AME230 Thermodynamics. McGrath

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1 AME230 Thermodynamics McGrath

2 Review Website and Syllabus

3 Fundamentals of Engineering Thermodynamics

4 Using thermodynamics Analyze and design systems and processes for human needs Examples: Increase in output product Reduced input of scarce resource Reduction in total cost Lower environmental impact Types of questions: Can more work be done by an engine? Is there a maximum amount? If so, how close to that maximum are we? How much can a room/house be cooled for certain conditions? How to decide if some inventions are actually impossible?

5 Relationship to Other AME & Engineering Courses Fluid Mechanics (AME331) Heat Transfer (AME432) Propulsion, Design, Projects, Defining Systems Mass balance (Mass conservation) Open and closed systems Energy balance (Energy conservation)

6 ENGINEERING CONTEXT The word thermodynamics stems from the Greek words therme (heat) and dynamis (force). Although various aspects of what is now known as thermodynamics have been of interest since antiquity, the formal study of thermodynamics began in the early nineteenth century through consideration of the motive power of heat: the capacity of hot bodies to produce work. Today the scope is larger, dealing generally with energy and with relationships among the properties of matter. Thermodynamics is both a branch of physics and an engineering science. The scientist is normally interested in gaining a fundamental understanding of the physical and chemical behavior of fixed quantities of matter at rest and uses the principles of thermodynamics to relate the properties of matter. Engineers are generally interested in studying systems and how they interact with their surroundings. To facilitate this, engineers extend the subject of thermodynamics to the study of systems through which matter flows. The objective of this chapter is to introduce you to some of the fundamental concepts and definitions that are used in our study of engineering thermodynamics. In most instances the introduction is brief, and further elaboration is provided in subsequent chapters.

7 Boulton and Watt Steam Engine. Watt s use of the double-acting piston, an external condenser, and planetary gearing to change reciprocal into rotary motion made the steam engine into a practical power producer. (British Science Museum, London)

8 Example Applications

9 Automobile

10 Engine Compartment for Hybrid Spark-Ignition/ Battery Powered Automobile

12 Space Exploration

13 Launch of US Air Force early warning satellite- conversion of internal (chemical) energy into kinetic energy. (Courtesy USAF)

14 Solar Energy Powered. How much energy required? Conversions? Mars Rover Chris Lewicki, AE, BS 97, MS 00 NASA JPL: Senior Flight Systems Engineer and Flight Director- Mars Exploration Rovers

15 Energy Conversion: Power Production

16 Steam rising from the cooling tower of a nuclear power plant. Nuclear to Electrical

17 Geothermal to Electrical

18 Wind Turbines Direct conversion of wind s kinetic energy into work Work can drive an electrical generator Pecos County, Texas 25.5 MW Clear Sky Wind Power Facility (photo 2004, General Electric Co. All rights reserved.)

19 Solar Photovoltaic Cells: Direct conversion of solar radiation (e.g., sunlight) into electricity

20 A field of mirrors concentrates solar energy onto the Solar Two Power Tower. This concentrated solar energy is used to drive a vapor power cycle. (Image Courtesy US DOE)

21 External Combustion (EC): Nuclear & solar energy possible

22 Fuel Cells Direct conversion of chemical energy into electricity

23 Energy Transfer: Heating

24 Heat Exchangers Allows heat transfer from one fluid to another without mixing Example: Car Radiator

25 Energy Transfer: Cooling

26 Refrigeration and Heat Pumps While heating is an ancient technology, the widespread application of cooling technologies occurred only after a firm understanding of Thermodynamic cycles was established.

27 Air Conditioners and Heat Pumps V-C Cycle for Refrigeration

28 Air Conditioners and Heat Pumps V-C Cycle for Air Conditioning

29 PowerPoint frozen? Click here and try again Mixing Devices

30 Air Conditioners and Heat Pumps V-C Cycle for Heat Pump

31 Biomedical Engineering

32 Biomedical Engineering

37 Sub-Ablative Thermotherapy of Shoulder: Heat-Assisted Capsular Shift (HACS) (Arthroscopic Shoulder Capsulorraphy) Humeral Head Humerus Glenoid probe shoulder capsule heated region Biceps Tendon Shoulder Anatomy Capsulorraphy Humerus Capsule Glenoid

