What happens to dry saturated high-pressure steam (150-200 kg/cm2) when throttled down to atmospheric pressure_______________?
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Answer: A. wet
Explanation
Throttling is an isenthalpic process where high-pressure steam expands through a narrow valve or orifice without doing external work. For high-pressure dry saturated steam in the range of 150 to 200 kg/cm2, the constant enthalpy line slopes downward into the wet region. Consequently, the sudden pressure drop causes a portion of the steam to condense, resulting in a wet steam mixture. Enthalpy remains constant during a pure throttling process because heat transfer and external work output are negligible. High-pressure saturated steam possesses high enthalpy values that cross into the two-phase dome when expanded across a valve. Mollier diagrams plotting enthalpy against entropy illustrate this downward sloping path into the wet vapor region clearly.
Superheated is incorrect because throttling high-pressure saturated steam leads into the wet saturation dome instead. Remaining dry saturated is impossible because the enthalpy drop during expansion alters the thermodynamic state away from the saturated liquid-vapor line. Dry steam without moisture is incorrect since phase condensation occurs due to the specific slope of high-pressure saturation curves.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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