A triple-effect evaporator with forwarding feed is evaporating a sugar solution with the negligible boiling-point rise (less than 1.0 K, which will be neglected) and containing 5 wt % solids to 25% solids. Saturated steam at 205 kPa abs is being used. The pressure in the vapor space of the third effect is 13.65 kPa. The feed rate is 22 680 kg/h and the temperature 299.9 K. The liquid heat capacity is c _p = 4.19 – 2.35 x, where cp is in kJ/kg · K and x in wt fraction. The heat-transfer coefficients are U ₁ = 3123, U ₂ = 1987, and U ₃ = 1136 W/m ² ·K. Calculate the surface area of each effect if each effect has the same area and the steam rate.

Answer rating: 100% (QA)

Step 1 From steam table at P3 134 kPa get Tsat 5167 C Using the BPR equation for third effect with xL 05 44 BPR3 178 05 622 052 245 C T3 5167 245 5412 C BPR T Ts Step 2 Making an overall and a solids ... View the full answer