Questions and Answers of Fundamentals Of Thermodynamics

One lbm of air at 540 R is mixed with 2 lbm air at 720 R in a process at a constant 15 psia and Q = 0. Find the final T and the entropy generation in the process.
One lbm air at 15 psia is mixed with 2 lbm air at 30 psia, both at 540 R, in a rigid, insulated tank. Find the final state (P, T) and the entropy generation in the process.
A reversible process in a steady flow with negligible kinetic and potential energy changes is shown in Fig. P7.3. Indicate the change he − hi and transfers w and q as positive, zero, or negative.
A reversible process in a steady flow of air with negligible kinetic and potential energy changes is shown in Fig. P7.4.Indicate the change he −hi and transfers w and q as positive, zero, or
A reversible isothermal expander (a turbine with heat transfer) has an inlet flow of carbon dioxide at 3MPa, 80◦C and an exit flow at 1 MPa, 80◦C. Find the specific heat transfer from the entropy
A compressor in a commercial refrigerator receives R-410a at −25◦C and unknown quality. The exit is at 2000 kPa, 60◦C and the process is assumed to be reversible and adiabatic. Neglect kinetic
An expander receives 0.5 kg/s air at 2000 kPa, 300 K with an exit state of 400 kPa, 300 K. Assume the process is reversible and isothermal. Find the rates of heat transfer and work, neglecting
A steam turbine in a power plant receives 5 kg/s steam at 3000 kPa, 500◦C. Twenty percent of the flow is extracted at 1000 kPa to a feedwater heater, and the remainder flows out at 200 kPa. Find
A small turbine delivers 1.5 MW 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 is
An adiabatic air turbine receives 1 kg/s air at 1500 K, 1.6 MPa and 2 kg/s air at 400 kPa, T2 in a setup similar to that with an exit flowat 100 kPa. What should the temperature T2 be so that the
A flow of 5 kg/s water at 100 kPa, 20◦C should be delivered as steam at 1000 kPa, 350◦C to some application. We have a heat source at constant 500◦C. If the process should be reversible, how
A two-stage compressor having an intercooler takes in air at 300 K, 100 kPa, and compresses it to 2MPa, as shown in Fig. P7.45. The cooler then cools the air to 340 K, after which it enters the
An insulted cylinder/piston has an initial volume of 0.15 m3 and contains steam at 400 kPa, 200◦C. The steam is expanded adiabatically, and the work output is measured very carefully to be 30 kJ.
A piston/cylinder has a water volume separated in VA = 0.2 m3 and VB = 0.3 m3 by a stiff membrane similar to the one in Fig. P6.128. The initial state in A is 1000 kPa, x = 0.75, and in B it is 1600
A steel piston/cylinder of 1 kg contains 2.5 kg ammonia at 50 kPa,−20◦C. Now it is heated to 50◦Cat constant pressure through the bottom of the cylinder from external hot gas at 200◦C, and we
Water in a piston/cylinder, shown in Fig. P6.177, is at 1 MPa, 500◦C. There are two stops, a lower one at which Vmin = 1 m3 and an upper one at Vmax = 3 m3. The piston is loaded with a mass and
A resistor in a heating element is a total of 0.5 kg with specific heat of 0.8 kJ/kgK. It is now receiving 500 W of electric power, so it heats from 20◦C to 180◦C. Neglect external heat loss and
Two tanks contain steam and they are both connected to a piston/cylinder, as shown in Fig. P6.182. Initially the piston is at the bottom, and the mass of the piston is such that a pressure of 1.4 MPa
A rigid tank with 0.5 kg ammonia at 1600 kPa, 160◦C is cooled in a reversible process by giving heat to a reversible heat engine that has its cold side at ambient temperature, 20◦C, shown in Fig.
Asmall halogen light bulb receives electrical power of 50W. The small filament is at 1000 K and gives out 20% of the power as light and the rest as heat transfer to the gas, which is at 500 K; the
Saturated water vapor at 20 psia is compressed to 60 psia in a reversible adiabatic process. Find the change in v and T.
Find the missing properties of P, v, s, and x for ammonia, NH3.a. T = 190 F, P = 100 psiab. T = 80 F, h = 650 Btu/lbmc. T = 120 F, v = 1.6117 ft3/lbm
Find the missing properties and give the phase of the substance.a. H2O s = 1.75 Btu/lbm R, T = 150 F h = ? P = ? x = ?b. H2O u = 1350 Btu/lbm, P = 1500 lbf/in.2 T = ? x = ? s = ?
