a) It is an isothermal line, at which the condensation completes
b) Saturation line of water is also called Wilson line
c) It represents the limiting condition of undercooling at which the condensation begins
d) It represents an Isobaric line, at which the condensation commences
Q.2.
Considering metastable expansion to be in effect, the flow of wet steam though a convergent-divergent nozzle shall result in a discharge slightly less than the calculated one.
a) True
b) False
Q.3.
The sudden expansion of dry saturated steam in the absence of dust, doesn’t lead to condensation until its density is about 8 times that of the saturated vapor of the same pressure.
a) True
b) False
Q.4.
Calculate the enthalpy drop steam enters a convergent-divergent nozzle atbar and 250°C and leaves at 1 bar. The expansion is to be considered metastable.
a) 427031.34 kJ/kg
b) 55648.32 kJ/kg
c) 323654.25 kJ/kg
d) 158469.21 kJ/kg
Q.5.
Steam atbar and 300°C enters a convergent-divergent steam nozzle and leaves at 3 bar. If the expansion of the steam is metastable, calculate the supercooled temperature.
a) 165°C
b) 143°C
c) 154°C
d) 120°C
Q.6.
Steam atbar and 300°C enters a convergent-divergent steam nozzle and is discharged at 3 bar. Considering the effects of supersaturation calculate the degree of undercooling.
a) 36.65°C
b) 45.54°C
c) 23.32°C
d) 62.87°C
Q.7.
Calculate the degree of supersaturation if steam atbar 250°C is discharged at 2 bar by a convergent-divergent nozzle. Consider metastable steam expansion and negligible inlet velocity.
a) 5.65
b) 3.11
c) 2.15
d) 2.36
Q.8.
Steam atbar pressure and 250°C enters a convergent-divergent steam nozzle and leaves at 4 bar. The mass flow rate is 5 kg/s. Calculate the exit area of the nozzle if the expansion is metastable.
a) 0.00542187 m2
b) 0.0029147 m2
c) 0.036521 m2
d) 0.003265 m2
Q.9.
What is the value of index of expansion for supersaturated steam. (Pvn=C, n is the index of expansion)
a) 1.300
b) 1.013
c) 1.135
d) 1.000
Q.10.
Which of the following statement about metastable expansion of steam through a steam nozzle is FALSE?
a) It increases the discharge through the nozzle
b) Steam is undercooled to a temperature less than that corresponding to its pressure
c) Density of steam is increased
d) Exit velocity of the steam is increased
Q.11.
The point on the h-s diagram at which the condensation beings and normal conditions of thermal equilibrium are restored is said to be on _____
a) wilson line
b) saturation vapor curve
c) constant dryness fraction line
d) constant pressure line
Q.12.
Which of the following is NOT an effect of supersaturation in steam flowing through a convergent-divergent nozzle?
a) Increase in specific volume of steam
b) Increase in the entropy of steam
c) Improvement in dryness fraction
d) Increase in the enthalpy drop
Q.13.
Determine the exit pressure of steam if the steam enters a nozzle atbar and 300°C. At the outlet it is observed that the specific volume of the steam is 0.m3/kg. The expansion of steam is metastable.
a) 4 bar
b) 3 bar
c) 2 bar
d) 1 bar
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