Natural convection in attics subject to instantaneous and ramp cooling boundary conditions
Saha, Suvash C., Patterson, John C. , & Lei, Chengwang (2010) Natural convection in attics subject to instantaneous and ramp cooling boundary conditions. Energy and Buildings, 42(8), 1192-1204 .
A fundamental study of the fluid dynamics inside an attic shaped triangular enclosure with cold upper walls and adiabatic horizontal bottom wall is reported in this study. The transient behaviour of the attic fluid which is relevant to our daily life is examined based on a scaling analysis. The transient phenomenon begins with the instantaneous cooling and the cooling with linear decreases of temperature up to some specific time (ramp time) and then maintain constant of the upper sloped walls. It is shown that both inclined walls develop a thermal boundary layer whose thicknesses increase towards steady-state or quasi-steady values. A proper identification of the timescales, the velocity and the thickness relevant to the flow that develops inside the cavity makes it possible to predict theoretically the basic flow features that will survive once the thermal flow in the enclosure reaches a steady state. A time scale for the cooling-down of the whole cavity together with the heat transfer scales through the inclined walls has also been obtained through scaling analysis. All scales are verified by the numerical simulations.
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|Item Type:||Journal Article|
|Keywords:||Natural convection, Ramp cooling, Boundary layer, Unsteady flow, Cooling down time|
|Subjects:||Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > MECHANICAL ENGINEERING (091300) > Numerical Modelling and Mechanical Characterisation (091307)|
|Divisions:||Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering|
Past > Schools > School of Engineering Systems
|Copyright Owner:||Copyright 2010 Elsevier S.A.|
|Deposited On:||22 Aug 2011 09:59|
|Last Modified:||28 Mar 2013 05:27|
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