An Analysis of Vapor Void Profiles in Heated Channels

The coupled nonlinear differential equations representing the void fraction and the liquid temperature in a heated channel have been solved by neglecting the slip velocity and assuming that there is no nucleation in the bulk liquid. In agreement with the experimental data for uniformly heated channels, the general solution of the void fraction equations predicts a sigmoidal vapor fraction profile. Theoretical temperature profiles show that, even in the high void fraction region, thermal equilibrium is not attained in the channel, indicating that the Martinelli-Nelson approach does not apply and that the void profiles at high vapor fractions are still a complicated function of the liquid velocity, heat flux, vapor production, and channel spacing.