Islamic Azad University,

Karaj Branch

Introduction I n s t r u c t o r : D r . M . K h o s r a v y

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Engineering Thermodynamics

Description: • Fundamental laws of thermodynamics; application to:

– Flow processes – Nonreacting mixtures; – Chemical reactions; – Nonideal solutions, – Phase diagrams – Electrochemistry – Biothermodynamics

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Objectives: Understanding and use of: •  first and second laws of thermodynamics

•  terminology: system, properties, processes,, •  reversibility and equilibrium,

•  phases, components; phase rule

•  open and closed systems •  heat engines and power cycles

•  solution thermodynamics (nonideality) •  construction of phase diagrams

•  chemical thermodynamics

•  uses of electrochemistry •  Thermodynamics in human biology

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Outcomes: be able to: •  Analyze processes: isothermal, isobaric, isentropic, cyclic

•  Analyze steam power cycles for electricity production

•  Use equations of state for nonideal gases and solids

•  Apply equilibrium criteria to - isolated systems - chemical/materials systems - biological systems

•  Relate thermodynamic properties via partial derivatives,

•  Construct phase diagrams from free energy vs composition curves

•  Deal with homogeneous and heterogeneous systems

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Grading Homework & Quizzes 5% MidTerm* 25% Final* 70%

TEXT Cengel, Y. A. and Boles, M. A. THERMODYNAMICS: An Engineering Approach. McGraw Hill, 6th Edition 2008.

* Closed book

General Course Information

!  Most materials are available from course web

"  http://kiau.ac.ir/~mostafa.khosravy

!  Reading the handout may not be sufficient. It is useful to take notes as the instructor explains concepts and elaborates on the handout.

!  Studying for an exam: do some of the problems that were not assigned as homework;

!  Do not request solutions to all problems in a chapter.

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Islamic Azad University,

Karaj Branch

Historical Background of Thermodynamics

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A Brief History of Thermodynamics

•  The driving force for the development of thermodynamics was the invention of the steam engine at about 1700

•  From 1700 to 1900, thermodynamic theory was slowly and painfully developed

•  By 1900, “classical” thermodynamics was essentially complete

•  In time, various special branches of thermodynamics developed

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The Concept of Temperature

• Lavoisier (1780) realized that matter is composed of discrete atoms and molecules

•  Dalton (1808), temperature interpreted as a measure of particle speed (gas) or vibration (solid)

• Without realizing its significance, Galileo (ca 1630) developed a crude thermometer

• Fahrenheit (1715); measured temperature by expansion of a fluid (mercury) • Celsius (1742) defined 0oC as the melting point of ice; 100oC as the boiling point of water; with a scale in between linear with expansion of fluid – why?

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• Kelvin (ca 1885) introduced the notion of the absolute zero temperature, where all atomic motion stops: T(K) = T(oC ) + T0; absolute zero is 0 K or -T0

oC . How to determine T0 ?

Boiling water X

Solid CO2 x

-273=T0

Ice x

T,oC

pgas 0

0

Absolute zero = - 273 oC

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Gas Thermometer

Heater

Relief valve

~ 1.6 m

Flask Vol = VF

Oil

• Air in the flask expands with temperature and exerts pressure on the surface of the oil, causing it to rise in the column. •  with ice in the air flask: TF = 0 + 273 = 273 K - Relief valve open - po = 1 atm

- moles gas = To = 22 + 273 = 295 K

Column Area = AC

Reservoir

Tubing, vol = Vt

n1

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•  Relief value closed & ice removed ‒ air flask at room temperature (22 oC)

•  oil rises to height h1

Initial oil level

•  repeat for flask at T = 100oC

Homework problem! solve for h1

roil = 0.84 g/cm3 g = 9.8 m/s2

Volumes:

- Air flask 500 cm3

- Tubing from air flask to

oil flask: 2 cm3

- Oil flask neck inside diam. = 3 cm

- Column inside diameter 0.95 cm

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Finally, the temperature scales are fixed:

