An Investigation into the Mechanics of Joule-Thomson Valve Plug Formation
A. study was undertaken to examine the phenomenology of plug formation via contaminant condensation in sonic flow Joule-Thomson (J-T) orifices. An apparatus was constructed which allowed plug formation to be visually observed. The cold end of the apparatus consists of a pre-cooler, a counterflow heat exchanger and the J-T expander. Because this is the normal configuration of a cascaded J-T refrigerator cold end, the knowledge gained is directly applicable to existing systems. The test apparatus uses nitrogen gas as the refrigerant and water vapor as the contaminant. Plug formation in a glass J-T expansion valve was observed through a microscope and photographically documented. It was discovered that, for the straight sonic orifices used during these tests, plug formation occurred only in the orifice itself. No contamination condensation was observed on the orifice faces. Mechanisms are proposed which describe the observed characteristics of the plug nucleation and growth.
KeywordsMass Flow Rate Refrigeration System Orifice Diameter Plug Formation Expansion Valve
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