Discussion Forum

Hi,

I try to model a pump port that is connected to 4 turbo molecular pumps via 4 pumping tubes. There are Neon cooling cycles (30K) around the pump connections where they hit the pump port and also nitrogen cycles (80K). There is heat comming into the pump port from the TMP's (rotor temperature circa 60°C). To absorb the radiation from the pumps there is a copper radiation shield in the pump connections through the pump port. The shield is cooled down to 80K by the nitrogen cooling tubes.
There are also different bellows in the pump-pump port connection that hinder the heat conduction (to make the model easier I used a simple cylindric geometry for the bellows and gave them a modified heat conduction coefficient).
The flanshes where the pumps are sitting are on room temperature.
I used surface to surface radiation on each inner surface (at least the major ones).
The Temperature distribution I get out of that model shows a temperature at the pump port of around 30 K - 32K. There is no sudden jump or something like that just a steep rise near the 30K cooling.
I though that the pump port would get much warmer due to the radiation coming from the pumps (and also the flanshes at room temperature). So is there some mistake in my model? Maybe the cooling tubes set the temperature for the surface they are touching? Do I need to form an assembly where the cooling tubes touch my pump port geometry?
Any ideas? (the model is to large to upload is, its a complicated geometry)

Thanks
Laura