38 Defense/Military

39 Gas Power Cycles Turbojet-powered Raptor fighter aircraft

41 Transportation

43 Inlet compressor blades for a high-performance aircraft engine. (Courtesy General Electric Power Turbines)

46 Vapor Power Cycles Work fluid changes phases: Liquid Vapor Vapor Liquid External Combustion Engines Historically used in Trains (steam locomotives) Boats/ships (steam boats) Power plants (steam power plants) Today biggest application in power generation Most of electricity in U.S. generated in coal and nuclear power plants that use vapor power cycle

47 Union Pacific Diesel-Electric Locomotive Pair Pulling a Fast Freight

54 PowerPoint frozen? Click here and try again 3.8 Gases

Tank Filling Simplest USUF analysis: No outlet flow Assume adiabatic Mass Balance: Energy Balance: m =m m IN 2 1 t QIN + W IN + m + + 2

56 Tank Filling Simplest USUF analysis: No outlet flow Assume adiabatic Mass Balance: Energy Balance: m =m m IN 2 1 t QIN + W IN + m INhIN - QOUT WOUT m t= t OUT (t)(h OUT (t)dt 1 2 v = m u + + 2g c gz g c CV,2 2 v gz m u + + 2gc g c CV, 1 ( ) ( ) m h = mu mu IN IN CV,2 CV, 1

58 Superheated Vapor

59 Superheated Vapor T = C & P = 3000 kpa T SAT (3000 kpa) = C Since T > T SAT (P) Superheated Vapor

61 Second Law Analysis of Systems Reversible process produces maximum work PowerPoint frozen? Click here and try again

63 PowerPoint frozen? Click here and try again 3.8 Gases

65 Isentropic Processes in Diesel Cycle PowerPoint frozen? Click here and try again

66 Diesel Train Engine

67 Otto Cycle Analysis Idealization of IC Gasoline Engine cycle 4-Stroke: Large engines, e.g., car engines 2-Stroke: Small engines, e.g., lawnmowers

68 Aircraft Gas Turbine Engines: Turbojet PowerPoint frozen? Click here and try again

69 Aircraft Gas Turbine Engines: Turbofan Shaft work powers high speed fan blades inside engine cowling providing thrust Pratt and Whitney PW 4000 Turbofan Engine

71 Introduction Thermodynamics is the study of energy It covers a wide range of applications we choose the system of interest The surroundings are external to our system of interest

72 The system, the system boundary, the surroundings, and the universe.

73 Closed System (Control Mass) No mass can cross system boundary Energy may cross system boundary Volume is NOT fixed in this example Volume CAN be fixed in a closed system Importance of Defining a System with a Boundary

fixed Energy crosses system boundary Control Volumes

74 Open System/Control Volume Mass crosses system boundary (control surface) Volume may/may not be fixed Energy crosses system boundary Control Volumes may operate at steady state, or change with time (empty/fill)

75 Combustion in Open & Closed Systems PowerPoint frozen? Click here and try again

76 Isolated System X Mass Energy X X X Mass NO mass or energy crosses system boundaries NO interaction between system and surroundings Energy Boundary

77 Macroscopic and Microscopic Views of Thermodynamics Macroscopic (Classical) This what we do in this course Gross or overall behavior No model of matter at molecular, atomic or sub-atomic level used Microscopic (Statistical): Concerned directly with structure of matter Objective is characterize by statistical means average behavior of particles Making up a system and relate this to macroscopic behavior of system Essential for lasers, plasmas, high-speed gas flows, chemical kinetics, cryogenics Classical macroscopic thermodynamics simpler mathematically and captures essence of many systems and applications

78 Properties Properties are Macroscopic characteristics Examples: mass, volume, temperature, pressure, energy (kinetic, potential, internal) Are special because they are NOT dependent on history of system. Process from state 1 to state 2 doesn t matter. Can test if a quantity is a property: A quantity is a PROPERTY if its change in value between two states is independent of process. If it depends on process, it can t be a property. Have numerical values and units (eg. 3 kg, 5 m 3, 100 K, 100 kpa, 10 J)

79 Thermodynamic State: State Collection of all Thermodynamic properties of system Ability to define system s state essential in Thermodynamics Using state principle (Ch 3), can use limited set of property data to determine state and all property data.

