ME2121 - ME2121E Slides Chapter 1 (2014)

7/21/2019 ME2121 - ME2121E Slides Chapter 1 (2014)

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Mechanical Engineering,

NUS

Introduction for students who aspire to become a practicing Mechanical

Engineer. with a title, Er (by the Professional Engineers Board).

Thermodynamic functions of machines and cycles a key subject ofMechanical Engineering

Topics to be covered Review of fundamentals, definitions etc. (Tutorial #1),,

Properties of pure substances, state diagrams, how to use steamtables, temperature measurements and scale. (Tutorial #2)

First Law of thermodynamics, steady flow energy equations,

applications (Tutorial #3), Second Law of Thermodynamics, statements of 2nd Law, Clausius

inequality, Clausius Clapeyron equation, entropy, entropy increase.

(Tutorial #4).

ME2121- Thermodynamics

Chapter 1 1/ 9


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Texts & References

Cengel YA and MA Boles, Thermodynamics: anengineering approach, 4th edition, McGraw Hill,2002

van Wylen GJ and RE Sonntag, Fundamentals ofclassical thermodynamics, John Wiley & Sons, 1993

Rogers GFC & YR Mayhew, EngineeringThermodynamics, Longmann, 1992

Engineering and Chemical Thermodynamics by MDKoretsky, Wiley, 2004 (Advance reading)

Thermodynamics and Transport properties of fluids (SIUnits) by GFC Rogers and YR Mayhew, Blackwell.


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What is Thermodynamics?

A science that deals with the properties of matter and therelationship between key variables -energy, heat, work,temperature, enthalpy, entropy, etc.

Treats all matters behave in a continuum manner,

Based on simple postulates or laws, axioms forbehaviour of matters,

To quantify efficiency, useful effects (work), etc.

A tool to evaluate the viability of a machine or system To make investment decision on the thermo-economics

of projects, eg., micro-power plants, cooling and heatingplants, aeroplanes, fleet of vehicles, etc.


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Historical background people associated with thermodynamics


Chapter 1 4 / 9

1. Joseph Black (1728-1799)-Noted forhis fundamental work on latent and

specific heats and for his discovery

of carbon dioxide.

2. http://www.chem.gla.ac.uk/~alanc/dept/black.htm

1. Benjamin Thomson (1753-1814)noted for his early statement on

the 1st Law, disproved the

caloric theory of heat.

http://www.english.upenn.edu/Projects/knarf/People/rumford.html


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Chapter 1 5/9

Robert Mayer (1814-1878) reported

the conversion between heat and

work.

http://www.mhtl.uwaterloo.ca/courses/

me354/mayer.html

James P Joule (1818-1889) noted for

his experiments in heat, formulated

the amount of heat to produce a unit

of work- the Joule Law.

http://www.mhtl.uwaterloo.ca/courses/me354/joule.html


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Chapter 1 6/9

Sadi Carnot(1796-1832) noted for

the heat input to steam engine

and the work derived from it, laidthe foundation to 2nd Law (1824)

in the thesis, the motive of fire.

http://www.mhtl.uwaterloo.ca/courses

/me354/carnot.html

Rudolf Clausius (1822-1888) unified

the statements of 2nd Law

axioms of thermodynamics.

http://www.mhtl.uwaterloo.ca/courses/

me354/clausius.html


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Chapter 1 7/9

Lord Kelvin (1824-1907) noted for the

absolute temperature scale.

Scottish Mathematician & physicist

http://www-groups.dcs.st-

and.ac.uk/~history/Mathematicians/

Thomson.html

JW Gibbs (1839-1903) noted for the

Gibbss law. First person to obtain

PhD in USA (Yale).

http://en.wikipedia.org/wiki/Josiah_Willar

d_Gibbs


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Useful applications of Thermodynamics

Power plants electricity production

Internal Combustion engines work horse of our mode oftransportation,

Gas turbines air transportation, ships, etc.

http://www.geae.com/engines/commercial/genx/2b_fett.html

Compressors for air conditioning chillers, highpressurized air, etc.

Desalination plants multi-stage, adsorption, etc.

Biological processes oxygenation in blood streams,heart of animals, humans, etc.

Heat exchangers chillers, heaters, processes, reactors,

Separation reactors- chemical plants


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Mechanism of Photosynthesis a thermodynamic

view point.

1. Fraction of useful wavelength of

solar spectrum = 0.25

2. Fraction of photons reaching the

leaves (containing chlorophyll) is

0.7 (70%).

3. Each photon of sunlight has 1.7

eV energy (1eV=1.609 x 10-19J)

4. I unit of glucose (plant matter) is

equivalent to 5 eV energy.However, the process of

achieving 1 unit of plant matter

requires 8 photons (due to

losses)

CO2 O2

H 2O


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Photosynthesis a thermodynamic process

that occurs in plants

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06.035.07.025.0

)7.18()5(cos

eVxphotonsincidenttoeVegluinenergy

storedofamtoffraction

foilageinspectrumlightabsorbedoffraction

lightincidentfromeffectwavelengthusefuloffraction

esisphotosynth xx

chlorophyll Plant experiments:- 3744 Cal/g or 15665 J/g of glucose

(by EC Pielou The energy of nature)


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Kenaf plant known as a miracle plant for CO2 capture.

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CO2 capture by Kenaf Plants an excellent crop

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Internal combustion engines


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(http://en.wikipedia.org/wiki/Image:4-Stroke-Engine.gif(for engine)

http://www.dula.tv/watch.php?file=how-the-drinking-bird-works.flv (drinking bird)

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ME2121 - ME2121E Slides Chapter 1 (2014)