4 replies to this topic

[Ten]

How feasible is an upflow in a vertical condensate pipe, without using a pressurized (flash) tank?

Please assume modulating steam condition: 60.000 - 6.000 lb/h steam consumption (450°F @ 110 psi) and ~10% flash steam (atmospheric pressure).

Am I correct when I say for a modulating flow it is possible but not recommended?

[joerd]

Two phase flow is a tricky subject - but generally it is safe to say if you have flow turndown of 10:1 (like in your case) the flow at turndown will most likely be unstable, assuming the pipe is sized for the higher flow. This means that the velocity of the mixture is too low in the turndown case to push out the liquid, which will fall back down. The n, the pressure at the bottom will build up and blow out the slug, and the sequence starts all over again. This will cause pretty bad vibration of the system.

[Ten]

Thanks Joerd, for your answer.

So the flow pattern in the pipe depends on the velocity of the condensate load. Because of the modulation steam consupmtion, the condensate rate is obviously modulating as well. Could therefore be concluded that an upflow in a vertical condensate pipe, without pressurized (flash) tank would not work, and would only create water hammer in de condensate pipes?

[joerd]

The condensate flow regime in the low-flow case will most likely be an unstable slug flow. This is not exactly the same as steam/condensate hammer, but will cause a lot of vibration and shaking. Usually, the way to get out of the slug flow regime is to make the pipe diameter smaller, but this will cause excessive pressure drop in the high pressure case.

[Ten]

Joerd, thanks again.

Edited, 03/23/06