Correlations of Thermodynamic Effects for Developed Cavitation

Abstract

The net positive suction head (NPSH) requirements for a pump are determined by the combined effects of cavitation, fluid properties, pump geometry, and pump operating point. An important part of this determination is the temperature depression (ΔT) defined as the difference between ambient liquid temperature and cavity temperature. Correlations are presented of the temperature depression for various degrees of developed cavitation on venturis and ogives. These correlations, based on a semiempirical entrainment theory, express ΔT in terms of the dimensionless numbers of Nusselt, Reynolds, Froude, Weber, and Pe´cle´t, and dimensionless cavity length (L/D). The ΔT data were obtained in Freon 114, hydrogen, and nitrogen for the venturis and in Freon 113 and water for the ogives.