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The volumetric thermal expansion coefficient (β) describes how much a fluid expands per degree of temperature rise. It is reported here in units of β × 10−5 1/K. The volume change is:
ΔV = V0 × β × ΔT
where V0 is the initial volume and ΔT is the temperature change in Kelvin.
In closed-loop heating and cooling systems, fluid volume changes with temperature must be accommodated by an expansion tank. Undersizing the expansion tank (by using water's expansion coefficient when the system actually contains a Ethylene glycol solution) can result in system overpressure, relief valve discharge, or pipe damage. Ethylene glycol solutions expand more than water at equivalent temperatures, making accurate β values essential for expansion tank sizing calculations.
Note: β increases with both temperature and glycol concentration. Always size expansion tanks using the highest expected operating temperature.