Engineering Fundamentals- Thermodynamics
Engineering FundamentalsThermodynamicsBy Professor Paul A. Erickson
Basic Thermodynamics Conservation of MassConservation of EnergyPrinciple of State and PhasePrinciple of EntropyThermodynamic Cycles– Carnot– Rankine– Air Standard Cycles Otto Diesel Brayton– Refrigeration Cycle (also Heat Pump) Air/Water Mixtures
Basic Thermo Processes and Terms AdiabaticIsothermalIsobaricIsometric or IsochoricIsentropicIsenthalpicPolytropic Ideal Gas Incompressiblesubstances Intensive and Extensive Properties Compressibility Reduced Temperature andPressure Constant and Variable SpecificHeat Relative Pressure and Volume Flow Work Boundary Work Enthalpy Entropy Thermal Efficiency and COP Relative and Absolute Humidity
Conservation of MassEpicurus (341–270 BC). Describing the nature of theuniverse, "the sum total of things was always such as it isnow, and such it will ever remain."Input Storage- OutputMust be linked with Conservation of EnergyE mc2
Continuity EquationConservation of Mass(Total Mass Entering a System)-(Total Mass Leaving the System) Net change in mass within systemmimcvmeSteady flow implies no change in mass within cv m e - m i dmcv 0dt
Conservation of EnergyLights on or offEnergy is alwaysconserved Butthat isn't what theymean! Energy is neither created nor destroyed
1st Law of ThermodynamicsConservation of EnergyEnergy can neither be created nor destroyedInput Output StorageW Q meout d in meme cv 0dtWhere W is the work done by the system Q isthe heat transferred to the system andV2e h gz2
Using Conservation of EnergyWhat is the output shaft power?ENG 1058
Using Conservation of EnergyA refrigeration cycle has heat transfer Qout 3200 Btu and net work of Wcycle1200 Btu. Determine the coefficient of performance for the cycle.High Temperature ReservoirQhC.M.QlWQh Ql WLow Temperature ReservoirENG 1059
Using Conservation of EnergyA heat pump cycle whose coefficient of performance is 2.5 delivers energy by heattransfer to a dwelling at a rate of 20 kW.(a) Determine the net power required to operate the heat pump,in kW.(b) Evaluating electricity at 0.08 per determine thecost of electricity in a month when the heat pump operatesfor 200 hours.ENG 10510
Using Conservation of EnergyFor a power cycle, the heat transfers are Qin 25,000 kJ and Qout 15,000kJ. Determine the net work, in kJ, and the thermal efficiency.High Temperature ReservoirQhC.M.QlWQh-Ql WLow Temperature ReservoirENG 10511
Perpetual MotionW Q meout d in meme cv 0dt
Perpetual Motion is a Technical FoulB.S.
Principle of State and Phase-Terms Intensive and extensive properties (State Postulate)Pure substanceEquilibriumSpecific propertiesCompressed (Sub Cooled) LiquidQualityTwo-phase regionCan You find Properties?Vapor domeSuperheated regionCritical propertiesIdeal gasGas constantCompressibility factorReduced temperature and pressureCompressed liquid assumption
Thermodynamic Properties Volume– Specific Volume– Density Pressure– Gauge– Absolute– Units Temperature– Units and Scales Energy– Internal Energy– Enthalpy (internal energy boundary/flow work)– Kinetic and Potential Quality Entropy
The state postulateThe minimum number of independent intensive properties to find the statefor a simple compressible system is two. Two-phase region Superheatedvapor Triple line Saturation state Compressedliquid Vapor dome Critical pointFundamentals of Thermal Fluid Sciences 3rd EditionYunus A. CengelRobert H. TurnerJohn M. Cimbala2008
Look up Properties for Each CasePressure is 100kPa Review Quality Equations subscripts f,fg,g (a) is saturated liquid (a) is liquid at 20 C (b) is two phasequality (x) of .7 (c) is saturated vapor (c) is superheatedvapor at 120 CSpecific volume, specific internal energy, specificenthalpy, and specific entropy as propertiesIntroduction to ThermalSystems Engineering:Thermodynamics, Fluid Mechanics,and Heat TransferMichael J. MoranHoward N. ShapiroBruce R. MunsonDavid P. DeWittJohn Wiley & Sons, Inc.2003
Saturated WaterPressure TableIntroduction to ThermalSystems Engineering:Thermodynamics, Fluid Mechanics,and Heat TransferMichael J. MoranHoward N. ShapiroBruce R. MunsonDavid P. DeWittJohn Wiley & Sons, Inc.2003
