Questions and Answers of Fundamentals Of Thermodynamics

A steam turbine inlet is at 1200 kPa, 400◦C. The exit is at 200 kPa, 200◦C. What is the isentropic efficiency?
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 isentropic compressor efficiency.
A steam turbine has an inlet of 2 kg/s water at 1000 kPa, 400◦C with velocity of 15 m/s. The exit is at 100 kPa, 150◦C and very low velocity. Find the power produced and the rate of entropy
An emergency drain pump, shown in Fig. P7.134, should be able to pump 0.1 m3/s liquid water at 15◦C, 10 m vertically up, delivering it with a velocity of 20 m/s. It is estimated that the pump,
A gas turbine with air flowing in at 1200 kPa, 1200 K has an exit pressure of 200 kPa and an isentropic efficiency of 87%. Find the exit temperature.
A gas turbine with air flowing in at 1200 kPa, 1200 K has an exit pressure of 200 kPa. Find the lowest possible exit temperature. Which efficiency does that correspond to?
Ammoniais brought from saturated vapor at 300 kPa to 1400 kPa, 140◦C in a steady-flow adiabatic compressor. Find the compressor specificwork, entropy generation, and its isentropic efficiency.
A centrifugal compressor takes in ambient air at 100 kPa, 17◦C and discharges it at 450 kPa. The compressor has an isentropic efficiency of 80%. What is your best estimate for the discharge
Redo Problem 7.41, assuming the compressor and turbine in the turbocharger both have isentropic efficiency of 85%.Data from Problem 7.41 A turbocharger boosts the inlet air pressure to an
Carbon dioxide enters an adiabatic compressor at 100 kPa, 300 K and exits at 1000 kPa, 520 K. Find the compressor efficiency and the entropy generation for the process.
A refrigerator uses carbon dioxide that is brought from 1MPa,−20◦C to 6MPa using 2kWpower input to the compressor with a flow rate of 0.02 kg/s. Find the compressor exit temperature and its
A compressor in an industrial air-conditioner compresses ammonia from a state of saturated vapor at 200 kPa to a pressure 800 kPa. At the exit, the temperature is measured to be 100◦C and the mass
Repeat Problem 7.48 assuming the turbine and the pump each has an isentropic efficiency of 85%.Data from Problem 7.48Consider a steam turbine power plant operating near critical pressure, as shown in
A nozzle in a high-pressure liquid water sprayer has an area of 0.5 cm2. It receives water at 350 kPa, 20◦C and the exit pressure is 100 kPa. Neglect the inlet kinetic energy and assume a nozzle
A flow of saturated liquid R-410a at 200 kPa in an evaporator is brought to a state of superheated vapor at 200 kPa, 20◦C. Assuming the process is reversible, find the specific heat transfer and
A flow of R-410a at 2000 kPa, 40◦C in an isothermal expander is brought to a state of 1000 kPa in a reversible process. Find the specific heat transfer and work.
A vortex 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, as shown in Fig. P7.162. The tube has no external heat transfer and no
In a heat-powered refrigerator, a turbine is used to drive the compressor using the same working fluid. Consider the combination shown in Fig. P7.165, where the turbine produces just enough power to
A flow of nitrogen, 0.1 kg/s, comes out of a compressor stage at 500 kPa, 500 K and is now cooled to 310 K in a counterflowing intercooler by liquid water at 125 kPa, 15◦C that leaves at 22◦C.
A horizontal insulated cylinder has a frictionless piston held against stops by an external force of 500 kN, as shown in Fig. P7.173. The piston cross sectional area is 0.5 m2, and the initial volume
A certain industrial process requires a steady 0.5 kg/s of air at 200 m/s at the condition of 150 kPa, 300 K, as shown in Fig. P7.176. This air is to be the exhaust from a specially designed turbine
A compressor receives R-134a at 20 F, 30 psia with an exit of 200 psia, x = 1. What can you say about the process?
A condenser receives R-410a at 0 F and quality 80%, with the exit flow being saturated liquid at 0 F. Consider the cooling to be a reversible process and find the specific heat transfer from the
The exit nozzle in a jet engine receives air at 2100 R, 20 psia with negligible kinetic energy. The exit pressure is 10 psia, and the process is reversible and adiabatic. Use constant heat capacity
In a heat pump that uses R-134a as the working fluid, the R-134a enters the compressor at 30 lbf/in.2, 20 F. In the compressor the R-134a is compressed in an adiabatic process to 150 lbf/in.2 using
A compressor in a commercial refrigerator receives R-410a at −10 F and unknown quality. The exit is at 300 psia, 140 F and the process is assumed to be reversible and adiabatic. Neglect kinetic
A compressor brings a hydrogen gas flow at 500 R, 1 atm up to a pressure of 10 atm in a reversible process. How hot is the exit flow, and what is the specific work input?
