Fluid flow and heat transfer over a micro-sphere

Due to the increased power dissipation for the new generation of microprocessors, cooling technologies represent a challenge to the manufacturers of such components. This is especially true as the component size is getting smaller and hence the heat generated per unit area is increasing significantly. Moreover, the importance of the microscale fluid flow rises from the new applications of micro-scale electromechanical systems that encounter fluid flow, such as micro-pumps, micro-turbines and micro-robotics. An understanding of the basic flow field and heat transfer in the case of external flow around miniature components is an essential tool to find proper means for cooling these small electronic/electromechanical devices. This work introduces a fundamental investigation of the external flow field and heat transfer characteristic around a micro sphere. In this study, the fluid flow and forced convection heat transfer characteristics over a micro-sphere at moderate to high values of Reynolds number are numerically investigated. The classical boundary condition of uniform wall temperature is considered in this work. In spite of the significance of this topic in understanding the basic flow and heat transfer features about a miniature sphere, it received little attention in the open literature. In this model, the effect of the engineering parameters such as Reynolds number and Knudsen number on the velocity and temperature profiles are investigated. The numerical code has the capability of accurate determination of the angle of external flow separation. The Knudsen number values used are limited by the continuity range where the Navier-Stokes Equations are used. Therefore, The Knudsen number is assumed small enough to apply a continuum model for the flow field with a temperature jump and frictional slip at the sphere's surface.