A 29.6-kg iron block initially at 370°C is quenched in an insulated tank that contains 136.3 kg of water at 11°C. Assuming the water that vaporizes during the process condenses back in the tank, determine the total entropy change during this process.

Solution

A 51-kg copper block initially at 114°C is dropped into an insulated 
tank that contains 174 L of water at 20°C. Determine the final 
equilibrium temperature and the total entropy change for this process. 

PDF: kau

Solution

A 1.1-ft3 well-insulated rigid can initially contains refrigerant R-134a at 140 
psia and 50 F. Now a crack develops in the can, and the refrigerant starts to leak out 
slowly. Assuming the refrigerant remaining in the can has undergone a reversible, 
adiabatic process, determine the mass in the can when the pressure drops to 30 psia

Chegg: Book Solution

Solution

0.5 kg of R-134a is expanded isentropically from 600 kpa to 30 degreesC to 140 kpa. Determine the total heat transfer and work production for this expansion.

Solution

Steam is expanded in an isentropic turbine with a single inlet and outlet. At the inlet, the steam is at 2 MPa and 360 degrees C. The steam pressure at the outlet is 100 kPa. Calculate the work produced by the turbine, in kJ/kg.

PDF: ku

Solution

A piston–cylinder device contains 1.4 kg of saturated water vapor at 200°C. Heat is now transferred to steam, and steam expands reversibly and isothermally to a final pressure of 800 kPa. Determine the heat transferred and the work done during this process. 

PDF: kau
PDF: ku

Solution

A heavily insulated piston–cylinder device contains 0.039 m3 of steam at 300 kPa and 150°C. Steam is now compressed in a reversible manner to a pressure of 1 MPa. Determine the work done on the steam during this process.

Chegg: Book Solution

Solution

A piston-cylinder device contains 2 lbm of refrigerant R-134a at 120 psia and 100 °F. The refrigerant is now cooled at constant pressure until it exists as a liquid at 50 °F. Determine the entropy change during the process.

Solution

Liquid water at 120 kPa enters a 7-kW pump where pressure is raised to 5 MPa, elevation difference from inlet to exit levels is 10 m, determine highest mass flow rate this pump can handle. Neglect kinetic energy change and take specific volume of water to be 0.001m^3/kg

PDF: tufts
PDF: kau
Chegg: Homework Help

Solution

Helium gas is compressed from 16 psia and 85°F to 120 psia at a rate of 10 ft3/s. Determine the power input to the compressor, assuming the compression process to be 
(a) isentropic
(b) polytropic with n = 1.2
(c) isothermal
(d) ideal two-stage polytropic with n = 1.2.

Solution

Liquid water enters a 25-kW pump at 100-kPa pressure at a rate of 5 kg/s. Determine the highest pressure the liquid water can have at the exit of the pump. Neglect the kinetic and potential energy changes of water, 
and take the specific volume of water to be 0.001 m3/kg. 

PDF: kau
PDF: tufts
Chegg: Homework Help

Solution

A constant-volume tank contains 4.840 kg of air at 100 kpa and 327 degreesC. The air is cooled to the surroundings temperature of 27 degreesC. Assume constant specific heats at 300 K. 

Determine the entropy change of the air in the tank during the process and the net entropy change of the universe do to this process.

Chegg: Book Help

Solution

An ideal gas at 101 kPa and 27 degrees C enters a steady-flow compressor. The gas is compressed to 404 kPa, and 10% of the mass that entered the compressor is removed for some other use. The remaining 90% of the inlet gas is compressed to 580 kPa before leaving the compressor. The entire compression process is assumed to be reversible and adiabatic. The power supplied to the compressor is measured to be 32.2 kW. If the ideal gas has constant specific heats such that c(v)=0.71 kJ/kg*K and c(p)=1.26 kJ/kg*K,

determine the temperature of the gas at the two compressor exits
determine the mass flow rate of the gas into the compressor

Chegg: Homework Help

Solution

A piston cylinder device contains 1.289 kg of nitrogen gas at 120 kPa and 27oC. The gas is now compressed slowly in a polytropic process during which PV1.48 = constant. The process ends when the volume is reduced by one-half. Determine the entropy change of nitrogen during this process.

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Solution

Air is expanded from 200 psia and 470F to 107 psia and 42F. Assuming constant specific heats at room temperature, determine the change in specific entropy of air.