Saturated WaterTemperatureTableIntroduction to ThermalSystems Engineering:Thermodynamics, Fluid Mechanics,and Heat TransferMichael J. MoranHoward N. ShapiroBruce R. MunsonDavid P. DeWittJohn Wiley & Sons, Inc.2003
Introduction to ThermalSystems Engineering:Thermodynamics, Fluid Mechanics,and Heat TransferMichael J. MoranHoward N. ShapiroBruce R. MunsonDavid P. DeWittJohn Wiley & Sons, Inc.2003
THE IDEAL-GAS EQUATION OF STATE Equation of state: Any equation that relates the pressure, temperature,and specific volume of a substance.The simplest and best-known equation of state for substances in the gasphase is the ideal-gas equation of state. This equation predicts the P-v-Tbehavior of a gas quite accurately within some properly selected region.Ideal gas equationof stateR: gas constantM: molar mass (kg/kmol)Ru: universal gas constantDifferent substances have differentgas constants.
Ideal GaspV mRTpV nRuTIdeal gas model only valid awayfrom two phase region andcritical pointFundamentals of Thermal Fluid Sciences 3rd EditionYunus A. CengelRobert H. TurnerJohn M. Cimbala2008
An automobile tire is inflated with air. The pressure rise of air in the tire when the tire is heated to 50 C andthe amount of air that must be bled off to reduce the pressure to the original value are to be determined.Assumptions 1 At specified conditions, air behaves as an ideal gas. 2 The volume of the tire remainsconstant.Properties The gas constant of air is R 0.287 kPa.m3/kg.KAnalysis Initially, the absolute pressure in the tire isP1 Pg Patm 210 100 310kPaTreating air as an ideal gas and assuming the volume of the tireto remain constant, the final pressure in the tire can bedetermined fromP1V1 P2V2T323 K P2 2 P1 (310 kPa) 336 kPaT1T2T1298 KInitial ConditionTire25 C210kPaThus the pressure rise is P P2 P1 336 310 26 kPaThe amount of air that needs to be bled off to restore pressure to its original value isP1V(310 kPa)(0.025 m3 )m1 0.0906 kgRT1 (0.287 kPa m3/kg K)(298 K)P1V(310 kPa)(0.025 m3 )m2 0.0836 kgRT2 (0.287 kPa m3/kg K)(323 K) m m1 m2 0.0906 0.0836 0.0070 kg
Compressibility cedspecific volumeComparison of Z factors for various gases.Gases deviate from theideal-gas behavior themost in the neighborhoodof the critical point.
Charles’ and Boyle’s LawUses ideal gas law and conservation of mass in steady flow to determine volume atanother pressure and temperature.V2 P2 T1V1 T2 P1DeriveExhaust emissions at collected temperature and pressure to standard temperatureand pressureAmbient Standard 1 bar 25 CStandard 1 atm 0 C
Specific Heat Constant volume (Internal Energy)Constant pressure (Enthalpy)Ratio of specific heatsSpecific heat– Solids– LiquidsIntroduction to ThermalSystems Engineering:Thermodynamics, Fluid Mechanics,and Heat TransferMichael J. MoranHoward N. ShapiroBruce R. MunsonDavid P. DeWittJohn Wiley & Sons, Inc.2003
The compressed liquid propertiesdepend on temperature much morestrongly than they do on pressure.y v, u, or hA more accurate relation for hA compressed liquidmay be approximatedas a saturated liquid atthe given temperature.At a given Pand T, a puresubstance willexist as acompressedliquid ifCompressedLiquidAssumption
Principle of Entropy Total Entropy is ALWAYS increasing 2nd Law of Thermodynamics ed expansionHeat TransferMixingResistance etc Carnot Efficiency and Coefficient of Performance Isentropic Efficiency
What creates Entropy Major Irreversibilities– Friction– Unrestrained Expansion– Heat Transfer Minor– Mixing, spontaneous reaction– ResistanceTotal entropy alwaysincreases
Carnot Heat EngineSh S gen SlThQhSh Th0ShCyclicalProcessSgenQlSl TlQhSlQlTlQl Qh Tl ThWQlTl 1 1 QhTh maxTl 1 Th
Any thermal efficiency above Carnot thermalefficiency is a violation of the Second Law Perpetual Motion Machine of the 2nd KindPMM-2 This concept applies to heat engines,refrigerators, heat pumps and any othersystem The best you can do is to have no changein entropy on the WHOLE system.(individual processes may see reductionsin entropy)
Perpetual Motion is a Technical FoulB.S.
