Model Boat Mayhem

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: Damned bubbles !  (Read 1323 times)

KBIO

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 512
  • Location: Dinan (France)
    • http://modelismenavalvapeur.forumactif.com
Damned bubbles !
« on: June 04, 2021, 08:32:35 am »

- Bubbles in the water gauge   
If you have the single strand of #22 Gauge copper wire? ....try it ...if it works ...well issue of the bubbles answered
1. where do the bubbles in boiling water come from?
2. are the exploding bibbles of gas helping to clean the internal surface of the boiler water sight glass?
A whole new subject..... 
Derek 



In the summer time, everybody have seen  the fishes coming up to the surface looking for air.
One thing we know. There is more disolved gas in fresh water than in warm one.
The salmon swimming up stream consumes a lot of energy and needs a lot of oxygen.
One of the most soluble gas in the water is the CO2 = soda , champagne , …
The 20% of O2 that is in the air is easily disolved in fresh water.
The 80 % N2 that is in the air  is a lot less soluble in the water and does not bother us.
That is why though ,there is O2 and other disolved gas (In Ex :carbon dioxin) in our boilers when we fill them up. But mainly dissolved 02 when it is fresh.


The surface of the glass (as any surface) is not smooth. But is a « carpet » of micro craters scratches and bumps. The glass is also more or less porous. That’s excellent traps for gas molecules.
Also , when drying off a glass of champagne , there is some fiber particules left of the surface. This is excellent to trap the gases. Same with our sight glasses when we clean them up.
We can see then , the bubbles exiting from the bore .


A quickstory !
One night I was invited in a party and I drunk a bit too much of champagne.
A lady came to me for an unformal chat . After a while I said to the lady :
- "You are looking so cute after some glasses of champagne ! «
- «  But I didn’t drink any, she laughed ! »
—« No ! I Know you didn’t ! But … I did ! »
KBIO is a gentleman !  :embarrassed:




So it is obvious that when warming up the water , this gas expands and bubbles up to the surface as the result of the well known Archimedes principle . This is where our bubbles are coming from.


Now , some say that inserting a string of copper in the water gauge will avoid the formation of bubbles and will solve the problem !
Magic ??
Surprised but being curious, I did a test with some friends. One inserted a copper string, another one a stainless steel one (guitar string) another one a piece of plastic.The result was as expected : there was logically more bubbles as there is a bigger surface able to trap gas..
Cannot go against physics laws.


Note ; up to 40°C , this is air & other gas disolved in the water  expanding and escaping . Above , starts the steam formation just above 1% saturated. From there to 100°C the bubbles are steam more and more saturated. At 100 °C , it is saturated steam = pure dry gas.
Remember ; air is air but steam is …..water .....then  it changes to gas.


One thing I can suggest to reduce the formation of bubbles , is to let the water bottle in the sun before to fill up the boiler. BUt this will not eliminate completly the bubbles formation.
As there is virtually no circulation between top and bottom, another solution to remove that damned bubble stucked in the middle of the sight glass is to install a bleed off valve on top of it. Or at he bottom. Not so handy !
Also note that a sight glass helps to show the level in the boiler when filling up , but is not 100% reliable when boiling in.
Have a clean sight glass helps for seeing the level but will not eliminate the bubbles formation.
Finally , for those who love the numbers, they can play with  W.Henry's formula to find out the gas concentratioon in a liquid.


I would appreciate if there is a smarter and fluent English speaking engineer to explain this better than I can do.


Hope this explains this ! But we have to live with the bubbles ! %)
Regards.

DBS88

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 492
  • Model Boat Mayhem is Great!
  • Location: Surrey
Re: Damned bubbles !
« Reply #1 on: June 04, 2021, 02:57:53 pm »

Yves thank you for your elloquant description of the bubbles issue, I follow your logic and agree, increasing the surface area by adding something else with nucleation points on it will increase bubble formation. Does increasing the diameter of the sight glass help get rid of the bubbles more easily, are they able to move up and away more easily? Every day is a school day so more than happy to learn from yours and others experiences, thank you for starting this interesting topic.
Logged

KBIO

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 512
  • Location: Dinan (France)
    • http://modelismenavalvapeur.forumactif.com
Re: Damned bubbles !
« Reply #2 on: June 04, 2021, 05:28:43 pm »

Hello !
Does increasing the diameter of the sight glass help get rid of the bubbles more easily .
Definitly ! I get rid of 4 & 5 mm glasses whenever I can , to go for 6 mm minimum or even more. depending of the boiler size.
But maybe ,  there is other solutions. Let see what the other fellows propose. ok2
Kind regards. :-)

SteamboatPhil

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,762
  • Location: Dieppe, France
Re: Damned bubbles !
« Reply #3 on: June 04, 2021, 06:48:42 pm »

I use 1/4 inch (ok sort of 6mm----old school me) gauge glass, not for the bubble problem but for the eye site problem.


I have never really had a problem with bubbles, but I have  blow down valves on all my  gauge glass fitting, so if I do get bubbles I blow them out  :-)) [size=78%] [/size]
Logged
Steamed up all the time

rhavrane

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 883
  • Steam passionate collector
  • Location: Saint-Mandé, Val-de-Marne, France
Re: Damned bubbles !
« Reply #4 on: June 04, 2021, 08:11:08 pm »

Bonjour,
Phil, not obvious to open/close the blow down valve at the bottom of a small hull  ok2

I also apply the trick of the copper wire : https://www.youtube.com/watch?v=RkK82YE44XI :-))
Logged
Raphaël
Raphaëlopoulos Steam Lines UnLimited
Membre du Modele Yacht Club de Paris http://mycparis.fr/
Membre de l'Offshore Club de Paris : http://site-ocparis.wifeo.com/
My YouTube channel: http://www.youtube.com/user/rhavrane
Pages: [1]   Go Up
 

Page created in 0.09 seconds with 22 queries.