Abstract
This dissertation is concerned with the analysis of flow and heat transfer characteristics and LIGA fabrication technique for a micro nozzle. The flow and heat transfer parameters in the nozzle flow are the Reynolds number and the Peclet number. The extremely small size of micro nozzle yields small values of Re and Pe. It is almost impossible to observe the flow behavior experimentally inside the micro nozzle. The order of Reynolds number in the micro nozzle is usually less than 10-4. To visualize the complex convective flow system, an experimental test model was built. The Reynolds number in the test model is not less than 10-2. Fortunately, the flows with Re= 10-4 to 10-2 are in the same flow regime of low Reynolds number. Therefore, it is expected to have the same flow characteristic. A numerical solution covers the range of Re=10-8 to 1.0 confirms that flow characteristics for Re=10-4 and 10-2 are the same. The value of Peclet number in the test model can be adjust to the value similar to that in the micro nozzle.An important application of the micro nozzle is for micro spinneret in textile industry. Polyethylene terephthalate (PET) is the material of the micro fiber. The relationship of shear rate and viscosity of PET at various temperature levels is correlated by a power law. The stream function, vorticity, and temperature distributions in a micro nozzle are calculated. The friction factor and Nusselt number analyses in the micro nozzle are also carried out. In the test model, glycerin was used as the working fluid to simulate the flow. The pressure distribution along the flow direction was measured and the flow pattern was visualized by using polyethylene (PE) powder of 20-40mm. could be expected after this exploration. LIGA technique including lithography, electroforming and molding processes, is a new technique for fabricating large number and high precision microstructures. The other advantages of using LIGA technique in making nozzles are its capability of high aspect ratio and flexibility of nozzle geometry. One uses an UV(ultraviolet) exposure to obtain Au mask for X-ray exposure to make a deep PMMA microstructure. After the processes of electroforming, polishing and etching, a production mold can be obtained. The production mold then can be used for making the nozzles by molding and electroforming processes. The textile industry requires a large quantity of micro spinnerets with high aspect ratio and different nozzle geometry. It is an ideal application of LIGA technique.