How to design a monotube steam separator?

A special section just for steam engines and boilers, as without these you may as well fit a sail.
Post Reply
Steam Captain
Full Steam Ahead
Full Steam Ahead
Posts: 150
Joined: Mon Oct 26, 2015 2:32 pm
Boat Name: No Boat Yet

How to design a monotube steam separator?

Post by Steam Captain » Tue Jul 16, 2019 4:19 pm

Hey,

Is there any rule to design a steam separator?

My monotube test boiler will have 9 sqft of HS equally split between radiation and convection HS and should spit out roughly around 50-60 pph.

To be clear, I am talking about the drum-like flask. is there a rot for how much water it has to contain or any other considerations that are important to know?
the arduino version steam engine indicator: https://app.box.com/s/b2i0z3gw6ny3rcfdet5xjg8ubrfu799i - app version coming soon
Excuse my occasional long response time. It's caused by the side effects from ptsd.
User avatar
fredrosse
Full Steam Ahead
Full Steam Ahead
Posts: 1906
Joined: Fri Nov 20, 2009 5:34 am
Boat Name: Margaret S.
Location: Phila PA USA
Contact:

Re: How to design a monotube steam separator?

Post by fredrosse » Fri Jul 19, 2019 6:07 am

Large plant practice dictates a steam/water inlet, tangential to the vertical main vessel, about half way between top and bottom. Vessel steam upflow velocity 3 feet per second (about 1 Meter per second), with minimum 1.5 main vessel diameters above for steam outlet, plus 1.5 vessel diameters below to water level.

The attached file is a separator tank on my steamer, used only to protect from water carryover if the boiler primes. The bottom outlet leads to a steam trap, which is fitted to discharge any water accumulation.
Attachments
MS-SEP.jpg
MS-SEP.jpg (68.57 KiB) Viewed 4475 times
Steam Captain
Full Steam Ahead
Full Steam Ahead
Posts: 150
Joined: Mon Oct 26, 2015 2:32 pm
Boat Name: No Boat Yet

Re: How to design a monotube steam separator?

Post by Steam Captain » Fri Jul 19, 2019 10:45 am

As always, many thanks. This is exactly what I was hoping for. By the way: Do you think your steam is very dry already? (In your "machine gun" monotube) I am asking because I was thinking of placing a cyclone separator inside the top of the flask. It'll definitely not hurt, but if the tangential inlet already works out fine, I wouldn't need to braze one together.
the arduino version steam engine indicator: https://app.box.com/s/b2i0z3gw6ny3rcfdet5xjg8ubrfu799i - app version coming soon
Excuse my occasional long response time. It's caused by the side effects from ptsd.
User avatar
fredrosse
Full Steam Ahead
Full Steam Ahead
Posts: 1906
Joined: Fri Nov 20, 2009 5:34 am
Boat Name: Margaret S.
Location: Phila PA USA
Contact:

Re: How to design a monotube steam separator?

Post by fredrosse » Fri Jul 19, 2019 12:36 pm

"Do you think your steam is very dry already? (In your "machine gun" monotube) I am asking because I was thinking of placing a cyclone separator inside the top of the flask. It'll definitely not hurt, but if the tangential inlet already works out fine, I wouldn't need to braze one together."

The monotube boiler in the canoe produced saturated steam, close to 100% Quality. All of the steam generating tubing was constantly kept with significant amounts of liquid water flowing in a mixture with the steam. This design assures that tube burnout or overheating would not occur, and needs a separating device obviously.

Many monotube boilers attempt to match feed flow to steam generation, with close control needed to avoid sending liquid water to the output pipe, or to avoid excessive steam temperatures, which can also damage an engine, and/or cause boiler tube burnout. Getting adequate control with this type of system has usually led to failure.

The effectiveness of steam/water separation devices is a technology already well developed, and yes, a centrifugal separator will improve efficiency of separation. The salient question here is: How well does the separator with the tangential inlet work, vs adding another complication? Just making the separator tank somewhat larger would accomplish the same result, but quantifying the benefits would take either some heavy calculations, or testing under controlled conditions.


A discussion about monotube boilers is already in another thread. Have a look there, and we can continue this discussion in that thread:

Monotube Boiler Design – Radical Thinking
Post by Tony
Attachments
sca-boilcoil.jpg
sca-boilcoil.jpg (76.48 KiB) Viewed 4455 times
Post Reply