What is Thermodynamics The study of energy in

What is Thermodynamics? The study of energy in the forms of heat and work and the exchange between the two. Work Heat http: //www. hybridmile. com/files/2008/10/engine--1. JPG Mechanical work– physical movement, e. g. lifting or pushing against friction. http: //www. nearfield. com/~dan/sports/bike/river/coyote/index. htm Electrical work – flow of current • 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

Sources of Energy (Heat and Work) • Nuclear reactions are a source of heat (which can then be converted to work). • Solar energy comes in the form of thermal radiation given off by the Sun. (Thermal radiation is a way to transfer heat from a hotter object to a colder object. ) The origin of the heat of the Sun is a nuclear reaction. • Chemical reactions are another source of heat (and hence work). • Gravitational forces can likewise be a source of mechanical energy (work), which can be converted to electrical energy. • Tidal energy originates from gravitational forces from the moon; can do work. Combustion of wood, oil, gas and coal http: //www. dailymail. co. uk/news/article-1043161/Anti-terror -patrols-secretly-stepped-power-stations. html http: //www. nearfield. com/~dan/sports/bike/river/coyote/index. htm

Forms of Solar Energy Form Explanation and Use Solar radiation Direct heating of objects (e. g. buildings) by absorption of radiation (in passive syst. ) http: //www. starlightnews. co. uk/Starlight. Solar. System The. Sun. html Generation of electricity by photovoltaic cells or thermalenergy conversion in the oceans (in active systems) Photosynthesis Solar energy is converted to chemical energy in plants and fossil fuels. Solids, liquids and gases are used in combustion. Wind power Heating of land, air and seas by solar radiation produces winds. Wind is used as a source of mechanical energy (e. g. windmills or sailing ships) or electrical energy (in generators) Water power Sun drives water cycle (evaporation, rain) which is converted to mechanical or electrical energy (usually using gravity). From P. A. Tipler, Physics, Ch. 18

Does enough heat come from the Sun to meet human needs? http: //www. stovesonline. co. uk/wood-is-best. html 1 tonne of crude oil (7 barrels) yields 4. 2 x 1010 J of heat. But humans consume about 1. 3 x 1013 W of energy – equivalent to 300 tonnes of crude oil per sec! What is a Joule (J)? What is a watt (W)?

Energy Radiated by the Sun Earth RSun RSE = 1. 5 x 1011 m RE=6378 km Power radiated per unit area at RSE: Stefan-Boltzmann equation tells us the power (energy per unit of time: W = J/s) radiated per unit area (m 2) of its surface: Power reaching the Earth: TSun = 5800 K RSun = 7 x 108 m Luminosity: L =PRA= 3. 8 x 1026 W Energy is emitted in all directions About 70% of radiation reaches Earth: 4. 9 x 1017 W: Plenty to meet human needs!

Why Study Thermodynamics: Are perpetual motion machines possible? Three Laws of Thermodynamics (plus Zeroth Law) http: //www. todayinsci. com/Books/Mech. App/chap 23/page 28. htm 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/

Why Study Thermodynamics? Thermal Expansion Joints in bridges are used to enable thermal expansion. Thermal expansion of girders was restricted by frictional forces. They could not expand lengthwise, so they buckled! (Pressure, volume and temperature are interrelated in solids. )

Why Study Thermodynamics? Understanding Gases Meteorology: high and low pressure http: //www. jamie. aarontastic. com/Low%20 Pressure%20 Example. JPG Measuring Lung Capacity Ideal Gas: Pressure, Volume and Temperature relationships http: //www. heart-watch-blog. com/images/blogs/7 -2007/lung-capacity-7810. jpg

Why Study Thermodynamics? Heat Dissipation http: //communication. howstuffworks. com/laptop. htm/printable Heat sinks, heat spreaders, and fans remove heat from the CPU of a laptop computer. (The objective is to do electrical work, but heat is also given off in the process. )

Why Study Thermodynamics? Thermal Radiation from Space Surface Temperature of Stars Class Crab Nebula 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 T determines the “colour”. http: //en. wikipedia. org/wiki/File: Crab_Nebula. jpg http: //cass. ucsd. edu/public/tutorial/Stars. html

Spectral Distribution of Thermal Radiation energy density Effective temperature of the Sun is 5780 K UV-visible radiation. UV-Vis. Planck distribution law infrared

Why Study Thermodynamics? Efficiency of New Types of Engines Compressed helium is cycled between heat exchangers (expanded and cooled), and the movement of the gas generates sound waves. Thermo-Acoustic Engine 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. Efficiency, h = 0. 18 (or 18%) h = Eelec/Qin Eelec = Electric energy out Qin = net heat energy in Power output: 8. 1 Watts per kg of engine Backhaus et al. , Applied Physics Letters (2004) 85, p. 1085

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)

What Happens when Thermodynamics Goes Wrong? Damage to the wing caused over-heating on re-entry into the atmosphere A failed O-ring allowed the escape of H 2 gas. The result was an explosion = sudden release of heat http: //www. ssqq. com/archive/disasters. htm Challenger Space Shuttle Disaster Columbia Space Shuttle Disaster

Greenhouse Effect: A Problem of Thermodynamics http: //www. dailymail. co. uk/sciencetech/article-483191/Arctic-ice-cap-melts-smallest-size. html http: //jcwinnie. biz/wordpress/? p=2235 Earth can be treated as a thermodynamic system.

Water and Carbon Dioxide Block Thermal Radiation from Earth Thermal radiation transmitted through atmosphere to Earth from Sun Wavelength (mm) Thermal radiation from colder Earth transmitted through atmosphere en. wikipedia. org/wiki/User: Dragons_flight/Images Most Intense Thermal Radiance from Earth http: //en. wikipedia. org/wiki/File: Atmosfaerisk_spredning. gif

Source of Nano-Scale Work: 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?

Source of Nano-Scale Work: Brownian Motion Sizes of rotors: between 4 -10 nm thick and about 5 -12 nm across. Hot gas side Heat flow Membrane Cold gas side M. van den Broek and C. Van den Broeck, Physical Review Letters (2008) 100, 130601