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physics
thermodynamics

Thermodynamics An Engineering Approach 8th edition Yunus A. Cengel, Michael A. Boles - Solutions

Complete this table for refrigerant-134a:
Complete this table for refrigerant-134a:
A 1.8-m3 rigid tank contains steam at 220oC. One-third of the volume is in the liquid phase and the rest is in the vapor form. Determine (a) The pressure of the steam, (b) The quality of the saturated mixture, and (c) The density of the mixture.
A piston-cylinder device contains 0.85 kg of refrigerant- 134a at 210oC. The piston that is free to move has a mass of 12 kg and a diameter of 25 cm. The local atmospheric pressure is 88 kPa. Now, heat is transferred to refrigerant-134a until the temperature is 15oC. Determine (a) The final
10-kg of R-134a fill a 1.348-m3 rigid container at an initial temperature of 240oC. The container is then heated until the pressure is 200 kPa. Determine the final temperature and the initial pressure.
A 9-m3 container is filled with 300 kg of R-134a at 10oC. What is the specific enthalpy of the R-134a in the container?
Refrigerant-134a at 200 kPa and 25oC flows through a refrigeration line. Determine its specific volume.
The average atmospheric pressure in Denver (elevation 5 1610 m) is 83.4 kPa. Determine the temperature at which water in an uncovered pan boils in Denver
The temperature in a pressure cooker during cooking at sea level is measured to be 2508F. Determine the absolute pressure inside the cooker in psia and in atm. Would you modifty your answer if the place were at a higher elevation?
A spring-loaded piston-cylinder device is initially filled with 0.13 lbm of an R-134a liquid vapor mixture whose temperature is 230oF and whose quality is 80 percent. The spring constant in the spring force relation F 5 kx is 37 lbf/in, and the piston diameter is 12 in. The R-134a undergoes a
One pound-mass of water fills a 2.4264-ft3 weighted piston-cylinder device at a temperature of 600oF. The piston-cylinder device is now cooled until its temperature is 200oF. Determine the final pressure of water, in psia, and the volume, in ft3.
Three kilograms of water in a container have a pressure of 100 kPa and temperature of 150oC. What is the volume of this container?
Water is to be boiled at sea level in a 30 - cm-diameter stainless steel pan placed on top of a 3 - kW electric burner. If 60 percent of the heat generated by the burner is transferred to the water during boiling, determine the rate of evaporation of water.
Repeat Prob, 3 - 39 for a location at an elevaion of 1500 m where the atmospheric pressure is 84.5 kPa and thus the boiling temperature of water is 95oC.
10-kg of R-134a at 300 kPa fills a rigid container whose volume is 14 L. Determine the temperature and total enthalpy in the container. The container is now heated until the pressure is 600 kPa. Determine the temperature and total enthalpy when the heating is completed.
100-kg of R-134a at 200 kPa are contained in a piston-cylinder device whose volume is 12.322 m3. The piston is now moved until the volume is one-half its original size. This is done such that the pressure of the R-134a does not change. Determine the final temperature and the change in the total
Water initially at 200 kPa and 300oC is contained in a piston-cylinder device fitted with stops. The water is allowed to cool at constant pressure until it exists as a saturated vapor and the piston rests on the stops. Then the water continues to cool until the pressure is 100 kPa. On the T-v
Saturated steam coming off the turbine of a steam power plant at 40oC condenses on the outside of a 3-cmouter- diameter, 35-m-long tube at a rate of 130 kg/h. Determine the rate of heat transfer from the steam to the cooling water flowing through the pipe.
Water in a 5 - cm-deep pan is observed to boil at 98oC. At what temperature will the water in a 40 - cm-deep pan boil? Assume both pans are full of water.
A cooking pan whose inner diameter is 20 cm is filled with water and covered with a 4-kg lid. If the local atmospheric pressure is 101 kPa, determine the temperature at which the water starts boiling when it is heated.
Reconsider Prob. 3-46. Using EES (or other) software, investigate the effect of the mass of the lid on the boiling temperature of water in the pan. Let the mass vary from 1 kg to 10 kg. Plot the boiling temperature against the mass of the lid, and discuss the results.
