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engineering
mechanical engineering

Questions and Answers of Mechanical Engineering

A foundry form box with 25 kg of 200C hot sand is dumped into a bucket with 50 L water at 15C. Assuming no heat transfer with the surroundings and no boiling away of liquid water,
A large slab of concrete, 5 8 0.3 m, is used as a thermal storage mass in a solar-heated house. If the slab cools overnight from 23C to 18C in an
Find the total work the heat engine can give out as it receives energy from the rock bed as described in Problem 7.22. Hint: write the entropy balance equation for the control volume that is the
Liquid lead initially at 500C is poured into a form so that it holds 2 kg. It then cools at constant pressure down to room temperature of 20C as heat is transferred to the room. The
A hollow steel sphere with a 0.5-m inside diameter and a 2-mm thick wall contains water at 2 MPa, 250C. The system (steel plus water) cools to the ambient temperature, 30C, calculate
A mass of 1 kg of air contained in a cylinder at 1.5 MPa, 1000 K, expands in a reversible isothermal process to a volume 10 times larger. Calculate the heat transfer during the process and the change
A mass of 1 kg of air contained in a cylinder at 1.5 MPa, 1000 K, expands in a reversible adiabatic process to 100 kPa. Calculate the final temperature and the work done during the process, using a.
Consider a Carnot-cycle heat pump having 1 kg of nitrogen gas in a cylinder/piston arrangement. This heat pump operates between reservoirs at 300 K and 400 K. At the beginning of the low-temperature
A rigid tank contains 2 kg of air at 200 kPa and ambient temperature, 20C. An electric current now passes through a resistor inside the tank. After a total of 100 kJ of electrical work has
A handheld pump for a bicycle has a volume of 25 cm3 when fully extended. You now press the plunger (piston) in while holding your thumb over the exit hole, so that an air pressure of 300 kPa is
An insulated cylinder/piston contains carbon dioxide gas at 120 kPa, 400 K. The gas is compressed to 2.5 MPa in a reversible adiabatic process. Calculate the final temperature and the work per unit
Consider a small air pistol with a cylinder volume of 1 cm3 at 250 kPa, 27C. The bullet acts as a piston initially held by a trigger. The bullet is released so the air expands in an adiabatic
A rigid storage tank of 1.5 m3 contains 1 kg argon at 30C. Heat is then transferred to the argon from a furnace operating at 1300C until the specific entropy of the argon has
A piston/cylinder, contains air at 1380 K, 15 MPa, with V1 = 10 cm3, Acyl = 5 cm2. The piston is released, and just before the piston exits the end of the cylinder the pressure inside is 200 kPa. If
Two rigid tanks each contain 10 kg N2 gas at 1000 K, 500 kPa. They are now thermally connected to a reversible heat pump, which heats one and cools the other with no heat transfer to the
Repeat the previous problem, but with variable heat capacities.
We wish to obtain a supply of cold helium gas by applying the following technique. Helium contained in a cylinder at ambient conditions, 100 kPa, 20C, is compressed in a reversible isothermal
A 1-m3 insulated, rigid tank contains air at 800 kPa, 25C. A valve on the tank is opened, and the pressure inside quickly drops to 150 kPa, at which point the valve is closed. Assuming that
An uninsulated cylinder fitted with a piston contains air at 500 kPa, 200C, at which point the volume is 10 L. The external force on the piston is now varied in such a manner that the air
A rigid container with volume 200 L is divided into two equal volumes by a partition. Both sides contain nitrogen one side is at 2 MPa, 200C, and the other at 200 kPa, 100C. The
Nitrogen at 600 kPa, 127C is in a 0.5 m3 insulated tank connected to a pipe with a valve to a second insulated initially empty tank of volume 0.5 m3. The valve is opened and the nitrogen
Neon at 400 kPa, 20C is brought to 100C in a polytropic process with n 1.4. Give the sign for the heat transfer and work terms and explain.
A cylinder/piston contains carbon dioxide at 1 MPa, 300C with a volume of 200 L. The total external force acting on the piston is proportional to V 3. This system is allowed to cool to room
A cylinder/piston contains 1 kg methane gas at 100 kPa, 20C. The gas is compressed reversibly to a pressure of 800 kPa. Calculate the work required if the process is a. Adiabatic b.
The power stroke in an internal combustion engine can be approximated with a polytropic expansion. Consider air in a cylinder volume of 0.2 L at 7 MPa, 1800 K. It now expands in a reversible
Helium in a piston/cylinder at 20C, 100 kPa is brought to 400 K in a reversible polytropic process with exponent n = 1.25. You may assume helium is an ideal gas with constant specific heat.
