Physical Change
Increase in the space occupied by a liquid as its temperature rises occurs due to the increased kinetic energy of the molecules. Volumetric fluid expansion is a critical factor in the design of sealed hydraulic systems but becomes negligible in gases where pressure effects dominate.
Coefficient Determination
Rate of change is quantified by the volume expansion coefficient which is measured in units of reciprocal temperature. For a typical 10 cst silicone oil, volumetric fluid expansion occurs at a rate of approximately 0.001 per degree Celsius. This value is relatively constant over moderate ranges but changes considerably near the boiling or freezing points.
System Impact
Pressure inside a rigid enclosure will rise rapidly if the liquid is heated without room for growth. This volumetric fluid expansion can exceed the burst pressure of a diaphragm or the seal of a valve. Accumulators or bellows are integrated into the design to absorb the excess volume and maintain a stable internal pressure.
Metrological Correction
Instrumentation for flow or level measurement must account for the density changes associated with heating. Because volumetric fluid expansion alters the mass per unit volume, a temperature sensor is often paired with the primary transducer.
