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Unformatted text preview: plant installs a regenerator
that has an effectiveness of 82 percent. If the cost of natural gas
is $0.52/therm (1 therm 105,500 kJ), determine how much cen54261_ch07.qxd 12/19/03 12:36 PM Page 342 342
FUNDAMENTALS OF THERMAL-FLUID SCIENCES energy and money the regenerator will save this company per
year and the annual reduction in entropy generation.
Hot milk 4°C Heat
section) Regenerator Cold
milk FIGURE P7–119
7–120 Stainless-steel ball bearings [r
8085 kg/m3 and
Cp 0.480 kJ/(kg · °C)] having a diameter of 1.2 cm are to be
quenched in water at a rate of 1400 per minute. The balls leave
the oven at a uniform temperature of 900°C and are exposed to
air at 30°C for a while before they are dropped into the water.
If the temperature of the balls drops to 850°C prior to quenching, 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.
7–121 Carbon-steel balls [r...
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