Transient conjugate two-phase heat transfer during depressurization of pipelines containing flashing liquids is examined in this paper. A numerical model for transient flashing liquid flow in a pipe is formulated. The model takes into account the transient radial heat conduction and the forced convection effects. Numerical simulation of flashing two-component (propane and butane) flow is performed in order to investigate the effect of wall friction on the heat transfer conditions in the pipe. The simulation results are compared with predictions of the model that are based on a new formulation of energy equation proposed by the author in an early study. A comparison of the results obtained allows one to determine the range of applicability of the new energy equation formulation. A procedure is proposed for choosing an appropriate model for predicting transient conjugate two-phase heat transfer during releases of flashing liquids from pipes. A criterion of thermodynamic similarity for flashing liquids flows in pipes or channels is formulated. The proposed criterion provides the basis for selecting model fluids and for constructing experimental models of systems containing flashing (volatile) liquids with scaled thermodynamic conditions. An example of its use is given. [S0022-1481(00)02001-6]

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