Project ForgeThermodynamics
First Law of Thermodynamics
GATE 2011
Medium
If a mass of moist air in an airtight vessel is heated to a higher temperature, then
- Aspecific humidity of the air increases
- Bspecific humidity of the air decreases
- Crelative humidity of the air increases
- relative humidity of the air decreases
Explanation
In a sealed rigid vessel, both the dry-air and water-vapour masses (and hence specific humidity, their ratio) stay fixed as temperature rises. But the saturation vapour pressure rises much faster (exponentially, via Clausius-Clapeyron) than the actual vapour partial pressure (which only rises linearly with T at fixed volume), so relative humidity = pv/psat decreases.
Source: GATE ME 2011 (2011)
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