When simulating a pump, how should the presence of 0.0003 of gas phase in the inlet be handled?
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When simulating a pump, the message “vapour in inlet stream” appears and further calculation cannot proceed because there is 0.0003 of gas phase in the inlet. In normal operation, such a small amount of gas phase should not affect the proper functioning of the pump. Questions: 1. How can this warning be ignored to allow calculation to continue? 2. The inlet of this pump is at the bottom of a distillation tower; how can it be adjusted so that this small amount of gas phase at the bottom of the tower can be eliminated as conveniently as possible? Last edited by yfq4308 on 2009-3-6 10:07
1. If the nozzle at the bottom of the tower is set to 0, set the nozzle of the pump to -50m; this pressure difference caused by the height may eliminate the vapor phase. After that, set the outlet valve or the nozzle of the outlet stream to the same value as that at the bottom of the tower. I was told this method by an older person, but I haven’t tried it yet. Oh, the original poster, you’ll be my test subject. Hehehehe, with a sly smile... Let me know if it works... 2. Logically speaking, as long as there is a liquid level at the bottom of your distillation tower, there shouldn’t be any vapor present. Since no specific details were given, I’m not sure what the reason is. However, if a valve is installed before the pump, a pressure drop occurs before and after the valve, and the vapor phase may be generated as a result of this valve. Increasing the CV value of the valve can prevent the formation of a vapor phase. This is just my assumption; I hope the seniors can correct me...
In principle, no gas should be present at the pump inlet; the liquid drawn from the bottom of the distillation tower should be a saturated liquid, free of gas. If the gas flow is caused by pipes or valves, it is simple to set the pipe resistance to 0 or remove the valves.
Simulate it with software; try reducing the rotation speed
If VAPOR is non-condensable, it is possible to consider adding a virtual FLASH unit; the pressure in this unit will be the same as that at the bottom of the tower, allowing the VAPOR to be separated out. Compressors and pump outlets are also involved in this process.