Visual Study And Analysis On Flow And Heat Transfer In Microchannel

With the wide use in bioengineering and biotechnology, aerospace, microelectronics, materials processing and manufacturing etc, the technologies about MEMS and Micro thermal system (MTS) have become significant important. As a result, the studies on micro heat and mass transfer concerning MEMS and MTS become worldwide hot toptics. Even though a lot of researches have been performed on micro flow and heat transfer, the conclusions and the results have obvious confusions or contradictions each other. The main purpose of the present study is to clarify some heat and mass transfer mechanisms about fluid flowing through micro tubes. The detailed of this paper include the following concents.Firstly, the viscous dissipation effect induced by the fluid flow in microtube is studied by analysis, numerical simulation and experiments. Distilled water used as working fluid flows through smooth quartz microtubes with inner diameter 25pm and 50p.m. Non-contact temperature measuring method-infrared imaging technology is used to obtain the surface temperature distribution of microtube wall. Using SIMPLEC algorithm, the viscous dissipation effect is studied numerically and the relationship between Re and the temperature rise is yielded. The experimental results agree well with those of numerical simulation.In the second part, water, ethanol and tetrachloromethane are used as working fluid and flow through the stainless steel micrtubes with inner diameters 168μm, 399μm, 799μm and the quartz glass microtubes with inner diameters 242μm, 315μm, 520μm. The relationship between friction factor and Reynolds number is obtained by measuring the pressure drop and the flow rate. The experimental results show that the friction factors in microtubes, except the stainless steel microtube with inner diameter 168pm, are in rough agreement with the conventional theory when Re is less than 1200-1800. For microtube with inner diameter 168 μm and 8%~10% relative roughness, the values of the friction factor is 10%~15% high than those predicted by the classical theory when Reynolds number is more than 800. At the...