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# ch09_eng - SOLUTION MANUAL ENGLISH UNIT PROBLEMS CHAPTER 9...

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SOLUTION MANUAL ENGLISH UNIT PROBLEMS CHAPTER 9 FUNDAMENTALS of Thermodynamics Sixth Edition SONNTAG BORGNAKKE VAN WYLEN

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Sonntag, Borgnakke and Wylen CONTENT SUBSECTION PROB NO. Concept-Study Guide Problems 134-141 Steady Single Flow Devices 142-149 Steady Irreversible Processes 150-155 Transient Processes 156-157 Reversible Shaft Work, Bernoulli 158-163 Device Efficiency 164-170 Review Problems 171-172 This problem set compared to the fifth edition chapter 9 set and the current SI unit problems. New 5th SI New 5th SI New 5th SI 134 new 6 147 new 33 160 105 82 135 new 8 148 new 35 161 106 84 136 new 9 149 97 39 162 new 94 137 new 14 150 94 47 163 107 90 138 new 17 151 95 52 164 109 96 139 new 18 152 108 54 165 110 101 140 new 19 153 new 53 166 111 107 141 new 20 154 98 56 167 117 111 142 91mod 22 155 99 60 168 115 - 143 29 24 156 101 69 169 114 114 144 96 30 157 100 73 170 118 - 145 new 31 158 103 77 171 102 131 146 93 37 159 104 79 172 112 133
Sonntag, Borgnakke and Wylen Concept Problems 9.134 E 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? Solution: Properties for R-134a are found in Table F.10 Inlet state: s i = 0.4157 Btu/lbm R Exit state: s e = 0.4080 Btu/lbm R Steady state single flow: s e = s i + i e dq T + s gen Since s decreases slightly and the generation term can only be positive, it must be that the heat transfer is negative (out) so the integral gives a contribution that is smaller than -s gen .

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Sonntag, Borgnakke and Wylen 9.135 E A large condenser in a steam power plant dumps 15 000 Btu/s at 115 F with an ambient at 77 F. What is the entropy generation rate? Solution: This process transfers heat over a finite temperature difference between the water inside the condenser and the outside ambient (cooling water from the sea, lake or river or atmospheric air) C.V. The wall that separates the inside 115 F water from the ambient at 77 F. Entropy Eq. 9.1 for steady state operation: Condensing water Sea water cb 115 F 77 F dS dt = 0 = Q . T + S . gen = Q . T 115 Q . T 77 + S . gen S . gen = [ 15 000 536.7 15 000 115 + 459.7 ] Btu s R = 1.85 Btu s R
Sonntag, Borgnakke and Wylen 9.136 E Air at 150 psia, 540 R is throttled to 75 psia. What is the specific entropy generation? Solution: C.V. Throttle, single flow, steady state. We neglect kinetic and potential energies and there are no heat transfer and shaft work terms. Energy Eq. 6.13: h i = h e T i = T e (ideal gas) Entropy Eq. 9.9: s e = s i + i e dq T + s gen = s i + s gen Change in s Eq.8.24: s e s i = i e C p dT T R ln P e P i = R ln P e P i s gen = s e s i = 53.34 778 ln 75 150 = 0.0475 Btu lbm R

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Sonntag, Borgnakke and Wylen 9.137 E A pump has a 2 kW motor. How much liquid water at 60 F can I pump to 35 psia from 14.7 psia? Incompressible flow (liquid water) and we assume reversible. Then the shaftwork is from Eq.9.18 w = −∫ v dP = v P = 0.016 ft 3 /lbm (35 – 14.7) psia = 46.77 lbf-ft/lbm = -0.06 Btu/lbm W . = 2 kW = 1.896 Btu/s m . = W . -w = 1.896 0.06 = 31.6 lbm/s
Sonntag, Borgnakke and Wylen 9.138 E A steam turbine inlet is at 200 psia, 900 F. The exit is at 40 psia. What is the lowest possible exit temperature? Which efficiency does that correspond to?

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ch09_eng - SOLUTION MANUAL ENGLISH UNIT PROBLEMS CHAPTER 9...

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