Engineering Thermodynamics Set 20

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This set of Engineering Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on Engineering Thermodynamics Set 20

Q1 | What is the effect of reheat pressure on mean temperature of heat addition Tml?
  • reheat pressure is directly proportional to tml
  • reheat pressure is inversely proportional to tml
  • reheat pressure is equal to tml
  • tml is independent of reheat pressure
Q2 | Which of the following problems are posed by increasing the number of reheats?
  • cost & fabrication problems arise
  • heat transfer problems arise
  • frictional losses arise
  • none of the mentioned
Q3 | What is the most preferable dryness fraction of the exhaust steam?
  • 0.99
  • 0.77
  • 0.66
  • 0.88
Q4 | Which of the following represents the specific volume during phase transition.
  • vf-vg
  • vg-vf
  • vf+vg
  • none of the mentioned
Q5 | An 80 litre vessel contains 4 kg of R-134a at a pressure of 160 kPa. Determine the volume occupied by the vapour phase.
  • 0.0775 m3
  • 0.0575 m3
  • 0.0975 m3
  • 0.0375 m3
Q6 | 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
Q7 | 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
Q8 | Which of the following contributes to the improvement of efficiency of Rankine cycle in a Thermal Power Plant?
  • reheating of steam at intermediate stage
  • regeneration use of steam for heating boiler feed water
  • use of high pressures
  • all of the mentioned
Q9 | A simple Rankine cycle operates the Boiler at 3 MPa with an outlet temperature of 350°C and the Condenser at 50 kPa. Assuming ideal operation and processes, what is the thermal efficiency of this cycle?
  • 7.7
  • 17.7
  • 27.7
  • 37.7
Q10 | How many types of feedwater heaters are present?
  • one
  • two
  • three
  • four
Q11 | The temperature of feedwater leaving a heater is          the saturation temperature at steam extraction pressure.
  • less than
  • equal to
  • more than
  • none of the mentioned
Q12 | The following also gave two-constant equations of state.
  • berthelot
  • dieterici
  • redlich-kwong
  • all of the mentioned
Q13 | Which of the following is true about compressibility of real gases?
  • z = 1
  • z < 1
  • z > 1
  • both z < 1 and z > 1 view answer
Q14 | 1 mole of cyclohexane (z = 1.2) is filled in a container at 27oC and 4 atm, what is the volume of container?
  • 3.8 liter
  • 4.4 liter
  • 5.6 liter
  • 7.4 liter view answer
Q15 | If a relation exists among variables x,y,z then z may be expressed as a function of x and y as, dz=Mdx+Ndy .
  • true
  • false
Q16 | A pure substance which exists in a single phase has          independent variables.
  • zero
  • one
  • two
  • three
Q17 | Which of the following is not a Maxwell equation?
  • (∂t/∂v) = -(∂p/∂s)
  • (∂t/∂p) = -(∂v/∂s) c) (∂p/∂t) = (∂s/∂v) d) (∂v/∂t) = -(∂s/∂p)
Q18 | The Clausius-Clapeyron equation is given by
  • dp/dt = l / t(vf+vi)
  • dp/dt = l / t(vf-vi)
  • dt/dp = l / t(vf+vi)
  • dt/dp = l / t(vf-vi)
Q19 | Water          on melting and has the fusion curve with a          slope.
  • contracts, negative
  • contracts, positive
  • expands, negative
  • expands, positive
Q20 | At the triple point, l(sublimation) = l(vaporization) – l(fusion).
  • true
  • false
Q21 | The slope of sublimation curve is          the slope of the vaporization curve at triple point.
  • equal to
  • less than
  • greater than
  • none of the mentioned
Q22 | An application requires R-12 at −140°C. The triple-point temperature is −157°C. Find the pressure of the saturated vapour at the required condition.
  • 0.0058 kpa
  • 0.0098 kpa
  • 0.0068 kpa
  • 0.0088 kpa
Q23 | The expression which represents the pressure exerted by a gas is
  • nvrt
  • nrt/v
  • v/nrt
  • 1/nvrt
Q24 | Which of the following relation is correct?
  • mole fraction of the kth gas = moles of the kth gas / total number of moles of gas
  • partial pressure of kth gas = (mole fraction of the kth gas)*(sum of the partial pressures)
  • sum of mole fractions of all the gases is unity
  • all of the mentioned
Q25 | The total entropy of a mixture of gases is the          of the partial entropies.
  • average
  • weighted mean
  • sum
  • difference of the highest and the lowest