Question 2
Orange juice is being concentrated in a backward feed double effect evaporator from
7% to 50%.It can be assumed that boiling point rise(BPR's) can be neglected.The
feed enters the second effect at 28C at a rate of 7 200 kg/h.Dry saturated steam
enters the calandria of the first effect at 260 kPa while the second effect is operated
at 35 kPa.
Additional information:
Cp is taken to be 4.2 kJ/kg K
The heat transfer surfaces are the same in both effects
The overall heat transfer coefficients are as follows:
First effect=1.8 kW/m2K Second effect=2.5 kW/m2 K
Since the feed enters as a cold stream,the first effect reguires more heat than
the second effect.T must be increased and T must be decreased
proportionately.In this case,assume T is increased by 1.5c and T is
decreased by 1.5c
2.1. Draw a flowsheet for this process and define the applicable operating conditions
for each effect.
(2) (21)
2.2. Calculate the steam consumption required?