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Posted by Rolly on July 23, 2004 at 18:56:23:
In Reply to: Steam Drum design posted by Chris on June 07, 2004 at 10:48:13:
Chris
You have to take the whole boiler into a complete picture. All the water in the boiler will give up its steam (heat) at the same time. Not only the water in the drum but all the water in the boiler. Lets suppose it’s a water tube three drum with downcommers. You can’t lower the pressure in just the drum. When you open the main valve all the water in the vessel has its pressure lowered, hence all the water gives up its heat at the same time.
What you have to be concerned with is swell. The water rising in the drum and not having carry over. All this has to do with the over all design and the length of the tubes.
Back to your question, How big should the drum be? I cannot tell you why but I design the size of the drum so that the center cross-section, length width and height of one quarter of the height of the drum is one fourth in volume of all the water in the pressure vessel.
Rolly