Numerical study on two-phase boiling heat transfer performance of interrupted microchannel heat sinks

The conventional straight microchannel heat sinks have been reported to inadequately remove the increasing power density of electronics. In recent years, an effective heat transfer enhancement method, flow disruptions have attracted the attention of researchers, where interrupted structures are arranged in the microchannel to enhance flow mixing and heat transfer. However,previous numerical studies of interrupted microchannel heat sinks(I MCHS) mainly focus on single-phase flow condition, and the characteristics of the boiling heat transfer of I MCHS in two-phase flow condition have been rarely explored. Thus, the flow and heat transfer characteristics of two I MCHS based on rectangular microchannel heat sink(R MCHS) are investigated by modeling both single-phase and two-phase flow conditions. These two interrupts consist of a combination of cavities and ribs,namely elliptical cavities and elliptical side ribs(EC-ESR), and elliptical cavities and elliptical central ribs(EC-ECR). The results show that for single-phase flow condition, the maximum Nusselt number is increased by 187% in the EC-ESR design and150% in the EC-ECR design compared with the R MCHS. For subcooled boiling(i.e., two-phase flow) condition, the EC-ECR design is a promising structure to enhance boiling heat transfer with 6.7 K reduction of average wall temperature and 29%increment of local heat transfer coefficient when compared with those of R MCHS. However, the local heat transfer coefficient in the EC-ESR design is decreased by 22% compared with the R MCHS due to the formation of a rare flow pattern(i.e., inverted annular flow with vapor film separation) in the microchannel. This flow pattern can induce departure from nucleate boiling(DNB), thereby deteriorating the heat transfer on the channel walls.