Questions and Answers of Thermodynamics Concepts And Applications

Starting with the relationship P–v’ = constant, derive Eq. 7.14a. Tvr-1 = constant T2 T₁ = V1 V2 7-1 Eq. 7.14a
Compare the values of the specific volume of superheated steam at 2MPa and 500 K found in Appendix B with those calculated assuming ideal-gas behavior. Discuss.
Consider a piston–cylinder assembly containing 0.1 kg of dry air initially at 300 K and 200 kPa (state 1). Energy is added to the air (by heat transfer) at constant pressure until the final
Consider a T–s diagram. Show that the constant specific volume line (v) must have a steeper slope than a line of constant pressure (P). N₂ V₂ N₂ V₂ = 10V₁
Isothermal heat transfer of 45 kJ of energy occurs from the surroundings at 120° C to a system at 30° C. For an isothermal process with no internal irreversibilities:A. Determine the entropy change
Solve Problems 7.94 and 7.95 and compare your results. Why is the change in entropy of the world greater for Problem 7.95?Problems 7.94The air in a piston–cylinder device initially has a volume of
In Problem 7.94, there are two ways to calculate the change in entropy of the system during this reversible process. Find the entropy of the system using both of these methods.Problem 7.94The air in
Use spreadsheet (or other) software to calculate and plot the Gibbs function of one kmol of O2 for temperatures from 1000 K to 3000 K. The pressure is 1 atm. Repeat your calculations and plot on the
Use the Clausius–Clapeyron to determine saturation pressures from 373.12 K to 500 K and the percentage difference from the values from NIST or the steam tables in Appendix B. Use the known enthalpy
Use the curve-fit coefficients for the standardized enthalpy from Table H.2 to verify the enthalpies of formation at 298.15 K in Table H.1 for methane, propane, and hexane.
Using the property data in Appendix D, reproduce Fig. 13.4. Note that the initial temperature and pressure are 298 K and 1 atm, respectively. Spreadsheet software is recommended to facilitate your
Distinguish between bulk system energy and internal energy. Illustrate your discussion with three examples.
An automobile engine has a compression ratio (v1/v2) of 8.0. If the compression is isentropic and the initial temperature and pressure are 30° C and 101 kPa, respectively, determine (a) The
Ethanol (C2H5OH) is burned at stoichiometric conditions in a space heater at atmospheric pressure. Assume the air is 79% N2 and 21% O2 by volume.A. Determine the mass air–fuel ratio and the
Determine the density of propane (C3H8) at a fixed temperature (300 K) for the following pressures: 200 kPa, 400 kPa, and 600 kPa. Also determine the compressibility factors Z for these conditions.
Consider an ideal Rankine cycle operating between 5 kPa and 10 MPa and using H2O as the working fluid. Steam enters the turbine as saturated at a flow rate of 8 kg/s.A. Plot the ideal cycle on
Consider an ideal Rankine cycle operating between 5 kPa and 10MPa with a maximum cycle temperature of 750 K. The working fluid is H2O.A. Plot the cycle in T–s coordinates.B. Determine the fraction
Repeat Problem 9.1 but assume now that the turbine isentropic efficiency 95% and the pump isentropic efficiency is 85%. Also compare the steam quality at the turbine exit with the value from Problem
Consider the ideal Rankine cycle and operating conditions specified in Problem 9.1. River water is to be used as the cooling fluid in the steam condenser. The river water is available at 295 K, and
Review the most important equations presented in this chapter (i.e., those with a yellow background). What physical principles do they express? What restrictions (approximations) apply?