Water is being heated in a vertical piston-cylinder device. The piston has a mass of 40 kg and a cross-sectional area of 150 cm2. If the local atmospheric pressure is 100 kPa, determine the temperature at which the water starts boiling.
Water is boiled in a pan covered with a poorly fitting lid at a specified location. Heat is supplied to the pan by a 2 - kW resistance heater. The amount of water in the pan is observed to decrease by 1.19 kg in 30 minutes. If it is estimated that 75 percent of electricity consumed by the heater is
A rigid tank with a volume of 1.8 m3 contains 15 kg of saturated liquid-vapor mixture of water at 90oC. Now the water is slowly heated. Determine the temperature at which the liquid in the tank is completely vaporized. Also, show the process on a T-v diagram with respect to saturation lines.
A piston-cylinder device contains 0.005 m3 of liquid water and 0.9 m3 of water vapor in equilibrium at 600 kPa. Heat is transferred at constant pressure until the temperature reaches 200oC.(a) What is the initial temperature of the water?(b) Determine the total mass of the water.(c) Calculate the
Reconsider Prob. 3 - 51. Using EES (or other) software, investigate the effect of pressure on the total mass of water in the tank. Let the pressure vary from 0.1 MPa to 1 MPa. Plot the total mass of water against pressure, and discuss the results. Also, show the process in Prob. 3 - 51 on a P-v
A 5-ft3 rigid tank contains 5 lbm of water at 20 psia. Determine (a) The temperature, (b) The total enthalpy, and (c) The mass of each phase of water.
A 5-ft3 rigid tank contains a saturated mixture of refrigerant-34a at 50 psia. If the saturated liquid occupies 20 percent of the volume, determine the quality and the total mass of the refrigerant in the tank.
Superheated water vapor at 180 psia and 500oF is allowed to cool at constant volume until the temperature drops to 250oF. At the final state, determine (a) The pressure, (b) The quality, and (c) The enthalpy. Also, show the process on a T-v diagram with respect to saturation lines.
Reconsider Prob. 3-55E. Using EES (or other) software, investigate the effect of initial pressure on the quality of water at the final state. Let the pressure vary from 100 psi to 300 psi. Plot the quality against initial pressure, and discuss the results. Also, show the process in Prob. 3 - 55E on
A rigid tank contains water vapor at 250oC and an unknown pressure. When the tank is cooled to 124oC, the vapor starts condensing. Estimate the initial pressure in the tank.
A piston-cylinder device initially contains 1.4-kg saturated liquid water at 200oC. Now heat is transferred to the water until the volume quadruples and the cylinder contains saturated vapor only. Determine (a) The volume of the tank, (b) The final temperature and pressure, and (c) The internal
How much error would one expect in determining the specific enthalpy by applying the incompressible-liquid approximation to water at 3000 psia and 400oF?
100 grams of R-134a initially fill a weighted piston-cylinder device at 60 kPa and 220oC. The device is then heated until the temperature is 100oC. Determine the change in the device's volume as a result of the heating.
A rigid vessel contains 8 kg of refrigerant-134a at 500 kPa and 120oC. Determine the volume of the vessel and the total internal energy
A rigid tank initially contains 1.4-kg saturated liquid water at 200oC. At this state, 25 percent of the volume is occupied by water and the rest by air. Now heat is supplied to the water until the tank contains saturated vapor only. Determine(a) The volume of the tank,(b) The final temperature and
A piston-cylinder device initially contains 50 L of liquid water at 408C and 200 kPa. Heat is transferred to the water at constant pressure until the entire liquid is vaporized.(a) What is the mass of the water?(b) What is the final temperature?(c) Determine the total enthalpy change.
What is the difference between R and Ru? How are these two related?
Propane and methane are commonly used for heating in winter, and the leakage of these fuels, even for short periods, poses a fire danger for homes. Which gas leakage do you think poses a greater risk for fire? Explain.
A 400-L rigid tank contains 5 kg of air at 25oC. Determine the reading on the pressure gage if the atmospheric pressure is 97 kPa.
A 3-ft3 container is filled with 2-lbm of oxygen at a pressure of 80 psia. What is the temperature of the oxygen?
A 2-kg mass of helium is maintained at 300 kPa and 27oC in a rigid container. How large is the container, in m3?
