A model of heat transfer coefficient for supercritical water considering the effect of heat transfer deterioration

Abstract

Supercritical water has been widely used as working fluid in many thermodynamic cycles, predicting heat transfer coefficients of supercritical water precisely is of great importance to the system design. However, most of the existed correlations could not give satisfying results when heat transfer deterioration happens. In view of this, based on the mechanism of heat transfer deterioration, a physical model considering the effect of buoyancy and flow acceleration under heat transfer deterioration in the vertically upward flow of the supercritical water is presented in this paper. The modification of the shear stress under the combined effect of buoyancy and flow acceleration is theoretically analyzed, and the relationship between the shear stress modification and heat transfer deterioration is obtained. Based on this model, a heat transfer correlation is derived using a semi-theoretical, semi-empirical approach. The performance of the newly-developed correlation is evaluated and compared with the existed ones. The results show that the present correlation gives reasonable prediction accuracy and is capable of predicting the heat transfer behaviors of heat transfer deterioration of supercritical water.