Boiling Flow Simulation for Evaporation Section of Separated Heat Pipes in Nuclear Power Plant Containments

To improve the inherent safety of nuclear power plant containments, a passive containment cooling system (PCCS) was designed by adopting separated heat pipes. The boiling flow in evaporation section of a large separated heat pipe with inner diameter of 80 mm was simulated using CFD method, while the two-phase flow was analyzed with VOF model, thus obtaining the flow pattern and finding the influence factors on the heat-transfer effectiveness in the evaporation section. Results show that the flow patterns are different in evaporator pipes with different inclined angles; the external convective heat transfer coefficient and external fluid temperature are the main factors influencing the heat transfer coefficient of evaporator pipes; the total mass flow has little effect and the inclination of evaporation section has a certain effect on the heat transfer coefficient; when the evaporation section of separated heat pipe is arranged at an angle of 50°-80°, optimal heat transfer effectiveness could be achieved.