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engineering
mechanical engineering
Questions and Answers of
Mechanical Engineering
A cylinder fitted with a frictionless piston that is restrained by a linear spring contains R-22 at 20C, quality 60% with a volume of 8 L. The piston cross-sectional area is 0.04 m2, and the
A 1-L capsule of water at 700 kPa, 150°C is placed in a larger insulated and otherwise evacuated vessel. The capsule breaks and its contents fill the entire volume. If the final pressure should not
A cylinder with a frictionless piston contains steam at 2 MPa, 500C with a volume of 5 L. The external piston force is proportional to cylinder volume cubed. Heat is transferred out of the
Superheated refrigerant R-134a at 20°C, 0.5 MPa is cooled in a piston/cylinder arrangement at constant temperature to a final two-phase state with quality of 50%. The refrigerant mass is 5 kg, and
Calculate the heat transfer for the process described in Problem 4.20. Consider a piston cylinder with 0.5 kg of R-134a as saturated vapor at -10°C. It is now compressed to a pressure of 500 kPa in
Calculate the heat transfer for the process described in Problem 4.26. A piston cylinder setup similar to Problem 4.24 contains 0.1 kg saturated liquid and vapor water at 100 kPa with quality 25%.
A piston/cylinder contains R-12 at 30C, x 20%. The volume is 0.2 m3. It is known that V stop 0.4 m3, and if the piston sits at the bottom, the
Ammonia, NH3, is contained in a sealed rigid tank at 0C, x 50% and is then heated to 100C. Find the final state P2, u2 and the specific work and heat transfer.
A house is being designed to use a thick concrete floor mass as thermal storage material for solar energy heating. The concrete is 30 cm thick and the area exposed to the sun during the day time is
A car with mass 1275 kg drives at 60 km/h when the brakes are applied quickly to decrease its speed to 20 km/h. Assume the brake pads are 0.5 kg mass with heat capacity of 1.1 kJ/kg K and the brake
A copper block of volume 1 L is heat treated at 500C and now cooled in a 200-L oil bath initially at 20C. Assuming no heat transfer with the surroundings, what is the final
Saturated, x = 1%, water at 25C is contained in a hollow spherical aluminum vessel with inside diameter of 0.5 m and a 1-cm thick wall. The vessel is heated until the water inside is
An ideal gas is heated from 500 to 1500 K. Find the change in enthalpy using constant specific heat from Table A.5 (room temperature value) and discuss the accuracy of the result if the gas isa.
A rigid insulated tank is separated into two rooms by a stiff plate. Room A of 0.5 m3 contains air at 250 kPa, 300 K and room B of 1 m3 has air at 150 kPa, 1000 K. The plate is removed and the air
An insulated cylinder is divided into two parts of 1 m3 each by an initially locked piston. Side A has air at 200 kPa, 300 K, and side B has air at 1.0 MPa, 1000 K. The piston is now unlocked so it
A cylinder with a piston restrained by a linear spring contains 2 kg of carbon dioxide at 500 kPa, 400C. It is cooled to 40C, at which point the pressure is 300 kPa. Calculate the
A piston/cylinder in a car contains 0.2 L of air at 90 kPa, 20C. The air is compressed in a quasi-equilibrium polytropic process with polytropic exponent n 1.25 to a final
Water at 20C, 100 kPa, is brought to 200 kPa, 1500C. Find the change in the specific internal energy, using the water table and the ideal gas water table in combination.