•  International Committee (1954): defines the unique state of water: the triple point

•  where ice, water, and water vapor (only) coexist at 0.01oC and 611 Pa (0.00611 atm)

•  The triple-point temperature anchors the temperature scale

•  Does not affect absolute zero (-273.15oC)

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Heat •  Since the 18th Cent., heat was viewed as a “fluid” (caloric)

that moves from a body at high temperature to one at low temperature

•  During the 19th Cent., the correct view of heat was uncovered:

- increasing the temp.of a body

- melting a body

- vaporizing a liquid

- producing mechanical work

Heat is energy in motion from a hot system to cold surroundings (or vice versa)

•  Some effects of heat :

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Work •  Known from mechanics since Newton (1687) as

force x distance.

•  Heat and Work are two aspects of energy in motion; work is completely convertible to heat (Rumford, Joule (1840)) but not vice versa! (e.g., steam engine)

•  Forms of Work: -  expansion/contraction: like a balloon -  rotating equipment: steam or gas turbine -  electrical work: electric cars -  mechanical: moving levers, lifting weights, etc.

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Count Rumford’s canon-boring experiment (1797)

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- heat in calories (to raise the temp. of 1 gram of water 1oC) - work in Joules (force of 1 Newton over 1 m)

4.184 Joules per calorie •  With energy, heat and work in the same units the 1st law was ready to be established

Joule (ca 1850) – the first thermodynamic experimentalist measured:

The Mechanical Equivalent of Heat

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But what is energy? We have no knowledge of what energy is …it is an abstract thing… (Richard Feynman)

•  Energy comes in many interconvertible forms: - internal (atomic motion in solids, liquids & gases)

- electrical & magnetic -  surface

-  chemical - in molecular bonds (coal power)

-  kinetic (wind power)

-  potential – gravitational (hydropower)

-  radiant (solar power)

-  nuclear – in proton-neutron bonds (nuclear power)

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Energy and the First Law •  energy cannot be created or destroyed:

conservation of energy - Mayer (1842) - Helmholz, Clausius, (ca 1850)

• energy is related to heat and work

by the

•  Energy is a property of a body; heat and work are not

1st Law of Thermodynamics

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The Second Law •  Development of steam engines (Watt 1778) showed empirically that heat cannot be

completely converted to work •  Carnot (1824) showed theoretically why this is so •  proposed the concept of the reversible processes •  For an engine (of any kind) to produce work, hot and cold reservoirs are required to provide high-quality heat and receive reject low-quality heat •  practical cycles for producing work are developed (Rankine, Otto, Brayton) 19th Cent.

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By analyzing many experiments and processes involving transfer of heat, Clausius (ca 1850) uncovers a new thermodynamic property, which he names entropy

- related to the heat exchanged between system and surroundings - not related to work - places 2nd law in quantitative form

Qualitative statements:

Clausius: “It is impossible to convert heat completely to work”

Entropy and the 2nd Law

Kelvin – Planck: “It is impossible for any any engine to transfer heat from a cold source to a hot source without work being done”

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Chemical/Materials Thermodynamics •  This branch deals with:

- multiple components, multiple phases - chemically reacting mixtures - equilibrium at conditions of fixed p and T

•  Developed by Willard Gibbs (Yale Univ. 1890) •  Gibbs introduces the chemical potential – the driving

force for: - Chemical reactions -  Exchange of a species between phases

-  Diffusion of a species in a single phase

•  At equilibrium, these

processes STOP

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Statistical Thermodynamics •  Links atomic motions to thermodynamic properties

discovers the formula for the absolute entropy Boltzmann (ca 1885)

Planck (~ 1900) quantization of energy states

Einstein, Debye (1905) – quantum mechanical explanation of specific heats of solids Fermi, Dirac, Bose – quantum statistical thermodynamics Giauque (1930, UCB)- the 3rd Law: The entropy of a body is zero at 0 K

More Reading

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