6 replies to this topic

[Engib33r]

Hi,

 

I am trying to figure out if there is a way to estimate maximum water level in a kettle boiler with u-bundle before it starts flooding the boiler or there is insufficient vapor disengagement.

[breizh]

Hi,
your boiler is equipped with a weir to keep the level.
Breizh.

[breizh]

You consider the search engine in this forum to support your query.
Replies from Art and others

https://www.cheresou...ersion-heaters/
Breizh

[Pilesar]

When designing a kettle, I fix the liquid level at minimum of two inches above the bundle of tubes to make sure they are flooded. If there is high flux, I allow four more inches of liquid for foaming. The required vapor disengagement volume is dependent on the vapor flow rate and the shell operating pressure. The vapor disengagement volume is set by the designer -- not by adjusting the liquid level during operation. The liquid level above the bundle is controlled by the weir. If you are measuring level, you may be reading the liquid height after the weir which should not affect the operation as long as it is below the weir height.

[breizh]

Hi,

To add to the discussion:

https://go.gale.com/... by Tammami [8].

 

other literature:

 https://www.research...ettle_reboilers

 

Many more using your search engine

 

 

Breizh

[Engib33r]

Thank you breizh for your insight. I am still trying to figure the UI interface of the forum. I will take a look around. 

When designing a kettle, I fix the liquid level at minimum of two inches above the bundle of tubes to make sure they are flooded. If there is high flux, I allow four more inches of liquid for foaming. The required vapor disengagement volume is dependent on the vapor flow rate and the shell operating pressure. The vapor disengagement volume is set by the designer -- not by adjusting the liquid level during operation. The liquid level above the bundle is controlled by the weir. If you are measuring level, you may be reading the liquid height after the weir which should not affect the operation as long as it is below the weir height.

Pilesar, the 2" above tube bundle that would be the NLL level. The exchanger is not equipped with a weir. Wondering how one would determine the High High Liquid Level (HHLL) before significant reduction in heat transfer and risk of overflooding the exchanger?

[Pilesar]

Theoretically, the liquid entrainment in vapor from a kettle is predicted just as you would for a two-phase separator. The Souders-Brown equation is probably at least a part of the determination if you do not have empirical evidence. A web search for Souders-Brown will find much to read.The GPSA tech data book has been useful to me for two-phase separator calcs. I understand there is literature from TEMA about kettle design but I haven't found that source. The usual heat exchanger books will discuss kettle design. The book by Kern is often recommended in this forum, but I believe many of the later books are probably easier to follow. Anyway, predictive calculations are just predictions and may have a wide margin of error. Design calcs usually have built in safety factors allowing operations to push the equipment further than its design capacity. When I have designed kettles in the past, I calculated the needed vapor space using more than one method and chose the answer which was most conservative, then rounded up. There is not a lot of additional cost to make the shell larger. My exchanger designs are from an operating company perspective and I can add safety factors that an engineering company might not choose. I am graded 'pass/fail' on whether the exchanger works and no one knows how much overdesign I include. The cost to my company is very large if the plant has to be taken down to fix an undersized exchanger, so my reward for optimization is mostly self-satisfaction of good engineering and watching out for the company's costs where no one else would notice.