How to / DIY > Engines

Water Expansion

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biobill:
  Does anyone know how much water expands when it's heated. There must be a formula, but I can't find it. I need to allow for expansion in my unpressurized cooling system which utilizes a cast iron radiator. The hot inlet is almost at the top, so the radiator needs to stay completely full to keep the loop intact. Thought I'd run a small line from the bleed screw to a reservoir which I'd like to be as small as possible as it's in my living space. Trying to get it right the first time.

                                                   Bill

aqmxv:
here's a page giving the coefficient of thermal expansion of water and explaining how to do the math.  You'll have to convert your change in temperature to metric and you'll need to know the contained volume in the system (in metric as well).  Since there's going to be some volume expansion for the pipes, listeroid, tankage, etc as well it won't be ultra-precise, but should be close enough.

http://www.simetric.co.uk/si_water.htm

Geno:
Looks like about 4.5% from 0-100°C
http://hypertextbook.com/physics/thermal/expansion/
My total volume is just under 5 gal. and I guess my expansion tank goes up by a pint when up to temp. It seems about the same between pure water and 50/50 antifreeze.
Thanks, Geno

biobill:
Thanks Guys

I just love this forum,  Bill

phaedrus:
as a general rule pure liquids expand less than solutions. an anti-freeze solution in warter will expand more than an equal volume of water over the same temperature change - I'm pretty sure about this. I'd buy a bladder type expansion tank for water - check with Grainger to see what they have.

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