ENGR 2213 Thermodynamics

ENGR 2213 ThermodynamicsENGR 2213 Thermodynamics

F. C. LaiSchool of Aerospace and Mechanical EngineeringUniversity of Oklahoma

SyllabusSyllabus

InstructorDr. F. C. Lai (FH 218A)Phone: 325-1748, Fax: 325-1088, Email: [email protected] Hours: 14:00-15:00 MTWR or by appointment

TextbookThermodynamics – An Engineering Approach by Y. A. Çengel and M. A. Boles, 4th edition, McGraw-Hill, 2002.

Course OutlineCourse OutlineIntroduction (1+)● Basic Concepts● Properties

First Law (2-6)● Energy Analysis for Closed System● Energy Analysis for Control Volumes

Second Law (7-12)● Entropy● Exergy (Availability)

Course OutlineCourse Outline

Power Systems (12-16)● Vapor Power Systems● Gas Power Systems

GradeGrade

● Homework (8-10) 25%● Quizzes (3) 45% ● Final Exam 30%

Final grade (in absolute scale)85+ A75-84 B65-74 C55-64 D55- F

IntroductionIntroduction

Thermo-dynamics heat force

● Energy → Engineers

● Properties of Matter → Scientists

History of DevelopmentHistory of Development

~1700 Building a steam engine (T. Savery and T. Newcomen)

1849 First use of the term “Thermodynamics”(Lord Kelvin)

1859 First textbook of “Thermodynamics”(W. Rankine)

>1900 Become a mature science

ApproachesApproaches

Macroscopic Approach (Classical Thermodynamics)

Microscopic Approach (Statistical Thermodynamics)

- is concerned with the overall behavior of a system- no model of the structure of matter at the molecular, atomic, and subatomic level is directly use

- is concerned directly with the structure of matter- characterize, by statistical means, the average behavior of the particles making up a system of interest and relate this information to the observed macroscopic behavior of the system

DefinitionsDefinitions• System the subject of the analysis• Surroundings everything external to the

system• Boundary the surface that separates the

system from its surroundings

systemsurroundings

DefinitionsDefinitions• System the subject of the analysis• Surroundings everything external to the

system• Boundary the surface that separates the

system from its surroundings

boundary

SystemsSystems

Closed Systems

Control Volumes

- A fixed quantity of matter- There can be no transfer of mass across its boundary- Energy, in the form of heat or work, can cross the boundary- The volume of a closed system does not have to be fixed

- A fixed volume in space through which mass may flow- It usually enclose a device which involves mass flow such as a compressor, turbine, or nozzle

SystemsSystems

Water HeaterPiston and Cylinder Assembly

Closed System

SystemsSystems

Water HeaterPiston and Cylinder Assembly

Closed System Control Volume

PropertiesProperties

Macroscopic characteristics of a system to which numerical values can be assigned.

Extensive Properties

Intensive Properties

Properties that their values depend on the size or extendof a system.

Properties that their values are independent of the size or extend of a system.

Examples: mass, volume

Examples: temperature, pressure

PropertiesProperties

● Divide and Conquer● Rule of “Sum”

For a quantity, if its value for a system is the sum of itsvalues of each partition, then it is an extensive property.

PropertiesProperties

● Divide and Conquer● Rule of “Sum”

For a quantity, if its value for a system is the sum of itsvalues of each partition, then it is an extensive property.

1 2 3 4

M = M1 + M2 + M3 + M4

Mass is an extensive property

PropertiesProperties

● Divide and Conquer● Rule of “Sum”

For a quantity, if its value for a system is the sum of itsvalues of each partition, then it is an extensive property.

1 2 3 4

V = V1 + V2 + V3 + V4

Volume is an extensive property

PropertiesProperties

● Divide and Conquer● Rule of “Sum”

For a quantity, if its value for a system is the sum of itsvalues of each partition, then it is an extensive property.

