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BASIC CONCEPTS                                   Lecture 2         Keith Vaugh BEng (AERO) MEngReference text: Chapter 2 -...
OBJECTIVES             }             KEITH VAUGH
OBJECTIVESIdentify the unique vocabulary associated withthermodynamics through the precise definition ofbasic concepts to f...
OBJECTIVESIdentify the unique vocabulary associated withthermodynamics through the precise definition ofbasic concepts to f...
OBJECTIVESIdentify the unique vocabulary associated withthermodynamics through the precise definition ofbasic concepts to f...
SYSTEMS AND CONTROL            VOLUMES                      }                      KEITH VAUGH
SYSTEMS AND CONTROL            VOLUMES     System: A quantity of matter or a region in     space chosen for study.        ...
SYSTEMS AND CONTROL            VOLUMES     System: A quantity of matter or a region in     space chosen for study.     Sur...
SYSTEMS AND CONTROL            VOLUMES     System: A quantity of matter or a region in     space chosen for study.     Sur...
SYSTEMS AND CONTROL            VOLUMES     System: A quantity of matter or a region in     space chosen for study.     Sur...
SYSTEMS AND CONTROL            VOLUMES     System: A quantity of matter or a region in     space chosen for study.     Sur...
KEITH VAUGH
KEITH VAUGH
Closed system (Control mass)A fixed amount of mass, and nomass can cross its boundaryIf energy is not allowed to crossthe b...
KEITH VAUGH
An open system (a control volume)with one inlet and one exit.                                    KEITH VAUGH
Open system (control volume)    A properly selected region in space.    It usually encloses a device that    involves mass...
KEITH VAUGH
A control volume with real andimaginary boundaries                                 KEITH VAUGH
A control volume with real and   A control volume with fixed andimaginary boundaries             moving boundaries         ...
PROPERTIES OF A SYSTEM                         }                         KEITH VAUGH
PROPERTIES OF A SYSTEM    Property                         }                         KEITH VAUGH
PROPERTIES OF A SYSTEM    Property    Any characteristic of a system. Some familiar properties    are pressure P, temperat...
PROPERTIES OF A SYSTEM    Property    Any characteristic of a system. Some familiar properties    are pressure P, temperat...
PROPERTIES OF A SYSTEM    Property    Any characteristic of a system. Some familiar properties    are pressure P, temperat...
PROPERTIES OF A SYSTEM    Property    Any characteristic of a system. Some familiar properties    are pressure P, temperat...
PROPERTIES OF A SYSTEM    Property    Any characteristic of a system. Some familiar properties    are pressure P, temperat...
PROPERTIES OF A SYSTEM    Property    Any characteristic of a system. Some familiar properties    are pressure P, temperat...
PROPERTIES OF A SYSTEM    Property    Any characteristic of a system. Some familiar properties    are pressure P, temperat...
PROPERTIES OF A SYSTEM    Property    Any characteristic of a system. Some familiar properties    are pressure P, temperat...
KEITH VAUGH
m   Intensive or Extensive?    To identify whether a property isV   either, divided the system into twoT   equal parts. Ea...
m            Intensive or Extensive?                  To identify whether a property is     V            either, divided t...
CONTINUUM            }            KEITH VAUGH
CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the ato...
CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the ato...
CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the ato...
CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the ato...
CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the ato...
Despite the large gaps between molecules,a substance can be treated as a continuumbecause of the very large number ofmolec...
DENSITY AND SPECIFIC            GRAVITY                       }                       KEITH VAUGH
DENSITY AND SPECIFIC            GRAVITY  Density  ρ=     m     V      ( m)            kg                 3                ...
DENSITY AND SPECIFIC            GRAVITY  Density  ρ=     m     V      ( m)            kg                 3                ...
DENSITY AND SPECIFIC            GRAVITY  Density  ρ=     m     V            ( m)                  kg                      ...
DENSITY AND SPECIFIC            GRAVITY  Density  ρ=     m     V            ( m)                  kg                      ...
