this part:
1) The heat sink data assumes a continuous power of 250 watts.

2) Maximum ambient air temperature (Ta) is 28 Deg. C. (0 sink-air=.29 Deg. C./W)

3) Maximum heat sink temperature (Ts) is 100 Deg. C. (0 case-sink=.11 Deg. C./W)

4) Maximum case temperature (Tc) is 128 Deg. C. This is controlled by the beryllium oxide substrate conduction with a combined thermal resistance value of .112 Deg. C. /Watt.

5) Successful heat sink convection is provided by Aavid 656703 U 12000 aluminum extrusion or any extrusion of equal thermal cross section. This cross section is 128.60 in sq./in for natural convection and the typical weight is 164.8 ounces.

6) The recommended best thermal resistance for this component is .28 Deg. C./Watt.

7) Curves below that show the heat sink temperature versus applied power. Heat sink thermal resistance versus applied power is also shown.

8) In the event that force convection is desired, a curve is provided using the same Aavid heat sink but with forced air. This will show the effect of rapid air movement and how a reduction of heat sink size can be achieved.

How to Read a Thermal Performance Graph
The performance graphs below fall into two categories: forced convection and free convection.

The two free convection graphs are used to show heat sink performance when used in a natural convection environment (i.e. without forced air). The horizontal axis represents the heat or power dissipated (watts) and the vertical axis shows either heat sink temperature rise above ambient or the effective thermal resistance. By knowing the power to be dissipated, the temperature rise of the mounting surface can be predicted. Thermal resistance is determined by dividing this temperature rise by the power input (t/W).

The two forced convection graphs are used to show heat sink performance when used in a forced convection environment (i.e. with forced air flow through the heat sink). The horizontal axis represents the air velocity over the heat sink (LFM or m/s) and the vertical axis shows either heat sink temperature rise above ambient or the effective thermal resistance. By knowing the air velocity, the temperature rise of the mounting surface can be predicted. Thermal resistance is determined by dividing this temperature rise by the power input (°C/W).