Question Bank • QB_DFE_GATE_002 NAT • 2 Marks

Section 7: Dairy and Food Engineering

Heat and Mass Transfer

Subtopic: Diffusive and convective mass transfer

Question Statement:

A single-effect evaporator concentrates $1500\text{ kg/h}$ of milk from $10\%$ to $30\%$ total solids. The steam economy of the evaporator is $0.75$. The rate of steam consumption is ________ $\text{kg/h}$ (round off to 1 decimal place).

Answer Key:

1333.3

Step-by-Step Solution & Explanation

Evaporator Mass Balance: 1. Solids balance: $1500 \times 0.10 = P \times 0.30 \implies P = 500\text{ kg/h}$. 2. Water evaporated ($V$): $V = 1500 - 500 = 1000\text{ kg/h}$. 3. Steam consumption ($S$): $S = \frac{V}{\text{Economy}} = \frac{1000}{0.75} = 1333.33\text{ kg/h}$ Rounding to 1 decimal place: **1333.3** $\text{kg/h}$.
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