סמינר מחלקתי Prof. Victoria Timchenko
School of Mechanical Engineering Seminar
Wednesday, December 24, 2014 at 15:00
Wolfson Building of Mechanical Engineering, Room 206
Natural Convection in Non-Uniformly Heated Open-Ended Channels
Prof. Victoria Timchenko
MSc/PhD Student of Prof. Supervisor
School of Mechanical and Manufacturing Engineering,
University of New South Wales, Sydney, Australia.
To improve understanding of the flow and heat transfer phenomena in narrow, open-ended, channel formed by the double skin façade numerical and experimental investigations have been undertaken. Non-uniform heating configurations in which heat sources alternated with unheated zones on both walls were studied to simulate opaque PV arrays and glazed panes/windows of the building. Heat transfer and flow measurements were obtained for periodicity 1/15 of heated/unheated zones and heat input, 220 W/m2 as well as large-eddy simulation has been utilized to capture the flow behaviour and possible transition to turbulence in similar non-uniform heating configuration. Several kinds of flow structures have been identified both experimentally and numerically. Intermittent flow structures are observed disrupting the thermal boundary layer allowing to increase heat transfer and to induce high levels of mixing. Vortices in corners of the channel promote horizontal heat transfer from the panels to the lateral walls. Recirculation zone caused by unheated area at the channel entrance contributes to the periodicity of flow within the channel and lower average temperatures. It has been shown that disturbances introduced at the system inlet improve mixing and heat transfer. In comparison to uniformly heating configuration, non-uniformly heating configuration enhances both convective heat transfer and chimney effect. This enhancement may reach 34% in the heat transfer and 12% in mass flow rate. Concerning the physical mechanisms involved, the results show that the flow does not necessarily undergo transition to turbulence but two walls non-uniformly heated arrangement induces better mixing and higher turbulence production in the channel.
