Explanation Write the energy balance equation for a closed system. E in − E out = Δ E system − W out = Δ U − W out = m ( u 2 − u 1 ) (I) Here, net energy transfer in to the control volume is E in , net energy transfer exit from the control volume is E out and change in internal energy of system is Δ E system , mass of refrigerant-134a is m , work output from the system is W out and internal energy of refrigerant-134a at inlet and outlet conditions are u 1 and u 2 respectively. Write the formula to calculate actual power input of the expansion process ( w a,out ) . w a,out = η T ( u 1 − u 2 s ) (II) Here, isentropic expansion efficiency is η T and internal energy of refrigerant-134a at state 2s is u 2 s . Write the formula to calculate actual internal energy at the end of the expansion process ( u 2 ) . u 2 = u 1 − w a,out (III) Here, isentropic expansion efficiency is η T . Write the formula to calculate useful work of the expansion process ( w u ) . w u = w a,out − w surr = w a,out − P 0 ( v 2 − v 1 ) (IV) Here, surrounding work is w surr , surrounding pressure is P 0 ,specific volume of refrigerant-134a at inlet and outlet conditions are v 1 and v 2 respectively. Write the formula to difference in exergy between the initial and final states of the expansion process ( Δ ψ ) . Δ ψ = ( ψ 1 − ψ 2 ) w a = ( u 1 − u 2 ) + P 0 ( v 1 − v 2 ) − T 0 ( s 2 − s 1 ) (V) Here, initial and final exergies of refrigerant-134a are ψ 1 and ψ 2 respectively, surrounding temperature is T 0 and specific entropies of refrigerant-134a at the inlet and outlet conditions are s 1 and s 2 respectively. Write the formula to calculate second-law efficiency of the expansion process ( η II ) . η II = w u Δ ψ (VI) Conclusion: Refer Table A-13,“ Superheated refrigerant-134a”, obtain the following properties of the refrigerant-134a at pressure of 1600 kPa and temperature of 80°C . v 1 = 0.014362 m 3 / kg u 1 = 282.11 kJ / kg s 1 = 0.9875 kJ / kg ⋅ K Refer Table A-11 " Saturated refrigerant-134a-Temperature table ", through Table A-13,“ Superheated refrigerant-134a”, obtain the following properties of the refrigerant-134a at pressure of 100 kPa . u 2 s = 223.20 kJ / kg Substitute 0.85 for η T , 282.11 kJ / kg for u 1 and 223.20 kJ / kg for u 2 s in Equation (II). w a,out = 0.85 ( 282.11 kJ / kg − 223.20 kJ / kg ) = 50.57 kJ / kg Substitute 50.57 kJ / kg for w a,out and 282.11 kJ / kg for u 1 in Equation (III). u 2 = 282.11 kJ / kg − 50.57 kJ / kg = 232.04 kJ / kg Refer Table A-13,“ Superheated refrigerant-134a”, obtain the following properties of the refrigerant-134a at pressure of 1600 kPa and internal energy of 232

CONNECT FOR THERMODYNAMICS: AN ENGINEERI

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ISBN: 9781260048636

Author: CENGEL

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Chapter 8.8, Problem 126RP

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The second-law efficiency of the expansion process.

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Chapter 8.8, Problem 125RP

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CONNECT FOR THERMODYNAMICS: AN ENGINEERI

Ch. 8.8 - What final state will maximize the work output of...Ch. 8.8 - Is the exergy of a system different in different...Ch. 8.8 - Under what conditions does the reversible work...Ch. 8.8 - How does useful work differ from actual work? For...Ch. 8.8 - How does reversible work differ from useful work?Ch. 8.8 - Is a process during which no entropy is generated...Ch. 8.8 - Consider an environment of zero absolute pressure...Ch. 8.8 - It is well known that the actual work between the...Ch. 8.8 - Consider two geothermal wells whose energy...Ch. 8.8 - Consider two systems that are at the same pressure...