STATE AND EQUILIBRIUM         Thermodynamics deals with equilibrium states                                                ...
STATE AND EQUILIBRIUMEquilibrium              Thermodynamics deals with equilibrium states                                ...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
STATE AND EQUILIBRIUMEquilibrium                                Thermodynamics deals with equilibrium statesA state of bal...
KEITH VAUGH
A system at two different states                                   KEITH VAUGH
A system at two different states   A closed system reaching thermal equilibrium                                           ...
KEITH VAUGH
The state of nitrogen is fixed by twoindependent, intensive properties                                  KEITH VAUGH
The State PostulateThe number of properties required tofix the state of a system is given by thestate postulate:  The state...
PROCESSES AND CYCLES                       }                       KEITH VAUGH
PROCESSES AND CYCLES       Process         }                       KEITH VAUGH
PROCESSES AND CYCLES       Process       Any change that a system undergoes from       one equilibrium state to another.  ...
PROCESSES AND CYCLES       Process       Any change that a system undergoes from       one equilibrium state to another.  ...
PROCESSES AND CYCLES       Process       Any change that a system undergoes from       one equilibrium state to another.  ...
PROCESSES AND CYCLES       Process       Any change that a system undergoes from       one equilibrium state to another.  ...
Quasistatic or quasi-equilibriumprocessWhen a process proceeds in sucha manner that the system remainsinfinitesimally close...
Process diagrams plotted by employingthermodynamic properties as coordinates are veryuseful in visualising the processes.S...
THE STEADY-FLOW PROCESS                      }                          KEITH VAUGH
THE STEADY-FLOW PROCESS      The term steady implies no change with time. The      opposite of steady is unsteady, or tran...
THE STEADY-FLOW PROCESS      The term steady implies no change with time. The      opposite of steady is unsteady, or tran...
THE STEADY-FLOW PROCESS      The term steady implies no change with time. The      opposite of steady is unsteady, or tran...
THE STEADY-FLOW PROCESS      The term steady implies no change with time. The      opposite of steady is unsteady, or tran...
THE STEADY-FLOW PROCESS      The term steady implies no change with time. The      opposite of steady is unsteady, or tran...
During a steady-flow process, fluid                         properties within the control                         volume may...
TEMPERATURE & THE ZEROTH    LAW OF THERMODYNAMICS                   If two bodies are in thermal equilibrium with a third ...
TEMPERATURE SCALES                 }                     KEITH VAUGH
TEMPERATURE SCALES  All temperature scales are based on some easily  reproducible states such as the freezing and  boiling...
TEMPERATURE SCALES  All temperature scales are based on some easily  reproducible states such as the freezing and  boiling...
TEMPERATURE SCALES  All temperature scales are based on some easily  reproducible states such as the freezing and  boiling...
Celsius scale: in SI unit systemFahrenheit scale: in English unitsystemThermodynamic temperature scale:A temperature scale...
KEITH VAUGH
P versus T plots of theexperimental data obtainedfrom a constant-volume gasthermometer using fourdifferent gases at differ...
T(K) = T(̊C) + 273.15T(R) = T(̊F) + 459.67T(R) = 1.8T(K)T(̊F) = 1.8T(̊C) + 32The reference temperature in the originalKelv...
PRESSURE       }           KEITH VAUGH
PRESSUREA normal force exerted by a fluid per unit area   }                                                 KEITH VAUGH
PRESSUREA normal force exerted by a fluid per unit area   }1Pa = 1 N           m21 bar = 10 5 Pa = 0.1MPa = 100kPa1 atm = 1...
Absolute pressureThe actual pressure at a given position. It is measured relative to absolute vacuum(i.e., absolute zero p...
Variation of Pressure with Depth   ΔP = P2 − P1 = ρ gΔz = γ s Δz               When the variation of density with         ...
In a room filled with a gas, the variationof pressure with height is negligible                                            ...
