Question
Download Solution PDFNozzles used in steam turbines convert ______
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
Steam nozzles:
A steam nozzle is a passage of varying cross-sections, which converts the heat energy of steam into kinetic energy. The main use of a steam nozzle is in a steam turbine, which produces a jet of steam with a high velocity.
- The smallest section of the nozzle is called the throat.
- The steam enters the nozzle with high pressure and negligible velocity. But leaves the nozzle with a high velocity and small pressure.
- The pressure, at which the steam leaves the nozzle, is known as back-pressure.
- No heat is supplied or rejected by the steam during flow through a nozzle. Therefore it is considered as an adiabatic flow, and the corresponding expansion is considered as an adiabatic expansion.
The following are the three type of nozzles:
(1) Convergent nozzle:
When the cross-section of a nozzle decreases continuously from the entrance to exit, it is called a convergent nozzle.
(2) Divergent nozzle:
When the cross-section of a nozzle increases continuously from the entrance to exit, it is called a divergent nozzle.
(3) Convergent-divergent nozzle:
When the cross-section of a nozzle first decreases from its entrance to the throat and then increases from its throat to exit, it is called a convergent-divergent nozzle. This type of nozzle is widely used these days in various types of steam turbines.
Additional Information
|
Process |
Properties |
|
Adiabatic process |
δQ = 0 |
|
Polytropic process |
δQ ≠ 0 |
|
Throttling |
h = constant |
|
Free expansion |
δQ = 0, δW = 0, du = 0 |
where, δQ = Change in heat, δW = Change in work, du = Change in internal energy, h = enthalpy.
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