Q 57. A small copper ball of 5 mm diameter at 500 K is dropped into an oil bath whose temperature is 300 K. The thermal conductivity of copper is 400 W/m.K ,its density 9000 kg/ and its specific heat 385 J/kg.K. If the heat transfer coefficient is 250 W/.K and lumped analysis is assumed to be valid, the rate of fall of the temperature of the ball at the beginning of cooling will be,in K/s,
(A) 8.7
(B) 13.9
(C) 17.3
(D) 27.7
Answer: (C)
Explanation:
