Enhancement of Pool Boiling Heat Transfer with an Optimum Sintered Copper Microporous Coating on Copper Surface

As a result of the Fukushima Daiichi Nuclear Power Plant disaster, there is a worldwide concern regarding the safety of nuclear power plants. When natural disaster like an earthquake or a tsunami occurs, the normal operation of the nuclear power plant is paralyzed, which may result in discharge of the molten corium outside the reactor vessel. Robust technology is required to confine the molten corium inside the reactor vessel even in case of a catastrophic failure. IVMR (InVessel Melt Retention) through ERVC (External Reactor Vessel Cooling) is one of the mitigation measures to retain the molten corium inside the reactor vessel. A key strategy considered herein is to improve the NBHT (Nucleate Boiling Heat Transfer) and CHF (Critical Heat Flux) on the reactor vessel wall. In order to enhance either NBHT or CHF on a metal substrate, numerous surface treatments have been developed so far. Among them, microporous coating is one of the most effective surface treatment due to the micron size pores including reentrant cavities. In this study, pool boiling heat transfer of water at atmospheric pressure is investigated experimentally on copper surfaces with HTCMC (High-temperature, Thermally-Conductive, Microporous Coatings). The HTCMC coatings are created by sintering copper powders on 1 cm x 1 cm copper surfaces in a vacuum or nitrogen environment. An optimized particle diameter of 67 μm and a thickness of 296 μm were determined based on numerous tests[1]. Heater orientation effects on pool boiling heat transfer of saturated water were investigated with the change of inclination angles of 0 o