NUMERICAL ANALYSIS TO PREDICT THE BEHAVIOR OF LIQUID VAPOR SLUG FLOW IN VERTICALLY PLACED U-SHAPED CLOSED CAPILLARY TUBE

Abstract

Numerical analysis of liquid vapor slug flow in a vertically placed U-shaped closed capillary tube is carried out with family of hydrocarbon fluid like Acetone, Ethanol, Methanol and Pentane. A 3D computational domain has been developed for vertically placed U-shaped capillary tube sealed at both end with three small turns in evaporator section, two small and one large turn in condenser section. The diameter of vertically placed U-shaped capillary tube is taken as 2mm. The volume of fluid (VOF) approach, suitable model of K-epsilon is used to predict the behavior of liquid vapor slug flow along the wall of capillary tube. Fill ratio (FR) of 61% is used with the working fluid that occupies 61% of the total volume of tube. At the start of iteration process the evaporator and condenser temperature are set to 343 K and 298 K. The liquid, vapor slug flow inside the capillary tube and flow patterns are observed for Acetone, Ethanol, Methanol and Pentane. The contours of liquid volume fraction and wall temperature are observed along the length of tube. Alternate liquid and vapor slug formation and the complex phenomenon of evaporation and condensation process are visualized in the analysis. The aim of the numerical analysis is to find the suitable working fluid, models, simulation settings that accurately predict the phase change phenomenon and to investigate the effect of liquid vapor slug flow, changing simulation parameters on the performance of U-shaped capillary tube.