Experimental Study On Pressure Drop And Heat Transfer Characteristics Of Micro-Channel Flow Boiling

With the development of Micro-Electro-Mechanical Systems(MEMS)technology,the miniaturization and miniaturization of microelectronic devices such as computer and information technology are increasing,due to a sharp increase in the amount of heat per unit space,seriously affect the normal operation of microelectronic devices.It is not only of scientific significance but also of great engineering value to explore efficient miniaturization and miniaturization of heat dissipation equipment and realize the efficient cooling of tiny space of electronic components.micro-channel boiling heat transfer due to the release of latent heat of vaporization has a greater heat transfer capacity,while as a highly efficient heat transfer structure,due to the advantages of large body area ratio,high heat transfer coefficient,and it gets more and more attention recently.In this paper,built heating and flow integration of micro-column group heat transfer experimental platform.Using deionized water as working fluid,the two-phase frictional pressure drop loss and boiling heat transfer characteristics were experimentally studied when the working medium flowed through micro-channels composed of micro-cylinder with 500 ?m in height and diameter.The CCD camera recorded the relationship between gas-liquid two-phase flow pattern and frictional pressure drop and boiling heat transfer under different heating powers in the channel.Finally,by comparing and analyzing the experimental data of boiling heat transfer of three different cross-sections of micro-channels and the empirical representative formula,the boiling heat transfer correlations suitable for the present experimental conditions are obtained.The experimental results show that the frictional pressure drop of two phases increases with the increase of heat flux at the same mass flow rate,and the boiling heat transfer coefficient shows a sharp decline.Influenced by the shape and arrangement of micro-cylinders,the frictional pressure drop of two-phase increases with the increase of mass flow rate and increases linearly with the heat flux density.At this time,the boiling in the channel develops to a completely saturated boiling state,and the mass flow rate affects the heat transfer coefficient weakening,boiling heat transfer coefficient tends to be stable.As the steam dryness increases,the degree of boiling in the channel tends to be uniform,the frictional pressure drop due to sub-cooling and the boiling heat transfer.Based on the visual observations,the bubble flow and annular flow are observed in the micro pin fin heat sink.The local boiling heat transfer coefficient of bubble flow is significantly higher than that of annular flow.Using the existing experimental data of different fin cross-sectional shapes and different mass flow rates,a comparative analysis is made between the experimental data and the Mudawar correlation.When the cross-sectional shape of the fin in the micro-channel is a circular shape,as the vapor quality increases,the correlation prediction result lower than the experimental data,while the diamond and oval fins data showed a sharp decline in the trend and the associated predictive value is slowly declining.Based on the Mudawar correlation,the correlation coefficient was modified by adding the two-phase friction factor.Finally,the experimental data of the same mass flow under the three cross-sectional shapes were selected to verify the modified correlation and the results were fit for this experiment conditions for the micro-channel boiling heat transfer correlation.