What is Thermodynamics?

Mechanical – physical movement, e.g. lifting or pushing against friction. Electrical – flow of current

http://www.hybridmile.com/files/2008/10/engine--1.JPG http://www.nearfield.com/~dan/sports/bike/river/coyote/index.htm

The study of energy in the forms of heat and work and the exchange between the two.

Heat Work

• Applies to all forms of matter: solid, liquid and gas

• Relevant to very large systems (e.g. Universe) and small systems (nano-scale)

• Classical physics – does not consider individual atoms or quantum effects

Heat produced in nuclear fusion reactions within the Sun.

Controlled nuclear reactions in power stations

http://www.dailymail.co.uk/news/article-1043161/Anti-terror-patrols-secretly-stepped-power-stations.html

http://www.starlight-news.co.uk/StarlightSolarSystemTheSun.html

Sources of Heat

Burning wood, oil, gas and coal

http://www.stovesonline.co.uk/wood-is-best.html

Release of potential energy held in chemical bonds

1 tonne of crude oil (7 barrels) yields 4.2 x1010 J of heat.But humans consume about 1.3x1013 W of energy – equivalent to 300 tonnes of crude oil per sec!

Energy Radiated by the Sun

Stefan-Boltzmann equation tells us the power (energy per unit of time: W = J/s) radiated per unit area (m2) of its surface:

4TPR

Sun

Earth

RSE = 1.5 x 1011 m

TSun = 5800 K

RSun = 7 x 108 m

Luminosity: L =PRA= 3.8 x 1026 WEnergy is emitted in all directions

Power radiated per unit area at RSE:

232

26

104.14

108.3 WmxR

Wx

Area

LS

SE

RE=6378 km

Power reaching the Earth:

2623 )10378.6()104.1(* mxWmxAreaS

About 70% of radiation reaches Earth:

4.9 x 1017 W: Plenty to meet human needs!

RSun

http://www.nearfield.com/~dan/sports/bike/river/coyote/index.htm

• Wind is an alternative source of work – but what is the energy source of wind?

• Similarly, what is the source of wave energy?

• The source of tidal energy can be traced back to gravitational forces.

The Challenge of Finding Alternative Sources of Energy (Heat or Work)

http://www.shivaranjan.com/2006/08/22/irish-company-claims-creation-of-perpetual-motion-machine/

http://theseep.wordpress.com/2008/02/10/could-perepiteia-perpetual-motion-machine-be-the-real-deal/

http://www.todayinsci.com/Books/MechApp/chap23/page28.htm

Why Study Thermodynamics: Are perpetual motion machines possible?

Three Laws of Thermodynamics (plus Zeroth Law)

Thermal expansion of girders was restricted by frictional forces. They could not expand lengthwise, so they buckled!

Joints in bridges are used to enable thermal expansion.

Why Study Thermodynamics? Thermal Expansion

Why Study Thermodynamics? Understanding Gases

http://www.jamie.aarontastic.com/Low%20Pressure%20Example.JPG

Meteorology: high and low pressure

Measuring Lung Capacity

http://www.heart-watch-blog.com/images/blogs/7-2007/lung-capacity-7810.jpg

Ideal Gas

http://communication.howstuffworks.com/laptop.htm/printable

Why Study Thermodynamics? Heat Dissipation

Heat sinks, heat spreaders, and fans remove heat from the CPU of a laptop computer.

http://en.wikipedia.org/wiki/File:Crab_Nebula.jpg

http://cass.ucsd.edu/public/tutorial/Stars.html

Class Temperature Sample star

O 33,000 K or more Zeta Ophiuchi

B 10,500–30,000 K Rigel

A 7,500–10,000 K Altair

F 6,000–7,200 K Procyon A

G 5,500–6,000 K Sun

K 4,000–5,250 K Epsilon Indi

M 2,600–3,850 K Proxima Centauri

Surface Temperature of Stars

Why Study Thermodynamics? Thermal Radiation from Space

Crab NebulaT determines the “colour”.

Radiation energy density

Planck distribution law

T1∝max

infraredUV-Vis.

Spectral Distribution of Thermal Radiation

Effective temperature of the Sun is 5780 K UV-visible radiation.

http://jcwinnie.biz/wordpress/?p=2235http://www.dailymail.co.uk/sciencetech/article-483191/Arctic-ice-cap-melts-smallest-size.html

Greenhouse Effect: A Problem of Thermodynamics

Earth can be treated as a thermodynamic system.

http://en.wikipedia.org/wiki/File:Atmosfaerisk_spredning.gif

Most Intense Thermal Radiance from Earth

Water and Carbon Dioxide Block Thermal Radiation from Earth

Wavelength (m)Thermal radiation

transmitted through

atmosphere to Earth from Sun

Thermal radiation from colder Earth

transmitted through

atmosphere

en.wikipedia.org/wiki/User:Dragons_flight/Images

Power output:

8.1 Watts per kg of engine

Efficiency, = 0.18 (or 18%)

= Eelec/Qin

Eelec = Electric energy out

Qin = net heat energy in

Thermo-Acoustic Engine

Backhaus et al., Applied Physics Letters (2004) 85, p.1085

Compressed helium is cycled between heat exchangers (expanded and cooled), and the movement of the gas generates sound waves.

The sound waves drive a piston, which moves a coiled copper wire through a magnetic field produced by a permanent magnet.

Electric current flows to power the spacecraft.

Why Study Thermodynamics? Efficiency of New Types of Engines

What Happens when Thermodynamics Goes Wrong?

A failed O-ring allowed the escape of H2 gas. The result was an explosion = sudden release of heat

Challenger Space Shuttle Disaster

http://www.ssqq.com/archive/disasters.htm

Columbia Space Shuttle Disaster

Damage to the wing caused over-heating on re-entry into the atmosphere

Thermodynamics Provides Equations to Describe Properties of Matter

Properties are inter-related:

• Mechanical (elastic modulus and compressibility)

• Thermo-mechanical (expansivity)

• Flow (viscosity)

• Thermal (heat capacity)

Brownian Motion

Random movement of sub-mm particles caused by asymmetric collisions (and momentum transfer) with surrounding molecules.

Can this random movement of particles be “harnessed” to do useful work?

Sizes of rotors: between 4-10 nm thick and about 5-12 nm across.

Membrane

Hot gas side

Cold gas side

New Directions: Brownian Motor

M. van den Broek and C. Van den Broeck, Physical Review Letters (2008) 100, 130601

Heat flow