Questions and Answers of Thermodynamics Concepts And Applications

The Dassault Falcon aircraft is powered by two TF37 turbofan jet engines. At a cruise condition, each engine consumes fuel at a rate of 0.232 kg/s with a concomitant air consumption of 16.4 kg/s. The
Carbon is burned with exactly the right amount of air (79% N2 and 21% O2 by volume) to form carbon dioxide.A. Determine the air–fuel ratio (by mass).B. Determine the mass of carbon dioxide per mass
Calculate and compare the stoichiometric air–fuel mass ratios for the following common fuels. Assume that air is a simple mixture of O2 and N2 in molar proportions of 1:3.76.A. Natural gas (assume
An automobile is traveling at 55 mph on a highway. The car’s engine is operating at 2000 revolutions per minute. The engine fills its cylinders with air each time two revolutions are completed,
The car in Problem 12.16 operates on liquefied petroleum gas (LPG). Assume the LPG can be approximated as C3H8. Assume the air composition is that of “simple air,” i.e, 1 kmol of O2 for every
A hydrocarbon fuel is burned with air. Assume the air to be a simple mixture of 21% O2 and 79% N2. On a dry basis (all the water vapor has been removed from the products), a volumetric analysis
Derive that (x + y/4)/Φ is the oxidizer coefficient a in the combustion reactionwhere Φ is the air–fuel equivalence ratio. Start by considering the case where Φ = 1; i.e., by doing C, H, O, and
Natural gas is burned to produce hot water to heat a clothing store. Assuming that the natural gas can be approximated as methane (CH4) and that the air is a simple mixture of O2 and N2 in molar
One mole of a hydrocarbon fuel (CHx) is burned with excess air. The volumetric analysis of the dry products (with H2O removed) yields:A. Determine the approximate composition of the fuel on a mass
Ethane burns with 150% stoichiometric air. Assume the air is 79% N2 and 21%O2 by volume. Combustion goes to completion. Determine (a) The air–fuel ratio by mass (b) The mole fraction
Rework Problem 12.24 but use propane as the fuel.Problem 12.24Ethane burns with 150% stoichiometric air. Assume the air is 79% N2 and 21%O2 by volume. Combustion goes to completion.
Ethanol (C2H5OH) is burned in a space heater at atmospheric pressure. Assume the air is 79% N2 and 21% O2 by volume.A. For combustion with 20% excess air, determine the mass air–fuel ratio and the
Methane (CH4) is burned with air (79% N2 and 21% O2 by volume) at atmospheric pressure. The molar analysis of the flue gas yields CO2 = 10.00%, O2 = 2.41%, CO = 0.52%, and N2 = 87.07%. Balance the
Determine the air–fuel ratio by mass when a liquid fuel with a composition of 16% hydrogen and 84% carbon by mass is burned with 15% excess air.
Compute the composition of the flue gases (percentage by volume on a dry basis) resulting from the combustion of C8H18 with 114% stoichiometric air.
A liquid petroleum fuel having a hydrogen/carbon ratio by weight of 0.169 is burned in a heater with an air–fuel ratio of 17 by mass. Determine the volumetric analysis of the exhaust gas on both
Consider the combustion of a fuel at constant pressure. Reproduce the coordinate system in the sketch and indicate and appropriately label the following items:A. HreacB. HprodC. The adiabatic flame
A gas mixture (60% methane, 30% ethane, and 10% nitrogen by volume) undergoes a complete reaction with 120% theoretical air (79% N2 and 21% O2 by volume). Determine the composition (in mole
Determine the equivalence ratio of a mixture of 1 mol of methane and 7 mol of air. Is the mixture lean or rich?
Compare the mass of CO2 produced per mass of fuel burned, i.e., the emission index of CO2 (kgCO2/kgfuel), for the following fuels for operation at stoichiometric (Φ = 1.0) and lean (Φ = 0.7)
Consider the combustion of a fuel at constant pressure. Reproduce the coordinate system in the sketch and indicate and appropriately label the following items:A. HreacB. HprodC. Heating value (HV)
Determine the standardized enthalpies of the following pure species at 4 atm and 2500 K: H2, H2O, and OH.
