What condition does dry saturated low-pressure steam (5-10 kg/cm2) reach when throttled to atmospheric pressure________________?
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Answer: B. superheated
Explanation
Throttling low-pressure dry saturated steam from 5 to 10 kg/cm2 down to atmospheric pressure is an isenthalpic expansion process. At these lower initial pressures, the constant enthalpy line crosses into the region of the Mollier diagram above the saturation line. This thermodynamic path causes the steam temperature to rise above the saturation temperature, producing superheated steam. Throttling processes conserve total enthalpy while experiencing a substantial pressure drop and a corresponding increase in entropy. Low-pressure saturated steam has different enthalpy characteristics compared to high-pressure steam when expanded across a restriction. The Joule-Thomson coefficient for steam under these specific low-pressure conditions permits this desirable superheating effect.
Wet is incorrect because low-pressure expansion moves the state into the superheated vapor zone rather than the wet dome. Remaining dry saturated is false because the drop in pressure without heat loss alters the temperature-pressure equilibrium. Dry without superheating is inaccurate since the resulting steam temperature clearly exceeds the saturation point at atmospheric pressure.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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