Abstract
In this study, pressure drop and local heat transfer characteristics for the condensation process of R744 were measured experimentally in a horizontal multi-port extruded tube of 0.36 mm in hydraulic diameter. Experiments were carried out in the mass velocity range of 470 to 830 kg/(m2 s) at pressure 5, 6 and 7 MPa. The pressure drop was measured between both ends of the test section of approximately 730 mm in length. The local heat transfer was measured in eight subsections of 75 mm in effective heating length. The measured pressure drop was compared with several correlations. The correlations of Friedel and Mishima - Hibiki comparatively show a good agreement at pressure of 5, 6 and 7 MPa. The local heat transfer coefficients were also compared with several correlations. The high vapor quality data agree comparatively with correlations of Moser et al. and Cavallini et al., while other data do not agree with any correlations well. The present experimental results suggest that the condensation in a rectangular mini channel is controlled not only by forced convection effect, but also by surface tension effect.
