An evaporator operating at 50 kPa is used to concentrate juice from a solids content of 5% to a solidscontent of 25% using steam at 120 kPa (which leaves as condensate at 80°C). The initial temperature andflow rate of the feed juice are 15 °C and 5 kg/s. The overall heat transfer coefficient is 3500 W/m²-K andthe area available for heat transfer is 25 m2. The feed juice has a boiling point rise of 12 °C and the specificheats of the feed, concentrated product and water are 3500 J/kg-K, 4000 J/kg-K and 4180 J/kg-Krespectively. Calculate:a) The steam economy for the evaporator and,b) Heat transfer area.

Answered: An evaporator operating at 50 kPa is…

Introduction to Chemical Engineering Thermodynamics

8th Edition

ISBN:9781259696527

Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart

Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart

Chapter1: Introduction

Section: Chapter Questions

Problem 1.1P

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Question

An evaporator operating at 50 kPa is used to concentrate juice from a solids content of 5% to a solids
content of 25% using steam at 120 kPa (which leaves as condensate at 80°C). The initial temperature and
flow rate of the feed juice are 15 °C and 5 kg/s. The overall heat transfer coefficient is 3500 W/m²-K and
the area available for heat transfer is 25 m2. The feed juice has a boiling point rise of 12 °C and the specific
heats of the feed, concentrated product and water are 3500 J/kg-K, 4000 J/kg-K and 4180 J/kg-K
respectively. Calculate:
a) The steam economy for the evaporator and,
b) Heat transfer area.

Expert Solution

Step 1

Evaporation is unit operation. The unit operation equipment is an evaporator that comes under heat transfer equipment. The amount of water is removed from the mixture by this there will be an increase in the concentration of the compound. the steam economy is obtained from the amount of water vaporized to the steam used. The heat transfer area is obtained from log mean temperature, heat, and overall heat transfer coefficient.