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dhayanandhan
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Engineering Fields - Mechanical Engineering - New Member

Join Date: May 2008
Location: CHENNAI, TAMIL NADU, INDIA.
Posts: 1851
Good Answers: 65

Re-Circulation Rate and Over-All Heat in Falling Film Evaporator for Evaporation

06/13/2010 2:20 AM

Hi CR4 MEMBERS,

What should be the Re-Circulation Rate for for Falling Film Evaporator.?

What is the deciding Criterion for the Re-Circulation and what is the min. and max limits for Re-Circulation.? What will be the Over all Heat Transfer Co-Efficient.?

This matter has become devided among technical experts. It is likely the work may hold up for this decision. This falling film evaporator is to be used in the sugar industry where the the juice to be evaporated will be heated to max of 112 to 114 Deg. C and heating medium is at 2 bar,130 Deg.C Steam.

Thanks,

DHAYANANDHAN.S,

CR4 MEMBER, INDIA
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bioramani
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Join Date: Jun 2009
Location: Bangalore, India
Posts: 725
Good Answers: 24
#1

Re: Re-Circulation Rate and Over-All Heat in Falling Film Evaporator for Evaporation

06/14/2010 12:19 PM

We used a falling film evaporator for a solvent extraction plant in the mid seventies. However, because of the the product was an oleoresin we had to avoid recirculation. The entire evaporation had to be done in one pass. We designed a wiped film tower in which the falling film was wiped by swinging blades, which squeezed the film between the edge of the blade and the cylindrical wall. This reduced Prandtl layer thickness and enormously increased the over all coefficient. In a 500 cm high 30 cm dia tower we could get throughputs of about 200 - 300 LPHr. Bulk of the evaporation took place in a small section at the top. The rest went to tarce solvent evaporation. Perhaps you should consider a once through evaporation by redesign. Bioramani

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PWSlack
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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
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#2

Re: Re-Circulation Rate and Over-All Heat in Falling Film Evaporator for Evaporation

06/16/2010 9:19 AM

→ Perry, "The Chemical Engineer's Handbook", any edition. Sugar evaporation is 'old hat'.

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