2. Questions Bank
  3. Railways
  4. NTPC (Technical Ability)
  5. Thermodynamics

Railways NTPC (Technical Ability) Thermodynamics Question Bank Thermodynamics

  • question_answer
    In a test of a water-jacketed compressor, the shaft work required is 90 kN\[\,-\,\]m/kg of air compressed. During compression, increase in enthalpy of air is 30 kJ/kg of air and increase in enthalpy of circulating cooling water is 40 kJ/kg of air. The change in velocity is negligible. The amount of heat lost to the atmosphere from the compressor per kg of air is:

    A) 20 kJ                

    B) 60 kJ

    C) 80 kJ                

    D) 120 kJ

    Correct Answer: D

    Solution :

    \[{{w}_{shaft}}=90\,\,kN.m/kg\,or\,\,90\,\,kJ/kg\] \[{{\left( \Delta h \right)}_{air}}=+\,\,30\,\,\text{kJ/kg}\] \[{{\left( \Delta h \right)}_{water}}=-\,\,40\,\,\text{kJ/kg}\]             \[q={{w}_{shaft}}+{{\left( \Delta h \right)}_{air}}+{{\left( \Delta h \right)}_{water}}\]             \[=90+30-40=80\,\,\text{kJ/kg}\,\,\text{or}\,\,\text{air}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner