exit velocity question

steampunk_2

just out of curiosity...let's say we have a boiler here, could be any boiler, and this boiler we have here has a 2" supply tapping.  so we go up about 3' with a 2" supply then down into a 3" drop header.  then, we come out of this drop header with a full-size 3" supply up about 3' into the 2" main.

so,my question is; is the EFFECTIVE exit velocity of our steam measured at the 2" supply tapping at the boiler section or is it taken at the 3" supply out of the header.

i was just curious.

thanks,guys

Steamhead

The highest velocity

would occur in two places. First, at the boiler steam outlet. Second, where the 3" header takeoff reduces to 2". The latter would be smaller if there is more than a little steam loss from condensation in the header.



But the steam should be pretty dry after going thru a header like that.

Jamie Hall

and the velocity you want to worry about

is the one at and near the tapping off the boiler -- that's the one that can suck up water and give you wet steam if it's too high.  By the time you get out of the dropped header, there shouldn't be much additional water to fling around...

steampunk_2

exit velocity question

thanks to all for the explanations.

Greg Maxwell

Exit Velocity

I would recommend going to a 3" riser off that supply for your header, before dropping back to 2". That would solve all velocity issues.

steampunk_2

exit velocity question

as it says in my original  question,that was my thinking,to come out of the 3" drop header with a full-size 3" supply up about 3' into the 2" main.  i was even considering going to a 4" drop header and supply  and probably would if i didn't have a bunch of 3" fittings left over from a prior job.  the main is a 2" counter-flow and i'm very concerned about new-boiler steam velocity causing a problem.

Steamhead

What make and model

is your boiler? 

steampunk_2

exit velocity question

what boiler?  well, i was originally going to use an mst-396 because of the burnham technology but decided against it because the measured edr is only 330 sq. ft. so i was considering a smith g-8 (8S-3H) rated at 350 sq.ft.

Steamhead

I'd go with the MegaSteam

it's not that much oversized, it's a bit more efficient, it's easier to maintain and has the best warranty in the business.



With either of those boilers, I'd use a 2-1/2" header. See:



http://www.heatinghelp.com/forum-thread/130212/Smith-G-8-Steamer-Install



http://www.heatinghelp.com/forum-thread/135345/MegaSteaming-on-Marylands-Eastern-Shore

steampunk_2

exit velocity

nice work those jobs.  appreciate it,  if it wasn't you or dan or a couple of certain others on the wall telling me that it will work ok for a mst-396 to supply 330 sq. ft, of radiation through a 2" counter-flow main i'd be concerned.