The constant kT shown in the above equation is the proportionality factor for liquid expansion
with increasing temperature. The difference in temperature between the measured condition (T)
and the reference condition (Tref ) multiplied by this factor determines how much less dense the
liquid is compared to its density at the reference temperature. It should be noted that some liquids
– notably hydrocarbons – have thermal expansion factors significantly greater than water. This
makes temperature compensation for hydrocarbon liquid flow measurement very important if the
measurement principle is volumetric rather than mass-based.