The pressure is the same at all points on a horizontalplane in a given fluid regardless of geometry, providedthat the point...
Pascal’s LawThe pressure applied to a confinedfluid increases the pressurethroughout by the same amount          F1 F2  F2 A...
The Barometer and Atmospheric PressureAtmospheric pressure is measured by a device called a barometer; thus,the atmospheri...
The ManometerIt is commonly used to measure small andmoderate pressure differences. A manometercontains one or more fluids ...
Measuring the pressure drop across aflow section or a flow device by adifferential manometerP1 + ρ1g ( a + h ) − ρ2 gh − ρ1g...
Systems and control volumesProperties of a systemDensity and specific gravityState and equilibrium    The state postulateP...
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SSL2 Basic Concepts

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Basic concepts for thermofluids

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  • Other pressure measurement devices\nBourdon tube: Consists of a hollow metal tube bent like a hook whose end is closed and connected to a dial indicator needle.\nPressure transducers: Use various techniques to convert the pressure effect to an electrical effect such as a change in voltage, resistance, or capacitance. \nPressure transducers are smaller and faster, and they can be more sensitive, reliable, and precise than their mechanical counterparts.\nStrain-gage pressure transducers: Work by having a diaphragm deflect between two chambers open to the pressure inputs.\nPiezoelectric transducers: Also called solid-state pressure transducers, work on the principle that an electric potential is generated in a crystalline substance when it is subjected to mechanical pressure.\n
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  • Transcript of "SSL2 Basic Concepts"

    1. 1. BASIC CONCEPTS Lecture 2 Keith Vaugh BEng (AERO) MEngReference text: Chapter 2 - Fundamentals of Thermal-Fluid Sciences, 3rd Edition Yunus A. Cengel, Robert H. Turner, John M. Cimbala McGraw-Hill, 2008 KEITH VAUGH
    2. 2. OBJECTIVES } KEITH VAUGH
    3. 3. OBJECTIVESIdentify the unique vocabulary associated withthermodynamics through the precise definition ofbasic concepts to form a sound foundation for thedevelopment of the principles of thermodynamics. } KEITH VAUGH
    4. 4. OBJECTIVESIdentify the unique vocabulary associated withthermodynamics through the precise definition ofbasic concepts to form a sound foundation for thedevelopment of the principles of thermodynamics. }Explain the basic concepts of thermodynamicssuch as system, state, state postulate, equilibrium,process, and cycle. KEITH VAUGH
    5. 5. OBJECTIVESIdentify the unique vocabulary associated withthermodynamics through the precise definition ofbasic concepts to form a sound foundation for thedevelopment of the principles of thermodynamics. }Explain the basic concepts of thermodynamicssuch as system, state, state postulate, equilibrium,process, and cycle.Review concepts of temperature, temperaturescales, pressure, and absolute and gage pressure. KEITH VAUGH
    6. 6. SYSTEMS AND CONTROL VOLUMES } KEITH VAUGH
    7. 7. SYSTEMS AND CONTROL VOLUMES System: A quantity of matter or a region in space chosen for study. } KEITH VAUGH
    8. 8. SYSTEMS AND CONTROL VOLUMES System: A quantity of matter or a region in space chosen for study. Surroundings: The mass or region outside } the system KEITH VAUGH
    9. 9. SYSTEMS AND CONTROL VOLUMES System: A quantity of matter or a region in space chosen for study. Surroundings: The mass or region outside } the system Boundary: The real or imaginary surface that separates the system from its surroundings. KEITH VAUGH
    10. 10. SYSTEMS AND CONTROL VOLUMES System: A quantity of matter or a region in space chosen for study. Surroundings: The mass or region outside } the system Boundary: The real or imaginary surface that separates the system from its surroundings. The boundary of a system can be fixed or movable. KEITH VAUGH
    11. 11. SYSTEMS AND CONTROL VOLUMES System: A quantity of matter or a region in space chosen for study. Surroundings: The mass or region outside } the system Boundary: The real or imaginary surface that separates the system from its surroundings. The boundary of a system can be fixed or movable. Systems may be considered to be closed or open. KEITH VAUGH
