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engineering
thermodynamics an engineering approach
Thermodynamics An Engineering Approach 9th Edition Yunus Cengel, Michael Boles, Mehmet Kanoglu - Solutions
What is the percentage of error involved in treating carbon dioxide at 5 MPa and 25°C as an ideal gas?
Saturated water vapor at 400°F 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.
A mass of 10 g of oxygen fill a weighted piston–cylinder device at 20 kPa and 100°C. The device is now cooled until the temperature is 0°C. Determine the change of the volume of the device during this cooling.
A mass of 1 lbm of argon is maintained at 200 psia and 100°F in a tank. What is the volume of the tank?
A 100-L container is filled with 1 kg of air at a temperature of 27°C. What is the pressure in the container?
What is the specific volume of oxygen at 25 psia and 80°F?
The spring-loaded piston–cylinder is filled with 0.5 kg of water vapor that is initially at 4 MPa and 400°C. Initially, the spring exerts no force against the piston. The spring constant in the spring force relation F = kx is k = 0.9 kN/cm and the piston diameter is D = 20 cm. The water now
A piston–cylinder device contains 0.6 kg of steam at 300°C and 0.5 MPa. Steam is cooled at constant pressure until one-half of the mass condenses.(a) Show the process on a T-v diagram.(b) Find the final temperature.(c) Determine the volume change.
A rigid tank with a volume of 1.8 m3 contains 40 kg of saturated liquid vapor mixture of water at 90°C. 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.
One kilogram of water vapor at 200 kPa fills the 1.1989-m3 left chamber of a partitioned system shown in Fig. P3–37. The right chamber has twice the volume of the left and is initially evacuated. Determine the pressure of the water after the partition has been removed and enough heat has
One kilogram of R-134a fills a 0.14-m3 weighted piston–cylinder device at a temperature of –26.4°C. The container is now heated until the temperature is 100°C. Determine the final volume of the R-134a.
What is the specific volume of R-134a at 20°C and 700 kPa? What is the internal energy at that state?
What is the specific internal energy of water at 50 kPa and 200°C?
10 kg of R-134a fill a 1.115-m3 rigid container at an initial temperature of –30°C. The container is then heated until the pressure is 200 kPa. Determine the final temperature and the initial pressure.
One pound-mass of water fills a container whose volume is 2ft3. The pressure in the container is 100 psia. Calculate the total internal energy and enthalpy in the container.
Reconsider Prob. 3–23E. Using appropriate software, determine the missing properties of water. Repeat the solution for refrigerant-134a, refrigerant-22, and ammonia.
Complete this table for H2O: T, °C Р, КРа U, m/kg Phase description 140 0.035 550 Saturated liquid 125 750 300 0.140
A propane tank is filled with a mixture of liquid and vapor propane. Can the contents of this tank be considered a pure substance? Explain.
Some engineers have suggested that air compressed into tanks can be used to propel personal transportation vehicles. Current compressed-air tank technology permits us to compress and safely hold air at up to 4000 psia. Tanks made of composite materials require about 10 lbm of construction materials
The performance of a device is defined as the ratio of the desired output to the required input, and this definition can be extended to nontechnical fields. For example, your performance in this course can be viewed as the grade you earn relative to the effort you put in. If you have been investing
Pressure changes across atmospheric weather fronts are typically a few centimeters of mercury, while the temperature changes are typically 2–20°C. Develop a plot of front pressure change versus front temperature change that will cause a maximum wind velocity of 10 m/s or more.
