Standard air is defined as atmospheric air at_____________________?
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Answer: B. 20°C and 1 kg/cm2 and relative humidity 36%
Explanation
Standard air is conventionally defined in industrial engineering at specific reference conditions including temperature and humidity. These standardized parameters include a temperature of twenty degrees Celsius, one kilogram per square centimeter pressure, and humidity. Establishing standard air properties allows engineers worldwide to calculate fan capacities and thermodynamic performance consistently. Atmospheric air density and humidity fluctuate widely with geographic location, weather patterns, and seasonal temperature changes. Engineering calculations require a fixed baseline reference state to evaluate pneumatic machinery, compressors, and ventilation fans. Standard reference conditions provide a uniform basis for comparing performance test results across different manufacturing vendors.
Option A atmospheric conditions at specific locations vary constantly, making them unsuitable as a universal engineering standard. Option C zero degrees Celsius represents standard temperature and pressure for pure gases, not standard atmospheric air specifications. Option D fifteen degrees Celsius references alternative aviation standard atmosphere definitions rather than industrial standard air.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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