Research On Separation Of Gas-liquid Two-phase Flow In T-microchannel

With the advent of MEMS and the growth of micro-chemical technology,electronic devices tend to be miniaturized;gas-liquid two-phase flow is also widely used in microchannel heat transfer due to its good heat transfer performance;The in-depth study of the internal two-phase flow pattern control and its influence on heat transfer performance makes it possible to greatly improve the heat transfer performance of microchannel equipment.The T-type microchannel structure is the most simplified flow-type regulation structure,which is mainly divided into a downstream type and an impact type:the downstream type T-type microchannel mainly causes the gas-liquid two-phase to flow into the liquid-dividing branch pipe through the pressure difference of the two-phase flow interface.The surface tension at the junction of gas and liquid prevents the rupture of the gas bomb,thereby achieving the effect of two-phase separation,reducing the liquid content in the main channel and promoting the evolution of the flow pattern;and the two-phase flow in the impact type T-type microchannel.The inertial impact force of the fluid due to its own flow velocity acts as the main force,which promotes the separation movement of the gas-liquid two-phase flow in the microchannel.The two-phase channel structure has different action mechanism and different flow control effects.The in-depth study is the basis for obtaining the flow law of two-phase flow in complex microstructure.In this paper,the two-phase flow pattern in the monocrystalline silicon square microchannel and the downstream T-type liquid separation channel and the impact T-type liquid separation channel are used to control the two-phase flow pattern of the main channel,and the two-phase flow pattern is monitored by high-speed imaging.The law of evolution,the rapid pressure monitoring system monitors the pressure fluctuations during the flow pattern transition,and studies the gas-liquid interface motion of the two-phase flow in the microchannel.The control of the main channel flow pattern and the liquid separation capacity of the downstream T-type liquid microchannel and the impact T-type liquid microchannel were observed.The microchannel internal gas was obtained based on the evolution process of the flow pattern in the two channel structures.The correlation between liquid interface motion and macro-control parameters two-phase flow velocity,differential pressure,and channel size provides a theoretical basis for microchannel two-phase flow pattern regulation.The experimental results show that in the square microchannel scale studied in this paper,due to the interfacial tension,the two-phase flow pattern only has bubble flow,slug flow,block flow and annular flow,and there is no stratified flow.According to the main flow pattern of the slug flow,the deformation and expansion law of the gas-liquid interface at the liquid separation port under different pressure differences are obtained by adjusting the external control pressure of the T-type liquid separation channel.It can be seen that as the opening degree of the liquid separation valve at the liquid branching branch increases,the pressure of the main channel decreases,and the pressure difference between the pressure at the liquid separation channel and the main channel increases,and the back pressure increases,and the correlation between the research and the liquid separation ratio is studied.The back pressure is the determinant of the regulation of two-phase flow pattern in the T-channel.With the increase of back pressure,the expansion and contraction length of the gas bomb in the downstream T-type microchannel becomes longer,the expansion and contraction period remains basically unchanged,the liquid separation ratio is improved,and the liquid separation channel enhances the flow regulation performance of the main channel..For the impact type T-type microchannel,due to the 90° turn of the flow field in the mainstream fluid at the liquid-distributing structure,a secondary flow occurs in the two-phase flow,and the gas phase is measured on the inner wall,and the liquid phase exists on the outer wall.At this time,the liquid phase with large inertial force is the active fluid,and the back pressure of the liquid separation port has a significant influence on the liquid phase flow condition.As the back pressure increases,the expansion and contraction length of the gas bomb in the liquid branch pipe becomes longer,and the expansion and contraction period remains basically unchanged.The liquid separation ratio is improved to a certain extent,which is consistent with the liquid separation law in the downstream section.By comparing the liquid separation abilities of the two microchannel structures,it can be found that the liquid separation capacity of the impact section is significantly larger than that of the downstream flow section.