For an application the change in enthalpy of carbon dioxide from 30 to 1500°C at 100 kPa is needed. Consider the following methods and indicate the most accurate one.a. Constant specific heat, value
Air in a piston/cylinder at 200 kPa, 600 K, is expanded in a constant-pressure process to twice the initial volume (state 2). The piston is then locked with a pin and heat is transferred to a final
An insulated floating piston divides a cylinder into two volumes each of 1 m3, as shown in Fig. P5.70. One contains water at 100C and the other air at 3C and both pressures
Two containers are filled with air, one a rigid tank A, and the other a piston/cylinder B that is connected to A by a line and valve. The initial conditions are: mA = 2 kg, TA = 600 K, PA = 500 kPa
A 250-L rigid tank contains methane gas at 500C, 600 kPa. The tank is cooled to 300 K. a. Find the final pressure and the heat transfer for the process. b. What is the percent error in the
A piston/cylinder arrangement contains 10 g of air at 250 kPa, 300C. The 75-kg piston has a diameter of 0.1 m and initially pushes against the stops. The atmosphere is at 100 kPa and
Oxygen at 300 kPa, 100C is in a piston/cylinder arrangement with a volume of 0.1 m3. It is now compressed in a polytropic process with exponent, n 1.2, to a final temperature
A piston/cylinder contains 2 kg of air at 27C, 200 kPa, shown in Fig. P5.75. The piston is loaded with a linear spring, mass and the atmosphere. Stops are mounted so that V stop
A piston/cylinder contains 0.001 m3 airs at 300 K, 150 kPa. The air is now compressed in a process in which P V1.25 = C to a final pressure of 600 kPa. Find the work performed by the air and the heat
An air pistol contains compressed air in a small cylinder. Assume that the volume is 1 cm3, pressure is 1 MPa, and the temperature is 27C when armed. A bullet, m 15 g, acts
A spherical elastic balloon contains nitrogen (N2) at 20oC, 500 kPa. The initial volume is 0.5 m3. The balloon material is such that the pressure inside is proportional to the balloon diameter. Heat
A 10-m high cylinder, cross-sectional area 0.1 m2, has a mass less piston at the bottom with water at 20oC on top of it. Air at 300 K, volume 0.3 m3, under the piston is heated so that the piston
A cylinder fitted with a frictionless piston contains carbon dioxide at 500 kPa, 400 K, at which point the volume is 50 L. The gas is now allowed to expand until the piston reaches a set of fixed
A cylinder fitted with a frictionless piston contains R-134a at 40oC, 80% quality, at which point the volume is 10 L. The external force on the piston is now varied in such a manner that the R-134a
A piston/cylinder contains argon gas at 140 kPa, 10C, and the volume is 100 L. The gas is compressed in a polytropic process to 700 kPa, 280C. Calculate the heat transfer during the
Water at 150C, quality 50% is contained in a cylinder/piston arrangement with initial volume 0.05 m3. The loading of the piston is such that the inside pressure is linear with the square root
A piston/cylinder has 1 kg propane gas at 700 kPa, 40C. The piston cross-sectional area is 0.5 m2, and the total external force restraining the piston is directly proportional to the cylinder
A closed cylinder is divided into two rooms by a frictionless piston held in place by a pin. Room A has 10 L air at 100 kPa, 30C, and room B has 300 L saturated water vapor at 30C.
A small elevator is being designed for a construction site. It is expected to carry four 75-kg workers to the top of a 100-m tall building in less than 2 min. The elevator cage will have a
The rate of heat transfer to the surroundings from a person at rest is about 400kJ/h, suppose that the ventilation system fails in an auditorium containing 100 people.
Consider the 100-L Dewar (a rigid double-walled vessel for storing cryogenic liquids). The Dewar contains nitrogen at 1 atm, 90% liquid and 10% vapor by volume. The insulation holds heat transfer
A computer in a closed room of volume 200 m3 dissipates energy at a rate of 10 kW. The room has 50 kg wood, 25 kg steel and air, with all material at 300 K, 100 kPa. Assuming all the mass heats up
The heaters in a spacecraft suddenly fail. Heat is lost by radiation at the rate of 100kJ/h, and the electric instruments generate 75 kJ/h. Initially, the air is at 100 kPa, 25C 0with a
A cylinder fitted with a piston restrained by a linear spring has a cross-sectional area of 0.05 m2 and initial volume of 20 L. The cylinder contains ammonia at 1 MPa, 60C. The spring
A cylinder fitted with a piston contains 2 kg of R-12 at 10C, 90% quality. The system undergoes a quasi-equilibrium polytropic expansion to 100 kPa, during which the system receives a heat
A spherical balloon initially 150 mm in diameter and containing R-12 at 100 kPa is connected to a 30-L uninsulated, rigid tank containing R-12 at 500 kPa. Everything is at the ambient temperature of
Calculate the heat transfer for the process described. Two springs with same spring constant are installed in a mass less piston/cylinder with the outside air at 100 kPa. If the piston is at the
Calculate the heat transfer for the process described in Problem 4.46.
A cylinder fitted with a frictionless piston contains R-134a at 10oC, quality of 50%, and initial volume of 100 L. The external force on the piston now varies in such a manner that the piston moves,
A rigid 1-m3 tank contains butane at 500 K, 100 kPa. The tank is now heated to 1500 K.a) Is it reasonable to use the specific heat value from Table A.10 to calculate the heat transfer in this
A cylinder fitted with a frictionless piston contains 0.2 kg of saturated (both liquid and vapor present) R-12 at -20oC. The external force on the piston is such that the pressure inside the cylinder
A certain elastic balloon will support an internal pressure equal to Po 100 kPa until the balloon becomes spherical at a diameter of Do 1 m, beyond which P = Po +
A frictionless, thermally conducting piston separates the air and water in the cylinder shown in Fig. P5.100, the initial volumes of A and B are each 500 L, and the initial pressure on each side is
A closed, vertical cylinder is divided into two parts A and B by a thermally non-conducting frictionless piston. The upper part A contains air at ambient temperature, 20C, and the initial volume is
A hydraulic hoist raises a 3650 lbm car 6 ft in an auto repair shop. The hydraulic pump has a constant pressure of 100 lbf/in 2 on its piston. What is the increase in potential energy of the car and
A piston motion moves a 50 lbm hammerhead vertically down 3 ft from rest to a velocity of 150 ft/s in a stamping machine. What is the change in total energy of the hammerhead?