An average vehicle puts out nearly 20 lbm of carbon dioxide into the atmosphere for every gallon of gasoline it burns, and thus one thing we can do to reduce global warming is to buy a vehicle with higher fuel economy. A U.S. government publication states that a vehicle that gets 25 rather than 20
The elevator of a large building is to raise a net mass of 550 kg at a constant speed of 12 m/s using an electric motor. The minimum power rating of the motor should be(a) 0 kW (b) 4.8 kW (c) 12 kW(d) 45 kW (e) 65 kW
A fan is to accelerate quiescent air to a velocity of 9 m/s at a rate of 3 m3/s. If the density of air is 1.15 kg/m3, the minimum power that must be supplied to the fan is(a) 41 W (b) 122 W (c) 140 W(d) 206 W (e) 280 W
A 75-hp compressor in a facility that operates at full load for 2500 h a year is powered by an electric motor that has an efficiency of 93 percent. If the unit cost of electricity is $0.11/kWh, the annual electricity cost of this compressor is(a) $14,300 (b) $15,380 (c) $16,540(d)
Consider a refrigerator that consumes 320 W of electric power when it is running. If the refrigerator runs only one-quarter of the time and the unit cost of electricity is $0.13/kWh, the electricity cost of this refrigerator per month (30 days) is(a) $4.9 (b) $5.8 (c) $7.5(d)
The force required to expand the gas in a gas spring a distance x is given byF = Constant / xkwhere the constant is determined by the geometry of this device and k is determined by the gas used in the device. Such a gas spring is arranged to have a constant of 1000 N·m1.3 and k = 1.3. Determine
The force F required to compress a spring a distance x is given by F – F0 = kx where k is the spring constant and F0 is the preload. Determine the work, in kJ, required to compress a spring a distance of 1 cm when its spring constant is 300 N/cm and the spring is initially compressed by a force
A diesel engine with an engine volume of 4.0 L and an engine speed of 2500 rpm operates on an air–fuel ratio of 18 kg air/kg fuel. The engine uses light diesel fuel that contains 500 ppm (parts per million) of sulfur by mass. All of this sulfur is exhausted to the environment, where the sulfur is
Some engineers have developed a device that provides lighting to rural areas with no access to grid electricity. The device is intended for indoor use. It is driven by gravity, and it works as follows: A bag of rock or sand is raised by human power to a higher location. As the bag descends very
Reconsider Prob. 2–103. Using appropriate software, investigate the effect of the convection heat transfer coefficient on the surface temperature of the plate. Let the heat transfer coefficient vary from 10 to 90 W/m2·°C. Plot the surface temperature against the convection heat transfer
Large wind turbines with a power capacity of 8 MW and blade span diameters of over 160 m are available for electric power generation. Consider a wind turbine with a blade span diameter of 100 m installed at a site subjected to steady winds at 8 m/s. Taking the overall efficiency of the wind turbine
An 80-percent-efficient pump with a power input of 20 hp is pumping water from a lake to a nearby pool at a rate of 1.5 ft3/s through a constant-diameter pipe. The free surface of the pool is 80 ft above that of the lake. Determine the mechanical power used to overcome frictional effects in piping.
An exercise room has six weight-lifting machines that have no motors and seven treadmills each equipped with a 2.5-hp (shaft output) motor. The motors operate at an average load factor of 0.7, at which their efficiency is 0.77. During peak evening hours, all 13 pieces of exercising equipment are
Reconsider Prob. 2–56E. Using appropriate software, study the effects of the unit cost of energy, the new combustion efficiency on the annual energy, and cost savings. Let the efficiency vary from 0.7 to 0.9, and let the unit cost vary from $12 to $14 per million Btu. Plot the annual energy and
One way to improve the fuel efficiency of a car is to use tires that have a lower rolling resistance—tires that roll with less resistance. Highway tests at 65 mph showed that tires with the lowest rolling resistance can improve fuel efficiency by nearly 2 mpg (miles per gallon). Consider a car
Consider a 2100-kg car cruising at constant speed of 70 km/h. Now the car starts to pass another car by accelerating to 110 km/h in 5 s. Determine the additional power needed to achieve this acceleration. What would your answer be if the total mass of the car were only 700 kg?
A fan is to accelerate quiescent air to a velocity of 8 m/s at a rate of 9 m3/s. Determine the minimum power that must be supplied to the fan. Take the density of air to be 1.18 kg/m3.
