Critical heat flux in a vertical tube at low and medium pressures. Part II- new data representation

An analysis of the physical processes taking place in a dispersed-annular f low which govern dry-out type CHFs has been carried out. The analysis has s hown that the number of variables required to describe the critical phenome na can be reduced by the introduction of a new parameter: the length over w hich dispersed-annular flow takes place, L-dan. In this case only, for a gi ven tube diameter, pressure and mass flux, the critical heat flux may be ex pressed in terms of a single variable: L-dan. A correlation which may be us ed to determine this length has also been developed. The representation of the CHF data obtained at low pressures in terms of the coordinate system (L -dan, q(cr)") has shown that the dispersion of the data about the regressio n curves is considerably reduced as compared with the traditional presentat ion of the critical heat flux as a function of the thermodynamic duality at the end of the heated length. (C) 1999 Elsevier Science S.A. All rights re served.