Gas Flow Measurements and Controls

Authored by: Igor Bello

Vacuum and Ultravacuum

Print publication date:  November  2017
Online publication date:  November  2017

Print ISBN: 9781498782043
eBook ISBN: 9781315155364
Adobe ISBN:


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The amount of gas admitted or leaking into vacuum is usually given by the quantity of throughput, which is the product of gas pressure and volume (pV), passing via a given cross-sectional area per unit time and at a defined temperature (see Equation 1.32 and corresponding text). Throughput (Pa m 3/s = watt) is proportional to the mass flow rate (kg/s) and molar flow rate (kmol/s). These quantities and their units are mixed in many publications. All of them are related to the rate of gas flow, and therefore it can be acceptable to call them gas flow rates in general. We will use this term here, too, but we avoid mixing the unit of sccm with the quantity of mass flow rate whose unit is in kg/s, in contrast to many publications.

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