Abstract: To explore the boiling heat transfer mechanism in narrow channels,gas-liquid two-phase flow in z-shaped narrow channels was studied with two different types of media.The bubble generation,growth and departure processes were analyzed using numerical simulation and self-programming.The influence of interface movements and changes on internal pressure difference and average surface heat transfer coefficient was investigated by using geometry reconstruction and interface tracking,taking into account gravity,surface tension and viscosity during calculation.The results show that the viscosity has great influence on generation modes and shapes of bubbles,that is,the lower the viscosity is,the smaller the diameter is when the bubble departs with a higher frequency.In addition,surface tension and viscosity significantly impact the pressure drop of boiling system,and different specific heat and boiling point values result in different heat transfer coefficients.The simulation results in this paper match well with the experimental data revealed in other sources,both show that the heat transfer coefficient of water is higher than that of ethanol and z-shaped channels have better heat transfer capability.