Questions and Answers of Fundamentals Of Thermodynamics

Some type of wood can be characterized as C1H1.5O0.7 with a lower heating value of 19 500 kJ/kg. Find its adiabatic flame temperature when burned with stoichiometric air at 100 kPa, 298 K.
A gas turbine burns methane with 200% theoretical air. The air and fuel come in through two separate compressors bringing them from 100 kPa, 298 K, to 1400 kPa, and after mixing they enter the
Extend the solution to the previous problem by using Table A.9 for the ΔHP terms.
A special coal burner uses a stoichiometric mixture of coal and an oxygen–argon mixture (1:1 mole ratio), with the reactants supplied at the reference conditions P0, T0. Find the adiabatic flame
Natural gas, we assume methane, is burned with 200% theoretical air, and the reactants are supplied as gases at the reference temperature and pressure. The products are flowing through a heat
Solid carbon is burned with stoichiometric air in a steady-flow process. The reactants at T0, P0 are heated in a preheater to T2 = 500 K, as shown in Fig. P13.97, with the energy given by the product
Consider the combustion of hydrogen with pure O2 in a stoichiometric ratio under steady-flow adiabatic conditions. The reactants enter separately at 298 K, 100 kPa, and the product(s) exit at a
Propene, C3H6, is burned with air in a steady-flow burner with reactants at P0, T0. The mixture is lean, so the adiabatic flame temperature is 1800 K. Find the entropy generation per kmol fuel,
A flow of 0.02 kmol/s methane, CH4, and 200% theoretical air, both at reference conditions, are compressed separately to P3 = P4 = 2 MPa, then mixed and then burned in a steady-flow setup (like a gas
Liquid butane at 25◦C is mixed with 150% theoretical air at 600 K and is burned in an adiabatic steady-state combustor. Use the generalized charts for the liquid fuel and find the temperature of
A mixture of 80% ethane and 20% methane on a mole basis is throttled from 10 MPa, 65◦C, to 100 kPa and is fed to a combustion chamber, where it undergoes complete combustion with air, which enters
Consider a methane–oxygen fuel cell in which the reaction at the anode isCH4 + 2H2O → CO2 + 8 e− + 8H+The electrons produced by the reaction flow through the external load, and the positive
Assume the PEC fuel cell in the previous problem. How large an area does the fuel cell have to deliver 1 kW with a current density of 1 A/cm2?
A SOC fuel cell at 900 K can be described by EMF = 1.06 V and the constants in Eq. 13.29 as b = 0 V, c = 0.1 V, ASR = 0.04 Ω cm2, ileak = 0.01, iL = 2, i0 = 0.13 all A/cm2. Find the voltage and the
A PEC fuel cell operating at 25◦C generates 1.0 V that also accounts for losses. For a total power of 1 kW, what is the hydrogen mass flow rate?
A gas turbine burns methane with 150% theoretical air. Assume the air is 25◦C, 100 kPa, and has a relative humidity of 80%. How large a fraction of the product mixture water comes from the moist
An oven heated by natural gas burners has the combustion take place inside a U-shaped steel pipe, so the heating is done from the outside surface of the pipe by radiation. Each burner delivers 15 kW
A slight disadvantage of the oxygen-enriched air for combustion is an increase in flame temperature, which tends to increase NOx. Find the flame temperature for the previous problem for both cases,
A gas turbine burns methane with 200% theoretical air. The air and fuel come in through two separate compressors bringing them from 100 kPa, 298 K, to 1400 kPa and enter a mixing chamber and a
Find the equivalent heat transfer qH to be used in a cycle calculation for constant- pressure combustion when the fuel is (a) Methane (b) Gaseous octane. In both cases, use water vapor
A gasoline engine is converted to run on propane as shown in Fig. P13.144. Assume the propane enters the engine at 25°C, at the rate of 40 kg/h. Only 90% theoretical air enters at 25°C, so 90% of
Phenol, C6H5OH (M = 94.11 kg/kmol, CP = 1.7 kJ/kg-K), is used in a combustion process being burned with stoichiometric air. The reactants are supplied at 1.21 MPa, the air at T0 and the phenol as
Carbon monoxide, CO, is burned with 150% theoretical air, and both gases are supplied at 150 kPa and 600 K. Find the heating value and the adiabatic flame temperature.
