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hermosyphon systems have a solid reputation in the industrial refrigeration industry, and are a popular choice for many . . . as long as they work. But when a thermosyphon system has problems, those problems are sometimes not easy to identify or correct. Gary Gneiting, director of engineering at Mericle Mechanical, Inc., said a vortex could be one reason at the bottom of a poorly performing system. “I wonder how many thermosyphon systems had design errors due to a vortex that were never resolved,” Gneiting said. “Now there is one more item to review in all thermosyphon systems to prevent vortices and costly field repairs.” A vortex is a conical, rotating liquid void that forms in a fluid body as a result of a low pressure area. When a vortex occurs, the opening allows gas from the surface to be drawn down through the center of the vortex into the pipes. A vortex can occur in the refrigeration industry in five ways:
10 because you’re moving nothing but air through the system.” Gneiting said he uncovered the issue with vortices when he reverse-engineered a thermosyphon system at a large ammonia cold storage facility to determine the cause of high discharge temperatures for five ammonia screw compressors. He observed vapor in the thermosyphon supply pipes that
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Is a Vortex to Blame for Your Poorly Functioning Thermosyphon System?
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Thermosyphon Vessel
1. When oil is drained from oil pots; 2. When liquid enters the high pressure receiver dip tube; 3. When liquid leaves the thermosyphon receiver through the thermosyphon supply line; 4. With pump suctions for ammonia recirculators; 5. In water pumps for evaporative condensers. In the case of a typical pump system, a vortex provides an opening for vapor to enter the liquid stream. Air is then drawn into the system, which inhibits water flow. “The pump is not designed to draw air; it’s made to pump a solid column of water,” Gneiting said. “So instead of 150 gallons per minute of flow, you might only get 42 |
CONDENSER | March 2016 | A Publication of the International Institute of Ammonia Refrigeration
www.iiar.org