The pressure gage on a 2.5-m3 oxygen tank reads 500 kPa. Determine the amount of oxygen in the tank if the temperature is 28oC and the atmospheric pressure is 97 kPa.
A spherical balloon with a diameter of 9 m is filled with helium at 27oC and 200 kPa. Determine the mole number and the mass of the helium in the balloon.
Reconsider Prob. 3 - 72. Using EES (or other) software, investigate the effect of the balloon diameter on the mass of helium contained in the balloon for the pressures of (a) 100 kPa and (b) 200 kPa. Let the diameter vary from 5 m to 15 m. Plot the mass of helium against the diameter for both
The air in an automobile tire with a volume of 0.53 ft3 is at 90oF and 20 psig. Determine the amount of air that must be added to raise the pressure to the recommended value of 30 psig. Assume the atmospheric pressure to be 14.6 psia and the temperature and the volume to remain constant.
A 1-m3 tank containing air at 10oC and 350 kPa is connected through a valve to another tank containing 3 kg of air at 35oC and 200 kPa. Now the valve is opened, and the entire system is allowed to reach thermal equilibrium with the surroundings, which are at 20oC. Determine the volume of the second
A rigid tank whose volume is unknown is divided into two parts by a partition. One side of the tank contains an ideal gas at 927oC. The other side is evacuated and has a volume twice the size of the part containing the gas. The partition is now removed and the gas expands to fill the entire tank.
Argon in the amount of 1.5 kg fills a 0.04-m3 piston-cylinder device at 550 kPa. The piston is now moved by changing the weights until the volume is twice its original size. During this process, argon's temperature is maintained constant. Determine the final pressure in the device.
A rigid tank contains 20 lbm of air at 20 psia and 70oF. More air is added to the tank until the pressure and temperature rise to 35 psia and 90oF, respectively. Determine the amount of air added to the tank.
Refrigerant-134a at 400 psia has a specific volume of 0.1384 ft3/lbm. Determine the temperature of the refrigerant based on (a) The ideal-gas equation, (b) The generalized compressibility chart, and (c) The refrigerant tables.
Determine the specific volume of superheated water vapor at 15 MPa and 350oC, using (a) The ideal-gas equation, (b) The generalized compressibility chart, and (c) The steam tables. Also determine the error involved in the first two cases.
Determine the specific volume of superheated water vapor at 3.5 MPa and 450oC based on (a) The ideal-gas equation, (b) The generalized compressibility chart, and (c) The steam tables. Determine the error involved in the first two cases.
Determine the specific volume of superheated water vapor at 3.5 MPa and 4508C based on (a) The ideal-gas equation, (b) The generalized compressibility chart, and (c) The steam tables. Determine the error involved in the first two cases.
Somebody claims that oxygen gas at 160 K and 3 MPa can be treated as an ideal gas with an error of less than 10 percent. Is this claim valid?
Ethane in a rigid vessel is to be heated from 50 psia and 1008F until its temperature is 540oF. What is the final pressure of the ethane as predicted by the compressibility chart?
Ethylene is heated at constant pressure from 5 MPa and 20oC to 200oC. Using the compressibility chart, determine the change in the ethylene's specific volume as a result of this heating.
What is the percentage of error involved in treating carbon dioxide at 7 MPa and 380 K as an ideal gas?
Saturated water vapor at 350oC is heated at constant pressure until its volume has doubled. Determine the final temperature using the ideal gas equation of state, the compressibility charts, and the steam tables.
In what kind of pot will a given volume of water boil at a higher temperature: a tall and narrow one or a short and wide one? Explain.
Methane at 10 MPa and 300 K is heated at constant pressure until its volume has increased by 80 percent. Determine the final temperature using the ideal gas equation of state and the compressibility factor. Which of these two results is more accurate?
Carbon dioxide gas enters a pipe at 3 MPa and 500 K at a rate of 2 kg/s. CO2 is cooled at constant pressure as it flows in the pipe and the temperature of CO2 drops to 450 K at the exit. Determine the volume flow rate and the density of carbon dioxide at the inlet and the volume flow rate at the
A 0.016773-m3 tank contains 1 kg of refrigerant-134a at 110oC. Determine the pressure of the refrigerant, using (a) The ideal-gas equation, (b) The generalized compressibility chart, and (c) The refrigerant tables.
