Numerical investigation on the heat transfer characteristics of unstable steam jet under different operating conditions

•Transient simulation study on steam bubble jet was carried out.•The dynamic change law of bubble interfacial heat transfer was obtained.•The transient visualization results of bubble interfacial heat transfer coefficient and internal velocity were discussed.•The effect of interphase heat transfer on bubble growth and necking stages was analyzed.•The change law of condensation force was obtained. Transient numerical study was performed to investigate the characteristics of interphase heat transfer in unstable steam jet under different operating conditions. Bubble radius change rate, interfacial heat transfer coefficient and overall condensation mass flux reached their maximum values during the bubble necking stage. The maximum peak value of interfacial heat transfer coefficient and bubble radius change rate decreased with the decrease of inlet pressure differential and water subcooling. The peak values of interfacial heat transfer coefficient and internal velocity were found in the bubble neck region. The effect of interphase heat transfer on bubble growth and necking stages was analyzed on the basis of overall force balance. Momentum force played a major role during the bubble growth stage, and the condensation force had a dominant effect on bubble necking stage. Condensation force first decreased and reached its minimum value during bubble rapid necking stage. Subsequently, the condensation force rapidly increased and promoted the movement of bubble necking. Moreover, the condensation force curves under different conditions had the same change law.