Experiment study of water film/air counter-current flow heat transfer on a vertical plate for passive containment cooling system

Passive containment cooling system (PCCS) is a key component of the passive safety system in the AP1000 type reactor design. The free falling water film spreading on the outer surface of containment helps to keep the temperature and pressure inside below safety limits. An experiment was setup to study the water film/air counter-current flow heat transfer on a vertical plate with back heating. There was a glass cover placed 0.3 m away from the plate surface forming an air flowing duct, and the heating plate was 5 m in length and 1.2 m in width. Water flowed down from the distribution box on the top of the plate, and then spread on it; while the air flowed in from the bottom of the plate. The inlet and outlet temperatures and flow rates of water and air, heat flux on the plate surface were measured or estimated under different water/air flow rates, water/air inlet temperatures, heating surface temperatures. A new correlation based on the experiment results was developed using heat and mass analogy and included effects from the entrance, plate temperature and gap height between the cover and the plate.