    12. 12. KEITH VAUGH
    13. 13. KEITH VAUGH
    14. 14. Closed system (Control mass)A fixed amount of mass, and nomass can cross its boundaryIf energy is not allowed to crossthe boundary, then that system iscalled an isolated system KEITH VAUGH
    15. 15. KEITH VAUGH
    16. 16. An open system (a control volume)with one inlet and one exit. KEITH VAUGH
    17. 17. Open system (control volume) A properly selected region in space. It usually encloses a device that involves mass flow such as a compressor, turbine, or nozzle. Both mass and energy can cross the boundary of a control volume. Control surface The boundaries of a control volume. It can be real or imaginary.An open system (a control volume)with one inlet and one exit. KEITH VAUGH
    18. 18. KEITH VAUGH
    19. 19. A control volume with real andimaginary boundaries KEITH VAUGH
    20. 20. A control volume with real and A control volume with fixed andimaginary boundaries moving boundaries KEITH VAUGH
    21. 21. PROPERTIES OF A SYSTEM } KEITH VAUGH
    22. 22. PROPERTIES OF A SYSTEM Property } KEITH VAUGH
    23. 23. PROPERTIES OF A SYSTEM Property Any characteristic of a system. Some familiar properties are pressure P, temperature T, volume V, and mass m. } KEITH VAUGH
    24. 24. PROPERTIES OF A SYSTEM Property Any characteristic of a system. Some familiar properties are pressure P, temperature T, volume V, and mass m. } Properties are considered to be either intensive or extensive. KEITH VAUGH
    25. 25. PROPERTIES OF A SYSTEM Property Any characteristic of a system. Some familiar properties are pressure P, temperature T, volume V, and mass m. } Properties are considered to be either intensive or extensive. Intensive properties: KEITH VAUGH
    26. 26. PROPERTIES OF A SYSTEM Property Any characteristic of a system. Some familiar properties are pressure P, temperature T, volume V, and mass m. } Properties are considered to be either intensive or extensive. Intensive properties: Those that are independent of the mass of a system, such as temperature, pressure, and density. KEITH VAUGH
    27. 27. PROPERTIES OF A SYSTEM Property Any characteristic of a system. Some familiar properties are pressure P, temperature T, volume V, and mass m. } Properties are considered to be either intensive or extensive. Intensive properties: Those that are independent of the mass of a system, such as temperature, pressure, and density. Extensive properties KEITH VAUGH
    28. 28. PROPERTIES OF A SYSTEM Property Any characteristic of a system. Some familiar properties are pressure P, temperature T, volume V, and mass m. } Properties are considered to be either intensive or extensive. Intensive properties: Those that are independent of the mass of a system, such as temperature, pressure, and density. Extensive properties Those whose values depend on the size—or extent—of the system. KEITH VAUGH
    29. 29. PROPERTIES OF A SYSTEM Property Any characteristic of a system. Some familiar properties are pressure P, temperature T, volume V, and mass m. } Properties are considered to be either intensive or extensive. Intensive properties: Those that are independent of the mass of a system, such as temperature, pressure, and density. Extensive properties Those whose values depend on the size—or extent—of the system. Specific properties: KEITH VAUGH
    30. 30. PROPERTIES OF A SYSTEM Property Any characteristic of a system. Some familiar properties are pressure P, temperature T, volume V, and mass m. } Properties are considered to be either intensive or extensive. Intensive properties: Those that are independent of the mass of a system, such as temperature, pressure, and density. Extensive properties Those whose values depend on the size—or extent—of the system. Specific properties: Extensive properties per unit mass. KEITH VAUGH
    31. 31. KEITH VAUGH
    32. 32. m Intensive or Extensive? To identify whether a property isV either, divided the system into twoT equal parts. Each part will have theP same value of intensive property but half the value of the extensiveρ property KEITH VAUGH
