Why is mass flow measurement preferred over volumetric flow in certain applications?

Mass flow measurement is preferred when: fluid density varies with temperature/pressure (gases, steam, cryogenic liquids), custody transfer billing is by weight, process reactions are mass-based (chemical reactors), or compressible fluids are measured. Volumetric flow (magnetic, ultrasonic, turbine meters) requires density compensation for mass determination. Coriolis and thermal mass flow meters directly measure mass flow, eliminating density compensation errors and providing more accurate process control and inventory management.