Laminar gas micro-flow convection characteristics due to steep density gradientsS. P. Mahulikar1, H. Herwig2, O. Hausner2 and F. Kock2
1 Department of Aerospace Engineering, Indian Institute of Technology Bombay P.O. IIT, Powai, Mumbai, 400 076, India
2 Technische Thermodynamik, Technische Universität Hamburg-Harburg Arbeitsbereich 6-08 - Denickestr. 17, D-21073 Hamburg, Germany
received 6 July 2004; accepted in final form 25 October 2004
published online 26 November 2004
We report numerical simulation of pure continuum-based laminar gas micro-flow convection with steep density gradients, which cause, for the case of heated air, flattening and rate of flattening of axial velocity profile. This flattening is similar to the characteristics in constant-properties slip flow, and high rate of flattening can cause hydrodynamic undevelopment of flow -the reverse process of hydrodynamic development. By continuity, radially outward velocities and radial convection are induced, which degrades convection performance. The low densities near the wall reduce the axial mass flux near the wall, which also degrades convection performance. In heated-gas micro-flows, these negative effects dominate to dictate the net convection characteristics, which differ considerably from the known characteristics of conventional continuum models. The identification of such microscale effects also has implications in possibly extending the limits of applicability of continuum models to higher Knudsen numbers.
44.27.+g - Forced convection.
44.15.+a - Channel and internal heat flow.
44.20.+b - Boundary layer heat flow.
© EDP Sciences 2004