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ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

Experimental and Theoretical studies of Time-Dependent Buoyancy Driven Flow

Get access (open in a dialog) DOI: 10.1615/IHTC10.3770
pages 173-178

Abstract

We consider a phenomenon known to meteorologists as 'penetrative convection'. The initial condition is that fluid is 'thermally stratified' - hotter, lower density material is located above colder fluid. But this highly stable situation is interrupted by sudden cooling from above. The consequent temperature patterns have implications when we consider the thermal design of heating and ventilation systems. In addition, the phenomenon is of interest to designers of nuclear reactors, wherein the impact of thermal shocks must be kept within well defined limits.
We have assessed the performance of a simple model for the development of temperature profiles, assuming perfect mixing in certain parts of the domain and idealisation to one dimensional geometry.
Experiments were carried out in a water-filled cubiform test cell, of 200 mm length. A number of features were noted either visually or from temperature measurements. These included (a) a boundary layer of the thickness expected for natural convection flows (typically 5 mm), (b) a region of water well mixed by buoyancy effects, (c) a distinct interface between the two.
The model produced predictions of the mean temperature of the mixed region vs. time.