Railways Technical Ability Refrigeration and Air-Conditioning Question Bank Refrigeration and Air-Conditioning

  • question_answer Water in an insulated evaporative cooler evaporates at the rate of 0.003 kg/s. Air flow rate is 1 kg/s. What is the air temperature decrease if the specific heat of humid air is 1 kJ/kg. K and latent heat of water is 2500 kJ/kg?

    A) \[2.5{}^\circ C\]                       

    B) \[3.0{}^\circ C\]

    C) \[7.5{}^\circ C\]                       

    D) \[10{}^\circ C\]

    Correct Answer: C

    Solution :

    \[{{m}_{w}}=0.003\,kg/s,\,{{m}_{a}}=1\,kg/s,\] \[{{c}_{pa}}\,\,=\,\,1kJ/kg.K,\,{{h}_{fg}}\,\,=\,\,2500kJ/kg,\] \[{{m}_{a}}\times {{c}_{pa}}\times \Delta t={{m}_{w}}\times {{h}_{fg}}\] \[1\times 1\times \Delta t=0.003\times 2500\] \[\Delta t=7.5{}^\circ C\]

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