pro mechanica bulk air temperature question

[tonz1984]

Hello

I'm using Pro Mechanica, with the 'Thermal' package to show the behaviour of the heat from an LED, through the PCB and heatsink, all exposed to air, at room temperature.

The results I get from an actual real-world test are completely different from the Mechanica results.

Is the bulk temperature ((Tb), stated when inputting the 'h' values on boundary conditions), the air temperature of the room, or is it the value of the temp of air touching that component?

For instance, say the LED gets to 100degrees C, would the bulk temp be higher here, than at the heatsink that only reaches 54degrees?

 

[Maxham1]

The bulk temperature is the air temperature of the room. The results that you get with Pro/Mechanica are going to be highly dependent of the "guessed" value for the convective heat transfer coefficient.

 

[tonz1984]

Thanks, I was just getting confused from reading about a boundary layer of mean temperature, between the surface and fluid temps. But I'm just going to use ambient / room temperature.