Why do all cryopumps require a return line?
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Why do all cryopumps require a return line?
Avoid overpressure to protect equipment and pipelines
When pre-cooling the liquid pump, reflux is used to reduce waste; during normal operation, it prevents overpressure and protects the equipment.
In addition to what the two people upstairs said, there is another point: during startup or when the liquid level is very low, activating the reflux mechanism can help maintain or better control the liquid level, thereby allowing the pump to keep running – such as in the case of liquid argon circulation pumps.
It has to do with the type of pre-cooling system! Some pre-cooling systems have only air-cooling towers and no water-cooling towers, in which case there is a return pipeline! Since there is no water-cooled tower, the low-temperature water that goes to the top of the air-cooled tower is, after passing through the freezer and the low-temperature pump, sent partly to the top of the tower while the other part returns to before the freezer where it mixes with the make-up water. This results in a lower water temperature before it enters the freezer, and after passing through the freezer, this temperature meets the requirements for cooling the air!
Low-temperature liquid filling pump: it can keep filling without stopping, which extends the pump’s service life and offers convenient operation.
Cryogenic liquids vaporize very easily; if the flow rate is controlled only through the outlet valve, heat cannot be removed in a timely manner, which leads to a drop in pressure in the pump as well as cavitation. Therefore, a return stream is used to maintain the outlet flow rate, thereby allowing the heat generated during pump operation to be carried away along with the cryogenic liquid. Hehe, just my personal additional opinion.
This post was last edited by wcq1010 on 2013-8-15 at 13:45. 1. Enable avoidance of rotation, allowing free switching with the backup pump. 2. Ensure that cavitation does not occur at low load levels. 3. Pre-cooling using a pump is available. As for overpressure! I don’t think it’s related; for excessive pressure in the pipelines, there are safety valves and frequency control for the pumps. It is said that backflow regulation pressure can also be used, but it’s a bit far-fetched as a primary condition.
What you said makes a lot of sense; thank you.
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