Heat Transfer
Multiple effect evaporation is generally recommended, when the

Corrosive liquids are to be concentrated
Fuel is cheaply available
Evaporation on small scale is to be done
Large scale evaporation of liquor is needed

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Heat Transfer
The advantage of backward feed multiple effect evaporators over forward feed units is that

Heat sensitive material can be handled
Most concentrated liquid is at highest temperature
Equal heat transfer co-efficients exist in various effects
There is no additional cost of pumping

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