Flow And Heat Transfer Characteristics In Microchannel In Velocity-Slip And Temperature-Jump Regime

As the rapid growth of the technique applied in microelectronics, microdevices fabrication, bioengineering, and microscale heat exchanger system, micro sensors, micro actuators, Micro-Electro-Mechanical System (MEMS) and so on, micron size mechanical devices are becoming more popular, both in commercial and in scientific research. Understanding deeply the momentum and heat transport performs in microdomain is the fundamental of developing these new technology and a new question in the heat transfer field. The momentum and energy equations combining with the boundary conditions of slip velocity and temperature jump derived from the kinetic theory, so called slip model, are solved for the hydraulic and thermal fully developed laminar flow of the incompressible fluid in microchannels. The theoretical analyses of slip flow resistances and heat transfer characteristics in slip flow and temperature jump regime are firstly obtained for micro-space parallel plates, micro-annular channel, rectangular microchannel, triangular microchannel, and the arbitrary cross section microchannel with various boundaries of velocity slip and thermal conditions. The slip flow resistance and heat transfer correlations and data are firstly obtained for above analyses and compared with the experimental results. Besides, a liquid microchannel cooler for integrate electronic unit were designed. Finally, the experiments were conducted for the flow and heat transfer performs in micro-rectangle channel of 0.4mm width, 2mm high, 20mm long with water and ethylene glycol. 1． The theoretical analyses and the correlations of slip flow and heat transfer performances were firstly obtained in the micro-space parallel plates with unsymmetrical heat flux and unsymmetrical temperature in slip flow regime. The predicted results show that the slip velocity near walls made the flow resistance in this microchannel decreases with increasing Kn. The Nusselt number ratio decreases with increasing Kn and decreasing thermal accommodation coefficient when one wall heated alone. The heat transfer correction coefficient ratio decreases with increasing Kn and decreasing thermal accommodation coefficient when the two walls heated unsymmetrically. But it increases with decreasing tangential momentum accommodation coefficient. At the same Kn, the Nusselt number ratio of the upper heated wall decreases, while that of the lower heated wall increases with increasing heat flux ratio. 2． The theoretical analyses and the correlations of slip flow and heat transfer performances were firstly obtained in the micro-annular channel with unsymmetrical heat flux and unsymmetrical temperature in slip flow regime. The predicted results show that the flow resistance coefficient in the micro-annular channel decreases with increasing Kn. When one wall heated alone, the curve of Nusselt number versus the ratio of inner diameter to outer diameter moves downwards with increasing Kn. Besides, at the same ratio of inner diameter to outer diameter, the decrease in the Nusselt number of inner wall heated alone is always greater than that of outer wall heated alone with increasing Kn. When two walls heated unsymmetrically, the decrease of Nusselt number ratio of the inner wall with increasing Kn diminishs with increasing ratio of inner diameter to outer diameter and enlarges with decreasing heat flux ratio. But effects of the above parameters on Nusselt number ratio of outer wall are converse. The theoretical analyses and the correlations for laminar flow in the microchannels3． of arbitrary cross section in slip flow regime are firstly obtained by applying a computation-oriented method of the orthonormal function analysis. The effects of the first-order or second-order slip and heat creep boundary conditions are discussed. As examples, the flow performances are calculated for the rectangular microchannels and the triangle microchannels and compared with the experimental data. The results show that the flow resistance coefficient with the first-order slip boundary condition...