PERTURBATION LENGTH OF AMMONIA TWO-PHASE FLOW IN THE HORIZONTAL AND VERTICAL LINES WITH ORIFICE THROTTLE

Abstract

The manuscript proposes the experimental study results dealing with the ammonia two-phase flow pattern observations in the horizontal and upflow transparent tube of ID 7.5 mm with the throttling orifice of ID 2 mm. The tests have been performed at a saturation temperature of 35 to 55°C, mass velocity of 80 to 160 kg•m-2s-1 and vapour quality of 0.1 to 0.7. Ammonia was chosen because it has zero greenhouse and ozone depleting potential, as well as the highest gravimetric coefficient of hydrogen content. The boundary conditions were chosen in accordance with the perspective of using ammonia as a working fluid not only in refrigeration equipment, but also in promising power plants, engines and systems for providing a warm regime. In this case, comprehensive experimental studies are required in the range of cold and hot source temperatures from 0 to 100 °C. The article analyzes the published works and shows the complete lack of experimental studies on the length of the flow disturbance not only for ammonia, but also for HFC liquids at pressures above 7 bar. This is due to the complexity of such an experiment due to very strict safety requirements (the main disadvantage of ammonia is its toxicity). The use of ammonia as a working medium for promising energy systems requires a more detailed study of the processes associated with, including, two-phase regimes at different orientations (horizontal and vertical) at high pressure. In the course of experimental studies, it was found and shown that the length of the perturbation behind the throttle does not depend on the saturation temperature, mass velocity, and mass vapor content. However, it depends on the two-phase flow regime at the inlet. Under the selected boundary conditions, it is shown for the first time that the perturbation length does not exceed the 23D distance of the horizontal line for the stratified-wavy pattern and 15D for the annular and annular-wavy flows. Plug and churn patterns give 24D perturbation length of the upflow line, while annular and annular-wavy patterns could be considered unchangeable at a distance of above 20D. The L-junction as a singularity does not show evidence of two-phase flow pattern change at a distance above 12D. The results of this study can be useful to researchers in the design of hydraulic and heat transfer experiments to avoid uncertainties arising from inlet and choke devices.