An expander receives 1 lbm/s air at 300 psia, 540 R with an exit state of 60 psia, 540 R. Assume the process is reversible and isothermal. Find the rates of heat transfer and work, neglecting kinetic
A 20 ft3 tank that contains carbon dioxide at 540 R, 20 psia is now filled from a supply of carbon dioxide at 540 R, 20 psia by a compressor to a final tank pressure of 60 psia. Assume the whole
R-410a at 240 F, 600 psia is in an insulated tank, and flow is now allowed out to a turbine with a backup pressure of 125 psia. The flow continues to a final tank pressure of 125 psia and the process
A river flowing at 2 ft/s across a 3-ft-high and 30-ft-wide area has a dam that creates an elevation difference of 7 ft. How much energy can a turbine deliver per day if 80% of the potential energy
How much liquid water at 60 F can be pumped from 14.7 psia to 35 psia with a 3-kW motor?
A wave comes rolling in to the beach at 6 ft/s horizontal velocity. Neglect friction and find how high up (elevation) on the beach the wave will reach.
An irrigation pump takes water from a river at 50 F, 1 atm and pumps it up to an open canal at a 150-ft-higher elevation. The pipe diameter into and out of the pump is 0.3 ft, and the motor driving
The underwater bulb nose of a container ship has a velocity relative to the ocean water of 30 ft/s. What is the pressure at the front stagnation point that is 6 ft 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 15 in. Assume we have a stagnation point at that hole when the boat is
A compressor in a commercial refrigerator receives R-410a at −10 F and x = 1. The exit is at 150 psia and 60 F. Is this compressor possible?
R-134a at 90 F, 125 psia is throttled in a steady flow to a lower pressure, so it comes out at 10 F. What is the specific entropy generation?
Two flow streams of water, one at 100 lbf/in.2, saturated vapor and the other at 100 lbf/in.2, 1000 F, mix adiabatically in a steady-flow process to produce a single flow out at 100 lbf/in.2, 600 F.
A steam turbine has an inlet of 4 lbm/s water at 150 psia and 550 F with a velocity of 50 ft/s. The exit is at 1 atm, 240 F and very low velocity. Find the power produced and the rate of entropy
A dual fluid heat exchanger has 10 lbm/s water enter at 104 F, 20 psia and leaving at 50 F, 20 psia. The other fluid is glycol coming in at 14 F, 22 psia and leaves at 50 F, 22 psia. Find the mass
A factory generates compressed air from ambient 15 psia, 62 F by compression to 150 psia, 1080 R, after which it cools in a constant-pressure cooler to 540 R by heat transfer to the ambient air. Find
A condenser in a power plant receives 10 lbm/s steam at 130 F, quality 90% and rejects the heat to cooling water with an average temperature of 62 F. Find the power given to the cooling water in this
An initially empty 5-ft3 tank is filled with air from 70 F, 15 psia until it is full. Assume no heat transfer and find the final mass and entropy generation.
An empty cannister of volume 0.05 ft3 is filled with R-134a from a line flowing saturated liquid R-134a at 40 F. The filling is done quickly, so it is adiabatic. How much mass of R-134a is in the
A steam turbine inlet is at 200 psia, 800 F. The exit is at 40 psia. What is the lowest possible exit temperature? Which efficiency does that correspond to?
A steam turbine inlet is at 200 psia, 800 F. The exit is at 40 psia. What is the highest possible exit temperature? Which efficiency does that correspond to?
A steam turbine inlet is at 200 psia, 800 F. The exit is at 40 psia, 600 F. What is the isentropic efficiency?