What is the physical significance of the two constants that appear in the van der Waals equation of state? On what basis are they determined?
A 3.27-m3 tank contains 100 kg of nitrogen at 175 K. Determine the pressure in the tank, using (a) The ideal-gas equation, (b) The van der Waals equation, and (c) The Beattie- Bridgeman equation. Compare your results with the actual value of 1505 kPa.
Methane is heated in a rigid container from 80 kPa and 20oC to 300oC. Determine the final pressure of the methane treating it as (a) An ideal gas and (b) A Benedict-Webb- Rubin gas.
Refrigerant-134a at 400 psia has a specific volume of 0.1144 ft3/lbm. Determine the temperature of the refrigerant based on (a) The ideal-gas equation, (b) The van der Waals equation, and (c) The refrigerant tables.
Nitrogen at 150 K has a specific volume of 0.041884 m3/kg. Determine the pressure of the nitrogen, using (a) The ideal-gas equation and (b) The Beattie- Bridgeman equation. Compare your results to the experimental value of 1000 kPa.
Reconsider Prob. 3 - 97. Using EES (or other) software, compare the pressure results of the ideal-gas and Beattie-Bridgeman equations with nitrogen data supplied by EES. Plot temperature versus specific volume for a pressure of 1000 kPa with respect to the saturated liquid and saturated vapor lines
1-kg of carbon dioxide is compressed from 1 MPa and 200oC to 3 MPa in a piston-cylinder device arranged to execute a polytropic process for which PV 1.2 5 constant. Determine the final temperature treating the carbon dioxide as (a) An ideal gas and (b) A van der Waals gas.
A refrigerator operating on the reversed Carnot cycle has a measured work input of 200 kW and heat rejection of 2000 kW to a heat reservoir at 27°C. Determine the cooling load supplied to the refrigerator, in kW, and the temperature of the heat source, in °C.
A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -35°C by rejecting waste heat to cooling water that enters the condenser at 18°C at a rate of 0.25 kg/s and leaves at 26°C. The refrigerant enters the condenser at 1.2 MPa and
The performance of a heat pump degrades (i.e., its COP decreases) as the temperature of the heat source decreases. This makes using heat pumps at locations with severe weather conditions unattractive. Consider a house that is heated and maintained at 20°C by a heat pump during the winter. What is
A heat pump is to be used for heating a house in winter. The house is to be maintained at 78°F at all times. When the temperature outdoors drops to 25°F, the heat losses from the house are estimated to be 70,000 Btu/h. Determine the minimum power required to run this heat pump if heat is
A Carnot heat pump is to be used to heat a house and maintain it at 25°C in winter. On a day when the average outdoor temperature remains at about 2°C, the house is estimated to lose heat at a rate of 55,000 kJ/h. If the heat pump consumes 4.8 kW of power while operating, determine(a) How
A Carnot heat engine receives heat from a reservoir at 900°C at a rate of 800 kJ/min and rejects the waste heat to the ambient air at 27°C. The entire work output of the heat engine is used to drive a refrigerator that removes heat from the refrigerated space at -5°C and transfers it to the same
A Carnot heat engine receives heat from a reservoir at 1700°F at a rate of 700 Btu/min and rejects the waste heat to the ambient air at 80°F. The entire work output of the heat engine is used to drive a refrigerator that removes heat from the refrigerated space at 20°F and transfers it to the
The structure of a house is such that it loses heat at a rate of 3800 kJ/h per °C difference between the indoors and outdoors. A heat pump that requires a power input of 4 kW is used to maintain this house at 24°C. Determine the lowest outdoor temperature for which the heat pump can meet the
An air-conditioner with refrigerant-134a as the working fluid is used to keep a room at 23°C by rejecting the waste heat to the outdoor air at 34°C. The room gains heat through the walls and the windows at a rate of 250 kJ/min while the heat generated by the computer, TV, and lights amounts
Derive an expression for the COP of a completely reversible refrigerator in terms of the thermal energy reservoir temperatures, TL and TH.
Why are today's refrigerators much more efficient than those built in the past?
Explain how you can reduce the energy consumption of your household refrigerator.
