Question Bank • QB_DFE_PF_011 NAT • 2 Marks

Section 7: Dairy and Food Engineering

Preservation of Food

Subtopic: Preservation of food by cooling and freezing

Question Statement:

A cold room chilling unit has a refrigeration capacity of $10.0\text{ TR}$ ($1\text{ Ton of Refrigeration} = 3.517\text{ kW}$). The compressor consumes $8.0\text{ kW}$ of electrical shaft power. The actual operating Coefficient of Performance (COP) of this refrigeration system is ________ (round off to two decimal places).

Answer Key:

4.40

Step-by-Step Solution & Explanation

Multi-Approach Solution: **Method 1: Direct Definition of COP** 1. Convert refrigeration capacity ($Q_L$) to $\text{kW}$: $Q_L = 10.0\text{ TR} \times 3.517\text{ kW/TR} = 35.17\text{ kW}$ 2. Electrical work input ($W$): $W = 8.0\text{ kW}$ 3. Coefficient of Performance: $\text{COP} = \frac{Q_L}{W} = \frac{35.17\text{ kW}}{8.0\text{ kW}} = 4.39625 \approx 4.40$ **Method 2: Fractional Form** $\text{COP} = \frac{35.17}{8} = 4.396 \approx 4.40$
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