80 Process: Changing the State of a System Process: Change in state of system 4 Common Processes: Isothermal: Constant Temperature Isobaric: Constant Pressure Isometric: Constant Volume Adiabatic: No Heat Transfer P = constant (isobaric) T = constant (isothermal) P v =constant (isometric) T v =constant (isometric) v v

81 Thermodynamic Cycle Cycle: Sequence of processes that begins and ends at same state Consequently, no NET change of state of system Many important examples: Next slide illustrates one (Diesel)

82 Isobaric & Isometric Processes PowerPoint frozen? Click here and try again Cycle: Sequence of processes Returns system to initial state

83 Properties 3 Types of thermodynamics properties: Extensive, Intensive, & Specific Extensive: Depend on mass/size of system (Volume [V]) Intensive: Independent of system mass/size (Pressure [P], Temperature [T]) Specific: Extensive/mass (Specific Volume [v])

84 Properties: Total & Specific Volumes Total Volume: V [m 3 ] Upper case V Specific Volume: v = V/m [m 3 /kg] Lower case v

85 Phase & Pure Substance Phase: Quantity of matter that is homogeneous in composition and Physical structure. Examples: Solid, Liquid and Vapor (Gas) Pure substance: Uniform & invariable in chemical composition Examples: Liquid water with water vapor Mixture of gases (air = N, O, +) considered pure substance if no chemical reaction or separation

86 Equilibrium & Non-Equilibrium Classical thermodynamics emphasizes equilibrium states and changes from one equilibrium state to another equilibrium state Mechanics: equilibrium is balance of forces Thermodynamics: more general concept with many types of equilibrium, all of which must be reached for complete Equilibrium Types: mechanical, thermal, phase and chemical equilibrium Test: isolate a system and see if observable changes occur If no changes, then implies system at equilibrium state

87 Thermal Example: Equilibrium & Non-Equilibrium Internal uniformity of properties when in equilibrium- no gradients

Quasi-Equilibrium Process Infinitesimal departure from equilibrium- An idealization An idealization such as: frictionless pulley, point mass Interest in

88 Quasi-Equilibrium Process Infinitesimal departure from equilibrium- An idealization An idealization such as: frictionless pulley, point mass Interest in such processes: Simple model yields qualitative or semi-quantitative information about real systems Instrumental in developing relations between properties

89 Primary and Secondary Units The System Internationale d Unites SI Take Mass (M) Length (L) Time (t) as Primary M L T kg (kilograms) ; mass standard at NIST m (meters) ; length traveled by light in vacuum in a specified time interval s (seconds) ; duration of 9,192,631,770 cycles of radiation emission with a transition of cesium atom

90 Secondary Units: Force Take Force (F) as secondary ; a derived quantity Derive Force using Newton s 2 nd Law F = ma 1 N = (1 kg)(1 m/s 2 ) = 1 kg-m/s 2 Example: What is the weight of an object whose mass is 1000 kg, at a place on earth where gravitational acceleration is standard value g= m/s 2?

91 SI Units for M, L, T, F

92 SI Unit Prefixes Giga- hertz Mega- watt Kilo-meter Nano-technology

93 English Units for M, L, T, F In the Old English system, M,L,T,F are all primary units This is different than SI system where Newton is derived M (lb m )..2.2 kg/lb m L (ft) 3.28 ft/m t (s) 1 lb f.. force of attraction of standard gravitational acceleration (g = ft/s 2 ) on 1 lb m Units of force are given a name, lb f

94 English Units for M, L, T, F Newton s 2 nd Law must still provide relationship between primary units: F = ma ; g c is a proportionality constant g c 1 lb f..force of attraction of standard gravitational acceleration (g = ft/s 2 ) on 1 lb m of mass 1 lbf = (1 lb m )( ft/s 2 ) g c = lb m -ft g c lb f -s 2 g c is a CONSTANT

95 English Units for M, L, T, F g c = lb m -ft lb f -s 2

96 Two Measurable Properties: Specific Volume and Pressure Continuum Hypothesis: Matter can be considered to be distributed continuously throughout a region. Smallest volume where properties Defined. Example of exception: very low pressure gas- too few molecules m Density: ρ = lim V V V Where V is smallest volume where definite ratio exits Units: SI (e.g. kg/m 3 ) English (e.g. lb/ft 3 )

97 Specific Volume Density may vary throughout system: m = ρ dv V Specific volume, v, is reciprocal of density. It is an Intensive property. v = 1 = V ρ m Units: SI (e.g. m 3 /kg) English (e.g. ft 3 /lb)

