View
228
Download
0
Category
Preview:
Citation preview
ME 3320: Thermodynamics II Handout #5
Homework #5: Problems 13-8, 13-10, 13-13, 13-28E, 13-30, 13-33, 13-39,
13-41E, 13-54, 13-61E
13-39 A mixture of air and methane is formed in the inlet
manifold of a natural gas-fueled internal combustion engine. The
mole fraction of the methane is 15 percent. This engine is
operated at 3000 rpm and has a 5-L displacement. Determine the
mass flow rate of this mixture in the manifold where the pressure
and temperature are 80 kPa and 20°C. Assume that this is a four-
stroke engine (1 cycle = 2 strokes). Answer: 0.1110 kg/s
13-41E A gaseous mixture consists of 75 percent methane and
25 percent ethane by mass. One million cubic feet of this mixture
is trapped in a geological formation as natural gas at 300°F and
2000 psia. Determine the mass of this gas (a) treating it as an
ideal gas mixture, (b) using a compressibility factor based on
Amagat’s law of additive volumes, and (c) using Kay’s
pseudocritical pressure and temperature.
13-50 The volumetic analysis of a mixture of gases is 30
percent oxygen, 40 percent nitrogen, 10 percent carbon dioxide,
and 20 percent methane. This mixture is heated from 20°C to
200°C while flowing through a tube in which the pressure is
maintained at 150 kPa. Determine the heat transfer to the mixture
per unit mass of the mixture. Assume that the component specific
heats are constant over the temperature range.
13-53 A mixture that is 20 percent carbon dioxide, 10 percent
oxygen, and 70 percent nitrogen by volume undergoes a process
from 300 K and 100 kPa to 500 K and 400 kPa. Determine the
mass fractions of the components, and determine the enthalpy
change per unit mass of mixture by: (a) Assuming that the
specific heats are constant over this temperature range, (b)
assuming that they are not constant over this temperature range.
13-61E Air enters the compressor of a simple ideal Brayton
cycle. The following heat exchanger represents the combustion
process. The gas that exits the combuston chamber has a
volumetric composition of 20 percent nitrogen, 5 percent oxygen,
40 percent carbon dioxide, and 35 percent water. The combustion
gases then pass through the turbine to generate power. Calculate
the thermal efficiency of this cycle when the air enters the
compressor at 10 psia and 40°F; the pressure ratio is 6; and the
temperature at the turbine inlet is 1400°F. Model the heat-
addition process using constant gas properties that are the average
of the inlet air and the exit combustion product gases.
Recommended