Question Bank • QB_DFE_023 NAT • 1 Mark

Section 7: Dairy and Food Engineering

Heat and Mass Transfer

Subtopic: Material and energy balances in food processing systems

Question Statement:

Skim milk entering a vacuum evaporator at a rate of $6000\text{ kg/h}$ with $9.0\%$ total solids is concentrated to condensed skim milk containing $40.0\%$ total solids. The rate of water removed by evaporation in $\text{kg/h}$ is ________ (answer in integer).

Answer Key:

4650

Step-by-Step Solution & Explanation

1. Solid balance: $F \times x_F = P \times x_P$ $6000 \times 0.09 = P \times 0.40 \implies 540 = 0.40 P \implies P = 1350\text{ kg/h}$ 2. Rate of water evaporated $W$: $W = F - P = 6000 - 1350 = 4650\text{ kg/h}$
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