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Railways NTPC (Technical Ability) Refrigeration and Air-Conditioning Question Bank Refrigeration and Air-Conditioning

  • question_answer
    The efficiency of a carnot engine is given as 0.75. If the cycle directions is reversed, what will be the valve of C.O.P. for the carnot refrigerator?

    A) 0.27                             

    B) 0.33

    C) 1.27                             

    D) 2.33

    Correct Answer: B

    Solution :

    \[{{\eta }_{HE}}=1-=\frac{{{T}_{2}}}{{{T}_{1\,}}}=0.75\,\,or\,\,\frac{{{T}_{2}}}{{{T}_{1}}}=0.25\] \[{{(COP)}_{\operatorname{Re}f}}=\frac{{{T}_{2}}}{{{T}_{1}}-{{T}_{2}}}=\frac{({{T}_{2}}/{{T}_{1}})}{1-({{T}_{1}}/{{T}_{1}})}=\frac{0.25}{1-0.25}\]             \[=\frac{0.25}{0.75}=\frac{1}{3}=0.33\]


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