puffing

[johnp]

i added a feed water heater, and seem to get alot of water blowing out the stack, expected iguess. i added a through hull exhaust and have the option to exhaust up the stack or out the back. woulf lengthening the pipe inside the stack help or huet my water problem? right now its about half way or less.

[DetroiTug]

I tried exhausting out the stack with an engine exhaust feedwater heater, had the same result. Installed a Tee in the line too and exhausted out of the bottom, it helps but does not remedy the problem. (Lengthening the pipe in the stack, is not likely to have much effect, remember, the flue gases at that point have cooled significantly) I wound up disconnecting the exhaust feedwater heater entirely and installing a 50' economizer in the funnel. It helps, but it's not fully adequate. Some of the steam car folks are using 3/8" copper economizers that are over a hundred feet long, and some up to 2 and 300 feet. As an added boost I'm now using a steampump with an exhaust feedwater heater. The boat has never ran better. I'm seeing about a 50 degree rise out of the pump and economizer each, making 180 ~ degree feedwater- and using a lot less wood. Through discussions with some ex Steam Navy engineers, some Navy steamships had as many as five feedwater preheaters. Very important for efficiency in a steam plant.

-Ron

[johnp]

Soft copper tubing is ok in the heat

[DetroiTug]

Yes, the copper is okay to use in the funnel, it's good to 406°F. The boiler flue have gases have cooled significantly by that point, generally around 350°F. It's not advisable as a superheater - directly in the flame of the firebox.

-Ron

[fredrosse]

Putting in enough heat transfer surface in the stack to evaporate the water in the wet steam that comes from the feedwater heater is difficult.

A small vertical separator tank, say 2-3 inches in diameter, 6-8 inches long, with exhaust steam entering in the middle, tangentially, will spin the water to the walls of the separator vessel. A top outlet gets almost dry steam, and a small drain flow off the bottom will take out the water.

The drawing below is for a high pressure separator, but an exhaust separator could easily be made from an empty 1 pound Propane cylinder or something similar.

[steamboatjack]

A separator is essential for puffing, as above but I would ensure two things.
1, the OUTLET steam pipe needs a dip tube so it picks up about half way down the chamber. and 2, Ideally a flat base is best with the drain line on the outer edge, this can be lead into the ash pan for coal burners.
and 3, engineers are famous for being able to count.
If you use an exhaust feed heater you will condense a good amount of the steam which the separator should get out. this rather limits the effect of a feed heater in these circumstances, with coal burning it is perhaps better to use this waste energy to help boost the draft.
Regards
Jack

[steamboatjack]

Looking at the drawing again, I would have the inlet higher and the dip tube mentioned is there to ensure that it draws from a level where the water is already entrained on the walls.
Jack