4- (Transient heat conduction) Stainless-steel ball bearings (k = 22.2 W/m K, a = 4.85 x 10-6 m 2 /s) which have uniformly been heated to 850°C are hardened by quenching them in an oil bath that is maintained at 40°C. The ball diameter is 20 mm, and the convection coefficient associated with the oil bath is 600 W/m2 K. (a) If quenching is to occur until the surface temperature of the balls reaches 100°C, how long must the balls be kept in the Oil? (b) If 10000 balls are to be quenched per hour, what is the rate at which energy must be removed by the oil-bath cooling system in order to maintain its temperature at 40°C?

4- (Transient heat conduction) Stainless-steel ball bearings (k = 22.2 W/m K, a = 4.85 x 10-6 m 2 /s) which have uniformly been heated to 850°C are hardened by quenching them in an oil bath that is maintained at 40°C. The ball diameter is 20 mm, and the convection coefficient associated with the oil bath is 600 W/m2 K. (a) If quenching is to occur until the surface temperature of the balls reaches 100°C, how long must the balls be kept in the Oil? (b) If 10000 balls are to be quenched per hour, what is the rate at which energy must be removed by the oil-bath cooling system in order to maintain its temperature at 40°C?

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Question

4- (Transient heat conduction) Stainless-steel ball bearings (k = 22.2 W/m K, a = 4.85 x 10-6 m 2 /s) which have uniformly
been heated to 850°C are hardened by quenching them in an oil bath that is maintained at 40°C. The ball diameter is 20
mm, and the convection coefficient associated with the oil bath is 600 W/m2 K. (a) If quenching is to occur until the
surface temperature of the balls reaches 100°C, how long must the balls be kept in the Oil? (b) If 10000 balls are to be
quenched per hour, what is the rate at which energy must be removed by the oil-bath cooling system in order to maintain
its temperature at 40°C?
Oil
T = 40°C
h = 1500 W/m²°C
-Ball bearing
D = 22.4 mm
= 600°C
T₁
To

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Step 2: To check whether the lumped capacitance method applicable or not and parameters

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Step 3: Calculations for dimensionless temperature parameter and Fourier Number

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Step 4: Time to kept ball in oil

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Step 5: Total amount of Energy removed from oil bath

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