THERMODYNAMICS(SI UNITS,INTL.ED)EBOOK>I
THERMODYNAMICS(SI UNITS,INTL.ED)EBOOK>I
8th Edition
ISBN: 9781307434316
Author: CENGEL
Publisher: INTER MCG
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Chapter 7.13, Problem 194RP

a)

To determine

The net power delivered to the generator by the turbine.

a)

Expert Solution
Check Mark

Answer to Problem 194RP

The net power delivered to the generator by the turbine is 20,448 kW.

Explanation of Solution

Write the expression for the final entropy, s2.

s4=sf+x4sfg (I)

Here, final entropy is s4s1, final dry fraction is x4, entropy of saturated liquid is sf and entropy of evaporation is sfg.

Write the expression to calculate the final enthalpy h2.

h4=hf+x4hfg (II)

Here, final enthalpy is s4s1, final dry fraction is x4, enthalpy of saturated liquid is sf and enthalpy of evaporation is sfg.

Express the energy balance equation for closed system.

EinEout=ΔEsystem (III)

Here, energy transfer in to the system is Ein, energy transfer from the system is Eout and change in internal energy of system is ΔEsystem.

Write the energy balance for the compressor using equation (III).

W˙comp,in+m˙airh1=m˙airh2

W˙comp,in=m˙air(h2h1) (IV)

Write the energy balance for the compressor using equation (III).

m˙steamh3=W˙turb,out+m˙steamh4

W˙turb,out=m˙steam(h3h4) (V)

Write the expression for the net work done.

W˙net,out=W˙turb,outWcomp,in (VI)

Conclusion:

From the Table A-1, “Molar mass, gas constant, and critical-point properties”, select the gas constant (R) for air gas as 0.287kJ/kgK.

Refer to Table A-17, “ideal gas properties of air”, obtain the following properties of air at a temperature of 295 K.

h1=295.17kJ/kgs1°=1.68515kJ/kgK

Refer to Table A-17, “ideal gas properties of air”, obtain the following properties of air at a temperature of 620 K.

h2=628.07kJ/kgs2°=2.44356kJ/kgK

From Table A-6E, “Superheated water”, select the enthalpy (h3) and entropy (s3) at the pressure of 12.5 MPa and temperature of 500°C as 3343.6 kJ/kg and 6.4651 kJ/kgK respectively.

Refer to Table A-3, “saturated water-pressure table”, obtain the following properties of water at pressure of 10 kPa.

hf=191.81 kJ/kghfg=2392.1kJ/kgsf=0.6492 kJ/kgKhfg=7.4996kJ/kgK

Substitute 0.6492 kJ/kgK for sf,0.92 for x4, and 7.4996 kJ/kgK for sfg in equation (I)

6.5432kJ/kgK=1.3028kJ/kgK+x2(6.0562kJ/kgK)x2=(6.54321.3028)kJ/kgK6.0562kJ/kgK=0.8653

Substitute 191.8kJ/kg for hf,0.92 for x4 and 2392.1kJ/kg for hfg in Equation (II).

h2=191.81kJ/kg+0.92(2392.1kJ/kg)=2392.5kJ/kg

Substitute 10 kg/s for mair, 628.07kJ/kg for h2,and 295.17kJ/kg for h1 in equation (IV).

W˙comp,in=(10 kg/s)(628.07kJ/kg295.17kJ/kg)=3329 kW

Substitute 25 kg/s for msteam, 3343.6kJ/kg for h3,and 2392.5kJ/kg for h4 in equation (V).

W˙turb,out=(25 kg/s)(3343.6kJ/kg2392.5kJ/kg)=23,777 kW

Substitute 23,777 kW for W˙turb,out and 3329 kW for W˙comp,in in equation (VI).

W˙net,out=23,777 kW3329 kW=20,448 kW

Thus, the net power delivered to the generator by the turbine is 20,448 kW.

b)

To determine

The rate of entropy generation with in the turbine and compressor during the process

b)

Expert Solution
Check Mark

Answer to Problem 194RP

The rate of entropy generation with in the turbine and compressor during the process is 28.02 kW/K_.

Explanation of Solution

Write the formula for the entropy change of compressor.

S˙gen,comp=m˙air(s2°s1°Rln(P2P1)) (VII)

Here, pressure at state point 2 is P2, pressure at state point 1 is P1, and mass flow rate of the air is m˙air.

Write the formula for the entropy change of turbine.

S˙gen,Turb=m˙steam(s4s3) (VIII)

Write the expression for the total entropy generation.

