Specifics of thermophysical properties and heat transfer at supercritical pressures

Abstract

Currently, SuperCritical Fluids (SFCs) are used in various industries worldwide. The largest application of SCFs is the use of SuperCritical Water (SCW) at SuperCritical Pressure (SCP) coal-fired power plants. Using SCP Rankine “steam” cycle allows to reach gross thermal efficiencies of a plant up to 55%. On contrary, current subcritical-pressure water-cooled Nuclear Power Plants (NPPs) of Generations II and III have significantly lower gross thermal efficiencies within the range of 30 - 36% (up to 37 - 38% for Generation III+ nuclear-power reactors). To increase efficiency of next generation – Generation IV NPPs higher parameters (mainly temperature) should be reached for reactors’ coolants and corresponding to that for power cycles. Analysis of Generation IV nuclear-reactor concepts shows that three concepts will be cooled with SCFs such as helium and water, and there is a possibility that other concepts will be linked to SCP Rankine cycle or to SCP Brayton cycle with helium or carbon dioxide working fluids. Therefore, specifics of thermophysical properties and heat transfer of SCFs are very important for reliability and safety of new thermal and nuclear power plants. Also, for SCW nuclear reactors heat transfer to SCW flowing inside various bundle geometries has to be understood and estimated.