ExamplesAn “inventor” claims to have built a device which receives 1000 kJ at500K and converts it to 410 kJ exhausting heat to the environment at300K. Is this Possible? Max Efficiency 1-Tl/Th 1(300K/500K) 40%
Isentropic Efficiency Processes are not Isentropic Isentropic cases are a best case scenario Efficiency can be related to the Isentropiccase– Turbines– Pumps and Compressors– Nozzles
Isentropic EfficiencyActual Turbine WorkWa h1 h2 a T Isentropic Turbine Work Ws h1 h2 sIsentropic Compressor Work Wsh2 s h1 C Actual Compressor WorkWah2 a h1Actual KEVa 2 N 2Isentropic KE Vs
2nd Law of ThermodynamicsKelvin-Planck: It is impossible to construct a device whichwill operate in a cycle and produce no effect other than(work) and the exchange of heat with a single reservoir.Clausius: It is impossible to construct a device whichoperates in a cycle and produces no effect other than thetransfer of heat from a cooler body to a hotter bodyThThQhW QhCyclicalProcessCyclicalProcessQlTl
Thermodynamic Cycles Carnot Heat Engine Rankine– Reheat Air Standards Cycles– Otto– Diesel– Brayton Regeneration Carnot Refrigerator and Heat Pump Ideal and Real Refrigeration Cycles
The Rankine Cycle The majority (75% ) of power plants arebased on the Rankine Cycle
Heat In2.3.BoilerTurbineBackWorkPump1.CondenserHeat OutNet Work4.
Simple Ideal Rankine Isentropic Compression of Liquid (Pump)Isobaric Heat Addition (Boiler)Isentropic Expansion (Turbine or Piston)Isobaric Heat Rejection (Condenser)Open and Closed CyclesWorking Fluid is typically water
Simple AnalysisHeat In2.3.BoilerBackWorkTurbine State 1 must beliquid State 2 must beliquid State 3 must besuperheated vapor State 4 must haveQuality better than0.85Pump1.Net Work4.CondenserHeat Out
Pump Pumps Liquid not Vapor (Cavitation)From 1st LawFor isentropic caseFor incompressible substances like liquids
Boiler Change in Enthalpyof SteamFrom 1st Law
Steam TurbineFrom 1st LawQuality of Turbine exit needs to stayabove 0.85
A typical single cylinder, simple expansion, double-acting high pressuresteam engine. Power takeoff from the engine is by way of a belt.1 - Piston2 - Piston rod3 - Crosshead bearing4 - Connecting rod5 - Crank6 - Eccentric valve motion7 - Flywheel8 - Sliding valve9 - Centrifugal governor.Steam PistonShaft Power torque x ω
Condenser Atmosphere Rivers or OceansFrom 1st Law (h4 h1 )Qout m
A Run Around the Simple IdealRankine CycleStart at Pump Inlet
BoilerTurbine is Isentropic
Summary1) Find enthalpy at all States2) Turn the mathematical crank
Simple Real Rankine
Real Systems
How to Increase Rankine CycleEfficiency Increase Boiler Temperature and Pressure(materials constraints) Decrease Condenser Pressure– increases moisture in turbine outlet– Large turbines required as density of steamdrops Reheat Preheat using Open and ClosedFeedwater heaters
Air Standard Cycles Otto Diesel BraytonPlanes, Trains, and Automobiles
Air Standard Assumptions Working fluid is air and acts as an idealgas All Processes are internally reversible Combustion process is replaced by heataddition Exhaust process is replaced by heatrejection Cold ASA are that properties of air areconstant at 25CRES 60255
ReciprocatingInternalCombustionEngines56
Otto Engine Spark Ignition (SI) High Power Density (aircraft, cars, etc) Most common power plant in USautomotive industry0.25 mile race at speeds over 300 mph(15 gallons of methanol used)57
