Natural convection in attics subject to instantaneous and ramp cooling boundary conditions

Saha, Suvash C., Patterson, John C., and Lei, Chengwang (2010) Natural convection in attics subject to instantaneous and ramp cooling boundary conditions. Energy and Buildings, 42 (8). pp. 1192-1204.

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Abstract

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 time scales, 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.

Item ID: 11957
Item Type: Article (Research - C1)
ISSN: 1872-6178
Keywords: natural convection; ramp cooling; boundary layer; unsteady flow; cooling-down time; Nusselt number
Date Deposited: 29 Sep 2010 05:30
FoR Codes: 09 ENGINEERING > 0915 Interdisciplinary Engineering > 091501 Computational Fluid Dynamics @ 100%
SEO Codes: 96 ENVIRONMENT > 9609 Land and Water Management > 960903 Coastal and Estuarine Water Management @ 100%
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