(18) A room contains 40 kg of dry air and 0.5 kg of water vapor at 20°C and 95 k
ID: 2087407 • Letter: #
Question
(18) A room contains 40 kg of dry air and 0.5 kg of water vapor at 20°C and 95 kPa total pressure. The relative humidity of air in the room is (a) 1.2% (b) 2.5% (c) 80% (d) 56% (e) 72% (19) A fuel is burned with 70 percent theoretical air. This is equivalent to (a) 30% excess air (b) 70% excess air (c) 30% deficiency (d) 70% deficiency (e) stoichiometric of air of air amount of air (20) The higher heating value of a hydrocarbon fuel C,H with m-8 is given to be 1340 MJ/kmol of fuel. Then its lower heating value is (a) 1164 MJ/kmol (b) 1466 MJ/kmol (c) 1330 MJ/kmol (d) 988 MJ/kmol (e)1551 MJ/kmolExplanation / Answer
18) Answer: C (80%)
Explanation: RH={wP/(0.622+w)Ps}*100
w= mass of vapor/ mass of dry air = 0.5/40
P= 95 kpa
Ps= 2.3331 Kpa at 20 degree Celsius. ( saturation pressure at 20-degree Celsius)
19) Answer: C ( 30% Deficiency of air)
Explanation: The amount of air less than a stoichiometric amount is called deficiency of air
20) Answer: A (1164 MJ/Kmol)
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