Diagrams for Ideal Otto CycleIsentropic compressionIsometric heat additionIsentropic expansionIsometric heat rejection3S constP4213TQh21VV const4QlSRES 60258
REAL (a) IDEAL(b)59
Mean EffectivePressure MEPFictitious pressure for cycle interms of average pressure for agiven displacementMuch lower than real pressuresseen through cycleDO NOT use MEP to calculaterequired strength of materials60
Otto Cycle Efficiency th ,Ottomc p T4 T1 Qh QlQl 1 1 QhQhmc p T3 T2 T2 V1 T1 V2 k 1T3 V4 T4 V3 T1 1 T2 T4 1 T1 T3 1 T2 k 1V4 V1V3 V2 V1 V2 k 1 V4 V3 k 1T2 T3T3 T4 T1 T4T2 T1RES 60261
Derivation continued th ,Ottomc p T4 T1 Qh QlQl 1 1 QhQhmc p T3 T2 T1 1 T2 T4 1 T1 T3 1 T2 T1 T2 th , O tto 1 But rememberT2 V1 T1 V2 r V1,4k 1 th ,Otto 1 V3, 2RES 6021rk 162
Modeled Otto Cycle efficiency th ,Otto 1 1rk 1 Increase temperature by increasingcompression ratio but autoignition occurs Use knock inhibitors to raise Octane number(lead was used in US until 1973-1996)63
64
A Run Around the Otto Cycle1 – 2 is Isentropic Compression65
2 – 3 Isometric or Isochoric Heat Addition66
3 - 4 Expansion is Isentropic4 – 1 Heat Rejection is Isometric67
68
Diesel Engines CI High Efficiency (trucks,buses, constructionequipment, ships, etc)(cars esp europe) Low power density(runs fuel lean)69
P-v Diagram for DieselIsentropic compressionIsobaric heat additionIsentropic expansionIsometric heat rejection70
Diesel Efficiencyrc or Alpha α is the cutoff ratiocorresponding to the volumechange during heat addition71
72
Diesel efficiency th,Dieselk 1 1 1 k 1 r k 1 Where α is the cutoff ratio v3/v2 corresponding to the burnduration73
74
A Run Around the Diesel CycleAt the beginning of the compression process of an air-standard Diesel cycleoperating with a compression ratio of 18, the temperatureis 300 K and the pressure is 0.1 MPa. The cutoff ratio for the cycle is 2.Determine (a) the temperature and pressure at the end of each process of thecycle, (b) the thermal efficiency, (c) the mean effective pressure, in MPa.Values from Tables (variable specific heat)isentropic compression process 1–2p2 5.39 MPaT2 898.3 K and h2 930.98 kJ/kg.isobaric heat addition process 2–3T3 rcT2 2*(898.3) 1796.6 Kh3 1999.1 kJ/kg75
isentropic expansion process 3–4T4 887.7 K.p4 0.3 MPau4 664.3 kJ/kg76
Large Diesel Engines for ShipsWartsila-Sulzer RTA96-C turbocharged twostroke diesel engineTotal engine weight: 2300 tons (Thecrankshaft alone weighs 300 tons.)Length: 89 feetHeight: 44 feetMaximum power: 108,920 hp at 102 rpmMaximum torque: 5,608,312 lb/ft at 102rpm50% efficiency77
78
Reality vs. Models Irreversible processes– Friction– Unrestrained Expansion– Heat Transfer Exhaust stroke Intake stroke Heat addition takes time in otto cycle andchanges pressure in diesel cycle Throttling losses (esp at low power/idle) Heat losses to cylinder wall k 1.4This accounts for the large differences (1/2) inmodeled versus real efficiencies in the ICE79
80
Improving Efficiency Decrease entropy generation– Friction– Unrestrained expansion of gases– Heat transfer Increase temperature Shorten burn time for diesel th ,Otto 1 1rk 1 th,Dieselk 1 1 1 k 1 r k 1 81
Brayton Cycle
George Brayton (1830-1892) Envisioned a continuousheat addition at constantpressure for a reciprocatingengine. Eventually this ideamorphed into a compressor,followed by burner followedby an expansion device. Gas turbine!
