Numerical studies of heat transfer enhancements in laminar separated flows

Numerical studies of unsteady heat transfer enhancements in grooved channel and sharp 180° bend flows of especial relevance to electronic systems are made. Prior to these, to find the most efficient numerical approaches, performances of various pressure correction, convective and temporal schemes are studied. To do this, the spatial development of an instability wave in a plane channel flow is modelled. Grooved channel flow predictions suggest a commonly used periodic flow assumption (for modelling rows of similar electronic components) may not always be valid over a significant system extent. For the bend flow, heat transfer enhancements due to passive and active control are considered. For the former, a thin tripping fin is attached at several inlet channel locations. If the fin is sufficiently high and far from the sharp bend edge, the flow becomes unsteady. Then, large-scale vortices emanating from the sharp edge cause a reduction in re-attachment length and a dramatic heat transfer enhancement. Active flow control is also studied for several inlet amplitudes and forcing frequencies. Like the passive fin, this active approach is effective at increasing heat transfer.