Mixing hot reheat steam in a Manifold

[mb73]

I am doing some research into what length of pipe is appropriate for mixing hot reheat steam before going to an IP turbine. Here's the facts. There are two boilers putting out a total of 5.9x10exp6 lbs/hr total at 585 psig. The steam from both boilers leave thru' 4 24" lines each and meet in a mixing manifold. Here they supposedly mix thoroughly and then go to the turbine. How long should the vertical manifolds be? Presently, they are 3 manifolds, 38.5" dia approx 25 feet high. What is the basis of the height to produce proper mixing so that the turbine does not receive steam with a temperature mis-match?

 

[davefitz]

I have seen such mixing manifolds in the past ( 2 pipes to 1 manifold then split to 2 leads to the IP turbine). The lengths were very short, only 6 manifold diameters long.

It depends on the steam turbine requirements- if the turbine has only 1 lead, it doesn't matter, but if it has 2 leads , some vendors limit this temperature differential to less than 50 F, others allow over 100F.

You should be able to model this on today's 3D CFD programs to determine the required turbulence or mixing length.

 

[mb73]

This one's a beaut!! It has 8 leads going into a three- lead vertical manifold. The three leads out of the manifold then go to the turbine.
Your observation of 6d seems okay since this is what we have, thereabouts. Just thought that there may be some calcs out there. The budget limits how much I can spend on computer models etc. Anyways, thanks a lot.