    33. 33. m Intensive or Extensive? To identify whether a property is V either, divided the system into two T equal parts. Each part will have the P same value of intensive property but half the value of the extensive ρ property½m½V ½m ½V } Extensive properties T T P ρ P ρ } Intensive properties KEITH VAUGH
    34. 34. CONTINUUM } KEITH VAUGH
    35. 35. CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the atomic nature of a substanceand view it as a continuous, homogeneous matter with no holes, thatis, a continuum. } KEITH VAUGH
    36. 36. CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the atomic nature of a substanceand view it as a continuous, homogeneous matter with no holes, thatis, a continuum. }The continuum idealisation allows us to treat properties as pointfunctions and to assume the properties vary continually in space withno jump discontinuities. KEITH VAUGH
    37. 37. CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the atomic nature of a substanceand view it as a continuous, homogeneous matter with no holes, thatis, a continuum. }The continuum idealisation allows us to treat properties as pointfunctions and to assume the properties vary continually in space withno jump discontinuities.This idealisation is valid as long as the size of the system we deal withis large relative to the space between the molecules. KEITH VAUGH
    38. 38. CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the atomic nature of a substanceand view it as a continuous, homogeneous matter with no holes, thatis, a continuum. }The continuum idealisation allows us to treat properties as pointfunctions and to assume the properties vary continually in space withno jump discontinuities.This idealisation is valid as long as the size of the system we deal withis large relative to the space between the molecules.This is the case in practically all problems. KEITH VAUGH
    39. 39. CONTINUUMMatter is made up of atoms that are widely spaced in the gas phase.Yet it is very convenient to disregard the atomic nature of a substanceand view it as a continuous, homogeneous matter with no holes, thatis, a continuum. }The continuum idealisation allows us to treat properties as pointfunctions and to assume the properties vary continually in space withno jump discontinuities.This idealisation is valid as long as the size of the system we deal withis large relative to the space between the molecules.This is the case in practically all problems.In this text we will limit our consideration to substances that can bemodelled as a continuum. KEITH VAUGH
    40. 40. Despite the large gaps between molecules,a substance can be treated as a continuumbecause of the very large number ofmolecules even in an extremely smallvolume KEITH VAUGH
    41. 41. DENSITY AND SPECIFIC GRAVITY } KEITH VAUGH
    42. 42. DENSITY AND SPECIFIC GRAVITY Density ρ= m V ( m) kg 3 } KEITH VAUGH
    43. 43. DENSITY AND SPECIFIC GRAVITY Density ρ= m V ( m) kg 3 Specific volume V 1 v= = m ρ } KEITH VAUGH
    44. 44. DENSITY AND SPECIFIC GRAVITY Density ρ= m V ( m) kg 3 Specific volume V 1 v= = m ρ } Specific gravity The ratio of density of a substance to the density of some standard substance at a specific temperature ρ SG = ρ H 2O KEITH VAUGH
    45. 45. DENSITY AND SPECIFIC GRAVITY Density ρ= m V ( m) kg 3 Specific volume V 1 v= = m ρ } Specific gravity The ratio of density of a substance to the density of some standard substance at a specific temperature ρ SG = ρ H 2O Specific weight The weight of a unit volume of a substance γ s = ρg ( m) N 3 KEITH VAUGH
    46. 46. STATE AND EQUILIBRIUM Thermodynamics deals with equilibrium states } KEITH VAUGH
    47. 47. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium states } KEITH VAUGH
    48. 48. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. } KEITH VAUGH
    49. 49. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. }Thermal equilibrium KEITH VAUGH
    50. 50. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. }Thermal equilibriumIf the temperature is the same throughout the entire system. KEITH VAUGH
    51. 51. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. }Thermal equilibriumIf the temperature is the same throughout the entire system.Mechanical equilibrium KEITH VAUGH