98 P = Force/Area Pressure P F = lim normal A A A Types: Generally Absolute pressures are used in thermodynamics, ie measured wrt zero pressure Atmospheric pressure is usual local reference Instruments often measure difference in pressure between system absolute pressure and absolute pressure of local atmosphere Gagepressure (above atm) Vacuumpressure (below atm)

99 P = Force/Area F P = lim normal A A A Types: Absolute used in thermodynamics Atmospheric (Ref) Gage (above atm) Vacuum (below atm) Pressure P = P + abs gage P atm 1 Standard pressure (atm) = x 10 5 N/m 2 = lbf/in 2

100 P (gage) > Patm P atm P (absolute) P (vacuum) < Patm H Patm (absolute) P tank P (absolute) P tan k P = atm ρgh g c 1 Standard pressure (atm) = x 10 5 N/m 2 = lbf/in 2

101 P(gage) = P(absolute) P atm (absolute) > 0 P(vacuum) = P atm (absolute) P(absolute) > 0

102 Pressure Pressure units SI: pascal (Pa) 1 pascal = 1 N/m 2 1 kpa= 10 3 N/m 2 1 bar = 10 5 N/m 2 1 MPa = 10 6 N/m 2 English: pound/ft 2 (lbf)

103 Temperature Intensive property Based on our senses Senses not quantitative- need methods and instruments (temperature scale and thermometers, etc)

104 Temperature -Temperature is an intensive property of matter -When are two bodies in thermal equilibrium? -What will happen if two bodies not in equilibrium are in contact? Q Basis for property called Temperature

105 Temperature Perfect insulation between two bodies would prevent any energy transfer = ADIABATIC process Process at constant temperature called ISOTHERMAL If two bodies in thermal equilibrium with a 3 rd body, the two bodies are in equilibrium with each other. = Zeroth Law of Thermodynamics Thermometer is 3 rd body Q??

106 Other devices: Gas thermometer, Thermocouples, Thermistors, infrared detectors/cameras

Relations among temperature scales T(C) = T(K) 273.15 T(R) = 1.

107 Relations among temperature scales T(C) = T(K) T(R) = 1.8 T(K); T(F) = 1.8 T(C) T(F) = T(R) T(F) = 1.8 T(C) + 32

108 Problem Solving in Thermodynamics Problem Statement Solution Diagram of System and Process (Boundary!) Given information Assumptions Governing Relations Property Data Analysis & Quantitative Solution Discussion of Results: Does the answer make sense? What are implications? Average engineers have difficulty here Great engineers excel here

109 Carry & Converting Units Thermodynamic analyses require unit conversions Blindly applying right units to numeric answer typically leads to wrong answer (i.e., points off on tests and exams. Space exploration fiascos) Keeping track of units can help identify errors Example: Convert 500 m to miles

110

111 Example Problems

112 Dry weight = doesn t include fuel Thrust, T, is force produced by rocket

113 Problem Solving in Thermodynamics Problem Statement Solution Diagram of System and Process (Boundary!) Given information Assumptions Governing Relations Property Data Analysis & Quantitative Solution Discussion of Results: Does the answer make sense? What are implications? Average engineers have difficulty here Great engineers excel here

114 Diagram of System and Process (Boundary!) 1) Define system with a boundary- what is our system?? 2) Define given information (what do we know?) 3) Assumptions (do we need to know anything else?) May, or may not be obvious at this point

115 Diagram of System and Process (Boundary!) 4) Governing relations? We need to get thrust for lift-off. This is a force. We are given weights (forces), accelerations and fuel consumed (mass) information. Suggests:

116 Diagram of System and Process (Boundary!) 5) Property data? Not applicable/required here Approach: thrust is force to lift-off; need mass, local acceleration on planet. Total mass on planet is rocket mass and remaining fuel mass. Need fuel mass

117

118 Note that local acceleration is reduced on planet, but conversion factor, gc, does not change. Note that conversion factor produces units of force

119

120

121 System defined for force balance Bournoulli Eq Accept as given- no system defined Force Balance on column i.e. the system. Form of Eq 1.15

122 Combine: and where: To yield an equation for desired velocity in terms of knowns: Note carry all units and check that final units are correct

123 END

Engineering Thermodynamics. Chapter 1. Introductory Concepts and Definition

Engineering Thermodynamics. Chapter 1. Introductory Concepts and Definition 1.1 Introduction Chapter 1 Introductory Concepts and Definition Thermodynamics may be defined as follows : Thermodynamics is an axiomatic science which deals with the relations among heat, work and properties