1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m2 and the overall heat transfer co-efficient to the liquid is 1500 W/m2.°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be__________________?

Correct answer: D. 51 min

  • A. 15 min
  • B. 22 min
  • C. 44 min
  • D. 51 min

Explanation

For batch heating with condensing steam at constant temperature, t = (mCp/UA) ln[(150−30)/(150−120)] = 3080 s, or about 51 minutes. Therefore option d is correct.

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