    52. 52. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. }Thermal equilibriumIf the temperature is the same throughout the entire system.Mechanical equilibriumIf there is no change in pressure at any point of the system with time. KEITH VAUGH
    53. 53. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. }Thermal equilibriumIf the temperature is the same throughout the entire system.Mechanical equilibriumIf there is no change in pressure at any point of the system with time.Phase equilibrium KEITH VAUGH
    54. 54. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. }Thermal equilibriumIf the temperature is the same throughout the entire system.Mechanical equilibriumIf there is no change in pressure at any point of the system with time.Phase equilibriumIf a system involves two phases and when the mass of each phasereaches an equilibrium level and stays there. KEITH VAUGH
    55. 55. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. }Thermal equilibriumIf the temperature is the same throughout the entire system.Mechanical equilibriumIf there is no change in pressure at any point of the system with time.Phase equilibriumIf a system involves two phases and when the mass of each phasereaches an equilibrium level and stays there.Chemical equilibrium KEITH VAUGH
    56. 56. STATE AND EQUILIBRIUMEquilibrium Thermodynamics deals with equilibrium statesA state of balance. In an equilibrium state there are no unbalancedpotentials (or driving forces) within the system. }Thermal equilibriumIf the temperature is the same throughout the entire system.Mechanical equilibriumIf there is no change in pressure at any point of the system with time.Phase equilibriumIf a system involves two phases and when the mass of each phasereaches an equilibrium level and stays there.Chemical equilibriumIf the chemical composition of a system does not change with time,that is, no chemical reactions occur. KEITH VAUGH
    57. 57. KEITH VAUGH
    58. 58. A system at two different states KEITH VAUGH
    59. 59. A system at two different states A closed system reaching thermal equilibrium KEITH VAUGH
    60. 60. KEITH VAUGH
    61. 61. The state of nitrogen is fixed by twoindependent, intensive properties KEITH VAUGH
    62. 62. The State PostulateThe number of properties required tofix the state of a system is given by thestate postulate: The state of a simple compressible system is completely specified by two independent, intensive properties.Simple compressible systemIf a system involves no electrical,magnetic, gravitational, motion, and The state of nitrogen is fixed by twosurface tension effects. independent, intensive properties KEITH VAUGH
    63. 63. PROCESSES AND CYCLES } KEITH VAUGH
    64. 64. PROCESSES AND CYCLES Process } KEITH VAUGH
    65. 65. PROCESSES AND CYCLES Process Any change that a system undergoes from one equilibrium state to another. } KEITH VAUGH
    66. 66. PROCESSES AND CYCLES Process Any change that a system undergoes from one equilibrium state to another. } Path KEITH VAUGH
    67. 67. PROCESSES AND CYCLES Process Any change that a system undergoes from one equilibrium state to another. } Path The series of states through which a system passes during a process. KEITH VAUGH
    68. 68. PROCESSES AND CYCLES Process Any change that a system undergoes from one equilibrium state to another. } Path The series of states through which a system passes during a process. To describe a process completely, one should specify the initial and final states, as well as the path it follows and the interactions with the surroundings. KEITH VAUGH
    69. 69. Quasistatic or quasi-equilibriumprocessWhen a process proceeds in sucha manner that the system remainsinfinitesimally close to anequilibrium state at all times, i.e.properties in one part of thesystem do not change are fasterthan those in another part.Nonquasi-equilibrium processWhen a process proceeds in sucha manner that the system rapidlychanges and cannot maintain anequilibrium state. KEITH VAUGH
