Numerical study of enhanced and deteriorated heat transfer phenomenon in supercritical pipe flow

Abstract

The mechanism of heat transfer enhancement and heat transfer deterioration for supercritical water flowing in vertical pipe is numerically studied using in-house 2D axi-symmetric CFD code, named NAFA. The numerical results obtained by the NAFA code for Yamagamata’s experiments, agree with their experimental results, thus validating the code. Simulations are carried out for low as well as high mass fluxes keeping the same heat flux to mass flux ratio. The study of effect of flow direction is also performed. The major contribution of this work is explanation of mechanism of heat transfer enhancement and deterioration in various conditions and various factors assisting or resisting the two. This explanation is given on the basis of radial variation of thermo-physical properties of the working fluid and turbulence parameters, plotted at selected axial locations where heat transfer coefficient ratio is high or low indicating enhancement/deterioration.