In order to enhance the heat transfer performance of R-407C, the "herringbone heat transfer tube", which has a unique inner surface geometry, was developed, and the heat transfer characteristics were experimentally investigated in this study. The local heat transfer coefficient and pressure drop vs. the vapor quality for R-407C flowing inside the horizontal herringbone tube were measured, and the data were compared with those for a conventional inner grooved tube. Additionally, the heat transfer enhancement mechanism for the herringbone tube was qualitatively verified by the experimental data. The experimental results show that the heat transfer coefficients for the herringbone tube were about 90% higher during evaporation and 200% (maximum) higher during condensation than those for the inner grooved tube. Although the significant increase in heat transfer was accomplished with about a 50% to 60% increase in pressure drop, a practical estimation of the heat transfer enhancement indicated that the herringbone tube has favorable potential for practical air conditioning.

Units: SI