Condensation heat transfer characteristic of high-speed steam/nitrogen mixture in horizontal rectangular channel

Steam condensation in the presence of nitrogen is experimentally performed in a horizontal rectangular channel with cross sectional dimension of 5 × 6 mm. Steam mass flux varies from 203.7 to 431.3 kg m⁻² s⁻¹, while the nitrogen mass fraction from is 0% to 15%. Coolant water flows countercurrent in a rectangular channel as well, which is the same size with the steam side. The steam channel is on top of the coolant channel, and the released heat from the steam is transferred to the coolant water by heat conduction only through the connecting part of each channel, the thickness of which is 3 mm. The coolant mass flow rate is from 500 to 1100 kg h⁻¹, while the corresponding coolant side Reynolds number is from 2.2 × 10⁴ to 5.1 × 10⁴ and the coolant side heat transfer coefficient is from 20.2 to 40.1 kW m⁻² K⁻¹. The results show that higher coolant Reynolds number results in significant promotion of the overall heat transfer coefficient, while the condensation heat transfer coefficient is reduced. In addition, larger steam mass flux leads to greater overall heat transfer coefficient and condensation heat transfer coefficient. However, the influence of nitrogen on condensation is not significant, especially for condensation with higher steam mass flux.