Experimental Study On Flow And Heat Transfer Characteristics In Quartz Micro-tube

MEMS has been developed rapidly in many field such as astronautics,war industry, life science and electronic,etc,during recent years.Therefore,great attention has been paid to flow and heat transfer characteristic in the MEMS,and many researchers do much effort to the investigate the flow and heat transfer characteristics in micro scale channels.Besides,a great deal of budgets are funded the research in many countries every year.In this paper,the viscous dissipation,flow and heat transfer characteristics are experimentally and theoretically investigated.The main purpose of the research is to obtain experimental data and calculated results of the flow and heat transfer characteristics in quartz micro-tubes,which will be useful for the future research.The viscous dissipation of flow in quartz micro-tubes with diameters of 19.6 m and 44.2 m,respectively,are numerically simulated.According to the Knudson criterion,the continuous approximation is still applicable to the flow in micro-tubes investigated in present research.The control equations are built.The boundary conditions of the equations are built in consideration of the EDL effect.The SIMPLER algorithm is employed to discretize the control equations,and then temperature fields with different Re numbers in micro-tubes are obtained.The experimental system consists of pressure source,flow pipes,data acquisition system and an IR camera,etc.The surface temperature distribution photos of the micro-tubes are taken by IR camera with different pressure at the outlet and different Re numbers.By comparing the experimental data and the numerical results,it can be know that the viscous dissipation effect in micro-tubes can not be neglected when the diameter is smaller than 50 m.Furthermore,the resistance characteristics of flow in microtube of 19.6 m with ultra pure water,carbon tetrachloride,and nitrogen as working fluid respectively are obtained by experimental investigation.Comparing the experimental results of resistance characteristics with theoretical results,the influence of EDL effect and rareness effect on the value of f is analyzed.Besides,deionized water,used as working fluid,flowed through various cross-section channel made up of micro-tubes with inner diameters of 304.1μm and 192.9μm and the values of f with abrupt expansion and abrupt contraction are obtained by investigating the flow in the quartz microtube.The results of the experiment are compared with the conventional theory and the relationship between the value of f and Re number is obtained.Heat transfer characteristics in micro-tubes with different diameters of 44.2 m, 91.7 m,141.1 m,respectively,which are heated by copper wires rolled on the outer surface of micro-tubes,are experimentally investigated.The relation between Nu number and Re number is obtained based on the experimental results.It can be know that the values of Nu are lower than theoretical results,which may be due to the change of thermo-physical properties of the working fluid.Besides,the value of Nu number increases with the rise of the Re number and exceeds the theoretical results and this phenomenon may be caused by the thinner liquid layer,the viscous dissipation effect and the roughness of the wall.