TURBULENT CONVECTION BETWEEN 2 HORIZONTAL PLATES

Data from parallel-plate heat flux experiments are reviewed and an alternative method of plotting results is introduced. The graphical form cq [ = Nu Ra 1 3] vs the logarithm of Ra is shown to highlight the role of the interplate spacing d in determining the heat flux. Plotting the data in this form shows that between heat flux transition points, the heat flux (for constant ΔT) increases to a maximum and then decreases with increasing Rayleigh number. This behaviour suggests a heat-transfer efficiency criteria based on the experimental geometry. In this form the data also show an overall decrease in cq with increasing Ra, towards a probable asymptote of between 0.04 and 0.06. © 1979.