When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be
A. Choked
B. Under-damping
C. Over-damping
D. None of these
Answer: Option A
Solution(By Examveda Team)
When the back pressure of a nozzle is below the designed value of pressure at the exit of the nozzle, the flow through the nozzle reaches sonic conditions at the throat. This means that the flow velocity at the throat equals the speed of sound. At this point, any further decrease in back pressure will not increase the mass flow rate through the nozzle. This condition is known as choked flow.In choked flow, the mass flow rate through the nozzle is at its maximum value for the given conditions, and further decreasing the back pressure will not increase the flow rate.
Therefore, when the back pressure of a nozzle is below the designed value of pressure at the exit of the nozzle, the nozzle is said to be choked.
Related Questions on Steam Boilers, Engines, Nozzles and Turbines
The expansion of steam in a nozzle follows
A. Carnot cycle
B. Rankine cycle
C. Joule cycle
D. Stirling cycle
A. Steam enters and exhausts through the same port
B. Steam enters at one end and exhausts at the centre
C. Steam enters at the centre and exhausts at the other end
D. None of the above
The mechanical draught _________ with the amount of smoke.
A. Increases
B. Decreases
C. Does not effect
D. None of these
A. Higher effectiveness of boiler
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C. Fouling of heat transfer surfaces
D. Raising of steam temperature
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