Write a program to solve the general case of Problem 7.26, in which the states, velocities, and area are input variables. Use a constant specific heat and find the diffuser exit area, temperature,
Small gasoline engine or electric motor-driven air compressors are used to supply compressed air to power tools, machine shops, and so on. The compressor charges air into a tank that acts as a
A reversible adiabatic compressor receives air at the state of the surroundings, 20◦C, 100 kPa. It should compress the air to a pressure of 1.2 MPa in two stages with a constant-pressure
Investigate the optimal pressure, P2, for a constant-pressure intercooler between two stages in a compressor. Assume that the compression process in each stage follows a poly tropic process and that
Consider a geothermal supply of hot water available as saturated liquid at P1 = 1.5 MPa. The liquid is to be flashed (throttled) to some lower pressure, P2. The saturated liquid and saturated vapor
Investigate the sizes of turbochargers and superchargers available for automobiles. Look at their boost pressures and check if they also have intercoolers mounted. Analyze an example with respect to
A heat pump uses carbon dioxide, and it must condense at a minimum of 22◦C and receives energy from the outside on a winter day at −10◦C. What restrictions does that place on the operating
A power plant for a polar expedition uses ammonia, which is heated to 80◦C at 1000 kPa in the boiler, and the condenser is maintained at−15◦C. Find the cycle efficiency.
A steam power plant has a high pressure of 3 MPa, and it maintains 60◦C in the condenser. A condensing turbine is used, but the quality should not be lower than 90% at any state in the turbine. For
Geo thermal water can be used directly as a source to a steam turbine. Consider 10 kg/s water at 500 kPa, 150◦C brought to a flash chamber, where it is throttled to 200 kPa, as shown in Fig. P9.26.
Some geothermal locations have higher pressure and temperature, so assume the geothermal power plant as in Problem 9.26 but with a supply as saturated liquid at 250◦C. For this case, the flash
With a higher supply pressure and temperature of the geothermal source, it is possible to have two flash evaporators, as shown in Fig. P9.28. Assume the supply is saturated water at 250◦C and the
Consider the ammonia Rankine-cycle power plant shown in Fig. P9.31. The plant was designed to operate in a location where the ocean water temperature is 25◦C near the surface and 5◦C at some
Do Problem 9.31 with carbon dioxide as the working fluid.Data from Problem 9.31Consider the ammonia Rankine-cycle power plant shown in Fig. P9.31. The plant was designed to operate in a location
An open FWH receives steam at 1 MPa, 200◦C from the turbine and 1 MPa, 100◦C water from the feedwater line. Find the required fraction of the extraction flow in the turbine.
A power plant for a polar expedition uses ammonia and the boiler exit is 80◦C, 1000 kPa, and the condenser operates at −15◦C. A single open FWH operates at 400 kPa with an exit state of
Find the cycle efficiency for the cycle in Problem 9.41.Data from Problem 9.41.A power plant for a polar expedition uses ammonia and the boiler exit is 80◦C, 1000 kPa, and the condenser operates at
A low-temperature power plant operates with R-410a maintaining−20◦Cin the condenser, a high pressure of 3 MPa with superheat to 80◦C. There is one open FWH operating at 800 kPa with an exit as
A power plant has a condenser temperature of 45◦C, a maximum pressure of 5 MPa, and a boiler exit temperature of 900◦C. It has one open FWH operating at 1 MPa. Find the fraction of extraction
In a nuclear power plant the reactor transfers the heat to a flow of liquid sodium, which in a heat exchanger transfers the heat to boiling water. Saturated vapor steam at 5 MPa exits this heat
A Rankine cycle flows 5 kg/s ammonia at 2 MPa, 140◦C to the turbine, which has an extraction point at 800 kPa. The condenser is at−20◦C, and a closed FWH has an exit state (3) at the
Assume that the power plant in Problem 9.45 has one closed FWH instead of the open FWH. The extraction flow out of the FWH is saturated liquid at 2033 kPa being dumped into the condenser, and the
Assume a variation of the cycle in Problem 9.49 with a closed FWH at 0.8 MPa and one open FWH at 100 kPa. A pump is used to bring the water leaving the condenser up to 100 kPa for an open FWH,and a
A Rankine cycle with water superheats to 500◦C at 3 MPa in the boiler, and the condenser operates at 100◦C. All components are ideal except the turbine, which has an exit state measured to be
Consider the boiler in Problem 9.21 where the geothermal hot water brings the R-134a to saturated vapor. Assume a counterflowing heat exchanger arrangement. The geothermal water temperature should be
