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Subject: network of tubes with primary vaccum : need help

Date: 12/20/01 at 11:43 AM
Posted by: Charles
E-mail: charlie_ldb@yahoo.fr
Message Posted:

In Reply to: Re: help: quality of primary vaccum posted by Pat McMahon on 12/19/01 at 2:47 PM:

I am a french student in an engineering school and I have to work on a network of tubes with primary vacuum.

My work is going on, and my new problem is to find a way to calculate the pressure you lose (in fact you win) in a network of circular tubes with primary vacuum (streamline flow).
For that, I need infos about the conductance in straight tubes, in "T" and in "L".

I also need the formulate to calculate the time required to reach a pressure P1 from the pressure P0 with S (capacity of aspiration of the pump), Plim (max pressure reachable by the pump), V (volume of the network of tubes) and Q (leakage rate).
I already have this formulate:

t=(V/Seff) * ln{[(P0-Plim)-(Q/Seff)]/[(P1-Plim)-(Q/Seff)]}

with Seff=(1/S)+(1/L)

L=conductance of the whole network.

Is somebody able to say me whether I'm right with this formulate? can somebody help me with conductance?
Any infos, web sites, people names, books, theorical formulates or any what else will help me.
My work is serious and you can trust in me for the confidentiality of the infos given if needed.

best regards, sorry for my english that is far from being perfect.

Charles


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