This paper presents the results of an experimental study of heat transfer and pressure drop during condensation of refrigerant R410A 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 R410A. 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 used. Local heat transfer coefficients and pressure drops were measured for the mass flux range 200 < G < 800 kg/m~2-s in small quality increments over the entire vapor-liquid region, spanning several different two-phase flow regimes. These data were compared with the heat transfer and pressure drop data obtained under similar conditions for R404A by Jiang and Garimella. The data were also compared with available correlations for condensation heat transfer according to the applicable flow regime to assess the validity of these models for refrigerant blend condensation at near-critical pressures. Possible explanations for deviations between the data and the models in the literature are also provided.
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