Calculation of Heat Transfer Rate and Enthalpies of Liquids


A double- effect evaporator is to be designed to concentrate a 5.0% (mass) NaOH solution to 30%. Steam is available at 3300F, 77.3 psia and the condensing temperature of the vapor from the lowest pressure effect is 1800 F. an initial guess for the T of the first effect results in the values shown below: 


Determine the information as required below. Fill in results on the diagram, but show work:

  • Mass fraction NaOH in the liquid leaving the first effect and flows of process streams (L’s and V’s), assuming equal vapor rates from each boiler.
  • Boiling temperature of solutions in each effect and boiling point elevation (note that the saturation temperature of water is given for condensing vapor streams).
  • Enthalpies of liquids (gray boxes) and vapors.
  • Heat transfer rate in each effect (Q1 and Q2)
  • Amount of steam required
  • Heat transfer area required for each effect if the overall heat transfer coefficient is 400 BTU/(ft2 hr 0F) in each effect.

Summary: This question belongs to heat transfer and discusses about a double- effect evaporator which is designed to concentrate a solution.

Answer is in image format


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