Question Bank • QB_DFE_EXP_020 NAT • 2 Marks

Section 7: Dairy and Food Engineering

Heat and Mass Transfer

Subtopic: Material and energy balances in food processing systems

Question Statement:

In a continuous pasteurizer, $1500\text{ kg/h}$ of cream is cooled from $85.0^\circ\text{C}$ to $5.0^\circ\text{C}$. Specific heat of cream is $3.60\text{ kJ/(kg}\cdot\text{K)}$. If chilled water absorbs this heat with a permissible temperature rise of $5.0^\circ\text{C}$ ($C_{p,w} = 4.18\text{ kJ/(kg}\cdot\text{K)}$), the required mass flow rate of chilled water in $\text{kg/h}$ is ________ (round off to nearest integer).

Answer Key:

20670

Step-by-Step Solution & Explanation

Heat balance: $\dot{m}_w C_{pw} \Delta T_w = \dot{m}_c C_{pc} \Delta T_c$ $\dot{m}_w \times 4.18 \times 5.0 = 1500 \times 3.60 \times (85.0 - 5.0)$ $\dot{m}_w \times 20.90 = 1500 \times 3.60 \times 80.0 = 432,000\text{ kJ/h}$ $\dot{m}_w = \frac{432,000}{20.90} \approx 20,669.86\text{ kg/h} \approx 20,670\text{ kg/h}$
← Previous (QB_DFE_EXP_015) Next (QB_DFE_EXP_068) →

Practice In Authentic CBT Exam Interface

Test your skills under authentic timed conditions with live scoring and AIR percentile ranking.

Launch CBT Mock Test