Aspects of laminar free convection from a vertical plate

Doctoral Thesis


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University of Cape Town

The thesis is comprised of a number of aspects pertaining to the phenomenon of laminar free convection from a vertical plate. A survey of literature is presented which brings out the fact, that the phenomenon although it has been investigated to a large extent, still gives rise to widespread dispute and uncertainties which need careful examination. An analytical approach is presented showing that the hydrodynamic boundary layer is equal to the thermal boundary layer. In the past it was simply assumed to be so, in order to limit the computations, and the assumption was justified by the excellent agreement between calculations and experimental data. An analysis is presented showing the analogy existing between the Grashof and Reynolds numbers, as it is expected in the case of low velocities and considerable temperature differences, i.e. in free convection. An extensive experimental investigation pertaining to average heat transfer rates from a vertical plate at low Grashof numbers is presented and provides the necessary evidence in a much disputed region. It is shown conclusively that as far as average heat transfer rates are concerned, the agreement with the already accepted relationship can be extended to Grashof numbers as low as 10.