Evaporation Theory

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Information about Evaporation Theory
Education

Published on July 22, 2018

Author: hariteja43

Source: authorstream.com

Slide1: Evaporation 1 S. SRI HAITEJA M. Pharm Assistant Professor Chalapathi Institute of Pharmaceutical Sciences Slide2: CONTENTS 2 What is meant by Evaporation? Theory and Mechanism of Evaporation Factors effecting the Rate of Evaporation Equation for Rate of Evaporation Material and Heat Balance Types of Evaporators Steam Jacketed Kettle Horizontal Tube Evaporator Vertical Tube Evaporator Forced Circulation Evaporator Falling Film Evaporator Climbing Film Evaporator Agitated Film Evaporator Multiple Effect Evaporator Slide3: What is Evaporation? 3 Evaporation is a Phase transition process in which a single solvent or a mixture of solvent in a solution is converted in to the vapour below the boiling point temperature in order to get a concentrated product. Slide4: What is Evaporation? 4 Concentrated liquid Temperature should be maintained below the B.P. Solvent Vapours Dilute liquid Slide5: Theory and Mechanism of Evaporation 5 High Energy: Will Escape as the Vapour Medium Energy: Will be pulled back Low Energy: Will remain in the bulk Slide6: Factors influencing the Evaporation 6 Temperature Surface area Atmospheric pressure Concentration of the feed Film and deposits Slide7: Factors influencing the Evaporation 7 Rate of Evaporation ∝ Temperature Tem p erature :- For molecules of a liquid moving in the proper direction, must have sufficient kinetic energy to overcome liquid-phase intermolecular forces . Since the kinetic energy of a molecule is proportional to its temperature, evaporation proceeds more quickly at higher temperatures. As the faster-moving molecules escapes and the remaining molecules have lower average kinetic energy will remain in the bulk. Slide8: Factors influencing the Evaporation 8 Temperature Surface area Atmospheric pressure Concentration of the feed Film and deposits Slide9: Factors influencing the Evaporation 9 S 1 S 2 S 1 < S 2 ‘S’ means Surface area Rate of Evaporation ∝ Temperature Surface area :- Surface area is the area of the liquid that exposed to the atmosphere. For molecules of a liquid to evaporate, they must be located on the surface. The molecules which have more kinetic energy they will move on to the top of the surface and then escapes into the atmosphere as vapour. Slide10: Factors influencing the Evaporation 10 Temperature Surface area Atmospheric pressure Time of evaporation Film and deposits Slide11: Factors influencing the Evaporation 11 Atmos p heric Pressure :- Evaporation happens faster if there is less exertion on the surface, keeping the molecules from launching themselves . Rate of Evaporation ∝   Atmospheric Pressure = 3 atm Atmospheric Pressure = 1 atm < Slide12: Factors influencing the Evaporation 12 Temperature Surface area Atmospheric pressure Concentration of feed Film and deposits Slide13: Factors influencing the Evaporation 13 Concentration of the Feed :- Rate of Evaporation ∝   Slide14: Factors influencing the Evaporation 14 Temperature Surface area Atmospheric pressure Concentration of the feed Film and deposits Slide15: Factors influencing the Evaporation 15 Films formation :- Film > S S Slide16: Factors influencing the Evaporation 16 Scalin g:- Slide17: Equation for Rate of Evaporation (M) 17 Rate of Evaporation ∝ Surface area Rate of Evaporation ∝ 1/Atmospheric pressure M   M = Amount of Vapour forming per unit time K = Constant S = Surface area V = Saturation vapour pressure V ’ = Actual vapour pressure P = Atmospheric pressure Slide18: Mass balance of a Single Effect Evaporator 18 Feed Steam Condensate Vapour Concentrated Product Calandria Input = Output m f = m V + m Cp Where m is the mass flow rate (Kg/Sec) m f m S m C m V m Cp Slide19: Heat balance of a Single Effect Evaporator 19 m f . H f m S . H S m S . H C m V . H V m Cp . H Cp Calandria Input = Output m f . H f + m S . H S = m V . H V + m Cp . H Cp + m S . H C Where m = mass flow rate (Kg/Sec) H = Enthalpy (KJ/Kg) m . H = Heat flow rate (KJ/Sec) Feed Steam Condensate Vapour Concentrated Product Slide20: Evaporators 20 Classification Natural Circulation Evaporators Evaporating pans (Steam jacketed – Kettle) Horizontal Tube Evaporators Vertical Tube Evaporators Forced Circulation Evaporators Film Evaporators Rising Film Evaporators Falling Film Evaporators Agitated Film Evaporators Slide21: References 21 Badger WL. Introduction to Chemical Engineering: Mc Graw Hill; 1987 . Wei J, Anderson JL, Denn MM, Seinfeld JH, Stephanopoulos G. Advances in Chemical Engineering: Elsevier Science; 1995 . Sambamurthy K. Pharmaceutical Engineering: New Age International (P) Limited; 2007 . Subrahmanyam CVS, Setty JT, Suresh S, Devi VK. Pharmaceutical Engineering: Principles and Practices: Vallabh Prakashan ; 2002 .

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