The critical heat flux (CHF) of gas-liquid flow plays an important role in the safety of industrial equipment. At present

the liquid film model is widely used for predicting critical heat flux in gas-liquid annular flow. It consists of onset of annular flow

entrainment fraction for the onset point and the equilibrium state

inception criteria for droplet entrainment

droplet deposition and entrainment rates

which all have decisive effect on prediction accuracy. Most parameters in this model can be determined by some empirical correlations valid under different conditions. However

up to now

the entrainment fraction for the onset of annular flow is always assumed. In this paper

the normalized data of the 2006 CHF look-up table adopted widely

especially in the nuclear industry

were used. The liquid film model was built for the limiting quality region. The entrainment fraction at the onset of annular flow was obtained when the predicted CHF of the model met the values in the look-up table. The empirical correlation including the Weber number and the Reynolds number of liquid was provided. Its prediction could mostly make the errors within ±30%.