Date of Award

Spring 2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical and Industrial Engineering

First Advisor

Zhiming Ji

Second Advisor

Chao Zhu

Third Advisor

R. S. Sodhi

Fourth Advisor

Bernard Koplik

Fifth Advisor

Edwin Hou

Abstract

Typical examples of the use of the vacuum environments in industry include vacuum coating, vacuum drying, vacuum packing, vacuum casting, vacuum heat treatment, vacuum cooling for food storage and leakage detection. Most of these applications require a comparatively small volume of vacuum environment. However, there are also many applications where enormous vacuum chambers are needed. For example, a large vacuum chamber is used to simulate the conditions of space.

This study investigates the design and the automated operation of a vacuum generation system based on the idea of the condensation-induced depressurization with prefilled condensable medium in a confined, adiabatic chamber. The operation process of this new system includes mainly four phases, steam filling phase, cooling phase, usage phase and transition phase, operating sequentially. An automated control system based on these phases is designed and implemented on a laboratory scaled experimental system. This experimental system serves as a vacuum environment application to demonstrate the automatic and continuous operation of the condensation-induced depressurization system. In order to obtain a better understanding on the selection of parameters for performance improvement, models of the first three process phases are developed and analyzed. These models provide a reference for the design of systems for other industry applications as well.

Methods of improving the system design and operation are investigated. The analysis shows that high pressure and fast flow steam source will accelerate the steam filling process. Removal of the transition phase improves the steam filling phase and speeds up the vacuum preparation. Improvement can also be achieved on the coordination between vacuum generation and usage through control elements, as well as the proper selection of volume ratio between usage chamber and preparation chambers.

The ultimate objective of this study is that the results can be used to develop guidelines for the design and operation of vacuum generation systems according to specific usage patterns of the vacuum environment applications.

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