Question

The evaporator economy is dependent on the ________

(a) Heat transfer rate

(b) Mass transfer rate

(c) Energy balance considerations

(d) Mass balance considerations

This question was posed to me in examination.

My query is from Solving Unsteady topic in section Unsteady – State Material and Energy Balances of Bioprocess Engineering

Answer 1

Right choice is (a) Heat transfer rate

Best explanation: There are three main measures of evaporator performance:

Capacity (kg vaporized/time), Economy (kg vaporized/ kg steam input), Steam consumption (kg/hr).

The performance of a evaporator is evaluated by the capacity and the economy.

The rate of heat transfer q through the heating surface of an evaporator, by the definition of overall heat transfer coefficient, is product of three factors

i) The area of heat transfer surface A

ii) The overall heat transfer coefficient U

iii) The overall temperature drop  ΔT

Q = U * A * ΔT.