| Summary: | 碩士 === 淡江大學 === 機械與機電工程學系碩士班 === 95 === The Direct Simulation Monte Carlo (DSMC) [1] method is employed to analyze the low-speed fluid dynamics characteristics of a three-dimensional (3-D) microstructure and its heat transfer activities with different diameters and ratios. The 3-D simulation is valuable and more authentic than the 2-D simulation, because the observations of the corner and center of the wall inside the microchannel cannot be made in the 2-D simulation. In addition, The Fanning friction coefficient and Poisseuille number to the corner and the center of the wall in the fluid are compared. Also, Nusselt number is utilized to discuss the heat transfer with different temperature and pressure. The VHS model and nitrogen have been applied to the experiment.
The result showed that the fluid flow to the corner of the wall inside the microchannel was different from the fluid flow to the center of the wall. The influence of fluid flow by the corner of the wall inside the microchannel in 3-D simulation was still different from 2-D simulation. The same result was observed when increasing the width-to-height ratio to five-fold. Furthermore, as the Knudsen number increased in the fluid flow, the friction coefficient (Cf) increased. At the same caliber of microchannel, Cf in the 1 microchannel had risen because of the molecular length per unit received greater pressure from compression. In contrast, the Poissruille number decreased as the Kn number increased. According to the inside of the microchannel, the amplitude of Poiseuille number in fluid flow with arising Kn decreased from 3 to 0.04, and then Poiseuille number became stable. When the temperature increased (273K – 373K), friction coefficient ( Cf ) and Poiseuille number ( Cf*Re ) decreased. Nusselt number decreased from 22 to 0.035 was the result of the increase in temperature (273K – 373K) and decrease in pressure (0.1atm – 0.1atm).
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