The effect of variable volumetric expansion coefficient in free convection heat transfer.

The volumetric expansion coefficient has an importance in determination
of the free convection heat transfer coefficient. The buoyant force in the fluid
which is the result of the variation of fluid density with temperature, is proportional
to this expansion coefficient, B. This coefficient of B varies with temperature
and it is important to understand under what conditions it should be evaluated in
order to get a good agrement between analytical and experimental studies.
In this report the effect of variation of B with temperature on Nusselt
Number is shown.
Calculating the volumetric expansion coefficient in fluid temperature will
cause an over - estimation of up to 20 per cent in Nusselt Number for the case of
free convection heat transfer in water. Employing the heated wan temperature for
evaluation of B, uuderestimates Nusselt Number. An excellent agreement is achieved
between experimental and analytical research work when a reference temp ere
which is the arithmatic mean of wall and fluid temperature, is used to calculate
the volumetric expansion coeffient.