Steam Hammer Prevention
Steam Hammer Prevention
(OP)
I assume the slope of piping on submarines changes as the vessel navigates. Where steam piping is installed, how is the piping designed to prevent steam hammer when the steam and condensate flow can vary from co-current to counter-current two-phase flow? Is there a specific velocity that is not exceeded for sucessful designs? Is there a maximum condensate depth, below which slug flow (steam hammer) will not be initiated?





RE: Steam Hammer Prevention
If the mixed flow is steady state, then you might generate slug-plug flow , but steam hammer and waterhammer are usually reserved for other phenomena.
For steam hammer , you initailly have a long pipe containing high pressure steam at a high velocity. At time T=0, a stop valve closes quickly ( such as a turbine stop valve in 0.2 sec), causing all steam in the pipe to lose momentum in 0.2 sec. Tha tchange in momentum leads to a sudden pressure spike and sever piping reactions.
For one form of water hammer , as similar phenomena occurs, but is usually caused by the closure action of a check valve. Another method of causing water hammer is to casue a steam bubble to form , then have the bubble collapse at the speed of sound , causing a severe pressure pulse.
RE: Steam Hammer Prevention
RE: Steam Hammer Prevention
The avoidance of slug-plug flow is a function of pressure, liquid by weight, mass flow, tube diameter, and slope. One would back in too the most reliable design by first determing the max velocity permitted based on limitations of pressure drop and erosion-corrosion issues, and confirm a single pipe will not experience slug plug flow. If it does, then one can either install internal spiral turbulators to ensure stable annular flow , or one can use multiple paralle smaller diameter pipes .
RE: Steam Hammer Prevention
I see such tools as useful theoretical guides. I anticipate that piping designers on ships/subs do not go to the Baker chart each time a pipe is sized. I further anticipate that there are simplified charts or table already developed for such conditions.
Your suggestions to use tubulators or multiple pipes is interesting. I know of the use of turbulators at low velocities, but would be concerned about erosion/corrosion at steam velocites 100 fps +/-. I can see multiple pipes could offer some advantages...but need to think about that some more.
RE: Steam Hammer Prevention
There are correlations for inclined tubes as well as horizontal and pure vertical tubes. See papers by Kiefer, Kohler and Hein ( from KWU Siemens ) in Int J of 2 phase flow for their referenced correlations.
RE: Steam Hammer Prevention
RE: Steam Hammer Prevention
"two phase flow in inclined parallel pipes" Int J multiphase flow 25(6-7) pp1491-1503 sept 99
"prediction of slug liquid holdup : horizontal to upward vertical flow" Int J Multiphase flow 26(3)517-521 Mar 2000
"A consistent approach for calculation of pressure drop in inclined slug flow" ChemEng Sci 45(5) pp1199-1206 1990