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Vacuum conductance calculation, tube closed by a disc. 
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#1
Apr2313, 07:32 AM

P: 32

Hi !
I'm trying to calculate a conductance for free molecular flow of a tube which is closed by a disc. The distance between the tube and the disc will be approx 10 micro meters while inner and outer radius of the tube is around r1~10cm ; r2~20cm. Here are some pictures: http://tinypic.com/r/5mjsbd/4, http://tinypic.com/r/2zi4eus/4 The conductance of the tube is given in most textbooks on this subject, but I don't know how to find a conductance of a volume enclosed by the disc and the wall thickness (r2r1) of the tube. My first idea was to approximate the enclosed volume by rectangular tubes and then integrate the relation for rectangular tube conductance from 0 to 2*Pi*r2, that is: [itex]\int[/itex][itex]^{2*Pi*r_{2}}_{0}[/itex](31.1[itex]\frac{b^{2}*c^{2}}{(b+c)L}[/itex])db where c is the rec. tube height, b ist the tube thickness and L=r2r1 is the length of the tube. But I'm not sure whether this is good. 


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