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Methods and Apparatuses for Purging Air from the Inside of a Vertical Cavity Disclosure Number: IPCOM000031684D
Publication Date: 2004-Oct-05
Document File: 9 page(s) / 29K

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The invention is related to the purging of gases from the inside of an open-ended vertical tubes initially containing air.  More particularly, it is related to the purging of gases from the inside of open-ended vertical, tubular heat exchangers initially containing air which is used for cooling optical fibers.

Open ended tubular (or similarly shaped) heat exchangers are often used to cool hot optical fibers during the drawing process.  The heat exchangers are designed to surround and assist in cooling the hot fibers.  These fibers can draw air (within a relatively thin boundary layer surrounding the hot optical fiber) down and into the heat exchangers.

Many have proposed processes that purport to solve this problem by injecting coolant gases into and in different regions of modified optical fiber coolant chambers.  Still others have proposed processes that purport to solve this problem through various schemes of suction and re-circulation of coolant gases that are designed to purify contaminated coolant gases and then re-inject the purified gases back into the fiber coolant chambers for re-use.  However, these solutions often do not prevent a significant amount of air from being drawn into the inside of the heat exchangers.

Thus, those skilled in the art will realize there is a need for improved methods

Summary of the Invention

An object of the present invention is to provide methods and apparatuses for purging essentially all air out of an open-ended vertical tube that initially contains air.

This object is achieved by the following method.  A flow rate of gaseous Helium is kept above a minimum flow rate and allowed to completely and continually fill an open ended vertical tube initially containing air).  The filling keeps essentially all air out of that tube unless air (or some other gas) is drawn into that tube from the topmost open end of the tube by some other process.

Brief Description of the Figure

            The Figure is a graph depicting the theoretical minimum flow rates of gaseous Helium needed to fill and flow through vertical tubes of varying internal radii

Detailed Description of the Invention

Experimental studies in our laboratories have proven that gaseous Helium, injected into a cavity at the bottom of a vertical tube (opened at both ends and initially filled with air) will rise (due to a buoyancy effect) through that tube and completely displace essentially all of the air in the original tube if the gaseous Helium flow rate is above a minimum flow rate.  If the Helium flow rate is too low, the Helium will still rise through the vertical tube but air will also be drawn upward and into the tube along with the Helium.  This is not a particularly favorable outcome if a very high purity Helium gas stream (within the tube) is a desirable end result of this process.  Alternately, if the Helium gas flow rate (into th...