A cylinder/piston contains air at ambient conditions, 100 kPa and 20C with a volume of 0.3 m3. The air is compressed to 800 kPa in a reversible polytropic process with exponent, n
An ideal gas having a constant specific heat undergoes a reversible polytropic expansion with exponent, n 1.4. If the gas is carbon dioxide will the heat transfer for this process be
A cylinder fitted with a piston contains 0.5 kg of R-134a at 60C, with a quality of 50 percent. The R-134a now expands in an internally reversible polytropic process to ambient temperature,
A cylinder/piston contains 100 L of air at 110 kPa, 25C. The air is compressed in a reversible polytropic process to a final state of 800 kPa, 200C. Assume the heat transfer is with
A mass of 2 kg ethane gas at 500 kPa, 100C, undergoes a reversible polytropic expansion with exponent, n 1.3, to a final temperature of the ambient, 20C, calculate the
A cylinder/piston contains saturated vapor R-22 at 10C; the volume is 10 L. The R-22 is compressed to 2 MPa, 60C in a reversible (internally) polytropic process. If all the heat
A closed, partly insulated cylinder divided by an insulated piston contains air in one side and water on the other, as shown in Fig. P8.59. There is no insulation on the end containing water. Each
A spring-loaded piston/cylinder contains water at 100 kPa with v 0.07237 m3/kg. The water is now heated to a pressure of 3 MPa by a reversible heat pump extracting Q from a reservoir
A cylinder with a linear spring-loaded piston contains carbon dioxide gas at 2 MPa with a volume of 50 L. The device is of aluminum and has a mass of 4 kg. Everything (Al and gas) is initially at
A cylinder fitted with a piston contains air at 400 K, 1.0 MPa, at which point the volume is 100 L. The air now expands to a final state at 300 K, 200 kPa, and during the process the cylinder
An insulated cylinder with a frictionless piston contains water at ambient pressure, 100 kPa, a quality of 0.8 and the volume is 8 L. A force is now applied, slowly compressing the water until it
Consider the process. The insulated tank A has a volume of 600 L, and contains steam at 1.4 MPa, 300C. The uninsulated tank B has a volume of 300 L and contains steam at 200 kPa,
A vertical cylinder/piston contains R–22 at 20C, 70% quality, and the volume is 50 L. This cylinder is brought into a 20C room, and an electric current of 10 A is passed
Redo Problem 8.57, but calculate the mass withdrawn by a first-law, control volume analysis. Compare the result to that obtained in Problem 8.57. Show from a differential step of mass out that the
A vertical cylinder is fitted with a frictionless piston that is initially resting on stops. The cylinder contains carbon dioxide gas at 200 kPa, 300 K, and at this point the volume is 50 L. A
A piston/cylinder contains 2 kg water at 5 MPa, 800C. The piston is loaded so pressure is proportional to volume, P = CV. It is now cooled by an external reservoir at 0C to a final
A gas in a rigid vessel is at ambient temperature and at a pressure, P1, slightly higher than ambient pressure, P0. A valve on the vessel is opened, so gas escapes and the pressure drops quickly to
Consider the steam power plant in Problem 7.57 and show that this cycle satisfies the inequality of Clausius.
Find the missing properties and give the phase of the substance a. H2O s 1.75 Btu/lbm R, P 4 lbf/in 2 h ? T ? x ? b.
In a Carnot engine with water as the working fluid, the high temperature is 450 F and as QL is received, the water changes from saturated liquid to saturated vapor. The water pressure at the low
Consider a Carnot-cycle heat pump with R-22 as the working fluid. Heat is rejected from the R-22 at 100 F, during which process the R-22 changes from saturated vapor to saturated liquid. The heat is
Do Problem 8.86 using refrigerant R-134a instead of R-22.
Water at 30 lbf/in 2, x = 1.0 is compressed in a piston/cylinder to 140 lbf/in 2, 600 F in a reversible process. Find the sign for the work and the sign for the heat transfer.
Two pound-mass of ammonia in a piston/cylinder at 120 F, 150 lbf/in 2 is expanded in a reversible adiabatic process to 15 lbf/in 2. Find the work and heat transfer for this process.
A cylinder fitted with a piston contains ammonia at 120 F, 20% quality with a volume of 60 in 3. The ammonia expands slowly, and during this process heat is transferred to maintain a constant
One pound-mass of water at 600 F expands against a piston in a cylinder until it reaches ambient pressure, 14.7 lbf/in 2, at which point the water has a quality of 90%. It may be assumed that the
A closed tank, V 0.35 ft3, containing 10 lbm of water initially at 77 F is heated to 350 F by a heat pump that is receiving heat from the surroundings at 77 F. Assume that this
A cylinder containing R-134a at 50 F, 20 lbf/in 2, has an initial volume of 1 ft3. A piston compresses the R-134a in a reversible, isothermal process until it reaches the saturated vapor state.
