Measurement of two-phase refrigerant liquid-vapor mass flow rate. Part 3: Combined turbine and venturi meters and comparison with other methods

In determining the mass flow rate of refrigerant R-134a liquid-vapor in a horizontal tube, a simple method that combines the outputs of venturi and turbine flowmeters, without the need for void fraction or quality measurement, was examined. The results showed that this method can be used to determine the two-phase mass flow rate relatively well for the entire quality range. This method was particularly accurate in determining the mass flow rate data in the high-quality range, i.e., in annular flow. Moreover, this method also showed a reasonable accuracy in predicting the void fraction. The use of this method in predicting the two-phase mass flow rate was compared with the use of a venturi meter or a turbine flowmeter and a void fraction meter. The comparison showed that at qualities higher than 0.6, the present method, which combines the output signals of both the turbine and venturi meters, is superior to those that use one of the flow signals and void fraction and/or quality measurement. At lower qualities, the present method still offers a fairly accurate technique for measuring the liquid-vapor refrigeration mass flow rate.