Expansion tank query

[widdowson2008]

Got a few thoughts/questions on the de-gassing tank stuff.
If we assume that
1 - the system is fully bled and the only air in the system is in top of the expansion tank (above FULL level)
2 - the only place excess air can escape is through the expansion tank filler cap

What does a de-gassing feature do?
Reason I'm asking this is:
If the degassing tank removes even more air (probably caused by pump cavitation), then surely you will finish up with a partial vaccuum in the expansion tank, and eventually, a full vaccuum. ie: all air has been expelled from the system.
Can more 'loose air' be conjured up from somewhere?

Just crap wazzing around my head at the moment. (probably fuelled by a couple of glasses of wine )
And definitely not suggesting this happens - just food for thought

I feel another explanatory sketch coming on

[munroman]

Water will contain what is called 'dissolved oxygen', that's what the bubbles you see in a kettle or pot of water coming to the boil are.

Presumably the degassing tank allows this oxygen to leave the coolant rather than be pulled back into the system, where it might randomly form airlocks with disastrous consequences.

After a few heat/cool cycles the coolant should have been purged of the dissolved oxygen, possibly this is what accounts for the change of coolant level after a coolant change?

The different sized inlet/outlets may contribute by possibly causing pressure changes within the system, in the same way that taking the top off a bottle of lemonade allows it to fizz as the pressure is released.

[dandywarhol]

Water will contain what is called 'dissolved oxygen', that's what the bubbles you see in a kettle or pot of water coming to the boil are.

Presumably the degassing tank allows this oxygen to leave the coolant rather than be pulled back into the system, where it might randomly form airlocks with disastrous consequences.

After a few heat/cool cycles the coolant should have been purged of the dissolved oxygen, possibly this is what accounts for the change of coolant level after a coolant change?

The different sized inlet/outlets may contribute by possibly causing pressure changes within the system, in the same way that taking the top off a bottle of lemonade allows it to fizz as the pressure is released.

But a pressurised system won't be anywhere near boiling point so there won't be bubbles.
Approx. 1.5 deg per 1psi so a Bongo system won't reach bubbling point til approx 120 deg.

[bigdaddycain]

Very good thinking Munroman. Most of the post bleed coolant drop is down to displacement though, the air that was lurking further down is now in the top of the tank, the space it took up now replaced with coolant. hence, such a level drop.

[The Great Pretender]

But a pressurised system won't be anywhere near boiling point so there won't be bubbles.
Approx. 1.5 deg per 1psi so a Bongo system won't reach bubbling point til approx 120 deg.

You don't need to get close to boiling point, just look at a pan of water heating up. There sure are bubbles.

[widdowson2008]

As I am ignorant on the 'degassing principle', I am totally reliant on others to come up with ideas and those replys make sense. Thank you munroman, dandywarhol, bigdaddycain, and The Great Pretender for your input.

Also read through recommended reading by TGP re BDCs earlier post, and that now makes things a little clearer. Surprising (or perhaps not so) how overall knowledge advances quicker when onformation is pooled. Cheers guys - keep it coming.

Currently looking at the relationship between the tank cells in respect to their volumes, relative heights, FULL/LOW levels/volumes etc. Some interesting numbers keep turning up .
What started me on this tack is the shape of the tank. Didn't need to be such a wierd shape just to cntain a certain volume of fluid - could have been just a rectangular box. But it isnt!!!!!!!!!
When I get the numbers together, I'll be putting some theories forward as to WHY the wierd shape for your consideration.

[mikexgough]

What started me on this tack is the shape of the tank. Didn't need to be such a wierd shape just to cntain a certain volume of fluid - could have been just a rectangular box. But it isnt!!!!!!!!!
When I get the numbers together, I'll be putting some theories forward as to WHY the wierd shape for your consideration.

Nearly finished the degas write up theory of how it works and how applied to the Bongo system...... and the weird shape kind of goes with that.....

[widdowson2008]

What started me on this tack is the shape of the tank. Didn't need to be such a wierd shape just to cntain a certain volume of fluid - could have been just a rectangular box. But it isnt!!!!!!!!!
When I get the numbers together, I'll be putting some theories forward as to WHY the wierd shape for your consideration.

Nearly finished the degas write up theory of how it works and how applied to the Bongo system...... and the weird shape kind of goes with that.....

Preliminary numbers (accurate):
Total internal volume of tank = 1786cc
Coolant up to the FULL mark on tank, Coolant volume = 955cc, air 831cc.
Coolant up to the LOW mark on tank, Coolant volume = 360cc, air 1426cc.

The wierd shape of the tank is likely to be governed by two factors:
1 - The need for each section of the tank to have a specific capacity
2 - The physical space available under the bonnet

Checking later today how this info relates to a 'de-gas' tank detailed in a US/Japanese patent (supplied via Mike)
I'll be back

[widdowson2008]

Following input from member re ambiguity of flow paths, I produced this. Hope it makes things clearer.
Cell marked 'X' does NOT have a flow cell and is shown to be stationary. It is just a reservoir.

[bigdaddycain]

That's really neat Steve. Good work!

[widdowson2008]

Thanks bdc. The object of the excercise here is to keep the explanations SIMPLE and easily understood. Just a matter of getting the right format, and from responses, it looks as though this format is winning.
All I need to do now (as far as the tank is concerned) is to establish exactly how it 'does its thing'.

Gotta keep this cooling system fact sheet FACTUAL and SIMPLE for it to be of any value.

Got some rather interesting US/Japanese patents from Mike on degassing tanks explaining the 'what' but not the 'why/how'. Read through them and once you sort out the meat from the chaff, they are close to the Bongo tank, but not quite there.
So, not there yet but I'm working on it.

[mikexgough]

first draft of the how/why etc should be done tomorrow.....plus I also have a Land Rover patent from 2005...it is really only their slant on De-gas cooling for one of their models but the principles are the same....

[widdowson2008]

Sorry about this. Not one, but two errors on last sketch. Now corrected.

Look forward to getting summat to read Mike.

[mikexgough]

Look forward to getting summat to read Mike.

Soon, quite soon..... just trying to haggle with putting the info together......

[mikexgough]

Still at it...... almost finished draft 2 containing the de-gas tank principles and how it works on the Bongo, almost a eureka moment ........blimey it's 03:05.......