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engineering
mechanical engineering

Questions and Answers of Mechanical Engineering

Find the missing properties and give the phase of the substance a. H2O s = 7.70 kJ/kg K, P = 25 kPa h =? T =? x =? b. H2O u = 3400 kJ/kg, P = 10 MPa T =? x =? s =? c. R-12 T = 0°C, P = 200
Saturated liquid water at 20oC is compressed to a higher pressure with constant temperature. Find the changes in u and s when the final pressure is a. 500 kPa b. 2000 kPa c. 20 000 kPa
Saturated vapor water at 150oC is expanded to a lower pressure with constant temperature. Find the changes in u and s when the final pressure is a. 100 kPa b. 50 kPa c. 10 kPa
Determine the missing property among P, T, s, x for the following states: a. Ammonia 25oC, v = 0.10 m3/kg b. Ammonia 1000 kPa, s = 5.2 kJ/kg K c. R-134a 5oC, s = 1.7 kJ/kg K d. R-134a 50oC,
Consider a Carnot-cycle heat engine with water as the working fluid. The heat transfer to the water occurs at 300°C, during which process the water changes from saturated liquid to saturated vapor.
In a Carnot engine with ammonia as the working fluid, the high temperature is 60°C and as QH is received, the ammonia changes from saturated liquid to saturated vapor. The ammonia pressure at the
Water is used as the working fluid in a Carnot cycle heat engine, where it changes from saturated liquid to saturated vapor at 200°C as heat is added. Heat is rejected in a constant pressure process
Consider a Carnot-cycle heat pump with R-22 as the working fluid. Heat is rejected from the R-22 at 40°C, during which process the R-22 changes from saturated vapor to saturated liquid. The heat is
Do Problem 8.34 using refrigerant R-134a instead of R-22. Consider a Carnot-cycle heat pump with R-22 as the working fluid. Heat is rejected from the R-22 at 40°C, during which process the R-22
Water at 200 kPa, x = 1.0 is compressed in a piston/cylinder to 1 MPa, 250°C in a reversible process. Find the sign for the work and the sign for the heat transfer.
Water at 200 kPa, x = 1.0 is compressed in a piston/cylinder to 1 MPa, 350oC in a reversible process. Find the sign for the work and the sign for the heat transfer.
Ammonia at 1 MPa, 50oC is expanded in a piston/cylinder to 500 kPa, 20oC in a reversible process. Find the sign for both the work and the heat transfer.
One kilogram of ammonia in a piston/cylinder at 50°C, 1000 kPa is expanded in a reversible isothermal process to 100 kPa. Find the work and heat transfer for this process.
One kilogram of ammonia in a piston/cylinder at 50°C, 1000 kPa is expanded in a reversible isobaric process to 140°C. Find the work and heat transfer for this process.
One kilogram of ammonia in a piston/cylinder at 50°C, 1000 kPa is expanded in a reversible adiabatic process to 100 kPa. Find the work and heat transfer for this process.
A cylinder fitted with a piston contains ammonia at 50°C, 20% quality with a volume of 1 L. The ammonia expands slowly, and during this process heat is transferred to maintain a constant
An insulated cylinder fitted with a piston contains 0.1 kg of water at 100°C, 90% quality. The piston is moved, compressing the water until it reaches a pressure of 1.2 MPa. How much work is
Compression and heat transfer brings R-134a in a piston/cylinder from 500 kPa, 50oC to saturated vapor in an isothermal process. Find the specific heat transfer and the specific work.
One kilogram of water at 300°C expands against a piston in a cylinder until it reaches ambient pressure, 100 kPa, at which point the water has a quality of 90.2%. It may be assumed that the
Water in a piston/cylinder at 400oC, 2000 kPa is expanded in a reversible adiabatic process. The specific work is measured to be 415.72 kJ/kg out Find the final P and T and show the P-v and the T-s
A piston/cylinder has 2 kg ammonia at 50°C, 100 kPa which is compressed to 1000 kPa. The process happens so slowly that the temperature is constant. Find the heat transfer and work for the process
A piston cylinder has R-134a at –20oC, 100 kPa which is compressed to 500 kPa in a reversible adiabatic process. Find the final temperature and the specific work.
A closed tank, V = 10 L, containing 5 kg of water initially at 25°C, is heated to 175°C by a heat pump that is receiving heat from the surroundings at 25°C. Assume that this process is reversible.
A cylinder containing R-134a at 10°C, 150 kPa, has an initial volume of 20 L. A piston compresses the R-134a in a reversible, isothermal process until it reaches the saturated vapor state. Calculate
A heavily-insulated cylinder fitted with a frictionless piston, as shown in Fig. P8.51 contains ammonia at 5°C, 92.9% quality, at which point the volume is 200 L. The external force on the piston is
A piston/cylinder has 2 kg water at 1000 kPa, 250°C which is now cooled with a constant loading on the piston. This isobaric process ends when the water has reached a state of saturated liquid. Find
Water at 1000 kPa, 250°C is brought to saturated vapor in a piston/cylinder with an isothermal process. Find the specific work and heat transfer. Estimate the specific work from the area in the P-v
Water at 1000 kPa, 250°C is brought to saturated vapor in a rigid container, shown in Fig. P8.54. Find the final T and the specific heat transfer in this isometric process.
