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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