Improved Capacitive Quality Meter for a Two-Phase Fluid

A previously developed quality/flow meter has been redesigned to improve its performance as a device for measuring the quality (but not the flow) of two-phase (liquid + vapor) oxygen or nitrogen flowing in a pipe. As used in engineering disciplines concerned with two-phase flows, “quality” denotes, loosely, volume fractions of liquid or gas. Like some other quality meters, the previously developed meter and the present meter are based on a capacitance-measurement concept: The fluid flows through a space between electrodes, the capacitance between the electrodes is measured, and the volume fractions of liquid and gas are estimated from the effective permittivity, using the known relationships (a) between the effective permittivity and the capacitance and (b) between the volume fractions and the effective permittivity. The estimate of quality can be refined by use of additional data from pressure and temperature sensors.