Water is being heated in a closed pan on top of a range while being stirred by a paddle wheel. During the process, 30 kJ of heat is transferred to the water, and 5 kJ of heat is lost to the surrounding air. The paddle-wheel work amounts to 500 N·m. Determine the final energy of the system if its
Reconsider Prob. 1–116E. Using appropriate software, plot the equivalent wind chill temperatures in °F as a function of wind velocity in the range of 4 to 40 mph for the ambient temperatures of 20, 40, and 60°F. Discuss the results.Data from prob, 1-116E.It is well known that cold air feels
The drag force exerted on a car by air depends on a dimensionless drag coefficient, the density of air, the car velocity, and the frontal area of the car. That is, FD = FD(Cdrag, Afront, ρ, V). Based on unit considerations alone, obtain a relation for the drag force. Air V FIGURE P1-115
When measuring small pressure differences with a manometer, often one arm of the manometer is inclined to improve the accuracy of reading. (The pressure difference is still proportional to the vertical distance and not the actual length of the fluid along the tube.) The air pressure in a circular
A glass tube is attached to a water pipe, as shown in Fig. P1–107. If the water pressure at the bottom of the tube is 107 kPa and the local atmospheric pressure is 99 kPa, determine how high the water will rise in the tube, in m. Take the density of water to be 1000 kg/m3. Patm = 99 kPa h=? Water
The pilot of an airplane reads the altitude 6400 m and the absolute pressure 45 kPa when flying over a city. Calculate the local atmospheric pressure in that city in kPa and in mmHg. Take the densities of air and mercury to be 0.828 kg/m3 and 13,600 kg/m3, respectively. Altitude: 6.4 km P= 45 kPa
Reconsider Prob. 1–101. Using appropriate software, investigate the effect of the number of people carried in the balloon on acceleration. Plot the acceleration against the number of people, and discuss the results. Helium D = 12 m PHe =7 Pair %3D m= 170 kg FIGURE P1-101
A vertical piston–cylinder device contains a gas at a pressure of 100 kPa. The piston has a mass of 10 kg and a diameter of 14 cm. Pressure of the gas is to be increased by placing some weights on the piston. Determine the local atmospheric pressure and the mass of the weights that will double
A hydraulic lift is to be used to lift a 1900-kg weight by putting a weight of 25 kg on a piston with a diameter of 10 cm. Determine the diameter of the piston on which the weight is to be placed. Weight 1900 kg F1 25 kg F2 D2 10 cm FIGURE P1-90
The hydraulic lift in a car repair shop has an output diameter of 30 cm and is to lift cars up to 2500 kg. Determine the fluid gage pressure that must be maintained in the reservoir.
Consider the manometer in Fig. P1–73. If the specific weight of fluid B is 20 kN/m3, what is the absolute pressure, in kPa, indicated by the manometer when the local atmospheric pressure is 720 mmHg? Atmospheric pressure 12 cm 15 cm 5 cm Fluid B 8 kN/m 30 cm Fluid A 10 kN/m FIGURE P1-73
Consider the manometer in Fig. P1–73. If the specific weight of fluid A is 100 kN/m3, what is the absolute pressure, in kPa, indicated by the manometer when the local atmospheric pressure is 90 kPa? Atmospheric pressure 12 cm 15 cm 5 cm Fluid B 8 kN/m 30 cm Fluid A 10 kN/m FIGURE P1-73
Reconsider Prob. 1-58. Using appropriate software, investigate the effect of the spring force in the range of 0 to 500 N on the pressure inside the cylinder. Plot the pressure against the spring force, and discuss the results. 150 N Patm = 95 kPa m, = 3.2 kg A = 35 cm? FIGURE P1-58
Steam enters a heat exchanger at 300 K. What is the temperature of this steam in °F?
A steel rod of 0.5 cm diameter and 10 m length is stretched 3 cm. Young’s modulus for this steel is 21 kN/cm2. How much work, in kJ, is required to stretch this rod?
As a spherical ammonia vapor bubble rises in liquid ammonia, its diameter changes from 1 cm to 3 cm. Calculate the amount of work produced by this bubble, in kJ, if the surface tension of ammonia is 0.02 N/m.
How much work, in kJ, can a spring whose spring constant is 3 kN/cm produce after it has been compressed 3 cm from its unloaded length?
A spring whose spring constant is 200 lbf/in has an initial force of 100 lbf acting on it. Determine the work, in Btu, required to compress it another 1 in.
Determine the torque applied to the shaft of a car that transmits 225 hp and rotates at a rate of 3000 rpm
A construction crane lifts a prestressed concrete beam weighing 3 short tons from the ground to the top of piers that are 24 ft above the ground. Determine the amount of work done considering (a) The beam (b) The crane as the system. Express your answers in both lbf·ft and Btu.
An object whose mass is 100 kg is located 20 m above a datum level in a location where standard gravitational acceleration exists. Determine the total potential energy, in kJ, of this object.
Determine the specific potential energy, in kJ/kg, of an object 50 m above a datum in a location where g = 9.8 m/s2.
Calculate the total potential energy, in Btu, of an object that is 20 ft below a datum level at a location where g = 31.7 ft/s2 and which has a mass of 100 lbm.
Determine the specific kinetic energy of a mass whose velocity is 30 m/s, in kJ/kg.
The specific kinetic energy of a moving mass is given by ke = V2/2, where V is the velocity of the mass. Determine the specific kinetic energy of a mass whose velocity is 100 ft/s, in Btu/lbm.
