HEAT TRANSFER TO WATER AT SUPERCRITICAL PARAMETERS IN VERTICAL TUBES,ANNULAR CHANNELS, 3-AND 7-ROD BUNDLES

摘要

The data on deteriorated transfer to supercritical water in vertical tubes and channels simulating coolant flow in fuel assemblies obtained at the same experimental setup during more than dozen of years are considered and compared with some known results of the experimental studies performed by other authors. They involve the data for vast ranges of geometry, mass velocity, heat flux rate, and pressure, in some cases for up- and downward flow, for flow with and without thermoacoustic oscillations. For the first time the data illustrating deterioration of heat transfer in the bundles of fuel elements are presented. An attempt to explain the phenomena of "inlet" peak of wall temperature is made. It is shown that temperature regimes of the tubes cooled with supercritical water in a gaseous state (i.e., at bulk temperature above the pseudocritical temperature) are close to linear, stable and easily reproducible within a wide range of mass and heat fluxes. Some requirements to the experimental setup, coolant quality, test sections etc. that should be followed in studying thermal and hydraulic parameters of supercritical coolant are analyzed.