Determine the mass of CO2 produced (kg) per unit of energy released (kJ), i.e., the CO2 emission, for the complete combustion of the following fuels. The higher heating value (HHV) expresses the
Determine the total standardized enthalpy H (kJ) for a fuel–air reactant mixture containing 1 kmol CH4, 2.5 kmol O2, and 9.4 kmol N2 at 500 K and 1 atm. Also determine the mass-specific
Determine the heat transfer in the constant-volume combustion of 1 kg of carbon indicated in the following reaction:The reactants are at 298 K and the products are at 500 K. C + 1.5 0₂ CO2 + 0.5
A mixture of products of combustion contains the following constituents at 2000 K: 3 kmol of CO2, 4 kmol of H2O, and 18.8 kmol of N2. Determine the following quantities:A. The mole fraction of each
In Problem 12.54, you calculated the CO2 emission factor for several hydrocarbon fuels. Derive an expression for the CO2 emission factor for an arbitrary hydrocarbon CxHy in which the
A piston–cylinder arrangement initially contains 0.002 kmol of H2 and 0.01 kmol of O2 at 298 K and 1 atm. The mixture is ignited and burns adiabatically at constant pressure. Determine the final
Hydrogen burns with 200% stoichiometric air in a piston–cylinder arrangement. The process is carried out adiabatically and at constant pressure. The initial temperature and pressure are 298 K and 1
A mixture of 5 g of ethane and a stoichiometric amount of oxygen is contained in a piston–cylinder device at 25° C and 1 atm. The piston moves freely without friction. A spark ignites the mixture
A rigid spherical pressure vessel initially contains 0.002 kmol of H2 and 0.01 kmol of O2 at 298 K and 1 atm. The mixture is ignited and burns adiabatically. Determine the final temperature and
Determine the adiabatic constant-volume flame temperature for a stoichiometric mixture of propane (C3H8) and air. The reactants are at 1 atm and 298 K. Assume the air to be a simple mixture of 21% O2
Anticipating the coming of the “hydrogen economy,” an enthusiastic mechanical engineer invents a steam generator. Pure hydrogen, H2, enters the wellinsulated combustion chamber at 298 K with a
Show that Eq. 12.25 can be expressed equivalently on (a) A per unit mass of mixture basis (b) A per unit mass of fuel basis.Eq. 12.25 hreactants (T3) Specific enthalpy of reactant mixture at T3 per
Consider a stoichiometric reaction involving liquid octane and oxygen in a steady low reactor. The reactants enter at 25° C and 1 atm, and the products exit at the same conditions. Assuming liquid
Ethane flows into a combustion chamber at 1.5 kg/min along with zero percent excess air. The fuel, oxidizer, and products are all at 25° C. The reaction is complete and the water is liquid.
Consider the turbojet combustor described in Example 12.8. Determine the temperature of the combustion products exiting the combustor if the air–fuel ratio is reduced to 50:1.Example 12.8Consider a
The maximum temperature that the turbine blades can withstand limits the performance of a turbojet engine. This temperature, in turn, is controlled by the temperature of the combustion products
A 50–50 blend (by volume) of methane and propane is burned with 100% excess air in a steady-flow combustion chamber. The fuel mixture and the air each enter the combustion chamber at 298 K and 1
Propane is completely burned in a steady-flow process with 100% excess air. The propane and the air each enter the control volume at 25° C and 1 atm, and the combustion products leave at 600 K and 1
A stoichiometric mixture of carbon monoxide and air, initially at 25°C and 1 atm, reacts completely in an adiabatic, constant-pressure, steady-flow process. Determine the exit temperature (K) of the
A cutting torch burns a steady flow of acetylene gas at 25° C and 1 atm with stoichiometric air at 25° C and 1 atm. The products are at 1 atm. Assume reaction is complete (no dissociation) and
Hydrogen gas and 100% excess air each enter a steady-flow combustion chamber at 25° C and 1 atm. A complete reaction occurs with a heat loss of 40 MJ/kmol of fuel. Determine the temperature (K) of
Consider the theoretical combustion of methane in a steady-flow process at 1 atm. Determine the heat transfer per kmol and per kg of fuel from the combustion chamber for the following cases:A. The
Consider a system at fixed temperature and pressure in which the following equilibrium is maintainedThe reaction is exothermic as written. Draw a sketch showing the system entropy and temperature as
Determine the mass air–fuel ratio if gaseous propane (C3H8) is burned with air at 1 atm in a steady-flow reactor for the following conditions. The propane and air enter the reactor at 25° C, and
Consider a system at fixed temperature and pressure in which the following equilibrium is maintained:The reaction is exothermic as written. Draw a sketch showing the system Gibbs free energy (Gibbs
Air enters a turbojet engine with a velocity of 150m/s (at station 1) and a mass flow rate of 23.6 kg/s. Fuel is supplied to the engine at 0.3165 kg/s. The mass specific standardized enthalpy of the
Consider the following equilibrium reaction at 1 atm and 2500 K:A. Which is the exothermic direction for this reaction? To the left or to the right?B. If the temperature is increased to 4000 K, but
Create a spreadsheet model of a turbojet combustor in which the air temperature, fuel temperature, and air–fuel ratio are input quantities, and the combustion product temperature is an output
Ethane burns with 150% stoichiometric air. Assume complete combustion with no dissociation. Determine(a) The mole percentage of each product species.(b) The dew-point temperature of the products at 1
Rework Problem 12.76 but use propane as the fuel.Problem 12.76 Ethane burns with 150% stoichiometric air. Assume complete combustion with no dissociation. Determine(a) The mole percentage of
Consider the combustion of benzene, C6H6, with air. Determine the dew-point temperature of the combustion products if the mass air–fuel ratio is 20:1. The pressure is 1 atm.