Consider the falling of a rock off a cliff into seawater, and eventually settling at the bottom of the sea. Starting with the potential energy of the rock, identify the energy transfers and transformations involved during this process.
Consider a 2.5-m-deep swimming pool. The pressure difference between the top and bottom of the pool is(a) 2.5 kPa(b) 12.0 kPa(c) 19.6 kPa(d) 24.5 kPa(e) 250 kPa
An apple loses 3.6 kJ of heat as it cools per °C drop in its temperature. The amount of heat loss from the apple per °F drop in its temperature is(a) 0.5 kJ(b) 1.8 kJ(c) 2.0 kJ(d) 3.6 kJ(e) 6.5 kJ
Determine the maximum amount of load, in kg, the balloon described in Prob. 1–101 can carry. Helium D = 12 m PHe = Pair m = 170 kg FIGURE P1-101
The force generated by a spring is given by F = kx, where k is the spring constant and x is the deflection of the spring. The spring of Fig. P1–99 has a spring constant of 8 kN/cm. The pressures are P1 = 5000 kPa, P2 = 10,000 kPa, and P3 = 1000 kPa. If the piston diameters are D1 = 8 cm and D2 =
Solve this system of two equations with two unknowns using appropriate software:x3 − y2 = 5.93xy + y = 3.5
Consider a double-fluid manometer attached to an air pipe shown in Fig. P1–72. If the specific gravity of one fluid is 13.55, determine the specific gravity of the other fluid for the indicated absolute pressure of air. Take the atmospheric pressure to be 100 kPa. Air P = 69 kPa 40 cm SG, 28 cm
The pressure in a natural gas pipeline is measured by the manometer shown in Fig. P1–67E with one of the arms open to the atmosphere where the local atmospheric pressure is 14.2 psia. Determine the absolute pressure in the pipeline. Air 2 in Natural Gas 10 in 25 in 6 in `Mercury SG= 13.6 Water
Repeat Prob. 1–65 for a differential mercury height of 45 mm. Air h = 30 mm P = ? Mercury FIGURE P1-65
A mercury manometer (ρ = 13,600 kg/m3) is connected to an air duct to measure the pressure inside. The difference in the manometer levels is 30 mm, and the atmospheric pressure is 100 kPa.(a) Judging from Fig. P1–65, determine if the pressure in the duct is above or below the atmospheric
The piston of a vertical piston–cylinder device containing a gas has a mass of 60 kg and a cross-sectional area of 0.04 m2, as shown in Fig. P1–60. The local atmospheric pressure is 0.97 bar, and the gravitational acceleration is 9.81 m/s2.(a) Determine the pressure inside the
Consider a 1.75-m-tall man standing vertically in water and completely submerged in a pool. Determine the difference between the pressures acting at the head and at the toes of the man, in kPa.
The maximum safe air pressure of a tire is typically written on the tire itself. The label on a tire indicates that the maximum pressure is 35 psi (gage). Express this maximum pressure in kPa. FIGURE P1-48E
A manometer measures a pressure difference as 40 inches of water. What is this pressure difference in pound-force per square inch, psi?
The absolute pressure in a compressed air tank is 200 kPa. What is this pressure in psia?
The temperature of the lubricating oil in an automobile engine is measured as 150°F. What is the temperature of this oil in °C?
The temperature of a system rises by 130°C during a heating process. Express this rise in temperature in kelvins.
Is the number of moles of a substance contained in a system an extensive or intensive property?
The specific weight of a system is defined as the weight per unit volume (note that this definition violates the normal specific property-naming convention). Is the specific weight an extensive or intensive property?
How would you describe the state of the air in the atmosphere? What kind of process does this air undergo from a cool morning to a warm afternoon?
How would you define a system to determine the temperature rise created in a lake when a portion of its water is used to cool a nearby electrical power plant?
How would you define a system to determine the rate at which an automobile adds carbon dioxide to the atmosphere?
Solve Prob. 1–13 using appropriate software. Print out the entire solution, including the numerical results with proper units. Oil V= 2 m p= 850 kg/m m = ? FIGURE 1-13
A 2-kg rock is thrown upward with a force of 200 N at a location where the local gravitational acceleration is 9.79 m/s2. Determine the acceleration of the rock, in m/s2.
If the mass of an object is 10 lbm, what is its weight, in lbf, at a location where g = 32.0 ft/s2?
What is the difference between pound-mass and pound-force?
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