Air at 40°C, total pressure101.3 kPa, contains water vapour at 4.0 kPa. Saturation vapour pressure at 40°C is 7.37 kPa. Molecular masses water18.02,air28.97 kg/kmol. Find relative humidity in percent, to two decimals.
Relative humidity is the ratio of actual to saturation vapour partial pressure at the same temperature: RH=4.0/7.37×100=**54.27%**. Total pressure and molecular masses would be needed for a humidity-ratio conversion, but cancel from this relative-humidity calculation.
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