    70. 70. Process diagrams plotted by employingthermodynamic properties as coordinates are veryuseful in visualising the processes.Some common properties that are used ascoordinates are temperature T, pressure P, andvolume V (or specific volume v).The prefix iso- is often used to designate a processfor which a particular property remains constant.Isothermal processA process during which the temperature T remains constant.Isobaric processA process during which the pressure P remains constant.Isochoric (or isometric) processA process during which the specific volume v remains constant.CycleA process during which the initial and final states are identical. KEITH VAUGH
    71. 71. THE STEADY-FLOW PROCESS } KEITH VAUGH
    72. 72. THE STEADY-FLOW PROCESS The term steady implies no change with time. The opposite of steady is unsteady, or transient. } KEITH VAUGH
    73. 73. THE STEADY-FLOW PROCESS The term steady implies no change with time. The opposite of steady is unsteady, or transient. } A large number of engineering devices operate for long periods of time under the same conditions, and they are classified as steady-flow devices. KEITH VAUGH
    74. 74. THE STEADY-FLOW PROCESS The term steady implies no change with time. The opposite of steady is unsteady, or transient. } A large number of engineering devices operate for long periods of time under the same conditions, and they are classified as steady-flow devices. Steady-flow process KEITH VAUGH
    75. 75. THE STEADY-FLOW PROCESS The term steady implies no change with time. The opposite of steady is unsteady, or transient. } A large number of engineering devices operate for long periods of time under the same conditions, and they are classified as steady-flow devices. Steady-flow process A process during which a fluid flows through a control volume steadily. KEITH VAUGH
    76. 76. THE STEADY-FLOW PROCESS The term steady implies no change with time. The opposite of steady is unsteady, or transient. } A large number of engineering devices operate for long periods of time under the same conditions, and they are classified as steady-flow devices. Steady-flow process A process during which a fluid flows through a control volume steadily. Steady-flow conditions can be closely approximated by devices that are intended for continuous operation such as turbines, pumps, boilers, condensers, and heat exchangers or power plants or refrigeration systems KEITH VAUGH
    77. 77. During a steady-flow process, fluid properties within the control volume may change with position but not with timeUnder steady-flow conditions,the mass and energy contents ofa control volume remain constant KEITH VAUGH
    78. 78. TEMPERATURE & THE ZEROTH LAW OF THERMODYNAMICS If two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. By replacing the third body with a thermometer, the zeroth } law can be restated as two bodies are in thermal equilibrium if both have the same temperature reading even if they are not in contact.Two bodies reaching thermalequilibrium after being brought intocontact in an isolated enclosure KEITH VAUGH
    79. 79. TEMPERATURE SCALES } KEITH VAUGH
    80. 80. TEMPERATURE SCALES All temperature scales are based on some easily reproducible states such as the freezing and boiling points of water: the ice point and the steam point. } KEITH VAUGH
    81. 81. TEMPERATURE SCALES All temperature scales are based on some easily reproducible states such as the freezing and boiling points of water: the ice point and the steam point. } Ice point: A mixture of ice and water that is in equilibrium with air saturated with vapour at 1 atm pressure (0°C or 32°F). KEITH VAUGH
    82. 82. TEMPERATURE SCALES All temperature scales are based on some easily reproducible states such as the freezing and boiling points of water: the ice point and the steam point. } Ice point: A mixture of ice and water that is in equilibrium with air saturated with vapour at 1 atm pressure (0°C or 32°F). Steam point: A mixture of liquid water and water vapour (with no air) in equilibrium at 1 atm pressure (100°C or 212°F). KEITH VAUGH
    83. 83. Celsius scale: in SI unit systemFahrenheit scale: in English unitsystemThermodynamic temperature scale:A temperature scale that isindependent of the properties of anysubstance.Kelvin scale (SI) Rankine scale (E)A temperature scale nearly identicalto the Kelvin scale is the ideal-gastemperature scale. The temperatureson this scale are measured using aconstant-volume gas thermometer. KEITH VAUGH
