AVS 45th International Symposium
    Vacuum Technology Division Monday Sessions
       Session VT-MoP

Paper VT-MoP5
Pressure Wave Propagation by Gas Expansion in a High Vacuum Tube

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Vacuum Technology Poster Session
Presenter: T. Takiya, Hitachi Zosen Corporation, Japan
Authors: T. Takiya, Hitachi Zosen Corporation, Japan
F. Higashino, Tokyo Noko University, Japan
Y. Terada, Hitachi Zosen Corporation, Japan
A. Komura, Hitachi Zosen Corporation, Japan
Correspondent: Click to Email
This paper describes an unsteady tube flow model which accounts for the effect of contracted flow around the entrance orifice of a tube. The sudden expansion of gas introduced into a vacuum tube is an important phenomenon, which has to be studied in relation to leakage accidents of vacuum devices. In order to predict the pressure wave propagation speed, it is necessary to model the gas expansion in a vacuum tube. So we proposed an analytical model for gas expansion in a high vacuum tube, with the aim of preventing vacuum hazards at scientific experimental facilities. Setting a very high pressure drop between the outside and inside of the vacuum tube makes the model applicable to high vacuums, although the model is based on continuous fluid dynamics. We installed an orifice on the inlet end of the tube in the model, and investigated the orifice aperture effect on the propagation velocity of pressure waves. It was found that a rarefaction wave rather than a shock wave was primarily involved in vacuum accident damage, and that orifice aperture controls pressure increase rate in the low pressure regime more sensitively than in the high vacuum regime. This study was carried out to provide necessary data in designing vacuum protection for long tube-like devices, such as the beamline for synchrotron radiation, by solving the set of basic equations that incorporates important conditions.