• # question_answer In a Bell Coleman cycle refrigeration plant compression and expansion of air are isentropic if the temperatures of air entering and leaving the expander are 300 K and 180 K respectively, what is the coefficient of performance of the plant? A) 1.5                               B) 2.0C) 2.5                               D) 3.0

Solution :

${{T}_{3}}=300K,$${{T}_{4}}=180\,K$ ${{r}_{p}}=\frac{{{p}_{2}}}{{{p}_{1}}}\,\left( \frac{{{T}_{3}}}{{{T}_{4}}} \right){{\,}^{\frac{\gamma }{\gamma \,-\,1}}}\,={{\left( \frac{300}{180} \right)}^{3.5}}=5.977$ $COP=\frac{1}{{{r}_{p}}^{\gamma \,-\,1/\gamma }-1}=\frac{1}{(5.977){{\,}^{0.4\,\,/1.4}}-1}=1.5$ $COP=\frac{1}{\frac{{{T}_{3}}}{{{T}_{4}}}-1}=\frac{1}{\frac{300}{180}-1}=1.5$

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