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

  • question_answer
    If the specific heats of dry air and water vapour are \[1.00\,\,kJ/kg\,-K\] and \[1.88\,\,kJ/kg\,-K\]respectively and the humidity ratio is 0.011, then the specific heat of moist air at \[25{}^\circ C\] and 50% relative humidity will be

    A) \[1.0207\,\,kJ/kg-K\]       

    B) \[1.869\,\,kJ/kg-K\]

    C) \[1.891\,\,kJ/kg-K\]         

    D) \[0.9793\,\,kJ/kg-K\]

    Correct Answer: A

    Solution :

    \[{{c}_{p}}\] of moist air \[={{c}_{p}}\] of dry air + humidity ratio\[\times \,{{c}_{p}}\] Of water vapour \[=1.00\,\,+\,\,0.011\,\,\times \,\,1.88\] \[=1.0207\,kJ/kg.K\]


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