    84. 84. KEITH VAUGH
    85. 85. P versus T plots of theexperimental data obtainedfrom a constant-volume gasthermometer using fourdifferent gases at different (butlow pressures) KEITH VAUGH
    86. 86. T(K) = T(̊C) + 273.15T(R) = T(̊F) + 459.67T(R) = 1.8T(K)T(̊F) = 1.8T(̊C) + 32The reference temperature in the originalKelvin scale was the ice point, 273.15 K,which is the temperature at which waterfreezes (or ice melts)The reference point was changed to a muchmore precisely reproducible point, the triplepoint of water (the state at which all three Comparison of temperature scalesphases of water coexist in equilibrium),which is assigned the value 273.16 K. KEITH VAUGH
    87. 87. PRESSURE } KEITH VAUGH
    88. 88. PRESSUREA normal force exerted by a fluid per unit area } KEITH VAUGH
    89. 89. PRESSUREA normal force exerted by a fluid per unit area }1Pa = 1 N m21 bar = 10 5 Pa = 0.1MPa = 100kPa1 atm = 101, 325Pa = 101.325kPa = 1.01325 bars1 kgf = 9.807 N 2 = 9.807 × 10 4 N 2 = 9.807 × 10 4 Pa cm 2 cm m = 0.9807 bar = 0.9679 atm KEITH VAUGH
    90. 90. Absolute pressureThe actual pressure at a given position. It is measured relative to absolute vacuum(i.e., absolute zero pressure).Gage pressureThe difference between the absolute pressure and the local atmospheric pressure.Most pressure-measuring devices are calibrated to read zero in the atmosphere, andso they indicate gage pressure.Vacuum pressuresPressures belowatmospheric pressure. Pgage = Pabs − Patm Pvac = Patm − Pabs KEITH VAUGH
    91. 91. Variation of Pressure with Depth ΔP = P2 − P1 = ρ gΔz = γ s Δz When the variation of density with elevation is known 2 P = Patm + ρ gh or Pgage = ρ gh ΔP = P2 − P1 = − ∫ ρ g dz 1 The pressure of a fluid at rest increases Free-body diagram of a rectangular fluid with depth (as a result of added weight). in equilibrium. KEITH VAUGH
    92. 92. In a room filled with a gas, the variationof pressure with height is negligible Pressure in a liquid at rest increases linearly with distance from the free surface KEITH VAUGH
    93. 93. The pressure is the same at all points on a horizontalplane in a given fluid regardless of geometry, providedthat the points are interconnected by the same fluid KEITH VAUGH
    94. 94. Pascal’s LawThe pressure applied to a confinedfluid increases the pressurethroughout by the same amount F1 F2 F2 A2P1 = P2 → = → = A1 A2 F1 A1The area ratio is called the Idealmechanical advantage of thehydraulic lift Lifting of a large weight by a small force by the application of Pascal’s law KEITH VAUGH
    95. 95. The Barometer and Atmospheric PressureAtmospheric pressure is measured by a device called a barometer; thus,the atmospheric pressure is often referred to as the barometric pressure.A frequently used pressure unit is the standard atmosphere, which isdefined as the pressure produced by a column of mercury 760 mm inheight at 0°C (ρHg = 13,595 kg/m3) under standard gravitationalacceleration (g = 9.807 m/s2). The basic manometer The length or the cross- sectional area of the tube has no effect on the height of the fluid column of a barometer KEITH VAUGH
    96. 96. The ManometerIt is commonly used to measure small andmoderate pressure differences. A manometercontains one or more fluids such as mercury,water, alcohol, or oil P2 = Patm + ρ gh The basic manometer Patm + ρ1gh1 + ρ2 gh2 + ρ 3 gh3 = P1 In stacked-up fluid layers, the pressure change across a fluid layer of density ρ and height h is ρgh KEITH VAUGH
    97. 97. Measuring the pressure drop across aflow section or a flow device by adifferential manometerP1 + ρ1g ( a + h ) − ρ2 gh − ρ1ga = P2P1 − P2 = ( ρ2 − ρ1 ) gh Other pressure measurement devices KEITH VAUGH
    98. 98. Systems and control volumesProperties of a systemDensity and specific gravityState and equilibrium  The state postulateProcesses and cycles  The state-flow processTemperature and the zeroth law of thermodynamics  Temperature scalesPressure  Variation of pressure with depths KEITH VAUGH
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