Write an appropriate dimensionless correlation for the average Nusselt number for these data and state any limitations to your equation.

Suppose that the graph below shows measured values of hc for air in forced convection over a cylinder of diameter D plotted on a logarithmic graph of NuD as a function of ReDPr.



GIVEN

Forced convection of air over a cylinder

Experimental data given above

FIND

An appropriate dimensionless correlation for the average Nusselt number


The data lies along an approximately straight line on the log-log graph. Therefore, a straight line fit

will be used. Choosing two points on the graph



A straight line on the log-log plot is represented by



Substituting the two points into the equation and solving for a and b



Therefore



or





This is based on data in the range 1 < Red Pr < 103 and is therefore valid only in this range.

Physics & Space Science

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