Which of the following has the lowest overall heat transfer co-efficient?

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• The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000W/m2.K. The overall heat transfer co-efficient at this time is
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• The concept of overall coefficient of heat transfer is used in heat transfer problems of
• The concept of overall coefficient of heat transfer is used in case of heat transfer by
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• A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2 .°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be
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