Liquid acetylene, C2H2, is stored in a high pressure storage tank at ambient temperature, 25â¦C. The liquid is fed to an insulated combustor/steam boiler at a steady rate of 1 kg/s, along with
Liquid methanol is burned with stoichiometric air, both supplied at P0, T0 in a constant-pressure process, and the product exits a heat exchanger at 1600 R. Find the heat transfer per lbmol fuel.
In a new high-efficiency furnace, natural gas, assumed to be 90% methane and 10% ethane (by volume) and 110% theoretical air, each enter at 77 F, 15.7 lbf/in.2, and the products (assumed to be 100%
A rigid vessel initially contains 2 lbm of carbon and 2 lbm of oxygen at 77 F, 30 lbf/in.2. Combustion occurs, and the resulting products consist of 1 lbm ofCO2, 1 lbm of CO, and excess O2 at a
Acetylene gas, C2H2, is burned with stoichiometric air in a torch. The reactants are supplied at the reference conditions P0, T0. The products come out from the flame at 4500 R after some heat loss
Natural gas (methane) is burned with stoichiometric air with reactants supplied at the reference conditions P0, T0 in a steady-flow burner. The products come out at 1400 R. If the burner should
What is the higher heating value, HHV, of n-butane?
Find the enthalpy of combustion and the heating value for pure carbon.
Acetylene gas, C2H2, is burned with stoichiometric air in a torch. The reactants are supplied at the reference conditions P0, T0. The products come out from the flame at 5000 R after a heat loss by
A mixture of fuels is E85, which is 85% ethanol and 15% gasoline (assume octane) by mass. Assume we put the fuel and air, both at the reference conditions T0, P0, into a carburetor and vaporize the
Some type of wood can be characterized as C1H1.5O0.7 with a lower heating value of 8380 Btu/lbm. Find its adiabatic flame temperature when burned with stoichiometric air at 1 atm, 77 F.
A special coal burner uses a stoichiometric mixture of coal and an oxygen–argon mixture (1:1 mole ratio), with the reactants supplied at the reference conditions P0, T0. Find the adiabatic flame
In a test of rocket propellant performance, liquid hydrazine (N2H4) at 14.7 lbf/in.2, 77 F, and oxygen gas at 14.7 lbf/in.2, 77 F, are fed to a combustion chamber in the ratio of 0.5 lbm O2/lbm N2H4.
Propene, C3H6, is burned with air in a steady flow burner with reactants at P0, T0. The mixture is lean, so the adiabatic flame temperature is 3200 R. Find the entropy generation per lbmol fuel,
A car that runs on natural gas has it stored in a heavy tank with a maximum pressure of 3600 psi (25 MPa). Size the tank for a range of 300 miles (500 km), assuming a car engine that has a 30%
The cogenerating power plant shown in Problem 9.80 burns 170 kg/s air with natural gas, CH4. The setup is shown in Fig. P13.205, where a fraction of the air flow out of the compressor with pressure
Study the coal gasification process that will produce methane, CH4, or methanol, CH3OH. What is involved in such a process? Compare the heating values of the gas products with those of the original
When a power plant burns coal or some blends of oil, the combustion process can generate pollutants as SOx and NOx Investigate the use of scrubbers to remove these products. Explain the processes
How does the Gibbs function vary with quality as you move from liquid to vapor?
Must P and T be held fixed to obtain chemical equilibrium?
The change in the Gibbs function ΔG0 for a reaction is a function of which property?
In a steady-flow burner, T is not controlled; which properties are?
In a closed rigid-combustion bomb, which properties are held fixed?
Is the dissociation of water pressure sensitive?
If a reaction is insensitive to pressure, prove that it is also insensitive to dilution effects at a given T.
For a pressure-sensitive reaction, an inert gas is added (dilution); how does the reaction shift?
In a combustion process, is the adiabatic flame temperature affected by reactions?
In equilibrium, the Gibbs function of the reactants and the products is the same; how about the energy?