Using your computer solution from Problem 8.60, vary the pressure ratio from 1 (no compressor) to 40. Plot the outflow temperature and the compressor power as a function of the pressure ratio. Put
Consider a 600-MW regenerative-Rankine-cycle steam power plant with an open feedwater heater, as shown in Fig. 9.17. The boiler pressure is 1000 psia, the extraction pressure is 200 psia, and the
Repeat Problem 9.58 for a turbine having an isentropic efficiency of 90% and a pump having an isentropic efficiency of 85%.Problem 9.58A regenerative Rankine cycle operates with a first-stage turbine
Consider a Rankine cycle operating between 5 kPa and 10 MPa with a maximum cycle temperature of 750 K. The working fluid is H2O. Determine both the cycle thermal efficiency and the isentropic
In a Rankine cycle, steam leaves the boiler at 400° C and 5 MPa. The condenser pressure is 0.01 MPa. The water entering the pump is saturated. Determine the first-law thermal efficiency and compare
An engineer proposes to eliminate the condenser in an ideal Rankine cycle in order to form an open cycle. Lake water is available at 16° C. The lake water is pumped to 5 MPa and then heated at
A Rankine-cycle steam power plant operates with a turbine inlet temperature 1000 F and an exhaust pressure of 1 psia. If the turbine isentropic efficiency is 0.85, determine the maximum turbine inlet
The following data are for a simple steam power plant as shown in the sketch:Determine the following:A. Pipe size between condenser and pump if the velocity is not to exceed 20 ft/sB. Minimum pump
Consider a 50-MW Rankine-cycle steam power plant. The steam enters the turbine at 1000 F and 1200 psia and leaves at 1 psia with a quality of 0.90. Water leaves the condenser at 80 F and 1 psia. The
A solar-driven Rankine-cycle power plant uses refrigerant R-134a as the working fluid. During operation (i.e., daytime), the turbine inlet state is 220 F and 200 psia. The air-cooled condenser
Consider a 600-MW Rankine-cycle steam power plant. The boiler pressure is 1000 psia and the condenser pressure is 1 psia. The turbine inlet temperature is 1000 F and the pump inlet state is saturated
In a power plant operating on a Rankine cycle with superheat (Fig. 9.12), steam at 4.0 MPa and 700 K enters the turbine; the pressure is 3.5 kPa in the condenser. Modifying your EES program from
Repeat Problem 9.45 for a closed feedwater heater where the extraction steam pressure is dropped and then combined with the condenser feedwater, as shown in Fig. 9.19. Assume isentropic turbines and
Consider a 600-MW Rankine-cycle steam power plant. The boiler pressure is 1000 psia and the condenser pressure is 1 psia. The turbine inlet temperature is 1000 F. The condenser pressure is 1 psia and
A Rankine-cycle steam power plant operates at a boiler pressure of 5MPa and a condenser pressure of 0.01 MPa. The turbine inlet temperature is 500° C. The water entering the pump is saturated
Consider a 100-MW Rankine-cycle steam power plant. The peak cycle temperature is 1000 F. The condenser pressure is 1 psia. Plot the first-law thermal efficiency and mass flow rate (Mlbm/hr) as
Use EES to solve Problem 9.17. Find the cycle efficiency for at least six values of the boiler pressure, so as to create a smooth plot.Problem 9.17Consider a 100-MW Rankine-cycle steam power plant.
Repeat Problem 9.45 for a closed feedwater heater where the extraction steam is pumped to the boiler pressure before being combined with the condenser feedwater, as shown in Fig. 9.18. Assume
Consider a 100-MW Rankine-cycle steam power plant. The boiler pressure is 600 psia and the condenser pressure is 1 psia. Plot the first-law thermal efficiency and the mass flow rate (lbm/hr) as
Consider an ideal regenerative Rankine cycle utilizing an open feedwater heater, as shown in Fig. 9.17. The turbine inlet conditions are 10 MPa and 700 K, and the condenser pressure is 10 kPa. The
Use EES to solve Problem 9.19. Find the cycle efficiency for at least six values of the boiler pressure, so as to create a smooth plot.Problem 9.19Consider a 100-MW Rankine-cycle steam power plant.
Consider a Rankine-cycle steam power plant operating between a heat source at 500 ° C and a heat sink at 20° C. For safety reasons the boiler pressure cannot be more than 10MPa. The mass flow rate
Consider a 600-MW regenerative-Rankine-cycle steam power plant. The boiler pressure is 1000 psia, the extraction pressure is 200 psia, and the condenser pressure is 1 psia. The boiler exit
Compare your results for the Rankine cycle with an open feedwater heater in Problem 9.45 with your results for the simple Rankine cycle with superheat. Both problems consider Rankine cycles operating
Steam leaves the boiler of a 100-MW Rankine-cycle power plant at 700 F and 500 psia. The steam enters the turbine at 650 F and 475 psia. The turbine has an efficiency of 0.85 and exhausts at 2 psia.
A simple Rankine-cycle steam power plant operates with a steam flow rate of 500,000 lbm/hr. Steam enters the turbine at 500 psia and 1000 F. The turbine exhaust (condenser inlet) conditions are 1.0
In a power plant operating on a Rankine cycle, steam at 400 kPa and quality 100% enters the turbine; the pressure is 3.5 kPa in the condenser. Determine the cycle efficiency. How is the efficiency
Solve Problem 9.25 using EES.Problem 9.25In a power plant operating on a Rankine cycle, steam at 400 kPa and quality 100% enters the turbine; the pressure is 3.5 kPa in the condenser. Determine the
Consider a 600-MW regenerative-Rankine-cycle steam power plant with an open feedwater heater, as shown in Fig. 9.17. The boiler pressure is 8 MPa, the extraction pressure is 1.5 MPa, and the
Repeat Problem 9.54 for a closed feedwater heater where the extraction steam is pumped to the boiler pressure before being combined with the condenser feedwater, as shown in Fig. 9.18. Assume
Consider a Rankine cycle using R-134a as the working fluid. Saturated vapor leaves the boiler at 85° C and the condenser temperature is 40° C. What is the cycle efficiency?