Find the missing properties and give the phase of the substance. a. H2O u 1000 Btu/lbm, T 270 F h ? v ? x ? b. H2O
Find the missing properties among (P, T, v, u, h) together with x, if applicable, and give the phase of the substance. a. R-22 T 50 F, u 85 Btu/lbm b. H2O T
Water in a 6-ft3 closed, rigid tank is at 200 F, 90% quality. The tank is then cooled to 20 F. Calculate the heat transfer during the process. Discuss.
A cylinder fitted with a frictionless piston contains 4 lbm of superheated refrigerant R-134a vapor at 400 lbf/in 2, 200 F. The cylinder is now cooled so the R-134a remains at constant pressure until
Ammonia at 30 F, quality 60% is contained in a rigid 8-ft3 tank. The tank and ammonia are now heated to a final pressure of 140 lbf/in 2. Determine the heat transfer for the process.
A vertical cylinder fitted with a piston contains 10 lbm of R-22 at 50 F. Heat is transferred to the system causing the piston to rise until it reaches a set of stops at which point the volume has
Twenty pound-mass of water in a piston/cylinder with constant pressure is at 1100 F and a volume of 22.6 ft3. It is now cooled to 100 F. Show the P–v diagram and find the work and heat transfer for
A piston/cylinder contains 2 lbm of liquid water at 70 F, and 30 lbf/in 2. There is a linear spring mounted on the piston such that when the water is heated the pressure reaches 300 lbf/in 2 with a
A piston/cylinder arrangement has the piston loaded with outside atmospheric pressure and the piston mass to a pressure of 20 lbf/in 2, shown in Fig P5.28. It contains water at 25 F, which is then
A piston/cylinder contains 2 lbm of water at 70 F with a volume of 0.1 ft3. Initially the piston rests on some stops with the top surface open to the atmosphere, Po, so a pressure of 40 lbf/in 2 is
Two tanks are connected by a valve and line. The volumes are both 35 ft3 with R-134a at 70 F, quality 25% in A and tank B is evacuated. The valve is opened and saturated vapor flows from A into B
A water-filled reactor with volume of 50 ft3 is at 2000 lbf/in 2, 560 F and placed inside a containment room. The room is well insulated and initially evacuated. Due to a failure, the reactor
A piston/cylinder arrangement of initial volume 0.3 ft3 contains saturated water vapor at 360 F. The steam now expands in a polytropic process with exponent n 1 to a final pressure of
Calculate the heat transfer for the process described in Problem 4.72. A cylinder containing 2 lbm of ammonia has an externally loaded piston. Initially the ammonia is at 280 lbf/in 2, 360 F and is
Ammonia, NH3, is contained in a sealed rigid tank at 30 F, x 50% and is then heated to 200 F. Find the final state P2, u2 and the specific work and heat transfer.
A car with mass 3250 lbm drives with 60 mi/h when the brakes are applied to quickly decrease its speed to 20 mi/h. Assume the brake pads are 1 lbm mass with heat capacity of 0.2 Btu/lbm R and the
A copper block of volume 60 in3 is heat treated at 900 F and now cooled in a 3- ft3 oil bath initially at 70 F. Assuming no heat transfer with the surroundings, what is the final temperature?
An insulated cylinder is divided into two parts of 10 ft3 each by an initially locked piston. Side A has air at 2 atm, 600 R and side B has air at 10 atm, 2000 R. P5.64. The piston is now unlocked so
A cylinder with a piston restrained by a linear spring contains 4 lbm of carbon dioxide at 70 lbf/in 2, 750 F. It is cooled to 75 F, at which point the pressure is 45 lbf/in 2. Calculate the heat
A piston/cylinder in a car contains 12 in 3 of air at 13 lbf/in 2, 68 F. The air is compressed in a quasi-equilibrium polytropic process with polytropic exponent n 1.25 to a final
Water at 70 F, 15 lbf/in 2, is brought to 30 lbf/in 2, 2700 F. Find the change in the specific internal energy, using the water table and the ideal gas water table in combination.
