Flow pattern, heat transfer and pressure drop in flow condensation part I:Pure and azeotropic refrigerants

This study concerns the flow pattern, heat transfer, and pressure drop for flow condensation. The experimental results are recorded in tests with a sm ooth horizontal tube of 6 mm inner diameter and 2 to 10 m long. This manusc ript, which is part I of a two part series, focuses on pure and azeotropic fluids. Part II describes results with non-azeotropic refrigerant mixtures. A flow pattern map by Tandon et al. (1982) roughly predicts flow patterns a ssociated with pure and azeotropic fluids in this work. However, the Froude number is found to be a good additional indicator to identify transition b etween annular and wavy flows. The transition occurs mostly at Fr = 15 to 2 0 for both pure and azeotropic fluids. In the case of pure and azeotropic fluids, the hear transfer coefficient wa s found to be independent of the mass flux in wavy flow regions, but increa sed with an increasing mass flux in the annular flow regions. For pure and azeotropic fluids, a modified Tandon et al. correlation agreed best with ex perimental data from tests with R-12, R-22, R-134a, and R-502. For the loca l pressure drop it is correlated within +/-15% by using the Lockhart-Martin elli parameters. The experimental data for pure and azeotropic refrigerants can be predicted by using a correlation for overall pressure drop.