Numerical simulation of condensation induced waterhammer

Abstract

A numerical model for the simulation and analyses of the condensation induced waterhammer is presented. The modelling approach is based on the one-dimensional homogeneous two-phase flow model, tracking of the liquid-vapour interface and modelling of the direct condensation on subcooled liquid. The mass, momentum and enthalpy conservation equations are solved with the method of characteristics. The interface of vapour and liquid column is approximated with the cross section area of the flow channel. The liquid-vapour interface tracking is achieved with a third-order accurate solving of the enthalpy equation in space, where the thermodynamic quality (calculated from the enthalpy value) determines the presence of liquid, two-phase mixture or vapour. Heat transfer of condensation latent heat from the vapour-liquid interface to the subcooled liquid is described with a delta function term in enthalpy conservation equation, which integrates the heat flux at the interface. The transient friction is included in the momentum equation due to intensive accelerations of the liquid column. The model is applied to simulations and analyses of condensation induced water hammer in experimental facilities and of an interface tracking benchmark test. Numerical results are validated with measured data and verified with results of other computer codes and analytical solutions.