This paper presents the results of an experimental study on heat transfer and pressure drop during condensation of refrigerant R-404A inside a horizontal 9.4 mm I.D. tube. The experiments were conducted at nominal pressures of 80% and 90% of the critical pressure of R-404A. A novel technique that addresses the conflicting requirements imposed by the need for accurate measurement of low heat transfer rates for the small quality increments, and delineation of the tube-side heat transfer coefficient from the overall resistance, was developed. Local heat transfer coefficients and pressure drops were measured for the mass flux range 200 < G < 500 kg/m²-s in small quality increments over the entire vapor-liquid region, spanning several different two-phase flow regimes. These data were compared with existing correlations for condensation heat transfer to assess the validity of these models for this high-pressure refrigerant blend when operating near the critical pressure. The high reduced pressures in this study result in deviations from the predictions of the commonly used condensation heat transfer correlations, although the model by Cavallini et al. (2002) showed reasonable agreement with the heat transfer data from the present study.

Units: SI