S˙gen,total=S˙gen,comp+S˙gen,turb (IX)

Conclusion:

Substitute 10kg/s for m˙air,2.44356 kJ/kgK for s2°,1.68515 kJ/kgK for s1°,0.287kJ/kgK for R, 1000kPa for P2, and 98 kPa for P1 equation (VII).

S˙gen,comp=10kg/s(2.44356 kJ/kgK1.68515 kJ/kgK0.287kJ/kgK×ln(1000kPa98 kPa))=0.92 kW/K

Substitute 25kg/s for m˙steam,7.5489 kJ/kgK for s4, and 6.4651 kJ/kgK for s3 equation (VIII).

S˙gen,turb=25kg/s(7.5489 kJ/kgK6.4651 kJ/kgK)=27.1 kW/K

Substitute 0.92 kW/K for S˙gen,comp and 27.1 kW/K for S˙gen,turb in equation (IX).

S˙gen,total=0.92 kW/K+27.1 kW/K=28.02 kW/K 

Thus, the rate of entropy generation with in the turbine and compressor during the process is 28.02 kW/K_.

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Chapter 7 Solutions

THERMODYNAMICS(SI UNITS,INTL.ED)EBOOK>I

Ch. 7.13 - A pistoncylinder device contains nitrogen gas....Ch. 7.13 - A pistoncylinder device contains superheated...Ch. 7.13 - The entropy of steam will (increase, decrease,...Ch. 7.13 - Prob. 14PCh. 7.13 - Prob. 15PCh. 7.13 - Prob. 16PCh. 7.13 - Steam is accelerated as it flows through an actual...Ch. 7.13 - Prob. 18PCh. 7.13 - Prob. 19PCh. 7.13 - Prob. 20PCh. 7.13 - Heat in the amount of 100 kJ is transferred...Ch. 7.13 - In Prob. 719, assume that the heat is transferred...Ch. 7.13 - 7–23 A completely reversible heat pump produces...Ch. 7.13 - During the isothermal heat addition process of a...Ch. 7.13 - Prob. 25PCh. 7.13 - During the isothermal heat rejection process of a...Ch. 7.13 - Prob. 27PCh. 7.13 - Prob. 28PCh. 7.13 - Two lbm of water at 300 psia fill a weighted...Ch. 7.13 - A well-insulated rigid tank contains 3 kg of a...Ch. 7.13 - The radiator of a steam heating system has a...Ch. 7.13 - A rigid tank is divided into two equal parts by a...Ch. 7.13 - 7–33 An insulated piston–cylinder device contains...Ch. 7.13 - Prob. 34PCh. 7.13 - Prob. 35PCh. 7.13 - Onekg of R-134a initially at 600 kPa and 25C...Ch. 7.13 - Refrigerant-134a is expanded isentropically from...Ch. 7.13 - Prob. 38PCh. 7.13 - Refrigerant-134a at 320 kPa and 40C undergoes an...Ch. 7.13 - A rigid tank contains 5 kg of saturated vapor...Ch. 7.13 - A 0.5-m3 rigid tank contains refrigerant-134a...Ch. 7.13 - Prob. 44PCh. 7.13 - Prob. 45PCh. 7.13 - Steam enters an adiabatic diffuser at 150 kPa and...Ch. 7.13 - Prob. 47PCh. 7.13 - An isentropic steam turbine processes 2 kg/s of...Ch. 7.13 - Prob. 50PCh. 7.13 - 7–51 0.7-kg of R-134a is expanded isentropically...Ch. 7.13 - Twokg of saturated water vapor at 600 kPa are...Ch. 7.13 - Steam enters a steady-flow adiabatic nozzle with a...Ch. 7.13 - Prob. 54PCh. 7.13 - In Prob. 755, the water is stirred at the same...Ch. 7.13 - A pistoncylinder device contains 5 kg of steam at...Ch. 7.13 - Prob. 57PCh. 7.13 - Prob. 59PCh. 7.13 - A 50-kg copper block initially at 140C is dropped...Ch. 7.13 - Prob. 61PCh. 7.13 - Prob. 62PCh. 7.13 - A 30-kg aluminum block initially at 140C is...Ch. 7.13 - A 30-kg iron block and a 40-kg copper block, both...Ch. 7.13 - An adiabatic pump is to be used to compress...Ch. 7.13 - Prob. 67PCh. 7.13 - Can the entropy of an ideal gas change during an...Ch. 7.13 - An ideal gas undergoes a process between two...Ch. 7.13 - Prob. 72PCh. 7.13 - Prob. 73PCh. 