Consider a thermodynamic system consisting of liquid H2Oand H2O vapor. Which of the following conditions is/are necessary for thermodynamic equilibrium to prevail in the system? Note that there may
Consider one kmol of O2 at 1 atm and 2600 K. Calculate the Gibbs function of the O2 using the Gibbs function definition (G = H –TS).
Consider an arbitrary chemical equilibrium. What is the physical significance of Kp << 1 and Kp >> 1?
Consider one kmol of O atoms at 1 atm and 2600 K. Calculate the Gibbs function of the O atoms using the Gibbs function definition (G = H –TS).
Consider one kmol of CO2 at 1 atm and 2500 K. Calculate the Gibbs function of the CO2 using the Gibbs function definition (G = H –TS).
Explain how the second law of thermodynamics governs the equilibrium between the phases of a simple substance.
Consider one kmol of CO at 1 atm and 2500 K. Calculate the Gibbs function of the CO using the Gibbs function definition (G = H –TS).
Consider one kmol of H2O at 1500 K. Calculate the Gibbs function of the H2O for pressures of 1.0 and 100 atm.
Consider one kmol of O2 at 2400 K. Calculate and plot the Gibbs function of the O2 for pressures of 0.1, 1.0, 10, and 100 atm.
In a steam reforming process, natural gas (or other hydrocarbon or coal) is used to produce hydrogen. In this process, the water–gas shift equilibrium reaction H2O + CO ⇔ CO2 + H2 is important.
Consider the reaction O2 ⇔ 2 O. Determine a numerical value for the equilibrium constant Kp for the reaction as written for temperatures of 500 K and 5000 K.
Consider the reaction N2 ⇔ 2 N. Determine a numerical value for the equilibrium constant Kp for the reaction as written for temperatures of 500 K and 5000 K. Compare your results with Problem 13.19
Consider the reaction H2O + CO ⇔ CO2 + H2. Determine a numerical value for the equilibrium constant Kp for the reaction as written for a temperature of 1200 K.
Consider the reaction N2 + O2 , 2 NO. Determine a numerical value for the equilibrium constant Kp for the reaction as written for temperatures of 1000 K and 3500 K. Discuss
Consider the reaction 2 H2 + O2 ⇔ 2 H2O. Express the equilibrium constant Kp for the reaction using appropriate partial pressures. Also write an expression for the equilibrium constant when the
Express the equilibrium constant Kp for the following reactions using appropriate partial pressures: 2 H2 + O2 ⇔ 2 H2O and H2 + 1/2O2, H2O. How do the two Kps relate?
Consider a mixture of molecular nitrogen (N2) and atomic nitrogen (N) in equilibrium at 3 atm at an unknown temperature. Determine the value of the equilibrium constant Kp for the reaction N2 ⇔ 2N
Consider the equilibrium dissociation of carbon dioxide CO2 ⇔ CO + 1/2 O2. At 2500 K, the equilibrium constant is 0.03635. Calculate the enthalpy of reaction for this reaction at 2500 K and use
Ammonia is used as a refrigerant in large-scale refrigeration systems. Using data for ammonia (NH3) from the NIST resources, verify that the condition for phase equilibrium (Eqs.13.35) is met. Use
Calculate the enthalpy of reaction for CO + 1/2 O2 ↔ CO2 at 2000 K. Use your value of ΔH at 2000 K, along with the Kp value at 2000 K of 20.325, to estimate the equilibrium constant for a
Molecular nitrogen has a strong triple bond and, thus, high temperatures are required to achieve any significant dissociation, as compared with less strongly bonded diatomic molecules. Explore the
Consider the dissociation of oxygen molecules O2 ⇔ O + O at 3800 K and 2 atm. Determine the equilibrium partial pressures and mole fractions of the O atoms and molecular oxygen.