Does a dissociation process require energy or does it give out energy?
Consider a 2-km-deep gas well containing a gas mixture of methane and ethane at a uniform temperature of 30◦C. The pressure at the top of the well is 14 MPa, and the composition on a mole basis is
Carbon dioxide is heated at 100 kPa. What should the temperature be to see a mole fraction of CO as 0.25? For that temperature, what will the mole fraction of CO be if the pressure is 200 kPa?
Assume that a diatomic gas like O2 or N2 dissociates at a pressure different from P0. Find an expression for the fraction of the original gas that has dissociated at any T, assuming equilibrium.
Assume we have air at 400 kPa, 2000 K (as 21% O2 and 79% N2) and we can neglect dissociations of O2 and N2. What is the equilibrium mole fraction of NO? Find the enthalpy difference in the gases due
Assume the equilibrium mole fractions of oxygen and nitrogen are close to those in air. Find the equilibrium mole fraction for NO at 3000 K, 500 kPa, disregarding dissociations.
A mixture flows with 2 kmol/s CO2, 1 kmol/s Ar, and 1 kmol/s CO at 298 K and it is heated to 3000 K at constant 100 kPa. Assume the dissociation of CO2 is the only equilibrium process to be
A mixture of 1 kmol CO2, 2 kmol CO, and 2 kmol O2, at 25◦ C, 150 kPa, is heated in a constant pressure, steady-state process to 3000 K. Assuming that only these substances are present in the
Acetylene gas, C2H2, is burned with stoichiometric air in a torch. The reactants are supplied at the reference conditions P0, T0. The products come out from the flame at 2800 K after a small heat
Consider combustion of CH4 with O2 forming CO2 and H2O as the products. Find the equilibrium constant for the reaction at 1000 K. Use an average heat capacity of Cp = 52 kJ/kmol K for the fuel and
A piston/cylinder contains 0.1 kmol H2 and 0.1 kmol Ar gas at 25◦C, 200 kPa. It is heated in a Constant-pressure process, so the mole fraction of atomic hydrogen, H, is 10%. Find the final
A tank contains 0.1 kmol H2 and 0.1 kmol Ar gas at 25◦ C, 200 kPa, and the tank maintains constant volume. To what T should it be heated to have a mole fraction of atomic hydrogen, H, of 10%?
A stoichiometric combustion of butane C4H8 and air results in only half of the C atoms burning to CO; the other half generates CO. This means the products should contain a mixture of H2O, CO, CO2,
A liquid fuel can be produced from a lighter fuel in a catalytic reactor according to C2H4 + H2O ⇔ C2H5OH Show that the equilibrium constant is ln K = −6.691 at 700 K, using Cp = 63 kJ/kmol K for
One kilomole of CO2 and 1 kmol of H2 at room temperature and 200 kPa are heated to 1200 K, 200 kPa. Use the water–gas reaction to determine the mole fraction of CO. Neglect dissociations of H2 and
A special coal burner uses a stoichiometric mixture of coal and an oxygen–argon mixture (1:1 mole ratio) with the reactants supplied at the reference conditions P0, T0. Consider the dissociation of
Coal is burned with stoichiometric air, with the reactants supplied at the reference conditions P0,T0. If no dissociations are considered, the adiabatic flame temperature is found to be 2461 K. What
An important step in the manufacture of chemical fertilizer is the production of ammonia according to the reaction N2 + 3H2 ⇔ 2NH3. Show that the equilibrium constant is K = 6.202 at
Consider the previous reaction in equilibrium at 150◦C, 5 MPa. For an initial composition of 25% nitrogen, 75% hydrogen, on a mole basis, calculate the equilibrium composition.
