On Calculating Heat Transfer and Pressure Drop of Supercritical Pressure Coolants

Abstract

Specific features of thermophysical properties of singlephase supercriticalpressure (SCP) coolants and typical ranges of their thermodynamic state that determine heattransfer regularities are presented. A brief analysis of the existing concepts on SCPcoolants heat transfer under turbulent flow in tube is given. Typical features of normal and deteriorated heattransfer regimes are described. The simple classification of deteriorated heattransfer regimes at high heat loads that make it possible to distinguish the causes and appraise a degree of heattransfer deterioration danger is proposed. The results from the studies of the hydraulicresistance structure under the regimes of normal and deteriorated heat transfer are considered and the conditions, when a onedimensional (1D) (homogeneous) flow model can be used in hydraulic calculations, are revealed. Using sounding measurements data, the interrelation between heattransfer deterioration and radical changes in the averaged turbulent flow structure due to fluid thermal acceleration and Archimedes forces effects is analyzed. The recommendations on calculating normal heat transfer with an account of refined standards on thermophysical properties of water and carbon dioxide are presented. The review and analysis of the existing criteria for forecasting heattransfer deterioration and assessing the boundaries of the normal heattransfer range are given, and the correlations for describing deteriorated heat transfer are presented.