7.13 - Prob. 74PCh. 7.13 - Prob. 75PCh. 7.13 - A 1.5-m3 insulated rigid tank contains 2.7 kg of...Ch. 7.13 - An insulated pistoncylinder device initially...Ch. 7.13 - A pistoncylinder device contains 0.75 kg of...Ch. 7.13 - Prob. 80PCh. 7.13 - 7–81 Air enters a nozzle steadily at 280 kPa and...Ch. 7.13 - A mass of 25 lbm of helium undergoes a process...Ch. 7.13 - One kg of air at 200 kPa and 127C is contained in...Ch. 7.13 - Prob. 85PCh. 7.13 - Air at 3.5 MPa and 500C is expanded in an...Ch. 7.13 - 7–87E Air is compressed in an isentropic...Ch. 7.13 - An insulated rigid tank is divided into two equal...Ch. 7.13 - An insulated rigid tank contains 4 kg of argon gas...Ch. 7.13 - Prob. 90PCh. 7.13 - Prob. 91PCh. 7.13 - Prob. 92PCh. 7.13 - Air at 27C and 100 kPa is contained in a...Ch. 7.13 - Prob. 94PCh. 7.13 - Helium gas is compressed from 90 kPa and 30C to...Ch. 7.13 - Five kg of air at 427C and 600 kPa are contained...Ch. 7.13 - Prob. 97PCh. 7.13 - The well-insulated container shown in Fig. P 795E...Ch. 7.13 - Prob. 99PCh. 7.13 - Prob. 100PCh. 7.13 - It is well known that the power consumed by a...Ch. 7.13 - Prob. 102PCh. 7.13 - Prob. 103PCh. 7.13 - Saturated water vapor at 150C is compressed in a...Ch. 7.13 - Liquid water at 120 kPa enters a 7-kW pump where...Ch. 7.13 - Prob. 106PCh. 7.13 - Consider a steam power plant that operates between...Ch. 7.13 - Helium gas is compressed from 16 psia and 85F to...Ch. 7.13 - Nitrogen gas is compressed from 80 kPa and 27C to...Ch. 7.13 - Saturated refrigerant-134a vapor at 15 psia is...Ch. 7.13 - Describe the ideal process for an (a) adiabatic...Ch. 7.13 - Is the isentropic process a suitable model for...Ch. 7.13 - On a T-s diagram, does the actual exit state...Ch. 7.13 - Steam at 100 psia and 650F is expanded...Ch. 7.13 - Prob. 117PCh. 7.13 - Combustion gases enter an adiabatic gas turbine at...Ch. 7.13 - Steam at 4 MPa and 350C is expanded in an...Ch. 7.13 - Prob. 120PCh. 7.13 - Prob. 122PCh. 7.13 - Prob. 123PCh. 7.13 - Refrigerant-134a enters an adiabatic compressor as...Ch. 7.13 - Prob. 126PCh. 7.13 - Argon gas enters an adiabatic compressor at 14...Ch. 7.13 - Air enters an adiabatic nozzle at 45 psia and 940F...Ch. 7.13 - Prob. 130PCh. 7.13 - An adiabatic diffuser at the inlet of a jet engine...Ch. 7.13 - Hot combustion gases enter the nozzle of a...Ch. 7.13 - Refrigerant-134a is expanded adiabatically from...Ch. 7.13 - Oxygen enters an insulated 12-cm-diameter pipe...Ch. 7.13 - Prob. 135PCh. 7.13 - Prob. 136PCh. 7.13 - Steam enters an adiabatic turbine steadily at 7...Ch. 7.13 - 7–138 In an ice-making plant, water at 0°C is...Ch. 7.13 - Water at 20 psia and 50F enters a mixing chamber...Ch. 7.13 - Prob. 140PCh. 7.13 - Prob. 141PCh. 7.13 - Prob. 142PCh. 7.13 - Prob. 143PCh. 7.13 - In a dairy plant, milk at 4C is pasteurized...Ch. 7.13 - An ordinary egg can be approximated as a...Ch. 7.13 - Prob. 146PCh. 7.13 - Prob. 147PCh. 7.13 - In a production facility, 1.2-in-thick, 2-ft 2-ft...Ch. 7.13 - Prob. 149PCh. 7.13 - Prob. 150PCh. 7.13 - A frictionless pistoncylinder device contains...Ch. 7.13 - Prob. 152PCh. 7.13 - Prob. 153PCh. 7.13 - Prob. 154PCh. 7.13 - Prob. 155PCh. 7.13 - Liquid water at 200 kPa and 15C is heated