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Solution

An insulated, rigid tank is divided into two equal parts by a partition. One part of the tank contains 3.54 kmol of an ideal gas at 300 kPa and 65°C and the other side is evacuated. The partition is removed, and the gas fill the entire tank. Determine the total entropy change during this process

Chegg: Book

Solution

In a dairy plant, milk at 4 degreesC is pasteurized continuously at 72 degreesC at a rate of 12 L/s for 24 hours a day and 365 days a year. The milk is heated to the pasteurizing temperature by hot water heated in a natural-gas-fired boiler that has an efficiency of 82 percent. The pasteurized milk is then cooled by cold water at 18degreesC before it is finally refrigerated back to 4 degreesC. To save energy and money, the plant installs a re generator that has an effectiveness of 82 percent. If the cost of natural gas is $1.04/therm (1 therm = 105,500 kJ), determine how much more energy and money the re generator will save this company per year and the annual reduction in entropy generation. 

Solution

Heat is lost through a plane wall steadily at a rate of 750W. If the inner and outer surface temperatures of the wall are 50C and 15C respectively the rate of entropy generation within the wall is.

Chegg: Homework Help

Solution

Definitions and Equations:
Entropy = S
Heat Flow = Q =
Temperature = T
S = Q/T

Entropy Generated = ΔS = S_Out - S_In

Q = 750 W

T_In = 50^oC = 323K

T_Out= 15^oC = 288K

Caclculations:

S_In = Q/T_In = 750 W/ 323K = 2.322 W/K

S_Out = Q/T_Out = 750 W / 288K = 2.604 W/K

Therefore....

ΔS = S_{Out -} S_{In = (2.604 - 2.322) W/K = ......}

Steam expands in a turbine steadily at a rate of 40,000 kg/hr, entering at 8 MPa and 500°C and leaving at 40 kPa as saturated vapor. If the power generated by the turbine is 8.2 MW, determine the rate of entropy generation for this process. Assume the surrounding medium is at 25°C.

Solution

An ordinary egg can be approximated as a 5.5 cm diameter sphere.The egg is initially at a uniform
temperature of 8 oC and is dropped into boiling water at 97 oC. Taking the properties of the egg to be
ρ= 1020 kg/m3 and Cp = 3.32 kJ/(kg oC), determine how much heat is transferred to the egg by the time the average temperature of the egg rises to 70oC and the amount of entropy generation associated with this heat transfer process.

PDF: nus
PDF: lsu

Solution
I recommend the lsu pdf

Oxygen enters an insulated 12-cm-diameter pipe with a velocity of 70 m/s. At the pipe entrance, the oxygen is at 240 kPa and 20 C; and, at the exit, it is at 200 kPa and 18 C. Calculate the rate at which entropy is generated in the pipe.

Chegg: Book Solution

Solution

The exhaust nozzle of a jet engine expands air at 300 kPa and 180degC adiabatically to 100 kPa. Determine the air velocity at the exit when the inlet velocity is low and the nozzle isentropic efficiency is 96 percent.

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Solution

Argon gas enters a adiabatic compressor at 20psia and 90 F with a velocity of 60 ft/s, and it exits at 200 psi and 240 ft/s. If the isentropic efficiency of the compressor is 80%, determine (a) the exit temperature of the argon and (b) the work input to the compressor

tricity: pdf
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Solution

Air enters an adiabatic compressor at 100 kPa and 17 degrees Celsius at a rate of 2.4 m³/s, and it exits at 257 degrees Celsius. The compressor has an isentropic efficiency of 84 percent. Neglecting the changes in kinetic and potential energies, determine (a) the exit pressure of air and (b) the power required to drive the compressor.

Chegg: Homework Help
kau: pdf

Solution

Combustion gases enter an adiabatic gas turbine at 1540 F degrees and 120 psia and leave at 60 psia with a low velocity. Treating the combustion gases as air and assuming an isentropic efficiency of 82 percent, determine the work output of the turbine.

Chegg: Homework Help

Solution

Steam at 3 MPa and 400 °C is expanded to 30 kPa in an adiabatic turbine with an isentropic efficiency of 52. percent. Determine the power produced by this turbine when the mass flow rate is 1.4 kg/s. Submit your answer in kW


Chegg
Chegg

Solution