1 2 3 4

P = P1 = P2 = P3 = P4

Pressure is not an extensive property

PropertiesProperties

● Divide and Conquer● Rule of “Sum”

For a quantity, if its value for a system is the sum of itsvalues of each partition, then it is an extensive property.

1 2 3 4

T = T1 = T2 = T3 = T4

Temperature is not an extensive property

PropertiesProperties

Vvm

Specific Properties- Extensive properties per unit mass

Examples: specific volume

- A specific property is an intensive property

mV

density

Basic ConceptsBasic ConceptsState

ProcessThe condition of a system as described by its properties

A transformation from one state to another

At a given state, each property has a definite value that isIndependent of how the system arrived at that state.

Basic ConceptsBasic Concepts

The change in value of a property as the system is alteredfrom one state to another is determined solely by the twoend states and is independent of the particular way the change of state occurred.

A quantity is a property if, and only if, its change in valuebetween two states is independent of the process.

Basic ConceptsBasic Concepts

Denver

Latitude Longitude ElevationDenver 39º 45’ 104º 52’ 5280’OKC 35º 24’ 97º 36’ 1285’

OKC

Basic ConceptsBasic ConceptsPhaseA quantity of matter that is homogeneous throughout inboth chemical composition and physical structure.

Homogeneous in physical structure means that the Matter is all solid, all liquid, or all vapor (gas).

A system can contain one or more phases.For example: water and vapor 2 phases

Basic ConceptsBasic ConceptsPhaseA quantity of matter that is homogeneous throughout inboth chemical composition and physical structure.

Homogeneous in physical structure means that the Matter is all solid, all liquid, or all vapor (gas).

A system can contain one or more phases.For example: water and vapor 2 phases

water and oil 2 phases

Basic ConceptsBasic ConceptsPhaseA quantity of matter that is homogeneous throughout inboth chemical composition and physical structure.

Homogeneous in physical structure means that the Matter is all solid, all liquid, or all vapor (gas).

A system can contain one or more phases.For example: water and vapor 2 phases

water and oil 2 phases water and alcohol 1 phase

Basic ConceptsBasic ConceptsPhaseA quantity of matter that is homogeneous throughout inboth chemical composition and physical structure.

Homogeneous in physical structure means that the Matter is all solid, all liquid, or all vapor (gas).

A system can contain one or more phases.For example: water and vapor 2 phases

water and oil 2 phases water and alcohol 1 phase oxygen and nitrogen 1 phase

Basic ConceptsBasic ConceptsPure SubstanceOne that is uniform and invariable in chemical composition

A pure substance can exist in more than one phase

A uniform mixture of gases can be regarded as a puresubstance provided it remains a gas and does not reactchemically

EquilibriumEquilibrium

Thermodynamic Equilibrium● Thermal Equilibrium● Mechanical Equilibrium● Phase Equilibrium● Chemical Equilibrium

A state of balance

In an equilibrium state, there are no unbalancedpotentials (driving forces) within the system.

Thermodynamic EquilibriumThermodynamic Equilibrium

Mechanical Equilibrium

Thermal Equilibrium

● The pressure may vary within the system with elevation as a result of gravitational effect

● The system involves no temperature differentials● Temperature is uniform in the system

● No change in pressure at any point in the system

Thermodynamic EquilibriumThermodynamic Equilibrium

Chemical Equilibrium

Phase Equilibrium

● No chemical reactions occur

● The mass of each phase remains the same

● Chemical composition does not change with time

Basic ConceptsBasic ConceptsQuasi-Equilibrium ProcessA process that proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times

A quasi-equilibrium process is an idealized process to approximate an actual process

Basic ConceptsBasic ConceptsProcess PathThe series of equilibrium states through which a system passes during a processTo describe a process completely, one needs to specify the initial and final states of the process, as well as the path it follows

Steady StateProperties of the system does not change with time

CycleA sequence of processes that begins and ends at the same state