Experimental investigation on flow condensation heat transfer and pressure drop of nitrogen in horizontal tubes

The characteristics of flow condensation heat transfer and pressure drop of nitrogen are measured in smooth horizontal tubes with an inner diameter of 2 mm and 1 mm. The tests are conducted at saturation temperatures from 101.0 to 106.6 K, with mass fluxes from 13.1 to 78.6 kg/m2s for 2 mm tube, and from 65.5 to 262.0 kg/m2s for 1 mm tube. The impacts of mass flux, vapor quality, tube diameter and saturation temperature on the heat transfer coefficient and pressure drop are analyzed. Several previous correlations of flow condensation heat transfer coefficient and frictional pressure drop are compared with the experimental data. Since the thermal properties of nitrogen are different from that of non-cryogenic fluids, such as density, viscosity, surface tension and contact angle, the flow condensation heat transfer characteristic of nitrogen is different from that of non-cryogenic fluids. Considering the influence of thermal properties, a revised heat transfer coefficient correlation based on the Shah correlation is proposed for flow condensation of nitrogen in smooth horizontal tubes, with the mean absolute error of 11.2%.