A rigid, insulated vessel contains superheated vapor steam at 450 lbf/in 2, 700 F. A valve on the vessel is opened, allowing steam to escape. It may be assumed that the steam remaining inside the
A cylinder/piston contains 5 lbm of water at 80 lbf/in 2, 1000 F. The piston has cross-sectional area of 1 ft2 and is restrained by a linear spring with spring constant 60 lbf/in. The setup is
An insulated cylinder/piston contains R-134a at 150 lbf/in 2, 120 F, with a volume of 3.5 ft3. The R-134a expands, moving the piston until the pressure in the cylinder has dropped to 15 lbf/in 2. It
A mass and atmosphere loaded piston/cylinder contains 4 lbm of water at 500 lbf/in 2, 200 F. Heat is added from a reservoir at 1200 F to the water until it reaches 1200 F. Find the work, heat
A 1 gallon jug of milk at 75 F is placed in your refrigerator where it is cooled down to the refrigerators inside temperature of 40 F. Assume the milk has the properties of liquid water and find the
Water in a piston/cylinder is at 150 lbf/in 2, 900 F. There are two stops, a lower one at which Vmin 35 ft3 and an upper one at Vmax 105 ft3. The piston is loaded with
A cylinder/piston contains water at 30 lbf/in 2, 400 F with a volume of 1 ft3. The piston is moved slowly, compressing the water to a pressure of 120 lbf/in 2. The loading on the piston is such that
One pound mass of ammonia (NH3) is contained in a linear spring-loaded piston/cylinder as saturated liquid at 0 F. Heat is added from a reservoir at 225 F until a final condition of 125 lbf/in 2, 160
A foundry form box with 50 lbm of 400 F hot sand is dumped into a bucket with 2 ft3 water at 60 F. Assuming no heat transfer with the surroundings and no boiling away of liquid water, calculate the
A hollow steel sphere with a 2-ft inside diameter and a 0.1-in. thick wall contains water at 300 lbf/in 2, 500 F. The system (steel plus water) cools to the ambient temperature, 90 F. Calculate the
A handheld pump for a bicycle has a volume of 2 in 2 when fully extended. You now press the plunger (piston) in while holding your thumb over the exit hole so an air pressure of 45 lbf/in 2 is
A piston/cylinder contains air at 2500 R, 2200 lbf/in 2, with V1 1 in 3, Acyl = 1 in 2. The piston is released and just before the piston exits the end of the cylinder the pressure
A 25-ft3 insulated, rigid tank contains air at 110 lbf/in 2, 75 F. A valve on the tank is opened, and the pressure inside quickly drops to 15 lbf/in 2, at which point the valve is closed. Assuming
A rigid container with volume 7 ft3 is divided into two equal volumes by a partition. Both sides contain nitrogen one side is at 300 lbf/in2, 400 F, and the other at 30 lbf/in2, 200 F. The partition
Nitrogen at 90 lbf/in 2, 260 F is in a 20 ft3 insulated tank connected to a pipe with a valve to a second insulated initially empty tank of volume 20 ft3. The valve is opened and the nitrogen fills
A cylinder/piston contains carbon dioxide at 150 lbf/in 2, 600 F with a volume of 7 ft3. The total external force acting on the piston is proportional to V3. This system is allowed to cool to room
Helium in a piston/cylinder at 20C, 100 kPa is brought to 400 K in a reversible polytropic process with exponent n = 1.25. You may assume helium is an ideal gas with constant specific heat.
