Gas-droplet flow structure and heat transfer in an axisymmetric diffuser with a sudden expansion

This paper presents the results of a numerical study of the effect of a positive longitudinal pressure gradient in a sudden pipe expansion on the turbulent two-phase flow structure and local heat transfer. It is shown that the longitudinal pressure gradient has a significant effect on flow characteristics and heat transfer in a separated gas-droplet flow. Increasing the opening angle of the diffuser leads to a significant increase in the degree flow turbulence (almost twofold increase compared to gas-droplet flow in pipe with a sudden expansion at $\varphi=0^\circ$C). It is found that in the flow under study, the length of the recirculation zone increases in comparison with separation gas-droplet flow at $\varphi=0^\circ$C and the point of maximum heat transfer rate shifts downstream. In this case, the coordinate of the point of maximum heat transfer rate does not coincide with the coordinate of the reattachment point of the detached two-phase flow.