7121 carbon steel balls r 7833 kgm3 and cp 0465 kjkg c

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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. 72°C 72°C Hot milk 4°C Heat (Pasteurizing 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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