When wet steam undergoes throttling and remains in a wet state past the valve outlet, how do its temperature and dryness fraction behave respectively____________________?
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Answer: A. Decreases & increases
Explanation
Throttling wet steam through a valve causes an immediate drop in pressure while total enthalpy remains constant. This constant enthalpy expansion causes a portion of the liquid moisture to evaporate into vapor. As moisture evaporates, the dryness fraction increases and the saturation temperature drops to match the lower pressure. Throttling is an irreversible, constant-enthalpy process characterized by fluid expansion through a restricted flow area. In wet steam regions, the dryness fraction measures the mass proportion of vapor present in the total mixture. Thermodynamic Mollier diagrams illustrate how throttling processes move horizontally toward lower pressure lines.
Steam power engineers use throttling calorimeters to measure the initial dryness fraction of wet steam in pipelines. Pressure-reducing valves in industrial steam networks utilize throttling to deliver lower pressure steam to auxiliary equipment. Understanding steam throttling behavior is essential for designing efficient turbine governing and pressure control systems. Option B incorrectly suggests temperature increases during an adiabatic throttling expansion process. Option C incorrectly suggests the dryness fraction decreases when moisture actually evaporates into steam. Option D incorrectly suggests the dryness fraction decreases during pressure reduction throttling.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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