Critical heat flux under choking flow conditions Part II - Maximum values of flow parameters attained under choking flow conditions

Under conditions of forced convective boiling at low pressures and high mass fluxes, beyond a certain quality, choking flow may occur at the exit of a heated channel. An experimental investigation carried out by Olekhnovitch et al. (Olekhnovitch A., Teyssedou, A., Tye, P., Champagne, P., 2000. Critical heat flux under choking flow conditions. Part I - Outlet pressure fluctuations. Nucl. Eng. Des., this issue) has shown that the occurrence of choking flow does not radically influence the values of the critical heat flux (CHF). However, once the choking flow conditions have occurred, for a given mass flux and quality, the outlet pressure cannot be lowered below a certain value that is fixed by the flow itself. A model that allows this pressure to be determined and which must be used in conjuction with correlations for the prediction of the CHF is presented.