Ch. 8.8 - Prob. 11P Ch. 8.8 - Does a power plant that has a higher thermal...Ch. 8.8 - Prob. 13P Ch. 8.8 - Saturated steam is generated in a boiler by...Ch. 8.8 - One method of meeting the extra electric power...Ch. 8.8 - A heat engine that receives heat from a furnace at...Ch. 8.8 - Consider a thermal energy reservoir at 1500 K that...Ch. 8.8 - A heat engine receives heat from a source at 1100...Ch. 8.8 - A heat engine that rejects waste heat to a sink at...Ch. 8.8 - A geothermal power plant uses geothermal liquid...Ch. 8.8 - A house that is losing heat at a rate of 35,000...Ch. 8.8 - A freezer is maintained at 20F by removing heat...Ch. 8.8 - Prob. 24P Ch. 8.8 - Prob. 25P Ch. 8.8 - Prob. 26P Ch. 8.8 - Can a system have a higher second-law efficiency...Ch. 8.8 - A mass of 8 kg of helium undergoes a process from...Ch. 8.8 - Which is a more valuable resource for work...Ch. 8.8 - Which has the capability to produce the most work...Ch. 8.8 - The radiator of a steam heating system has a...Ch. 8.8 - A well-insulated rigid tank contains 6 lbm of a...Ch. 8.8 - A pistoncylinder device contains 8 kg of...Ch. 8.8 - Prob. 35P Ch. 8.8 - Prob. 36P Ch. 8.8 - Prob. 37P Ch. 8.8 - A pistoncylinder device initially contains 2 L of...Ch. 8.8 - A 0.8-m3 insulated rigid tank contains 1.54 kg of...Ch. 8.8 - An insulated pistoncylinder device initially...Ch. 8.8 - Prob. 41P Ch. 8.8 - An insulated rigid tank is divided into two equal...Ch. 8.8 - A 50-kg iron block and a 20-kg copper block, both...Ch. 8.8 - Prob. 45P Ch. 8.8 - Prob. 46P Ch. 8.8 - Prob. 47P Ch. 8.8 - A pistoncylinder device initially contains 1.4 kg...Ch. 8.8 - Prob. 49P Ch. 8.8 - Prob. 50P Ch. 8.8 - Prob. 51P Ch. 8.8 - Air enters a nozzle steadily at 200 kPa and 65C...Ch. 8.8 - Prob. 54P Ch. 8.8 - Prob. 55P Ch. 8.8 - Argon gas enters an adiabatic compressor at 120...Ch. 8.8 - Prob. 57P Ch. 8.8 - Prob. 58P Ch. 8.8 - The adiabatic compressor of a refrigeration system...Ch. 8.8 - Refrigerant-134a at 140 kPa and 10C is compressed...Ch. 8.8 - Air enters a compressor at ambient conditions of...Ch. 8.8 - Combustion gases enter a gas turbine at 900C, 800...Ch. 8.8 - Steam enters a turbine at 9 MPa, 600C, and 60 m/s...Ch. 8.8 - Refrigerant-134a is condensed in a refrigeration...Ch. 8.8 - Prob. 66P Ch. 8.8 - Refrigerant-22 absorbs heat from a cooled space at...Ch. 8.8 - Prob. 68P Ch. 8.8 - Prob. 69P Ch. 8.8 - Air enters a compressor at ambient conditions of...Ch. 8.8 - Hot combustion gases enter the nozzle of a...Ch. 8.8 - Prob. 72P Ch. 8.8 - A 0.6-m3 rigid tank is filled with saturated...Ch. 8.8 - Prob. 74P Ch. 8.8 - Prob. 75P Ch. 8.8 - An insulated vertical pistoncylinder device...Ch. 8.8 - Liquid water at 200 kPa and 15C is heated in a...Ch. 8.8 - Prob. 78P Ch. 8.8 - Prob. 79P Ch. 8.8 - A well-insulated shell-and-tube heat exchanger is...Ch. 8.8 - Steam is to be condensed on the shell side of a...Ch. 8.8 - Prob. 82P Ch. 8.8 - Prob. 83P Ch. 8.8 - Prob. 84P Ch. 8.8 - Prob. 85RP Ch. 8.8 - Prob. 86RP Ch. 8.8 - An aluminum pan has a flat bottom whose diameter...Ch. 8.8 - Prob. 88RP Ch. 8.8 - Prob. 89RP Ch. 8.8 - A well-insulated, thin-walled, counterflow heat...Ch. 8.8 - Prob. 92RP Ch. 8.8 - Prob. 93RP Ch. 8.8 - Prob. 94RP Ch. 8.8 - Prob. 95RP Ch. 8.8 - Nitrogen gas enters a diffuser at 100 kPa and 110C...Ch. 8.8 - Prob. 97RP Ch. 8.8 - Steam enters an adiabatic nozzle at 3.5 MPa and...Ch. 8.8 - Prob. 99RP Ch. 8.8 - A pistoncylinder device initially contains 8 ft3...Ch. 8.8 - An adiabatic turbine operates with air entering at...Ch. 8.8 - Steam at 7 MPa and 400C enters a two-stage...Ch. 8.8 - Prob. 103RP Ch. 8.8 - Steam enters a two-stage adiabatic turbine at 8...Ch. 8.8 - Prob. 105RP Ch. 8.8 - Prob. 106RP Ch. 8.8 - Prob. 107RP Ch. 8.8 - Prob. 108RP Ch. 8.8 - Prob. 109RP Ch. 8.8 - Prob. 111RP Ch. 8.8 - A passive solar house that was losing heat to the...Ch. 8.8 - Prob. 113RP Ch. 8.8 - A 4-L pressure cooker has an operating pressure of...Ch. 8.8 - Repeat Prob. 8114 if heat were supplied to the...Ch. 8.8 - Prob. 116RP Ch. 8.8 - A rigid 50-L nitrogen cylinder is equipped with a...Ch. 8.8 - Prob. 118RP Ch. 8.8 - Prob. 119RP Ch. 8.8 - Prob. 120RP Ch. 8.8 - Reconsider Prob. 8-120. The air stored in the tank...Ch. 8.8 - Prob. 122RP Ch. 8.8 - Prob. 123RP Ch. 8.8 - Prob. 124RP Ch. 8.8 - Prob. 125RP Ch. 8.8 - Prob. 126RP Ch. 8.8 - Prob. 127RP Ch. 8.8 - Water enters a pump at 100 kPa and 30C at a rate...Ch. 8.8 - Prob. 129RP Ch. 8.8 - Prob. 130RP Ch. 8.8 - Obtain a relation for the second-law efficiency of...Ch. 8.8 - Writing the first- and second-law relations and...Ch. 8.8 - Prob. 133RP Ch. 8.8 - Keeping the limitations imposed by the second law...Ch. 8.8 - Prob. 135FEP Ch. 8.8 - Prob. 136FEP Ch. 8.8 - Prob. 137FEP Ch. 8.8 - Prob. 138FEP Ch. 8.8 - A furnace can supply heat steadily at 1300 K at a...Ch. 8.8 - A heat engine receives heat from a source at 1500...Ch. 8.8 - Air is throttled from 50C and 800 kPa to a...Ch. 8.8 - Prob. 142FEP Ch. 8.8 - A 12-kg solid whose specific heat is 2.8 kJ/kgC is...

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Chapter 8 Solutions