Engineering Thermodynamics Set 15

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This set of Engineering Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on Engineering Thermodynamics Set 15

Q1 | The superheat or degree of superheat is given by
  • difference between the temperature of saturated liquid and saturation temperature
  • difference between the temperature of superheated vapour and saturation temperature
  • sum of the temperature of superheated vapour and saturation temperature
  • none of the mentioned
Q2 | When the temperature of a liquid is less than the saturation temperature at the given pressure, the liquid is called compressed liquid.
  • true
  • false
Q3 | Which of the following statement is true?
  • a subcooled liquid is one which is cooled below its saturation temperature at a certain pressure
  • subcooling is the difference between the saturation temperature and the actual liquid temperature
  • both of the mentioned
  • none of the mentioned
Q4 | Why is the steam not allowed to expand deep into the two phase region before it is taken to reheating?
  • to control flow rate
  • to control phase change
  • to protect reheat tubes
  • none of the mentioned
Q5 | Net Work output of the plant   with reheat.
  • decreases
  • increases
  • remains same
  • none of the mentioned
Q6 | What is the effect of decrease of reheat pressure on the quality of steam at turbine exhaust?
  • decreases
  • increases
  • remains same
  • none of the mentioned
Q7 | The optimum reheat pressure for most of the power plants is how many times of the initial steam pressure?
  • 0.1-0.15
  • 0.2-0.20
  • 0.2-0.25
  • 0.1-0.10
Q8 | What is the most preferable dryness
  • 0.99
  • 0.77
  • 0.66
  • 0.88
Q9 | For pressure ratio = 1, efficiency = 0, then?
  • reheat is used
  • reheat is not used
  • only reheat is used
  • none of the mentioned
Q10 | At critical point, value of Vg-Vf is
  • two
  • one
  • zero
  • infinity
Q11 | Above the critical point, the isotherms are continuous curves.
  • true
  • false
Q12 | A piston –cylinder device contains 0.06m3 of saturated water vapour at 350 kPa pressure. Determine the temperature and mass of the vapour inside the cylinder.
  • 0.104 kg
  • 0.124 kg
  • 0.134 kg
  • 0.114 kg
Q13 | A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapour form, determine the pressure in the tank.
  • 60.183 kpa
  • 70.183 kpa
  • 80.183 kpa
  • 90.183 kpa
Q14 | A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapour form, determine the volume of the tank.
  • 1.73 m3
  • 2.73 m3
  • 3.73 m3
  • 4.73 m3
Q15 | An 80 litre vessel contains 4 kg of R-134a at a pressure of 160 kPa. Determine the quality.
  • 0.127
  • 0.137
  • 0.147
  • 0.157
Q16 | Determine the specific volume of R-134a at 1 MPa and 50°C, using ideal gas equation of state.
  • 0.022325 m3/kg
  • 0.024325 m3/kg
  • 0.025325 m3/kg
  • 0.026325 m3/kg
Q17 | What is the unit of Heat rate?
  • kj/kw
  • kw/kj
  • kj
  • kw
Q18 | Rankine cycle operating on low pressure limit of p1 and high pressure limit of p2
  • has higher thermal efficiency than the carnot cycle operating between same pressure limits
  • has lower thermal efficiency than carnot cycle operating between same pressure limits
  • has same thermal efficiency as carnot cycle operating between same pressure limits
  • may be more or less depending upon the magnitudes of p1 and p2
Q19 | Rankine efficiency of a Steam Power Plant
  • improves in summer as compared to that in winter
  • improves in winter as compared to that in summer
  • is unaffected by climatic conditions
  • none of the mentioned
Q20 | Rankine cycle comprises of  
  • two isentropic processes and two constant volume processes
  • two isentropic processes and two constant pressure processes
  • two isothermal processes and two constant pressure processes
  • none of the mentioned
Q21 | In Rankine cycle, the work output from the turbine is given by  
  • change of internal energy between inlet and outlet
  • change of enthalpy between inlet and outlet
  • change of entropy between inlet and outlet
  • change of temperature between inlet and outlet
Q22 | What is the actual turbine inlet temperature in Rankine cycle?
  • 700c
  • 800c
  • 550c
  • 1150c
Q23 | Rankine cycle efficiency of a good Steam Power Plant may be in the range of?
  • 15 to 20%
  • 35 to 45%
  • 70 to 80%
  • 90 to 95%
Q24 | A simple Rankine cycle produces 40 MW of power, 50 MW of process heat and rejects 60 MW of heat to the surroundings. What is the utilization factor of this co generation cycle neglecting the pump work?
  • 50
  • 60
  • 70
  • 80
Q25 | Why both reheating and regeneration is used together?
  • the effect of reheat alone on efficiency is very small
  • regeneration has a marked effect on efficiency
  • both of the mentioned
  • none of the mentioned