A concentrated solar power plant receives the energy from molten salt coming in at 560◦C and leaving at 300◦C in a counter flow heat exchanger where thewater comes in at 3MPa, 60◦Cand leaves at
A steam power plant operates with a high pressure of 4 MPa and has a boiler exit of 600◦C receiving heat from a 750◦Csource. The ambient at 20◦Cprovides cooling to maintain the condenser at
A concentrated solar power plant receives the energy from molten salt coming in at 560◦C and leaving at 300◦C in a counter flow heat exchanger where the water comes in at 3MPa, 60◦Cand leaves
An air conditioner using R-410a is used in cooling mode. The high pressure is 3000 kPa and the low pressure is 800 kPa. It cools a house at 20◦C with a rate of 12 kW, and the outside ambient is at
Assume the house in Problem 9.129 has a combined 12 000 kg hardwood, 2500 kg gypsum plates (Cp = 1 kJ/kg-K), and 750 kg steel, all of which is at 20◦C. If the heat pump is turned off, how fast does
Consider an ideal dual-loop heat-powered refrigeration cycle using R-134a as the working fluid, as shown in Fig. P9.135. Saturated vapor at 90◦C leaves the boiler and expands in the turbine to the
For Problem 9.134, determine the change in exergy of the water flow and that of the air flow. Use these values to determine the second-law efficiency of the boiler heat exchanger.Data from Problem
Do Problem 9.31 with R-134a as the working fluid in the Rankine cycle.Data from Problem 9.31Consider the ammonia Rankine-cycle power plant shown in Fig. P9.31. The plant was designed to operate in a
A simple steam power plant is said to have the following four states: 1: (20◦C, 100 kPa), 2: (25◦C, 1 MPa), 3: (1000◦C, 1 MPa), 4: (250◦C, 100 kPa), with an energy source at 1100◦C, and it
Do the previous problem with a closed FWH that has a trap and drain to the condenser for the extraction flow.
A concentrated solar power plant receives the energy from molten salt coming in at 1000 F and leaving at 600 F in a counter flow heat exchanger in which the water comes in at 400 psia, 140 F and
Steam is supplied in a line at 400 lbf/in.2, 1200 F. A turbine with an isentropic efficiency of 85% is connected to the line by a valve, and it exhausts to the atmosphere at 14.7 lbf/in.2. If the
Consider an ideal dual-loop heat-powered refrigeration cycle using R-134a as the working fluid, as shown in Fig. P9.135. Saturated vapor at 200 F leaves the boiler and expands in the turbine to the
The effect of turbine exhaust pressure on the performance of the ideal steam Rankine cycle given in Problem 9.13 with superheat to 300◦C is to be studied. Calculate the thermal efficiency of the
The effect of evaporator temperature on the COP of a heat pump is to be studied. Consider an ideal cycle with R-134a as the working fluid and a condenser temperature of 40◦C. Plot a curve for the
A hospital requires 2 kg/s steam at 200◦C, 125 kPa for sterilization purposes, and space heating requires 15 kg/s hot water at 90◦C, 100 kPa. Both of these requirements are provided by the
Can the exhaust flow from a gas turbine be useful?
Where may a heat engine–driven refrigerator be useful?
In a Brayton cycle the inlet is at 300 K, 100 kPa, and the combustion adds 800 kJ/kg. The maximum temperature is 1400 K due to material considerations. Find the maximum permissible compression ratio
A Brayton cycle produces 50 MW with an inlet state of 17◦C, 100 kPa, and the pressure ratio is 14:1. The highest cycle temperature is 1600 K. Find the thermal efficiency of the cycle and the mass
Consider the power plant in Problem 9.41. Assume that the high temperature source is a flow of liquid water at 120◦C into a heat exchanger at constant pressure, 300 kPa and that the water leaves at
Find the entropy generation per unit mass leaving the open FWH in Problem 9.40.Data from Problem 9.40.An open FWH receives steam at 1 MPa, 200◦C from the turbine and 1 MPa, 100◦C water from the
A steam power plant has 4 MPa, 500◦C into the turbine, and to have the condenser itself deliver the process heat, it is run at 101 kPa. How much net power as work is produced for process heat of 13
Steam must be generated at 150◦C for process heat in a food production facility. This is done in a combined heat and power system as extraction steam from the turbine. Assume the standard cycle has
A 15 kg/s steady supply of saturated-vapor steam at 500 kPa is required for drying a wood pulp slurry in a paper mill (see Fig. P9.79). It is decided to supply this steam by cogeneration; that is,
In a cogenerating steam power plant the turbine receives steam from a high-pressure steam drum (h = 3445.9 kJ/kg, s = 6.9108 kJ/kg K) and a low-pressure steam drum (h = 2855.4 kJ/kg, s = 7.0592 kJ/kg
A smaller power plant produces 25 kg/s steam at 3 MPa, 600◦C in the boiler. It cools the condenser to an exit temperature of 45◦C, and the cycle is shown in Fig. P9.82. An extraction is done at

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