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The ratio of momentum diffusivity to thermal diffusivity is the ______________ number?

August 24, 2021March 3, 2019 by admin

The ratio of momentum diffusivity to thermal diffusivity is the ______________ number?

A. Prandtl
B. Nusselt
C. Stanton
D. Grashoff

Categories Chemical Heat Transfer

What is the thermal conductivity of a perfect heat insulator ?

A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is_________________?

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