Study about the flashing process through a metering expansion valve

In this paper, the results from an experimental campaign about the flashing process occurring through a metering manual expansion valve, are presented and discussed. The results involved the measurement at different lifts of the flow-rate flowing through the valve for three different refrigerants R22, R290 (propane) and R410A. First the experimental rig is described and the employed instrumentation is commented upon and the corresponding uncertainties analyzed. The test matrix is then presented and discussed. Then the geometry of the valve is described and an analysis about its geometric throat area as a function of the valve lift is also presented. The results of mass flow rate for different upstream pressure and temperature, subcooling, and downstream pressure are presented and the effect of each of those operating condition on the obtained mass flow rate is discussed. Different flow models are applied in order to evaluate the effective flow area of the valve at every valve lift and a comparison study is performed in order to elucidate which is the model which better explains the obtained results. Finally the results obtained with the best estimate model are shown for the full collection of tested points and the three tested refrigerants.