Estimate the specific heat transfer from the area in the T-s diagram and compare it to the correct value for the states and process in Problem 8.54.
Water at 1000 kPa, 250°C is brought to saturated vapor in a piston/cylinder with an isobaric process. Find the specific work and heat transfer. Estimate the specific heat transfer from the area in
A heavily insulated cylinder/piston contains ammonia at 1200 kPa, 60°C. The piston is moved, expanding the ammonia in a reversible process until the temperature is −20°C. During the process
Water at 1000 kPa, 250°C is brought to saturated vapor in a piston/cylinder with an adiabatic process. Find the final T and the specific work. Estimate the specific work from the area in the P-v
A rigid, insulated vessel contains superheated vapor steam at 3 MPa, 400°C. A valve on the vessel is opened, allowing steam to escape. The overall process is irreversible, but the steam remaining
A piston/cylinder contains 2 kg water at 200°C, 10 MPa. The piston is slowly moved to expand the water in an isothermal process to a pressure of 200 kPa. Any heat transfer takes place with an
One kg water at 500oC and 1 kg saturated water vapor both at 200 kPa are mixed in a constant pressure and adiabatic process. Find the final temperature and the entropy generation for the process.
The unrestrained expansion of the reactor water in Problem 5.48 has a final state in the two-phase region. Find the entropy generated in the process. A water-filled reactor with volume of 1 m3 is at
A mass and atmosphere loaded piston/cylinder contains 2 kg of water at 5 MPa, 100°C. Heat is added from a reservoir at 700°C to the water until it reaches 700°C. Find the work, heat transfer, and
Ammonia is contained in a rigid sealed tank unknown quality at 0oC. When heated in boiling water to 100oC its pressure reaches 1200 kPa. Find the initial quality, the heat transfer to the ammonia and
An insulated cylinder/piston contains R-134a at 1 MPa, 50°C, with a volume of 100 L. The R-134a expands, moving the piston until the pressure in the cylinder has dropped to 100 kPa. It is claimed
A piece of hot metal should be cooled rapidly (quenched) to 25°C, which requires removal of 1000 kJ from the metal. The cold space that absorbs the energy could be one of three possibilities: (1)
A piston cylinder has 2.5 kg ammonia at 50 kPa, -20oC. Now it is heated to 50oC at constant pressure through the bottom of the cylinder from external hot gas at 200oC. Find the heat transfer to the
A cylinder fitted with a movable piston contains water at 3 MPa, 50% quality, at which point the volume is 20 L. The water now expands to 1.2 MPa as a result of receiving 600 kJ of heat from a large
A piston cylinder loaded so it gives constant pressure has 0.75 kg saturated vapor water at 200 kPa. It is now cooled so the volume becomes half the initial volume by heat transfer to the ambient at
A piston/cylinder contains 1 kg water at 150 kPa, 20°C. The piston is loaded so pressure is linear in volume. Heat is added from a 600°C source until the water is at 1 MPa, 500°C. Find the heat
A piston/cylinder has ammonia at 2000 kPa, 80oC with a volume of 0.1 m3. The piston is loaded with a linear spring and outside ambient is at 20oC, shown in Fig. P8.71. The ammonia now cools down to
A cylinder/piston contains water at 200 kPa, 200°C with a volume of 20 L. The piston is moved slowly, compressing the water to a pressure of 800 kPa. The loading on the piston is such that the
A cylinder/piston contains water at 200 kPa, 200°C with a volume of 20 L. The piston is moved slowly, compressing the water to a pressure of 800 kPa. The loading on the piston is such that the
A piston/cylinder device keeping a constant pressure has 1 kg water at 20oC and 1 kg of water at 100oC both at 500 kPa separated by a thin membrane. The membrane is broken and the water comes to a
A piston cylinder has constant pressure of 2000 kPa with water at 20oC. It is now heated up to 100oC. Find the heat transfer and the entropy change using the steam tables. Repeat the calculation
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 18°C house, what is the net entropy change
A 4 L jug of milk at 25°C is placed in your refrigerator where it is cooled down to the refrigerators inside constant temperature of 5°C. Assume the milk has the property of liquid water and find
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, calculate the
A 5-kg steel container is cured at 500oC. An amount of liquid water at 15oC, 100 kPa is added to the container so a final uniform temperature of the steel and the water becomes 75oC. Neglect any
A pan in an auto shop contains 5 L of engine oil at 20oC, 100 kPa. Now 2 L of hot 100oC oil is mixed into the pan. Neglect any work term and find the final temperature and the entropy generation.