Torpedo Development (wet heater)
Gas Turbines Developed in WW2 independently byBritish and German researchers (conceptsknown in 1920s) Efficiency is lower than Otto and DieselHigh backwork required Significantly higher power density ME 262 could outclimb the P-51 Mustangand fly 100 mph faster. Less efficient butroughly double the power! Open Brayton Cyclehttp://www.rolls-royce.com/interactive games/journey02/flash.html
In 1942 Adolf Galland—director general of fightersfor the Luftwaffe, veteran of the Battle of Britain,and one of Germany's top aces—flew a prototypeMesserschmitt ME 262. "For the first time, I wasflying by jet propulsion and there was no torque, nothrashing sound of the propeller, and my jet shotthrough the air," he commented. "It was as thoughangels were pushing."Hitler delays production ofME 262 in favor of“Offensive” Aircraft andWeapons
Types of turbine engines TurbojetTurbofanTurbopropTurboshaft
Simple Brayton CycleGas Phaseworking fluidFuel2.3.Open or ClosedTurbineCompressorCombustorBack WorkHeat Exchanger1.4.HeatWork
Open Brayton Cycle Uses Atmosphere as the Heat Exchanger
Air Standard Assumptions Working fluid is air and acts as an idealgas All Processes are internally reversible Combustion process is replaced by heataddition Exhaust process is replaced by heatrejection Cold ASA are that properties of air areconstant at 25C
Ideal Brayton Cycle Isentropic CompressionIsobaric Heat AdditionIsentropic ExpansionIsobaric Heat Rejection
Gas TurbinesCan use direct thrust from momentum (mass flow rate x Velocity Force) orcan drive a shaft (helicopters, boats, turbo propeller aircraft). th ,brayton 1 1 rpk 1k
A Run around the Brayton CycleHeat In2.3.1.Back WorkNet WorkTurbineCompressorCombustor4.
Example of Calculations (continued)Isentropic Compressor WorkIsentropic Turbine Work
Example of Calculations (continued)Heat InWork Out
Example of Calculations (continued)Turbine exittemperature (659K)is significantly hotterthan compressor exit(492K) !
Entropy Major Irreversibilities– Friction– Unrestrained Expansion– Heat TransferTotal entropy alwaysincreases
Isentropic Efficiency Referenced toIsentropic Cases Always less thanUnity. turbine Wout actualWoutisentropic compressor WinisentropicWin actualWa WsWs Wa
Hot Exhaust (even without afterburners)
Hot Exhaust brings the advent of TricycleLanding GearNote how field catches on fireEarly Model Taildragger ME 262Later Model ME 262 w/ tricycle gear
Recuperation If temperature at exit of turbine is higherthan the temperature at exit of compressorone can use a recuperator to preheat airbefore the combustion process. Adds weight but increases efficiency. Closed heat exchanger required (the twostreams are at different pressures).
For 8:1 pressure ratio, Compressor entrance at 300K 1 bar, turbine entranceat 1200K (ideal and non ideal cases with and without regeneration)
Gas Turbine EnginesBrayton Cycle High back work Need thermal recuperation for highefficiency High Power Density Smooth Slow Dynamic Response (turbo lag) Relatively Low Torque Scalability?
Vapor compressionRefrigeration Cycle Can you imagine lifewithout refrigeration?
