Prediction Of Heat Transfer Coefficient In Saturated Flow Boiling In A Constant Cross-section Microchannel

With the progress of society and the development of computer technology,the microelectronic technology is more and more widely used in practical engineering.The miniaturization of equipment has become an important trend of development.The cooling problem of microelectronic devices has become a major obstacle to its development,While the two-phase boiling heat transfer within the microchannels is a potential solution to the problem of cooling the microchip with high heat flux density.In this paper,firstly,the research status and research methods of saturated boiling heat transfer coefficient of microchannels at home and abroad are introduced.The heat transfer coefficients of saturated boiling in microchannels are mainly studied experimentally and theoretically.In this paper,we mainly predict the saturated boiling heat transfer coefficient in a given cross-section microchannel theoretically.The main work includes:(1)First,the three-zone model applied to the circular cross-section is extended to the rectangular cross-section and the triangular cross-section microchannel.Due to the existence of a corner region,ie,a partially dry state during the saturated boiling heat transfer of the microchannels with rectangular and triangular cross-sections,a partially dryout zone is added on the basis of the three-zone model,and derive the four-zone model that suitable for the heat transfer coefficient of microchannels with rectangular and triangular cross-sections(liquid slug zone,elongated bubble zone,partially dryout zone and fully dryout zone).(2)Taking water as the working fluid,the boiling heat transfer coefficients in rectangular cross-section microchannels were respectively fitted by using the three-zone model and the four-zone model.A set of empirical parameters were obtained and corrected by experimental data.Finally,This parameter predicts the boiling heat transfer coefficient under different mass flow and heat flux density conditions and compares the predicted value with the experimental data.The results show that the three-zone model and the four-zone model can predict the trend of heat transfer coefficient with the vapor quality,and respectively 90.38% and 91.83% of the data error within 30%,the average error of 13.74%,13.2%.(3)Similarly,using acetone as working fluid,the boiling heat transfer coefficients under different mass flow and heat flux density conditions in the triangular cross-section microchannels are predicted by the three-zone model and the four-zone model,respectively.The results show that the three-zone model and the four-zone model can predict the trend of the heat transfer coefficient with the vapor quality,and the data error of 90.04% and 92.02% respectively is within 30% and the average error is 13.68%,12.54%.By comparing the predictions of the three modes and the four-zone model on the saturated boiling heat transfer coefficients in the microchannels,we can see that due to the presence of angular regions in the rectangular and triangular cross-sections,there is partially dryout state before complete drying.In the four-zone model the introduction of partially dryout zone can reflect the influence of local dry-up state on the heat transfer coefficient in saturated boiling heat transfer and provide some references for the study of saturated boiling heat transfer coefficient in microchannels with angular cross-section.