expansion tank

[mielke]

Is there any rule of thumb for determining the size of a diaphragm expansion tank for a simple closed loop water/glycol coolant system. (ie by a certain percent of total volume, or by anything else???)

 

[chicopee]

Go on line and type "sizing diaphragm expansion tanks". Engineeringtoolbox will come up.

 

[FredRosse]

Sizing an expansion tank depends on several variables, and there are generalized rules for typical systems, but unless you know the assumptions that went into the "rule of thumb", you can get very incorrect answers. Mark's Handbook has such a "rule of thumb", but it is only good for a specific number of boundary conditions, few of which are adequately defined.

For example, some water/glycol systems will fill the expansion tank when system temperature goes up, and other systems will actually experience a decreasing expansion tank inventory as the system is heated.

This all depends on the nature of the system fluid, the piping system, the temperature extremes, the pressure changes, etc.

 

[amorrison]

Check out ASHRAE HANDBOOK - SYSTEMS volume.