A cylinder/piston contains air at ambient conditions, 14.7 lbf/in 2 and 70 F with a volume of 10 ft3. The air is compressed to 100 lbf/in 2 in a reversible polytropic process with exponent, n
A cylinder/piston contains 4 ft3 of air at 16 lbf/in 2, 77 F. The air is compressed in a reversible polytropic process to a final state of 120 lbf/in 2, 400 F. Assume the heat transfer is with the
A cylinder with a linear spring-loaded piston contains carbon dioxide gas at 300 lbf/in 2 with a volume of 2 ft3. The device is of aluminum and has a mass of 8 lbm. Everything (Al and gas) is
Steam enters a turbine at 3 MPa, 450C, expands in a reversible adiabatic process and exhausts at 10 kPa. Changes in kinetic and potential energies between the inlet and the exit of the
In a heat pump that uses R-134a as the working fluid, the R-134a enters the compressor at 150 kPa, 10C at a rate of 0.1 kg/s. In the compressor the R-134a is compressed in an
Consider the design of a nozzle in which nitrogen gas flowing in a pipe at 500 kPa, 200C, and at a velocity of 10 m/s, is to be expanded to produce a velocity of 300 m/s. Determine the exit
A compressor is surrounded by cold R-134a so it works as an isothermal compressor. The inlet state is 0C, 100 kPa and the exit state is saturated vapor. Find the specific heat transfer and
Air at 100 kPa, 17C is compressed to 400 kPa after which it is expanded through a nozzle back to the atmosphere. The compressor and the nozzle are both reversible and adiabatic and kinetic
A small turbine delivers 150 kW and is supplied with steam at 700C, 2 MPa. The exhaust passes through a heat exchanger where the pressure is 10 kPa and exits as saturated liquid. The turbine
A counter flowing heat exchanger is used to cool air at 540 K, 400 kPa to 360 K by using a 0.05 kg/s supply of water at 20C, 200 kPa. The air flow is 0.5 kg/s in a 10-cm diameter pipe. Find
Analyse the steam turbine described in Problem 6.29. Is it possible?
A co-flowing heat exchanger has one line with 2 kg/s saturated water vapor at 100 kPa entering. The other line is 1 kg/s air at 200 kPa, 1200 K. The heat exchanger is very long so the two flows exit
Atmospheric air at -45C, 60 kPa enters the front diffuser of a jet engine with a velocity of 900 km/h and frontal area of 1 m2. After the adiabatic diffuser the velocity is 20 m/s. Find the
A Hilch tube has an air inlet flow at 20C, 200 kPa and two exit flows of 100 kPa, one at 0C and the other at 40C. The tube has no external heat transfer and no work and all
Two flow streams of water, one at 0.6 MPa, saturated vapor, and the other at 0.6 MPa, 600C, mix adiabatically in a SSSF process to produce a single flow out at 0.6 MPa, 400C. Find the
In a heat-driven refrigerator with ammonia as the working fluid, a turbine with inlet conditions of 2.0 MPa, 70C is used to drive a compressor with inlet saturated vapor at
A diffuser is a steady-state, steady-flow device in which a fluid flowing at high velocity is decelerated such that the pressure increases in the process. Air at 120 kPa, 30C enters a
A reversible SSSF device receives a flow of 1 kg/s air at 400 K, 450 kPa and the air leaves at 600 K, 100 kPa. Heat transfer of 800 kW is added from a 1000 K reservoir, 100 kW rejected at 350 K and
One technique for operating a steam turbine in part-load power output is to throttle the steam to a lower pressure before it enters the turbine. The steam line conditions are 2 MPa, 400C, and
Carbon dioxide at 300 K, 200 kPa is brought through a SSSF device where it is heated to 500 K by a 600 K reservoir in a constant pressure process. Find the specific work, heat transfer and entropy
One type of feedwater heater for preheating the water before entering a boiler operates on the principle of mixing the water with steam that has been bled from the turbine. For the states calculate
Air at 327C, 400 kPa with a volume flow 1 m3/s runs through an adiabatic turbine with exhaust pressure of 100 kPa Neglect kinetic energies and use constant specific heats. Find the lowest and
A certain industrial process requires a steady supply of saturated vapor steam at 200 kPa, at a rate of 0.5 kg/s. Also required is a steady supply of compressed air at 500 kPa, at a rate of 0.1 kg/s.
Air enters a turbine at 800 kPa, 1200 K, and expands in a reversible adiabatic process to 100 kPa. Calculate the exit temperature and the work output per kilogram of air, usinga. The ideal gas
Consider a steam turbine power plant operating at supercritical pressure. As a first approximation, it may be assumed that the turbine and the pump processes are reversible and adiabatic. Neglecting
A supply of 5 kg/s ammonia at 500 kPa, 20C is needed. Two sources are available one is saturated liquid at 20C and the other is at 500 kPa, 140C. Flows from the two sources
A turbo charger boosts the inlet air pressure to an automobile engine. It consists of an exhaust gas driven turbine directly connected to an air compressor. For a certain engine load the conditions
A stream of ammonia enters a steady flow device at 100 kPa, 50C, at the rate of 1 kg/s. Two streams exit the device at equal mass flow rates; one is at 200 kPa, 50C, and the other as
An initially empty 0.1 m3 canister is filled with R-12 from a line flowing saturated liquid at 5C. This is done quickly such that the process is adiabatic. Find the final mass, liquid

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