Hi Aspirant ,

The correct answer for the question is OPTION A - 1/5 power of plate length . This is because the average heat transfer co-efficient reduces with length as 1/5th power of length .   For laminar flow over a flat plate, the average value of a Nusselt number is prescribed by the relation
Nu = 0.664 (Re) (Pr)  , the dynamic viscosity has an inverse relation to 1/6 power. To double the convective heat transfer coefficient, the dynamic viscosity has to be decreased 64 times.

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