Determine the missing property among P, T, s, and x for R-410a ata. T =−20 F, v = 3.1214 ft3/lbmb. T = 60 F, v = 0.3121 ft3/lbmc. P = 30 psia, s = 0.3425 Btu/lbm-R
Consider a Carnot-cycle heat pump with R-410a as the working fluid. Heat is rejected from the R-410a at 110 F, during which process the R-410a changes from saturated vapor to saturated liquid. The
Do Problem 6.197E using refrigerant R-134a instead of R-410a.Data from Problem 6.197EConsider a Carnot-cycle heat pump with R-410a as the working fluid. Heat is rejected from the R-410a at 110 F,
R-410a at 150 psia and 140 F is expanded in a piston/cylinder to 75 psia, 80 F in a reversible process. Find the sign for both the work and the heat transfer for this process.
A piston/cylinder receives R-410a at 75 psia and compresses it in a reversible adiabatic process to 300 psia, 160 F. Find the initial temperature.
Consider a heat transfer of 100 Btu from 2400 R hot gases to a steel container at 1200 R that has a heat transfer of the 100 Btu out to some air at 600 R. Determine the entropy generation in each of
A constant-pressure piston/cylinder is 2 lbm steel and it contains 1 lbm air at 540 R, 60 psia. The system is now heated to 2600 R by a 2800 R source, and the steel has the same temperature as the
Nitrogen at 90 lbf/in.2, 260Fis ina20 ft3 insulated tank connected to pipe with a valve to a second insulated initially empty tank of volume 10 ft3. The valve is opened, and the nitrogen fills both
Do Problem 6.234E using Table F.5.Data from Problem 6.234EA constant-pressure piston/cylinder is 2 lbm steel and it contains 1 lbm air at 540 R, 60 psia. The system is now heated to 2600 R by a 2800
A room at 72 F is heated electrically with 1500W to keep a steady temperature. The outside ambient air is at 40 F. Find the flux of S (= ˙Q /T ) into the room air, into the ambient, and the rate of
A heat pump with COP = 4 uses 1 kW of power input to heat a 78 F room, drawing energy from the outside at 60 F. Assume the high/low temperatures in the heat pump are 120 F/32 F. Find the total rates
A window receives 800 Btu/h of heat transfer at the inside surface of 70 F and transmits the 800 Btu/h from its outside surface at 36 F, continuing to ambient air at 23 F. Find the flux of entropy at
A farmer runs a heat pump using 2.5 hp of power input. It keeps a chicken hatchery at a constant 86 F while the room loses 20 Btu/s to the colder outside ambient air at 50 F. What is the rate of
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 made of aluminum and has a mass of 8 lbm. Everything (Al and gas) is
Write a program to solve the general case of Problem 6.111, in which the initial state and the expansion ratio are input variables.Data from Problem 6.111The power stroke in an internal combustion
A piston/cylinder maintaining constant pressure contains 0.5 kg water at room temperature, 20◦C, 100 kPa. An electric heater of 500 W heats the water to 500◦C. Assume no heat losses to the
Air in a piston/cylinder is used as a small air spring that should support a steady load of 200 N. Assume that the load can vary with ±10% over a period of 1 s and that the displacement should be
If we follow a mass element going through a reversible adiabatic flow process, what can we say about the change of state?
Which process will make the statement in In-Text Concept Question e true?
A reversible steady isobaric flow has 1 kW of heat added with negligible changes in KE and PE; what is the work transfer?
To increase the work out of a turbine for given inlet and exit pressures, how should the inlet state be changed?
A tank contains air at 400 kPa, 300 K, and a valve opens up for flow out to the outside, which is at 100 kPa, 300 K. How does the state of the air that flows out change?
A turbine receives steam at 6 MPa, 600◦C with an exit pressure of 600 kPa. Assume the turbine is adiabatic and neglect kinetic energies. Find the exit temperature and the specific work.
Atmospheric air at −45◦C, 60 kPa enters the front diffuser of a jet engine, shown in Fig. P7.26, with a velocity of 900 km/h and a frontal area of 1 m2. After adiabatic diffuser process, the
Nitrogen gas flowing in a pipe at 500 kPa, 200◦C, and at a velocity of 10 m/s, should be expanded in a nozzle to produce a velocity of 300 m/s. Determine the exit pressure and cross-sectional area
A condenser receives R-410a at −20◦C and quality 80%, with the exit flow being saturated liquid at −20◦C. Consider the cooling to be a reversible process and find the specific heat transfer
A compressor brings a hydrogen gas flow at 280 K, 100 kPa up to a pressure of 1000 kPa in a reversible process. How hot is the exit flow and what is the specific work input?