Refrigeration CycleThQhQl W QhCyclicalProcessQlTlOutput Ql COPrInput WWQl1COPr Qh Ql Qh 1Ql
Carnot Refrigeration CycleSl S gen ShThQhSh Th0ShCyclicalProcessSgenQlSl TlQhQl Qh Tl ThWCOPr SlQlTl1Qh 1Ql COPmax 1Th 1Tl1Th 1Tl
Heat Pump CycleThQhQl W QhCyclicalProcessQlTlOutput Qh COPHPInputWWQh1COPHP Qh Ql 1 QlQh
Carnot Heat Pump CycleSl S gen ShThQhSh Th0ShCyclicalProcessSgenQlSl TlQhSlQlTlQl Qh Tl ThW11COPHP QlTl1 1 QhThCOPmax1 Tl1 Th
The System
Thermodynamics – T-S 1-2 Isentropic Compression– Compressor 2-3 Isobaric heat transfer– Condenser 3-4 Throttling process– Expansion valve 4-1 Isobaric heat transfer– Evaporator
Thermodynamics – P-h Pressure - Enthalpy 1 – Saturated vapor2 – Superheated vapor3 – Saturated liquid4 –
Engineering Fundamentals-Thermodynamics By Professor Paul A. Erickson . Basic Thermodynamics . Systems Engineering: Thermodynamics, Fluid Mechanics, and Heat Transfer Michael J. Moran Howard N. Shapiro Bruce R. Munson David P. DeWitt John Wiley & Sons, Inc.
1.4 Second Law of Thermodynamics 1.5 Ideal Gas Readings: M.J. Moran and H.N. Shapiro, Fundamentals of Engineering Thermodynamics,3rd ed., John Wiley & Sons, Inc., or Other thermodynamics texts 1.1 Introduction 1.1.1 Thermodynamics Thermodynamics is the science devoted to the study of energy, its transformations, and its
1. Fundamentals of Engineering Thermodynamics, 8th ed., by Moran, Shapiro, et al., John Wiley and Sons, 2014 (ISBN 9781118412930) 2. Thermodynamics for Engineers (Schaum's Outlines) 3rd Edition by Merle Potter 3. DOE Fundamentals Handbook Thermodynamics, Heat Transfer and Fluid Flow,Volume 1 of 3, DOE-HDBK-1012/3 -92 Optional References TBD
Reversible and Irreversible processes First law of Thermodynamics Second law of Thermodynamics Entropy Thermodynamic Potential Third Law of Thermodynamics Phase diagram 84/120 Equivalent second law of thermodynamics W Q 1 1 for any heat engine. Heat cannot completely be converted to mechanical work. Second Law can be formulated as: (A .
Thermodynamics an Engineering Approach by Yunus Cengel and Boles . Engineering Thermodynamics by Achuthan second edition. Thermal Science and Engineering Dr D.S.Kumar Thermodynamics is a science that deals with all aspects of energy conversion, energy exchange and energy
thermodynamics has undergone a revolution, both in terms of the presentation of fundamentals and in the manner that it is applied. In particula r, the second l aw of thermodynamics has eme rged as an e ffective tool for engineering analysis and design. Michael J. Moran Department of Mechanical Engineering
thermodynamics through the precise definition of basic concepts to form a sound foundation for the development of the principles of thermodynamics. Review the metric SI and the English unit systems. Explain the basic concepts of thermodynamics such as system, state, state postulate, equilibrium, process, and cycle.
Basic Thermodynamics . Prof. S. K. Som . Department of Mechanical Engineering . Indian Institute of Technology, Kharagpur . Lecture - 01 . Introduction and Fundamental Concepts . Good morning to all of you in this session of thermodynamics. I welcome you all to this session. Now first I will describe you, what the subject thermodynamics is?
1 Advanced Engineering Mathematics C. Ray Wylie, Louis C. Barrett McGraw-Hill Book Co 6th Edition, 1995 2 Introductory Methods of Numerical Analysis S. S. Sastry Prentice Hall of India 4th Edition 2010 3 Higher Engineering Mathematics B.V. Ramana McGraw-Hill 11 th Edition,2010 4 A Text Book of Engineering Mathematics N. P. Bali and Manish Goyal Laxmi Publications 2014 5 Advanced Engineering .
