Analysis Of Micro Scale Flow Characteristic And Heat Transfer And Calculation Of Temperature Field Of Platelet Unit

When the characteristic length of the flow field reaches micro or sub-micron level, some factors that can be neglected in macro level may take the dominant parts, which may result in some strange phenomenon. In this thesis, the flow characteristic and heat transfer is researched, and the couple temperature field of platelet transpiration unit is calculated, considering the micro effect.In this thesis, adopting second order velocity slip and temperature jump boundary condition, the micro Poisuelle flow characteristic and heat transfer are analyzed. The non-dimensional velocity slip and the resistance coefficient fRe decrease with the growth of Kn. Br denotes the effect of the viscosity dissipation. When the Br is small, the heat conduction controls the heat transfer characteristic; the temperature distribution is linear under different Kn, and the temperature jump at wall increases with Kn. While the Br is large, the temperature distribution shows obviously nonlinear. Nu of low temperature wall decreases as Kn increases, which means that the micro scale effect weakens the heat transfer at low temperature wall. It increases with the increasing of Br, as the viscosity dissipation can be taken as heat source, which increases the heat transfer through the low temperature wall. There exists singularity of Nu of high temperature wall.Total energy double-distribution-function LBM is adopted to simulate the micro flow. From the simulation results of two dimensional Couett flow, the model incorporates the viscous dissipation. From the analysis of two-dimensional micro Poisuelle flow, it can be concluded that as there is temperature jump at wall, heat transfer through the wall is weakened and local Nu decreases with the increasing Kn. The micro scale effect strengthens the heat exchange in the entry area, which shorten the entry length for the flow to reach thermal developed state. Conjunct heat transfer model is built to calculate the temperature field of platelet and coolant unit. If the micro scale effect is considered, the highest temperature of platelet is higher than it is neglected, and as Kn increases, the discrepancy gets larger. The thermal soaking depth decreases as coolant mass flow increases, and increases with the increasing platelet thickness. It increases almost linearly and the temperature decreases while the platelet thermal conductivity gets larger.The model of platelet unit stability analysis is built. According to the temperature distribution, parabolic distribution is assumed, and the critical thickness is obtained applying Galerkin method. If some flow passage is blocked, the temperature gets higher, larger critical thickness is needed to ensure the stability. The critical thickness is related toμandα. Calculation results illustrate that material with higherμor higherαis easier to get wrinkled.