Originally Posted by Sorade
Thanks for the reply. What kind of thermal expansion ? I thought that the density of liquids was rather unaffected by temperatures (unless it freezes).
The density of liquids decreases as the temperature increases. Water is a wonderful exception to this rule after the temperature falls below 4 degrees; at which point it starts to expand until it become ice which will float on water.
As a result, the bottom of the world's oceans are at about 4 degrees and if ice didn't float the astronomers reckon that the earth's oceans would be about four feet deep, the rest being ice!
However, this is only of marginal interest when discussing the effects of Thermal Expansion in an enclosed space!
Liquid is generally
regarded as being "incompressible". (There are some exceptions and they can all be compressed when subjected to pressure at the centre of a nuclear explosion but let's just assume that water and beer are incompressible.)
So, in an enclosed space such as a keg, vessel or a pipeline there has to be some method by which the pressure caused by the expansion of a liquid contained within the vessel is allowed to escape. In most cases this is covered by including a "head space" which is larger than any expected expansion of the liquid.
In pipelines and other industrial systems it is accomplished by the installation of Thermal Expansion Pressure Relief Valves which are installed around every
potential blockage. e.g. pipeline valves.
Hope this helps.
Have to go because SWMBO has just come in from the garage to report "That thingy is bubbling and there is something all over the bench!"