COMPARISON OF AUGMENTATION TECHNIQUES DURING IN-TUBE EVAPORATION OF R-113.
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An experimental study was conducted to determine the potential of three techniques for augmenting in-tube evaporation of refrigerants: high-fin tubes, micro-fin tubes, and twisted-tape inserts. Five tubes with internal fins and one smooth tube with a twisted-tape insert were tested. Additionally, experiments were performed with two reference smooth tubes having diameters similar to the maximum inside diameters of the finned tubes. All experiments involved evaporating Refrigerant 113 (R-113) by direct electrical heating of the tube wall. Local evaporation heat transfer coefficients were measured as a function of quality for a range of mass velocities and heat fluxes. Enhancement factors were calculated by forming ratios of the heat transfer coefficient for the augmented tube and a smooth tube of the same maximum inside diameter.