A one-dimensional, propagation/expansion model has been developed for large scale vapor explosions based on a fragmentation concept involving film collapse and coolant jet impingement and entrapment. This fragmentation model was combined with the nonequilibrium propagation/explosion model to predict the integral behavior in a vapor explosion such as pressure history and explosion conversion ratio. The model predicts the correct qualitative trends from available explosion data (e.g., the fully instrumented test series at Sandia National Laboratories) as a function of fuel composition, coolant temperature, ambient pressure, coolant/fuel mass ratio, and initial constraint. Quantitative agreement with data is found to be quite dependent on the initial mixing conditions, i.e., coolant vapor and liquid volume fractions in the explosion zone. Some of the predicted trends would change when the scale increases.