Railways Technical Ability Internal Combustion Engine (ICE) Question Bank Internal Combustion Engine (ICE)

  • question_answer If the specific heats of dry air and water vapour are \[1.00\,\,\text{kJ/kg}-K\] and \[1.88\,\,\text{kJ/kg}-K\] 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) \[1.0207\,\,\text{kJ/kg}-K\]          

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

    C) \[1.891\,\,\text{kJ/kg}-K\]

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

    Correct Answer: A

    Solution :

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

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