Use your EES program to solve for the thermal efficiency in Problem 9.31 when the condenser pressure is varied from 5 kPa to 50 kPa. Plot the thermal efficiency as a function of pressure in this
Repeat Problem 9.58 for a closed feedwater heater where the extraction steam is pumped to the boiler pressure before being combined with the condenser feedwater, as shown in Fig. 9.18. Assume
Consider a 100-MW reheat-Rankine-cycle steam power plant. Superheated steam enters the high-pressure turbine at 800° C and 10MPa. The steam enters the reheater at 700° C and 4MPa and is reheated at
Consider a 200-MW reheat-Rankine-cycle steam power plant. Superheated steam enters the high-pressure turbine at 1000 K and 12 MPa. The steam enters the reheater at 800 K and 3 MPa and is reheated at
Consider a 500-MW reheat-Rankine-cycle steam power plant. The boiler pressure is 8 MPa, the reheater pressure is 1 MPa, and the condenser pressure is 6 kPa. Both turbine inlet temperatures are 800 K.
Consider a 600-MW reheat-Rankine-cycle steam power plant. The boiler pressure is 1000 psia, the reheater pressure is 200 psia, and the condenser pressure is 1 psia. Both turbine inlet temperatures
Consider a 400-MW reheat-Rankine-cycle steam power plant. The boiler pressure is 6 MPa, the reheater pressure is 700 kPa, and the condenser pressure is 6 kPa. The exit temperatures of the boiler and
Repeat Problem 9.63, but assume a turbine inlet temperature of 1200 K.Problem 9.63Consider a gas-turbine engine operating with 30 kg/s of air entering at 300 K and a pressure ratio of 12.5. Using an
Consider a 400-MW reheat-Rankine-cycle steam power plant. The boiler pressure is 6 MPa, the reheater pressure is 700 kPa, and the condenser pressure is 6 kPa. The exit temperatures of the boiler and
Consider a 600-MW reheat-Rankine-cycle steam power plant. The boiler pressure is 1000 psia, the reheater pressure is 100 psia, and the condenser pressure is 1 psia. The exit temperatures of the
Show that Eq. 9.18 can be obtained from a simplification of the expression.Eq. 9.18 th, Brayton = 1 − (Rp)−(7−¹)/y.
Consider a gas-turbine engine operating with 30 kg/s of air entering at 300 K and a pressure ratio of 12.5. Using an ideal air-standard cycle as a model of this engine, determine the ideal thermal
Repeat Problem 9.63, but use a pressure ratio of 15.Problem 9.63Consider a gas-turbine engine operating with 30 kg/s of air entering at 300 K and a pressure ratio of 12.5. Using an ideal air-standard
Perform an air-standard-cycle analysis of a gas-turbine engine that employs regeneration (i.e., some of the energy in the hot exhaust stream is transferred to the air between the compressor and the
Use EES to solve Problem 9.63 with a variable turbine inlet temperature. Plot the thermal efficiency as a function of the turbine inlet temperature from 900 K to 1200 K in increments of 50 K.Problem
Consider an ideal air-standard Brayton cycle operating with inlet temperature (T1) and pressure (P1) of 300 K and 100 kPa, respectively. The heat added per unit mass, q2–3, is 1050 kJ/kg. Assume
Use EES to solve Problem 9.63 with a variable pressure ratio. Plot the thermal efficiency as a function of pressure ratio from 10 to 15. Use six different values of the pressure ratio to generate a
Repeat Problem 9.63 assuming a turbine isentropic efficiency of 96% and a compressor efficiency of 95%. Compare your results with those from Problem 9.63.Problem 9.63Consider a gas-turbine engine
Consider the same situation described in Problem 9.73, but now the turbine inlet temperature is a given quantity (T3 = 1700 K) and the heat added per unit mass, q2–3, is unknown.A. Calculate the
Air at 100 F and 20 psia has a dew-point temperature of 70 F. Determine the relative humidity and the humidity ratio. Also determine the mixture volume (ft3) containing 1 lbm of dry air.
Determine the water-vapor mole and mass fractions before and after the humidifying of the air as described in Problem 11.12.Problem 11.12.On an extremely cold winter day, the air temperature and
Define the wet-bulb temperature and the dry bulb temperature. How are these temperatures used in psychrometry?
