Experimental Investigation And Numerical Simulation On Flow And Heat Transfer Of Passive Falling Film On Arc-Shaped Plate

With the development of China's nuclear power industry, nuclear safety a growing concern. In AP1000 and Hualong One represented the third generation of advanced pressurized water reactor nuclear power thchnology, the introduction of passive containment cooling system, greatly enhance the safety and security of nuclear power. The cooling water flow from upper containment tank and spread down the steel containment vessel in a film. Falling cool liquid film in contact with the hot stainless steel containment vessel, heat and mass transfer happens in the process of liquid film evaporation phenomenon, Film and spontaneous combustion air convection, so that the inside of the containment heat loss to the environment, thus preventing containment from overheating, leading to structural failure caused by leakage of radioactive material. Studying the passive containment falling film flow and heat transfer mechanism is one of the urgent research subject in nuclear accident prevention and safety running.This paper designed and built the arc-shaped plate falling film flow and heat transfer bench. The experiment was carried out under the condition of different water film inlet flow and heating temperature with water as working medium. Experiments captured the water film instantaneous flow pattern and collected temperature data in the process of falling film cooling, and using dyed water trace film spreading form. Experiment show that the water flow with uniform film in stainless steel plate in the process of falling film, and the film has good cooling effect for stainless steel. When stainless steel heating temperature is higher than the saturation temperature film around it, there are a large number of steam evaporation obviously.Based on the experiment condition, this paper use the FLUENT software VOF in multiphase flow model and turbulent model for numerical calculation of falling film flow characteristics. By comparing the results of numerical simulation and experimental results, we found that the water film flow pattern have a high match degree. The mathematical model of falling film flow and the numerical simulation method are proved to be reliable and accuracy in this paper. On the basis of verification of falling film flow numerical simulation reliability, numerical simulation was carried out under different water film flow and we found that the greater the water film flow, the greater the water film thickness, and the fluctuations of water film on stainless steel plate occurred obviously on the vertical section.Falling film heat transfer experiment platform is built based on falling film flow experiment platform. Numerical simulation of the process of falling film evaporation is carried according to the experiment conditions that one do not reach saturation temperature of water membrane and the other reach saturation temperature of water membrane. Compared the numerical results with the experiment results, we found that the cooling process have high match degree. Although a certain error exist, we can control it in a small range. So the reliability of numerical simulation is verified for the two kinds of falling film cooling process. Based on this, falling film cooling experiment and numerical simulation is carried out under different water film flow,found that the greater the water film flow, cooling the faster, the higher the degree of cooling.This paper preliminarily explored characteristics and heat transfer mechanism of passive containment falling film flow and theoretical calculation-experiment measurement testing system is constructed. This provide scientific method and basis for the study of falling film flow and heat transfer mechanism and provide more accurate theoretical basis for the design, maintenance and safe operation of nuclear power plant system.