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Unformatted text preview: 7833 kg/m3 and Cp
0.465 kJ/(kg · °C)] 8 mm in diameter are annealed by heating
them first to 900°C in a furnace and then allowing them to cool
slowly to 100°C in ambient air at 35°C. If 2500 balls are to be
annealed per hour, determine (a) the rate of heat transfer from
the balls to the air and (b) the rate of entropy generation due to
heat loss from the balls to the air.
Answers: (a) 542 W, (b) 0.986 W/K
Air, 35°C Furnace Steel ball 900°C 100°C FIGURE P7–121
7–122 An ordinary egg can be approximated as a 5.5-cmdiameter sphere. The egg is initially at a uniform temperature
of 8°C and is dropped into boiling water at 97°C. Taking
the properties of the egg to be r
1020 kg/m3 and Cp
3.32 kJ/(kg · °C), determine how much heat is transferred to
the egg by the time the average temperature of the egg rises
Ti = 8°C FIGURE P7–122 to 70°C and the amount of entropy generation associated with
this heat transfer process.
7–123E In a production facility, 1.2-in.-thick, 2-ft
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- Spring '09