ME 300 Homework #08 - Spring 2016
Homework Due: Wednesday, March 9, 2016
Book Problem 13.6
(Answer: N/a)
Book Problem 13.21
(Answer: b. 0.15 lbmol/lbmol)
SP-21:
Gaseous acetylene (C2H2) is burned in a combustor with dry air entering at 110 kPa. The air-fuel
ratio is 17 kg air/kg fuel. Assume “complete” combustion.
(a) Calculate the percent theoretical air (%) in the combustor.
(b) What is the equivalence ratio?
(c) Determine the mole fraction of carbon dioxide in the product mixture.
(d) Find the dew point temperature (C) of the product mixture.
(e) What percent (%) of water vapor is condensed in the product mixture if the products are cooled
to 20C?
Suppose moist air (instead of dry air) enters the combustor with an absolute humidity of 0.016 kg
water vapor/kg dry air.
(f) Find the dew point temperature (C) of the product mixture
Answers: (a) 128%; (c) 0.1271; (d) 38.2C
Book Problem 13.47
(Answer: 0.0097 kg/s)
Book Problem 13.57
(Answer: -1,557,524 kJ; 1.1 atm )
SP-22:
One kmol of gaseous benzene (C6H6) is burned with air at an equivalence ratio of 0.769 in a closed,
rigid vessel. All hydrogen in the fuel is oxidized to water vapor; however, only 92% of the carbon
oxidizes to carbon dioxide while the remaining 8% produces carbon monoxide. The pressure of
the reactants is 1 atm and the temperature is 25C; while the temperature of the products is 727C.
(a) Calculate the pressure (atm) of the products.
(b) Determine the heat transfer (kJ/kg fuel) during the reaction.
Answer: (a) 3.4 atm (b) -28169.2 kJ/kg
Book Problem 13.62
(Answer: a. 47483 kJ/kg)
Book Problem 13.69
(Answer: N/a)
SP-23:
A mixture of 90% liquid octane (C8H18) and 10% liquid ethanol (C2H5OH) at 25C is burned with
air at the same temperature in an atmospheric pressure combustor operating at steady conditions.
Products of “complete” combustion exit the combustor at 25C.
(a) Write the balanced chemical reaction for “complete” combustion with 100% and 200%
theoretical air.
(b) Calculate the air-fuel ratio (kg air/kg fuel) with 100% and 200% theoretical air.
(c) Find the dew point temperature (C) of the product mixture with 100% and 200% theoretical
air.
(d) Determine the heat transfer (kJ/kg fuel) with 100% and 200% theoretical air.
Answer: (c) 52.7C, 40.2C