8.4-11 Tomato juice having a concentration of 12 % wt solids is being concentrat

Question

8.4-11

Tomato juice having a concentration of 12 % wt solids is being concentrated to 25% solids in a film type evaporator. the maximum allowable temperature for tomato juice is 135 F which will be the temperature if the product. the feed enters at 100 F. saturated steam at 25 psia is used for heating. The overall heat transfer coefficient U is 600 btu/h * ft^2 *F and the area A is 50 ft^2. The heat capacity of the feed cp is estimated as 0.95 btu/lbm * F. Neglect aby boiling point rise if present. Calculate the feed rate of tomato juice to the evaporator.

Edit: The question in the picture has been typed out below the picture for clarity because the picture is hard to read.

Explanation / Answer

from Q= UA * LMTR

U= 600 btu/hrft2 and A= 50 ft2 Temperature corresponding to steam pressure of 25 psia = 116 deg.c=240.8 deg.F

LMTD= (240.8- 100)- (240.8-135)/ ln{(240.8-100)/(240.8-135)=4.65

Q= 600*50* 4.65 =139500 btu/hr

let F= feed rate of solids .They contains 12% solids at inlet. Hence F*0.12= P*0.25

P is the products from the evaporator P= F*0.12/0.25= 0.48F

Water to be evaporated= F-0.48F= 0.52F

water at inlet   F*0.88

heat required to heat the solids = F*0.12*0.95*(135-100)=4F

heat required to heat the water =0.88F*4.18*(135-100)= 129F

Heat required to evaporate water = 2788 J/g*0.52F

total heat to be supplied = 4F+129F +1450 F =1583F= 139500

F= 139500/1583 =88.12 lb/hr

Related Questions

Navigate

• Browse (All)
• Browse 8
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.