David Jenkins
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| posted on 13/3/05 at 11:01 AM |
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Expanding water
Can any boffin tell me how much one litre of water will expand for every 10 degrees C it is heated? Or every 1 degree C, if that's easier.
I know it's an odd question, but I now have 2 coolant expansion tanks to choose from - Rover 200 or Astra. The Astra has a far greater air
space and therefore can take more water expansion, but is a PITA to fix to the car if I want to have the outlets pointing in a sensible direction (I
also have to make an adaptor for the vent pipe). The Rover one would be a doddle to fit, but has a very small air space and I'm not sure it
could cope with normal expansion if I fill it to the mark on the bottle.
This conversion to a pressurised system is annoying me!
David
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Mix
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| posted on 13/3/05 at 11:35 AM |
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http://www.simetric.co.uk/si_water.htm
See above for tables
Mick
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David Jenkins
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| posted on 13/3/05 at 02:11 PM |
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Magic - exactly what I need.
Cheers, Mick.
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theconrodkid
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| posted on 13/3/05 at 07:52 PM |
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as the water will be under pressure it wont expand as much (thats what i recon anyhow)
who cares who wins
pass the pork pies
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britishtrident
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| posted on 13/3/05 at 08:19 PM |
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The water dosen't expand that much what does expand an awful lot more is any trapped air and steam.
The pressure the water is at makes very little difference to the expansion of water as for practical purposes water is considered incompressible --
however water and steam are compressible.
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David Jenkins
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| posted on 13/3/05 at 09:06 PM |
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Yep - that's the way it works - the water to all intents and purposes is incompressable, and WILL expand with heat. I need to work out how much
extra water I should expect to get at normal running temperature.
Job for the train journey tomorrow morning!
David
[Edited on 13/3/05 by David Jenkins]
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rusty nuts
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| posted on 13/3/05 at 09:16 PM |
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Think what you perhaps need is the coeffiecient of volumetric expansion, covered this at college about 30years ago, Sorry can't remember exactly
how to work it out . H.T.H . Could you just fit a bigger header tank? have used one from a Rover which so far seems O.K. although car is not yet on
the road.
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David Jenkins
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| posted on 15/3/05 at 10:42 AM |
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It's the Rover one that's worried me! If you fill it to the mark shown on the side then you'll only get around 100mls airspace. If
you only fill it to the moulding mark then you'll get a fair bit more - but that means that you won't get much reserve in the header.
I'm just playing with numbers at the moment - no great stress...
David
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britishtrident
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| posted on 15/3/05 at 01:06 PM |
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You don't need much reserve in the header the important thing is there is enough expansion volume that water dosen't get ejected.
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David Jenkins
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| posted on 15/3/05 at 01:08 PM |
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That's what I'm checking...
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britishtrident
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| posted on 15/3/05 at 07:08 PM |
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The Rover one will work if its higher than the highest point on the main system Rover used the same tank on the 2 litre models which had a much bigger
water capcity due the old B series block.
Watch the Rover tank cap from encountering a couple of bad one on Rover 820 I know they aren't very reliable
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David Jenkins
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| posted on 15/3/05 at 08:47 PM |
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I've just done my sums...
Taking the cold temperature as 10C
Hot temperature at 100C
My coolant volume = 4600cc
Water's coefficient of expansion = 0.00021/deg C
Extra volume = (100-10) x 4600 x 0.00021 = 87cc (roughly)
Not as much as I expected! Allow a bit extra for unexpected over-heats, means that 100+cc airspace should be plenty - theoretically...
David
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907
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| posted on 16/3/05 at 08:59 PM |
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Hi David
Don't forget the block expands, thus making the waterways bigger......
and the rad.... and the hoses swell as well !!!
I'm an a**hole am I not ? tee hee hee
ATB
Paul G
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David Jenkins
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| posted on 16/3/05 at 10:09 PM |
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You're just a trouble-maker!
David
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