During mild exercise (e.g., walking) a person breathes in air at the rate of 20 liters/min and has a metabolism rate of 300 W. Atmospheric air is at 20 °C and 30% relative humidity, and the
A home heating system in Madison, Wisconsin, is designed to heat the outside air at 4.4 °C (40 F) and 100% relative humidity to 26.7 °C (80 F). Assume the pressure to be 1 atm everywhere. Determine
An adiabatic compressor receives air from the atmosphere at 60 F, 14.7 psia, and 75% relative humidity and discharges the air at 100 psia. The compressor isentropic efficiency is 0.80. Determine the
A moist gas (10% carbon dioxide, 70% nitrogen, 20% water vapor by volume) enters a reversible adiabatic turbine at 150° C and 0.4 MPa. The turbine exit pressure is 0.10135 MPa. The inlet volumetric
Moist air at 283 K and 40% relative humidity is heated at 1 atm to 305.3 K in a steady-flow process.A. Determine the relative humidity at the exit.B. For an inlet volumetric flow rate of 1000
Atmospheric air at 90 F and 60% relative humidity flows over a cooling coil at an inlet volumetric flow rate of 2000 ft3/min. The cooling coil temperature is 40 F. The condensed liquid is removed
A cogeneration plant as shown in Fig. 9.35 is designed to produce 600 MW power and 50 MW in process heat. The boiler pressure is 1000 psia, the extraction pressure is 200 psia, and the condenser
The combined cycle plant shown in Fig. 9.36 uses a gas-turbine engine operating a Brayton cycle with air as the working fluid. The air enters the compressor at 102 kPa and 15 C and exits at 612 kPa.
A turbojet-powered aircraft is flying at 530 mph and 34,000-ft altitude where the ambient temperature and pressure are -62 F and 3.63 psia, respectively. The pressure ratio of the compressor is 6 and
Air enters the compressor of a Brayton cycle at 250 K and 0.1 MPa. The pressure ratio is 4 to 1 and the maximum cycle temperature is 1300 K. The compressor and turbine efficiencies are 0.85. Using
Consider a 200-hp Brayton cycle using air. The compressor and turbine are both adiabatic but irreversible. There are pressure drops during heating and cooling. The following temperatures and
Consider the air-standard Otto cycle described in Problem 9.94 operating with a compression ratio of 8 (= Vmax/Vmin). The air just prior to compression is at 293 K and 1 atm. The maximum cycle
Consider the air-standard Otto cycle described in Problem 9.94 operating with a compression ratio of 10 (= Vmax/Vmin). The air just prior to compression is at 70 F and 14.7 psia. The maximum cycle
Rework Problem 9.100 for the following cycle.Data from in Problem 9.100Determine the efficiency for the air-standard cycle indicated in the sketch. Assume the pressures and temperatures are known
Consider the situation described in Problem 9.74, but now neither the compressor nor the turbine is ideal. Assume that the isentropic efficiency of the compressor is 0.82 and the isentropic
Air enters the compressor of a 100-hp Brayton cycle at 530 R and 14.7 psia. The constant-pressure heating process occurs at 80 psia with a peak temperature of 2200 R. Heat is rejected at 530 R.
Determine the efficiency for the air-standard cycle indicated in the sketch. Assume the pressures and temperatures are known quantities. PI 3 2 Q = 0 。
A 75-kW Brayton cycle has a compressor inlet state at 293 K and 1 atm and a turbine inlet state at 1200 K and 4 atm. Determine the thermal efficiency and the mass flow rate (kg/hr) for helium and air
Heat leaks from the air in a kitchen through the walls of a refrigerator into the refrigerated cold space at a rate of 1.43 kW. Determine the electrical power required to maintain a steady
Consider an ideal vapor-compression cycle using R-134a and operating between pressures of 0.28 and 1.75 MPa. Determine the coefficient of performance for the cycle for application (a) In a
Repeat Problem 9.117 using EES. Modify your EES program to find the coefficient of performance between pressures of 0.28 and 1.5 MPa. Plot T–s diagrams for the original cycle conditions and for the
Air enters the compressor of a 100-hp Brayton cycle at 530 R and 14.7 psia. The air is heated at 80 psia to 2200 R. The compressor and turbine efficiencies are each 0.90. After leaving the turbine,
Consider the heat pump described in Example 9.14. The heat pump now operates between 0.60 MPa and 1.4 MPa. Plot the vapor-compression cycle in T–s coordinates (use NIST) and determine the cycle
Consider a vapor-compression-cycle heat pump that uses R-134a as the working fluid. The flow rate of the R-134a is 0.08 kg/s. The temperatures and pressures at various points in the cycle are as
Consider the heat-pump-heated swimming pool discussed in Example 9.14. The rectangular (7.6m × 12 m) pool is filled to an average depth of 2.3 m. Estimate the rate at which the temperature of the
Consider the air-standard Otto cycle described in Problem 9.94. A particular cycle operates with a compression ratio of 7:1 and has a heat input of 2100 kJ/kg. The pressure and temperature at maximum
A heat pump uses the ground as a source to deliver 20,000 Btu/hr to heat a home. The heat pump coefficient of performance is 3.23. Determine (a) The electrical power required to operate the heat

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