in a...Ch. 7.13 - Prob. 157PCh. 7.13 - Prob. 158PCh. 7.13 - Prob. 159PCh. 7.13 - Prob. 160PCh. 7.13 - Prob. 161PCh. 7.13 - Prob. 162PCh. 7.13 - Prob. 163PCh. 7.13 - Prob. 164PCh. 7.13 - Prob. 165PCh. 7.13 - The space heating of a facility is accomplished by...Ch. 7.13 - Prob. 167PCh. 7.13 - Prob. 168PCh. 7.13 - Prob. 169RPCh. 7.13 - A refrigerator with a coefficient of performance...Ch. 7.13 - Prob. 171RPCh. 7.13 - Prob. 172RPCh. 7.13 - Prob. 173RPCh. 7.13 - A 100-lbm block of a solid material whose specific...Ch. 7.13 - Prob. 175RPCh. 7.13 - Prob. 176RPCh. 7.13 - A pistoncylinder device initially contains 15 ft3...Ch. 7.13 - Prob. 178RPCh. 7.13 - A 0.8-m3 rigid tank contains carbon dioxide (CO2)...Ch. 7.13 - Helium gas is throttled steadily from 400 kPa and...Ch. 7.13 - Air enters the evaporator section of a window air...Ch. 7.13 - Refrigerant-134a enters a compressor as a...Ch. 7.13 - Prob. 183RPCh. 7.13 - Three kg of helium gas at 100 kPa and 27C are...Ch. 7.13 - Prob. 185RPCh. 7.13 - 7–186 You are to expand a gas adiabatically from...Ch. 7.13 - Prob. 187RPCh. 7.13 - Determine the work input and entropy generation...Ch. 7.13 - Prob. 189RPCh. 7.13 - Prob. 190RPCh. 7.13 - Air enters a two-stage compressor at 100 kPa and...Ch. 7.13 - Steam at 6 MPa and 500C enters a two-stage...Ch. 7.13 - Prob. 193RPCh. 7.13 - Prob. 194RPCh. 7.13 - Prob. 196RPCh. 7.13 - Prob. 197RPCh. 7.13 - 7–198 To control the power output of an isentropic...Ch. 7.13 - Prob. 199RPCh. 7.13 - Prob. 200RPCh. 7.13 - A 5-ft3 rigid tank initially contains...Ch. 7.13 - Prob. 202RPCh. 7.13 - Prob. 203RPCh. 7.13 - Prob. 204RPCh. 7.13 - Prob. 205RPCh. 7.13 - Prob. 206RPCh. 7.13 - Prob. 207RPCh. 7.13 - Prob. 208RPCh. 7.13 - (a) Water flows through a shower head steadily at...Ch. 7.13 - Prob. 211RPCh. 7.13 - Prob. 212RPCh. 7.13 - Prob. 213RPCh. 7.13 - Consider the turbocharger of an internal...Ch. 7.13 - Prob. 215RPCh. 7.13 - Prob. 216RPCh. 7.13 - Prob. 217RPCh. 7.13 - Consider two bodies of identical mass m and...Ch. 7.13 - Prob. 220RPCh. 7.13 - Prob. 222RPCh. 7.13 - Prob. 224RPCh. 7.13 - The polytropic or small stage efficiency of a...Ch. 7.13 - Steam is compressed from 6 MPa and 300C to 10 MPa...Ch. 7.13 - An apple with a mass of 0.12 kg and average...Ch. 7.13 - A pistoncylinder device contains 5 kg of saturated...Ch. 7.13 - Prob. 229FEPCh. 7.13 - Prob. 230FEPCh. 7.13 - A unit mass of a substance undergoes an...Ch. 7.13 - A unit mass of an ideal gas at temperature T...Ch. 7.13 - Prob. 233FEPCh. 7.13 - Prob. 234FEPCh. 7.13 - Air is compressed steadily and adiabatically from...Ch. 7.13 - Argon gas expands in an adiabatic turbine steadily...Ch. 7.13 - Water enters a pump steadily at 100 kPa at a rate...Ch. 7.13 - Air is to be compressed steadily and...Ch. 7.13 - Helium gas enters an adiabatic nozzle steadily at...Ch. 7.13 - Combustion gases with a specific heat ratio of 1.3...Ch. 7.13 - Steam enters an adiabatic turbine steadily at 400C...Ch. 7.13 - Liquid water enters an adiabatic piping system at...Ch. 7.13 - Prob. 243FEPCh. 7.13 - Steam enters an adiabatic turbine at 8 MPa and...Ch. 7.13 - Helium gas is compressed steadily from 90 kPa and...
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