Air in a piston/cylinder at 30 lbf/in 2 1080 R it is expanded in a constant-pressure process to twice the initial volume (state 2). The piston is then locked with a pin, and heat is transferred to a
Two containers are filled with air, one a rigid tank A, and the other a piston/cylinder B that is connected to A by a line and valve. The initial conditions are: mA 4 lbm, TA
Oxygen at 50 lbf/in 2, 200 F is in a piston/cylinder arrangement with a volume of 4 ft3. It is now compressed in a polytropic process with exponent, n 1.2, to a final temperature of
A piston/cylinder contains 4 lbm of air at 100 F, 2 atm. The piston is loaded with a linear spring, mass, and the atmosphere. Stops are mounted so that V stop 100 ft3, at which point
An air pistol contains compressed air in a small cylinder. Assume that the volume is 1 in 3, pressure is 10 atm, and the temperature is 80 F when armed. A bullet, m 0.04 lbm, acts as
A 30-ft high cylinder, cross-sectional area 1 ft2, has a mass less piston at the bottom with water at 70 F on top of it. Air at 540 R, volume 10 ft3 under the piston is heated so that the piston
A cylinder fitted with a frictionless piston contains R-134a at 100 F, 80% quality, at which point the volume is 3 Gal. The external force on the piston is now varied in such a manner that the R-134a
A piston cylinder contains argon at 20 lbf/in 2, 60 F, and the volume is 4 ft3. The gas is compressed in a polytropic process to 100 lbf/in 2, 550 F. Calculate the heat transfer during the process.
Water at 300 F, quality 50% is contained in a cylinder/piston arrangement with initial volume 2 ft3. The loading of the piston is such that the inside pressure is linear with the square root of
A closed cylinder is divided into two rooms by a frictionless piston held in place by a pin. P5.85. Room A has 0.3 ft3 air at 14.7 lbf/in 2, 90 F, and room B has 10 ft3 saturated water vapor at 90 F.
A small elevator is being designed for a construction site. It is expected to carry four 150 lbm workers to the top of a 300-ft-tall building in less than 2 min. The elevator cage will have a
A computer in a closed room of volume 5000 ft3 dissipates energy at a rate of 10 hp. The room has 100 lbm of wood, 50 lbm of steel and air, with all material at 540 R, 1 atm. Assuming all the mass
Air at 35C, 105 kPa, flows in a 100 mm 150 mm rectangular duct in a heating system. The volumetric flow rate is 0.015m3/s what is the velocity of the air flowing in the duct?
A boiler receives a constant flow of 5000 kg/h liquid water at 5 MPa, 20C and it heats the flow such that the exit state is 450C with a pressure of 4.5 MPa. Determine the necessary
A natural gas company distributes methane gas in a pipeline flowing at 200 kPa, 275 K. They have carefully measured the average flow velocity to be 5.5 m/s in a 50 cm diameter pipe. If there is a
Nitrogen gas flowing in a 50-mm diameter pipe at 15C, 200 kPa, at the rate of 0.05 kg/s, encounters a partially closed valve. If there is a pressure drop of 30 kPa across the valve and
Saturated vapor R-134a leaves the evaporator in a heat pump system at 10C, with a steady mass flow rate of 0.1 kg/s. What is the smallest diameter tubing that can be used at this location if
Steam at 3 MPa, 400C enters a turbine with a volume flow rate of 5m3/s. An extraction of 15% of the inlet mass flow rate exits at 600 kPa, 200C. The rest exits the turbine at 20 kPa
A pump takes 10C liquid water in from a river at 95 kPa and pumps it up to an irrigation canal 20 m higher than the river surface. All pipes have diameter of 0.1 m and the flow rate is 15
A desuperheater mixes superheated water vapor with liquid water in a ratio that produces saturated water vapor as output without any external heat transfer. A flow of 0.5 kg/s superheated vapor at 5
Carbon dioxide enters a steady-state, steady-flow heater at 300 kPa, 15C, and exits at 275 kPa, 1200C, as shown in Fig. P6.9. Changes in kinetic and potential energies are negligible.
Saturated liquid nitrogen at 500 kPa enters a SSSF boiler at a rate of 0.005 kg/s and exits as saturated vapor. It then flows into a super heater also at 500 kPa where it exits at 500 kPa, 275 K.
A steam pipe for a 1500-m tall building receives superheated steam at 200 kPa at ground level. At the top floor the pressure is 125 kPa and the heat loss in the pipe is 110kJ/kg. What should the
In a steam generator, compressed liquid water at 10 MPa, 30C, enters a 30-mm diameter tube at the rate of 3 L/s. Steam at 9 MPa, 400C exits the tube. Find the rate of heat transfer to
A heat exchanger is used to cool an air flow from 800 to 360K, both states at 1 MPa. The coolant is a water flow at 15C, 0.1 MPa. If the water leaves as saturated vapor, find the ratio of the
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