On Calculating Heat Transfer and Pressure Drop of Supercritical-Pressure Coolants

Abstract

Specific features of thermophysical properties of single-phase supercritical-pressure (SCP) coolants and typical ranges of their thermodynamic state that determine heat-transfer regularities are presented. A brief analysis of the existing concepts on SCP-coolants heat transfer under turbulent flow in tube is given. Typical features of normal and deteriorated heat-transfer regimes are described. The simple classification of deteriorated heat-transfer regimes at high heat loads that make it possible to distinguish the causes and appraise a degree of heat-transfer deterioration danger is proposed. The results from the studies of the hydraulic-resistance structure under the regimes of normal and deteriorated heat transfer are considered and the conditions, when a one-dimensional (1-D) (homogeneous) flow model can be used in hydraulic calculations, are revealed. Using sounding measurements data, the interrelation between heat-transfer 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 heat-transfer deterioration and assessing the boundaries of the normal heat-transfer range are given, and the correlations for describing deteriorated heat transfer are presented.