At high temperature, NO can form oxygen and nitrogen. Natural gas (methane) is burned with 150% theoretical air at 100 kPa, and the product temperature is 2000 K. Neglect other reactions and find the
Consider the stoichiometric combustion of pure carbon with air in a constant-pressure process at 100 kPa. Find the adiabatic flame temperature (no equilibrium reactions). Then find the temperature
Methane is burned with theoretical oxygen in a steady-state process, and the products exit the combustion chamber at 3200 K, 700 kPa. Calculate the equilibrium composition at this state, assuming
One approach to using hydrocarbon fuels in a fuel cell is to “reform” the hydrocarbon to obtain hydrogen, which is then fed to the fuel cell. As part of the analysis of such a procedure, consider
Operation of an MHD converter requires an electrically conducting gas. A helium gas “seeded” with 1.0 mole percent cesium, as shown in Fig. P14.96, is used where the cesium is partly ionized (Cs
Are the three reactions in the Zeldovich mechanism pressure sensitive if we look at equilibrium conditions?
Assume air is at 3000 K, 1 MPa. Find the time constant for NO formation. Repeat for 2000 K, 800 kPa.
Consider air at 2600 K, 1 MPa. Find the equilibrium concentration of NO, neglecting dissociations of oxygen and nitrogen.
If air at 300 K is brought to 2600 K, 1 MPa, instantly, find the formation rate of NO.
At what temperature range does air become a plasma?
In a test of a gas-turbine combustor, saturated liquid methane at 115 K is burned with excess air to hold the adiabatic flame temperature to 1600 K. It is assumed that the products consist of a
Combustion of stoichiometric benzene,C6H6, and air at 80 kPa with a slight heat loss gives a flame temperature of 2400 K. Consider the dissociation of CO2 to CO and O2 as the only equilibrium process
Calculate the equilibrium constant for the reaction O2 ⇋ 2O at temperatures of 537 R and 10 800 R.
Consider the dissociation of oxygen, O2 ⇔2O, starting with 1 lbmol oxygen at 77 F and heating it at constant pressure, 1 atm. At what temperature will we reach a concentration of monatomic oxygen
Assume we have air at 4 atm, 3600 R (as 21% O2 and 79% N2), and we can neglect dissociations ofO2 andN2. What is the equilibrium mole fraction of NO? Find the enthalpy difference in the gases due to
Assume the equilibrium mole fractions of oxygen and nitrogen are close to those in air. Find the equilibrium mole fraction for NO at 5400 R, 75 psia, disregarding dissociations.
Acetylene gas, C2H2, is burned with stoichiometric air in a torch. The reactants are supplied at the reference conditions P0, T0. The products come out from the flame at 5000 R after a small heat
A special coal burner uses a stoichiometric mixture of coal and an oxygen–argon mixture (1:1 mole ratio), with the reactants supplied at the reference conditions P0, T0. Consider the dissociation
An important step in the manufacture of chemical fertilizer is the production of ammonia, according to the reaction N2 + 3H2 ⇔ 2NH3. Show that the equilibrium constant is K =6.826 at 300
Consider the previous reaction in equilibrium at 300 F, 750 psia. For an initial composition of 25% nitrogen, 75% hydrogen, on a mole basis, calculate the equilibrium composition.
Study the chemical reactions that take place when CFC-type refrigerants are released into the atmosphere. The chlorine may create compounds such as HCl and ClONO2 that react with the ozone, O3.
Examine the chemical equilibrium that takes place in an engine where CO and various nitrogen– oxygen compounds summarized as NOx may be formed. Study the processes for a range of air– fuel ratios
Most compressors have a small diffuser at the exit to reduce the high gas velocity near the rotating blades and increase the pressure in the exit flow. What does this do to the stagnation pressure?
A diffuser is a divergent nozzle used to reduce a flow velocity. Is there a limit for the Mach number for it to work this way?
Sketch the variation in V, T, P, ρ, and M for a sonic (M = 1) flow into a divergent nozzle with M = 2 at the exit plane.
Can a shock be located upstream from the throat?
A convergent-divergent nozzle is presented for an application that requires a supersonic exit flow. What features of the nozzle do you look at first?
A stationary thermometer measures 80◦C in an air flow that has a velocity of 200 m/s. What is the actual flow temperature?
Steam at 1600 kPa, 300◦C, flows so that it has a stagnation (total) pressure of 1800 kPa. Find the velocity and the stagnation temperature.
An object from space enters the earth’s upper atmosphere at 5 kPa, 100 K, with a relative velocity of 2500 m/s or more. Estimate the object’s surface temperature.

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