Consider an initial equimolar mixture of molecular oxygen and carbon monoxide. For the equilibrium reaction CO + 1/2 O2 ⇔ CO2 determine the equilibrium partial pressures and the mole fractions of
Consider an initially equimolar mixture of water vapor and carbon monoxide. For the equilibrium reaction H2O + CO ⇔ CO2 + H2 determine the equilibrium partial pressures and the mole fractions of
Carbon monoxide and oxygen (O2) exist in equilibrium with carbon dioxide. Determine the equilibrium composition (mole fractions) at 3200 K and 1 atm of an initial mixture of 2 kmol of carbon monoxide
Carbon monoxide and water react to form carbon dioxide and hydrogen (H2), the so-called water-gas shift reaction. Determine the equilibrium composition (mole fractions) of a mixture at 1100 K and 1
Carbon monoxide and water react to form carbon dioxide and hydrogen (H2), the so-called water–gas shift reaction. Determine the equilibrium composition (mole fractions) of a mixture at 1100 K and 1
Hydrogen and oxygen react to form water. Determine the equilibrium composition (mole fractions) at 4000 K and 1 atm of an initial mixture of 1 kmol of hydrogen (H2) and 1 kmol of oxygen (O2).
Nitric oxide (NO) is a major pollutant formed in high-temperature combustion processes, but typically in less than equilibrium amounts. Equilibrium values thus can be considered to be upper limits.
The conversion of nitric oxide (NO) to nitrogen dioxide (NO2) is important in atmospheric chemistry. National Ambient Air Quality Standards are set for NO2, a major component of photochemical smog.
Methanol has been proposed for use in fuel cells for automotive applications. The vapor pressure for methanol (CH3OH) was measured to be 4.02 and 352 kPa at 273 K and 373 K, repectively. Use these
Heptane is often used as a single-component fuel to model the behavior of gasoline. Volatility is important to the cold-start performance of gasoline in an automobile. Use the Clausius–Clapeyron to
Derive the Clausius–Clapeyron equation from the Clapeyron equation, assuming that the gas-phase specific volume is much, much greater than that of the liquid phase, and that the pressure is
Determine the number of degrees of freedom associated with the following systems. Also, use the NIST resources, and any other resources you can find, to determine numerical values associated with the
Determine the number of degrees of freedom associated with the following systems. Also, use the NIST resources, and any other resources you can find, to determine numerical values associated with the
Consider the liquid–vapor equilibrium of H2O at 20° C in which N2 is added to the gas phase to obtain a total pressure of 1 atm. Assuming that the N2 is both inert and insoluble in the liquid H2O,
Heptane is frequently used as a single-component surrogate fuel to represent gasoline. Using data for heptane from the NIST resources, verify that the condition for phase equilibrium (Eqs. 13.35) is
Carbon monoxide and oxygen (O2) react to form carbon dioxide. Determine the equilibrium composition (mole fractions) of a mixture at 298 K and 1 atm initially containing 2 kmol of carbon monoxide and
Derive a conversion factor relating pressure in pascals (N/m2) and in psi (lbf/in2). Compare your result with the conversion factor at the front of this book.
A thermometer reads 72 F. Specify the temperature in °C, K, and R.
At what temperature are temperatures expressed in Fahrenheit and Celsius numerically equal? Solve using algebra.
In a closed (fixed-mass) system, an ideal gas undergoes a process from an initial state with pressure 517 kPa and volume of 0.1416m3 to a final state with pressure 172.3 kPa and volume of
Determine the enthalpy change for air undergoing a process that causes a change of state from 300 K and 1 atm to 1000 K and 5 atms. Do this in two ways: (1) Assume ideal gas behavior and use Table
Consider an ideal gas. Indicate whether the following thermodynamic properties depend on pressure when the temperature is fixed: density, specific volume, molar-specific internal energy,
Water at 10.0 MPa (absolute) is heated from 350 K to 380 K. Determine the change in mass-specific enthalpy for this process in three ways.(1) Use the tables in Appendix B, interpolating as
How to Define a Thermodynamic State. Given the following property data for H2O, designate the region, line, or point in T–v or P– v space (i.e., compressed liquid, liquid–vapor mixture,
Wet steam at 375 K has a specific enthalpy of 2600 kJ/kg. Determine the quality of the mixture and the specific internal energy u.

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