Why is it important to clean the condenser coils of a household refrigerator a few times a year? Also, why is it important not to block airflow through the condenser coils?
Someone proposes that the refrigeration system of a supermarket be overdesigned so that the entire air-conditioning needs of the store can be met by refrigerated air without installing any air-conditioning system. What do you think of this proposal?
Someone proposes that the entire refrigerator/freezer requirements of a store be met using a large freezer that supplies sufficient cold air at -20°C instead of installing separate refrigerators and freezers. What do you think of this proposal?
The "Energy Guide" label of a refrigerator states that the refrigerator will consume $170 worth of electricity per year under normal use if the cost of electricity is $0.125/kWh. If the electricity consumed by the lightbulb is negligible and the refrigerator consumes 400 W when running, determine
The interior lighting of refrigerators is usually provided by incandescent lamps whose switches are actuated by the opening of the refrigerator door. Consider a refrigerator whose 40-W lightbulb remains on about 60 h per year. It is proposed to replace the lightbulb by an energy-efficient bulb that
It is commonly recommended that hot foods be cooled first to room temperature by simply waiting a while before they are put into the refrigerator to save energy. Despite this commonsense recommendation, a person keeps cooking a large pan of stew three times a week and putting the pan into the
It is often stated that the refrigerator door should be opened as few times as possible for the shortest duration of time to save energy. Consider a household refrigerator whose interior volume is 0.9 m3 and average internal temperature is 4°C. At any given time, one-third of the refrigerated
An air-conditioning system is used to maintain a house at a constant temperature of 20°C. The house is gaining heat from outdoors at a rate of 20,000 kJ/h, and the heat generated in the house from the people, lights, and appliances amounts to 8000 kJ/h. For a COP of 2.5, determine the required
A Carnot heat pump is used to heat and maintain a residential building at 75°F. An energy analysis of the house reveals that it loses heat at a rate of 2500 Btu/h per °F temperature difference between the indoors and the outdoors. For an outdoor temperature of 35°F, determine (a) The coefficient
A heat engine receives heat from a heat source at 1200°C and rejects heat to a heat sink at 50°C. The heat engine does maximum work equal to 500 kJ. Determine the heat supplied to the heat engine by the heat source and the heat rejected to the heat sink.
A heat pump creates a heating effect of 32,000 Btu/h for a space maintained at 530 R while using 1.8 kW of electrical power. What is the minimum temperature of the source that satisfies the second law of thermodynamics?
A refrigeration system uses water-cooled condenser for rejecting the waste heat. The system absorbs heat from a space at 25°F at a rate of 24,000 Btu/h. Water enters the condenser at 65°F at a rate of 1.45 lbm/s. The COP of the system is estimated to be 1.9. Determine (a) The power input to the
A heat pump with a COP of 2.8 is used to heat an air-tight house. When running, the heat pump consumes 5 kW of power. If the temperature in the house is 7°C when the heat pump is turned on, how long will it take for the heat pump to raise the temperature of the house to 22°C? Is this answer
A promising method of power generation involves collecting and storing solar energy in large artificial lakes a few meters deep, called solar ponds. Solar energy is absorbed by all parts of the pond, and the water temperature rises everywhere. The top part of the pond, however, loses to the
Consider a Carnot refrigeration cycle executed in a closed system in the saturated liquid-vapor mixture region using 0.96 kg of refrigerant-134a as the working fluid. It is known that the maximum absolute temperature in the cycle is 1.2 times the minimum absolute temperature, and the net work input
Reconsider Prob. 6-126. Using EES (or other) software, investigate the effect of the net work input on the minimum pressure. Let the work input vary from 10 to 30 kJ. Plot the minimum pressure in the refrigeration cycle as a function of net work input, and discuss the results. Prob. 6-126 Consider
Consider two Carnot heat engines operating in series. The first engine receives heat from the reservoir at 1400 K and rejects the waste heat to another reservoir at temperature T. The second engine receives this energy rejected by the first one, converts some of it to work, and rejects the rest to
A Carnot heat engine receives heat at 900 K and rejects the waste heat to the environment at 300 K. The entire work output of the heat engine is used to drive a Carnot refrigerator that removes heat from the cooled space at -15°C at a rate of 250 kJ/min and rejects it to the same environment at

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