Engineering Thermodynamics Set 20 MCQs

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