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Glass spheres of 2 mm radius and at 500 degree Celsius are to be cooled by exposing them to an air stream at 25 degree Celsius. Find the minimum time required for cooling to a temperature of 60 degree Celsius. Assume the following property values Density = 2250 kg/m3 Specific heat = 850 J/kg K Conductivity = 1.5 W/m K

Glass spheres of 2 mm radius and at 500 degree Celsius are to be cooled by exposing them to an air stream at 25 degree Celsius. Find the minimum time required for cooling to a temperature of 60 degree Celsius. Assume the following property values Density = 2250 kg/m3 Specific heat = 850 J/kg K Conductivity = 1.5 W/m K Correct Answer 14.78 seconds

t – t a/t I – t a = exponential (- h A T/p V c).

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