Find the total work the heat engine can give out as it receives energy from the rock bed as described in Problem 7.61 (see Fig P 8.81). Hint: write the entropy balance equation for the control volume
Two kg of liquid lead initially at 500°C are poured into a form. It then cools at constant pressure down to room temperature of 20°C as heat is transferred to the room. The melting point of lead is
A 12 kg steel container has 0.2 kg superheated water vapor at 1000 kPa, both at 200oC. The total mass is now cooled to ambient temperature 30oC. How much heat transfer was taken out and what is the
A 5 kg aluminum radiator holds 2 kg of liquid R-134a both at –10oC. The setup is brought indoors and heated with 220 kJ from a heat source at 100oC. Find the total entropy generation for the
A piston/cylinder of total 1 kg steel contains 0.5 kg ammonia at 1600 kPa both masses at 120oC. Some stops are placed so a minimum volume is 0.02 m3, shown in Fig. P8.85. Now the whole system is
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 the net
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. Compute heat transfer during the process and the change of
A piston/cylinder setup contains air at 100 kPa, 400 K which is compressed to a final pressure of 1000 kPa. Consider two different processes (i) a reversible adiabatic process and (ii) a reversible
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
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
Oxygen gas in a piston cylinder at 300 K, 100 kPa with volume 0.1 m3 is compressed in a reversible adiabatic process to a final temperature of 700 K. Find the final pressure and volume using Table A.5
Oxygen gas in a piston cylinder at 300 K, 100 kPa with volume 0.1 m3 is compressed in a reversible adiabatic process to a final temperature of 700 K. Find the final pressure and volume using constant
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
A piston/cylinder, shown in Fig P8.95, 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
Two rigid tanks, shown in Fig P8.96, 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
A spring loaded piston cylinder contains 1.5 kg air at 27oC and 160 kPa. It is now heated in a process where pressure is linear in volume, P = A + BV, to twice the initial volume where it reaches 900
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 increased by 0.343
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 crossed
Argon in a light bulb is at 90 kPa and heated from 20oC to 60oC with electrical power. Do not consider any radiation, nor the glass mass. Find the total entropy generation per unit mass of argon.
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 the air
Nitrogen at 200oC, 300 kPa is in a piston cylinder, volume 5 L, with the piston locked with a pin. The forces on the piston require a pressure inside of 200 kPa to balance it without the pin. The pin
A rigid container with volume 200 L is divided into two equal volumes by a partition, shown in Fig. P8.104. Both sides contain nitrogen, one side is at 2 MPa, 200°C, and the other at 200 kPa,
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, shown in Fig. P8.105. The valve is opened and
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 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.
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 positive,
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.
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. Find
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, shown in Fig. P8.111. It now expands in
A gas at 20°C may be rarefied if it contains less than 1012 molecules per mm3. If Avogadro’s number is 6.023E23 molecules per mole, what air pressure does this represent?
The earth’s atmosphere can be modeled as a uniform layer of air of thickness 20 km and average density 0.6 kg/m3 (see Table A-6). Use these values to estimate the total mass and total number of
For the triangular element in Fig P1.3, show that a tilted free liquid surface, in contact with an atmosphere at pressure pa, must undergo shear stress and hence begin to flow.
The quantities viscosity μ, velocity V, and surface tension Y may be combined into a dimensionless group. Find the combination which is proportional to μ. This group has a customary name,
A formula for estimating the mean free path of a perfect gas is: ℓ = 1.26 μ/p√R|T) = 1.26 μ/p √ (RT) Where the latter form follows from the ideal-gas law, ρ = p/RT.
If p is pressure and y is a coordinate, state, in the {MLT} system, the dimensions of the quantities (a) ∂p/∂y; (b) ∫ p dy; (c) ∂2p/∂y2; (d) Vp
A small village draws 1.5 acre-foot of water per day from its reservoir. Convert this water usage into (a) Gallons per minute; and (b) Liters per second.
Suppose that bending stress σ in a beam depends upon bending moment M and beam area moment of inertia I and is proportional to the beam half-thickness y. Suppose also that, for the particular
The dimensionless Galileo number, Ga, expresses the ratio of gravitational effect to viscous effects in a flow. It combines the quantities density ρ, acceleration of gravity g length scale L,
The Stokes-Oseen formula [10] for drag on a sphere at low velocity V is: F = 3πμ DV + 9π/16pV2D2 Where D = sphere diameter, μ = viscosity, and ρ = density. Is the formula
Test, for dimensional homogeneity, the following formula for volume flow Q through a hole of diameter D in the side of a tank whose liquid surface is a distance h above the hole position: Q = 0.68D2
For low-speed (laminar) flow in a tube of radius ro, the velocity u takes the form u = B Δp/μ (r2- r2) Where μ is viscosity and Δp the pressure drop. What are the dimensions of
The efficiency η of a pump is defined as η = Q∆p / Input Power Where Q is volume flow and Δp the pressure rise produced by the pump. What is η if Δp = 35 psi, Q =
The volume flow Q over a dam is proportional to dam width B and also varies with gravity g and excess water height H upstream, as shown in Fig. P1.14. What is the only possible dimensionally
As a practical application of Fig P1.14, often termed a sharp-crested weir, civil engineers use the following formula for flow rate: Q ≈ 3.3 BH3/2, with Q in ft3/s and B and H in feet. Is this

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