A diffuser is a steady-state 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 diffuser with a velocity
A highly cooled compressor brings a hydrogen gas flow at 300 K, 100 kPa up to a pressure of 800 kPa in an isothermal process. Find the specific work assuming a reversible process.
A reversible adiabatic compression of an air flow from 20◦C, 100 kPa to 200 kPa is followed by an expansion down to 100 kPa in an ideal nozzle. What are the two processes? How hot does the air get?
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, as shown in Fig. P7.39. The steam line conditions are
A heat-powered portable air compressor consists of three components: (a) An adiabatic compressor,(b) A constant-pressure heater (heat supplied from an outside source), and (c) An adiabatic
Consider a steam turbine power plant operating near critical pressure, as shown in Fig. P7.48. As a first approximation, it may be assumed that the turbine and the pump processes are reversible and
A turbocharger boosts the inlet air pressure to an automobile engine. It consists of an exhaust gas driven turbine directly connected to an air compressor, as shown in Fig. P7.41. For a certain
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.
A certain industrial process requires a steady 0.75 kg/s supply of compressed air at 500 kPa at a maximum temperature of 30◦C, as shown in Fig. P7.47. This air is to be supplied by installing a
A 10-m-tall, 2-m2 cross-sectional-area water tank is on a tower, so the bottom is 5 m up from ground level and the top is open to the atmosphere. It is initially empty and then is filled by a pump
A 0.5-m3 tank containing carbon dioxide at 300 K, 150 kPa is now filled from a supply of carbon dioxide at 300 K, 150 kPa by a compressor to a final tank pressure of 450 kPa. Assume the whole process
A tank contains 1 kg of carbon dioxide at 6 MPa, 60◦C, and it is connected to a turbine with an exhaust at 1000 kPa. The carbon dioxide flows out of the tank and through the turbine until a final
R-410a at 120◦C, 4 MPa is in an insulated tank, and flow is now allowed out to a turbine with a backup pressure of 800 kPa. The flow continues to a final tank pressure of 800 kPa, and the process
A river flowing at 0.5 m/s across a 1-m-high and 10-m-wide area has a dam that creates an elevation difference of 2 m. How much energy can a turbine deliver per day if 80% of the potential energy can
How much liquid water at 15◦C can be pumped from 100 kPa to 300 kPa with a 3-kW motor?
A wave comes rolling into the beach at 2 m/s horizontal velocity. Neglect friction and find how high up (elevation) on the beach the wave will reach.
Liquid water at 300 kPa, 15◦C flows in a garden hose with a small ideal nozzle. How high a velocity can be generated? If the water jet is directed straight up, how high will it go?
An irrigation pump takes water from a river at 10◦C, 100 kPa and pumps it up to an open canal at a 50-m higher elevation. The pipe diameter into and out of the pump is 0.1 m, and the motor driving
Saturated R-410a at−10◦C is pumped/compressed to a pressure of 2.0 MPa at the rate of 0.5 kg/s in a reversible adiabatic process. Calculate the power required and the exit temperature for the two
The underwater bulb nose of a container ship has a velocity relative to the ocean water of 10 m/s. What is the pressure at the front stagnation point that is 2 m down from the water surface?
A speedboat has a small hole in the front of the drive with the propeller that extends down into the water at a water depth of 0.4 m. Assuming we have a stagnation point at that hole when the boat is
A flow of air at 100 kPa, 300 K enters a device and goes through a polytropic process with n = 1.3 before it exits at 800 K. Find the exit pressure, the specific work, and the heat transfer using
R-410a at−5◦C, 700 kPa is throttled, so it becomes cold at −40◦C. What is exit P and the specific entropy generation?
Ammonia is throttled from 1.5MPa, 35◦Cto a pressure of 291 kPa in a refrigerator system. Find the exit temperature and the specific entropy generation in this process.
A compressor in a commercial refrigerator receives R-410a at−25◦C and x=1. The exit is at 1000 kPa, 40◦C. Is this compressor possible?
A compressor in a commercial refrigerator receives R-410a at−25◦C and x=1. The exit is at 2000 kPa, 80◦C. Neglect kinetic energies and find the specific entropy generation.
