A manufacturing process has a large amount of waste heat available at 200°C in a location where the local environmental temperature is 20°C. Determine the COP of a Carnot refrigerator operating between these temperatures.

This question was previously asked in
NHPC JE Mechanical 6 April 2022 (Shift 2) Official Paper
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  1. 9.54
  2. 3.56
  3. 6.54
  4. 1.63

Answer (Detailed Solution Below)

Option 4 : 1.63
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Detailed Solution

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Concept:

COP of a Carnot Refrigerator:

\({\bf{CO}}{{\bf{P}}_{\bf{R}}} = \frac{{{{\bf{T}}_{\bf{L}}}}}{{{{\bf{T}}_{\bf{H}}} - {{\bf{T}}_{\bf{L}}}}}= \frac{{Refrigerating\;Effect}}{{Work\;Input}}\)

where TL = Lower temperature, TH = Higher temperature.

Calculation:

Given:

TL = 20°C = 293 K, TH = 200°C = 473 K.

\({\bf{CO}}{{\bf{P}}_{\bf{R}}} = \frac{{{{\bf{T}}_{\bf{L}}}}}{{{{\bf{T}}_{\bf{H}}} - {{\bf{T}}_{\bf{L}}}}}\)

\({\bf{CO}}{{\bf{P}}_{\bf{R}}} = \frac{293}{473-293}=\frac{293}{180}=1.63\)

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