GATE Mechanical Engineering (ME) 2016 Shift 2 Solved Paper

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Question : 53 of 65
 
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Two cylindrical shafts A and B at the same initial temperature are simultaneously placed in a furnace. The surfaces of the shafts remain at the furnace gas temperature at all times after they are introduced into the furnace. The temperature variation in the axial direction of the shafts can be assumed to be negligible. The data related to shafts A and B is given in the following Table.
Quantity
Shaft A
Shaft B
Diameter (m)
0.4
0.1
Thermal conductivity (W/m-K)
40
20
Volumetric heat capacity (J/m3-K)
2 × 106
2 × 107
 
The temperature at the centreline of the shaft A reaches 400°C after two hours. The time required (in hours) for the centreline of the shaft B to attain the temperature of 400°C is ________ 
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