A factory generates compressed air from ambient 100 kPa, 17◦C by compression to 1000 kPa, 600 K, after which it cools in a constant-pressure cooler to 300 K by heat transfer to the ambient. Find
A mixing chamber receives 5 kg/min ammonia as saturated liquid at −20◦C from one line and ammonia at 40◦C, 250 kPa from another line through a valve. The chamber also receives 325 kJ/min energy
Carbon dioxide at 300 K, 200 kPa is brought through a steady-flow device, where it is heated to 600 K by a 700 K reservoir in a constant-pressure process. Find the specific work, specific heat
A dual fluid heat exchanger has 5 kg/s water enter at 40◦C, 150 kPa and leave at 10◦C, 150 kPa. The other fluid is glycol coming in at −10◦C, 160 kPa and leaving at 10◦C, 160 kPa. Find the
Two flows of air are both at 200 kPa; one has 2 kg/s at 400 K, and the other has 1 kg/s at 290 K. The two flows are mixed together in an insulated box to produce a single exit flow at 200 kPa. Find
A condenser in a power plant receives 5 kg/s steam at 15 kPa, quality 90% and rejects the heat to cooling water with an average temperature of 17◦C. Find the power given to the cooling water in
A large supply line has a steady flow of R-410a at 1000 kPa, 60◦C. It is used in three different adiabatic devices shown in Fig. P7.101: a throttle flow, an ideal nozzle, and an ideal turbine. All
A two-stage compressor takes nitrogen in at 20◦C, 150 kPa and compresses it to 600 kPa, 450 K. Then it flows through an intercooler, where it cools to 320 K, and the second stage compresses it to
A counterflowing heat exchanger has one line with 2 kg/s at 125 kPa, 1000 K entering, and the air is leaving at 100 kPa, 400 K. The other line has 0.5 kg/s water coming in at 200 kPa, 20◦C and
A large supply line has a steady air flow at 500 K, 200 kPa. It is used in the three different adiabatic devices shown in Fig. P7.101. All the exit flows are at 100 kPa. Find the exit temperature and
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 −20◦C. The
Repeat Problem 7.106 for the throttle and the nozzle when the inlet air temperature is 2000 K and use the air tables.Data from Problem 7.106A large supply line has a steady air flow at 500 K, 200
Carbon dioxide used as a natural refrigerant flows through a cooler at 10 MPa, which is supercritical, so no condensation occurs. The inlet is at 200◦C and the exit is at 40◦C. Assume the heat
Saturated liquid nitrogen at 600 kPa enters a boiler at a rate of 0.005 kg/s and exits as saturated vapor. It then flows into a super heater, also at 600 kPa, where it exits at 600 kPa, 280 K. Assume
A steam turbine in a power plant receives steam at 3000 kPa, 500◦C. The turbine has two exit flows; one is 20% of the flow at 1000 kPa, 350◦C to a feedwater heater, and the remainder flows out at
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 shown in
A coflowing (same direction) heat exchanger, shown in Fig. P7.113, has one line with 0.5 kg/s oxygen at 17◦C, 200 kPa entering, and the other line has 0.6 kg/s nitrogen at 150 kPa, 500 K entering.
A 1-m3 rigid tank contains 100 kg R-410a at a temperature of 15◦C, as shown in Fig. P7.116. A valve on top of the tank is opened, and saturated vapor is throttled to ambient pressure, 100 kPa and
A 1-L can of R-134a is at room temperature, 20◦C, with a quality of 50%. A leak in the top valve allows vapor to escape and heat transfer from the room takes place, so we reach a final state of
A 10-m-tall, 0.1-m-diameter pipe is filled with liquid water at 20◦C. It is open at the top to the atmosphere, 100 kPa, and a small nozzle is mounted in the bottom. The water is now let out through
An insulated piston/cylinder contains 0.1 m3 air at 250 kPa, 300 K and it maintains constant pressure. More air flows in through a valve from a line at 300 kPa, 400 K, so the volume increases 60%.
A balloon is filled with air from a line at 200 kPa, 300 K to a final state of 110 kPa, 300 K with a mass of 0.1 kg air. Assume the pressure is proportional to the balloon volume as P = 100 kPa + CV.
A steam turbine inlet is at 1200 kPa, 400◦C. The exit is at 200 kPa. What is the lowest possible exit temperature? Which efficiency does that correspond to?
A steam turbine inlet is at 1200 kPa, 400◦C. The exit is at 200 kPa. What is the highest possible exit temperature? Which efficiency does that correspond to?

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