Question

In a rising film evaporator, the temperature difference need not be as high as that in a falling film evaporator.

(a) True

(b) False

I have been asked this question in unit test.

I need to ask this question from Unit Operations topic in section Heat Transfer Equipment, Microwave Heating, Evaporation, Diffusion and Mass Transfer and Dehydration of Food Engineering

Answer 1

Right option is (b) False

To explain: In a rising film evaporator, the temperature difference has to be high otherwise the vapor formation won’t be possible at a low residence time. Whereas, in a falling film evaporator, the temperature difference can be relatively lower than that in rising film. (It’s only comparative; the temperature difference in falling film is also required to be pretty high.)