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Demos. Shuttle Tile and Oven Mohair fuzz Candle Fire Syringe Deck of Cards Pasco Cylinder and Temp Sensor Bicycle Tire and Digital Thermometer Steam Engine and generator + bulb Stirling Engine DI Water , Ethanol. Thermodynamics, Heat Energy, and how we benefit from it. Outline.

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demos
Demos
  • Shuttle Tile and Oven
  • Mohair fuzz
  • Candle
  • Fire Syringe
  • Deck of Cards
  • Pasco Cylinder and Temp Sensor
  • Bicycle Tire and Digital Thermometer
  • Steam Engine and generator + bulb
  • Stirling Engine
    • DI Water , Ethanol
outline
Outline
  • What is Thermodynamics
  • What is Heat and temperature
    • Definition
    • What makes Heat flow (heat transfer)
  • Specific Heat
  • How heat flows
    • Conduction
    • Convection
    • Radiation
      • Electromagnetic Spectrum
  • Laws of Thermodynamics and Entropy
  • Doing work on a Fluid
    • Fire Piston - before the invention of the Match Head
  • Some common thermodynamic cycles
    • Otto Cycle and other heat engines
      • Combustion Process
    • Stirling
    • Refrigeration and heat pumps
  • Why 100% efficiency is theoretically impossible (the Heat Tax)
  • Common engines
    • Steam Engine
    • Diesel Engine
    • Electric Engine
what is thermodynamics
What is Thermodynamics?

Thermo means “heat" and Dynamics relates to "movement"; in essence thermodynamics studies the movement of heat energy and how that energy makes mechanical movement (i.e. does work).

slide5
Thermodynamics is a science about the effects of changes in temperature, pressure, and volume and how these changes effect a physical system.

(e.g. a car engine, an air conditioner)

what is heat
What is Heat?

Heat Energy is a type of kinetic energy

Heat Energy relates to Thermal Energy (or internal energy)

Thermal Energy is the sum of the kinetic energy, ½ mv2 , of ALL the individual atoms in a system or object.

Heat is the energy that flowsfrom one object to anotherdue to a temperature difference.

slide7
When Energy flows from a hot object to a cold object, the energy is called Heat

http://hop.concord.org/htu/htu.concepts.flow.html

before 1800 heat was thought to be an invisible fluid that flowed between objects
Before 1800, Heat was thought to be an invisible fluid that flowed between objects
  • Objects were thought to contain fixed quantities of heat.
  • Benjamin Thompson observed that canons bored with dull tools became very hot while those bored with sharp tools did not get as hot. The heat generated had nothing to do with the size of the canon.
  • Thompson suggested that heat came from friction (or mechanical energy).

http://honolulu.hawaii.edu

james joule tests the predictions
James Joule tests the predictions:

James Joule’s experiment proved that heat was a form of energy. In this experiment the kinetic energy of the paddle is transferred to thermal energy in the water, as measured with a sensitive thermometer.

http://www.geocities.com/bioelectrochemistry/joule.htm

two objects in contact on a microscopic level
Two objects in contact on a microscopic level:

Fast moving

Slow moving

http://hop.concord.org/htu/htu.concepts.flow.html

Fast moving atoms with a lot of random motion collide with slower moving atoms.

As kinetic energy is transferred from the fast moving atoms to the slower moving atoms, we say that the warmer side gave up heat to the colder side and that heat was transferred.

what is temperature
What is Temperature?

Temperature is a measurement of the average thermal energy of the particles in a substance.

Heat flows due to temperature differences.

No heat is transferred between two objects that are at the same temperature (i.e. in thermal equilibrium).

A cup of boiling water is at the same temperature as a gallon of boiling water, but the gallon of boiling water has more thermal energy than the cup.

which object has higher thermal energy
Which object has higher thermal energy?

http://picasaweb.google.com/peppermint.patti1960

heat capacity
Heat Capacity
  • Heat Capacity of an object is the required energy needed to raise the object’s temperature by one degree.
  • A large quantity of matter has a larger heat capacity than something smaller
  • Our oceans and atmosphere have large heat capacities due to their large sizes.
specific heat
Specific Heat

The measure of the heat energy required to increase the temperature of a unit quantity of a substance by one degree.

Copper 0.385 Joule/gr oC

Dry Air 1.0035 Joule/gr oC

Humid Air 1.0102 Joule/gr oC

Water 4.1813 Joule/gr oC

Concrete 0.88 Joule/gr oC

Sand 0.42 Joule/gr oC

Second highest specific heat, next to Ammonia

specific heat of water
Specific Heat of Water
  • Very high
  • Earth’s ocean store vast amounts of thermal energy – these large heat reservoirs regulate the earth’s temperature.
  • Unfrozen lakes moderate surrounding climate
  • Water filled walls make good thermal mass
water filled walls as thermal mass
Water filled walls as thermal mass

http://www.energybulletin.net

using plant material as solar mass
Using plant material as solar mass

McGill University, Montreal – Solar Decathlon 2007

http://www.solardecathlon.org/

how does heat flow
How does Heat flow?
  • Conduction – the transfer of heat energy by making direct contact with the atoms/molecules of the hotter object
  • Convection – the transfer of heat due to a bulk movement of matter from hotter to colder areas
  • Radiation – energy transferred by electromagnetic waves

http://www.williams.edu

conduction
Conduction
  • When two objects are in direct contact, particles in the hotter object are moving faster and will collide with slower moving objects in the colder object.
  • When this happens, heat flows.
  • Energy is transferred from the hot object to the cold object.
touch the wood table and then touch the metal legs of the table
Touch the wood table and then touch the metal legs of the table…

Both Objects are at the same temperature, but the metal feels colder, why?

You are at a higher temperature than any non-living object in the room, therefore heat is transferred from your body to both the wood and the metal.

The metal conducts heat better than the wood because there are a lot of free electrons in metals, therefore mobile electrons take heat from your hand faster than wood.

slide21
The rate of heat transfer depends on:
  • The Temperature difference
  • And the Thermal Conductivity of the Materials

Shuttle Tile white-hot at 2300 oF

The tile is 10% pure silica fibers and 90% air. The high percentage of air makes the tiles very lightweight.

Tile has very low thermal conductivity due to trapped air and the low conductivity of long glass fibers.

http://www.answers.com/topic/space-shuttle-thermal-protection-system

is air a good thermal insulator
Is air a good thermal insulator?
  • Thermal Insulation is the method of preventing heat from entering or escaping from a container.
  • Stagnant air is a good thermal insulator
  • Coats, feathers, fur, hair, fiberglass insulation, & straw bales all trap tiny pockets of air.
  • The ocean of air over your head helps keep the earth cool during the day and warm during the night.
  • Air has high specific heat.
slide23
Heat energy is transmitted

by collisions from neighboring atoms/molecules.

http://www.ucar.edu/

more examples of conduction
More examples of Conduction

www.backpackgeartest.org

www.broadys.co.nz

convection
Convection

Buoyancy forces cause bulk movement of the water.

www.physics.arizona.ed

more examples of convection
More examples of Convection

www.physics.arizona.edu

www.weatherquestions.com

Rising hot air and falling cool air sets up convection cells.

slide27
Heat from the earth’s core comes from ancient energy left from earth’s formation and radioactive elements which decay and release heat.

http://www.incois.gov.in

Heat from the earth’s core causes slow moving convection cells in the earth’s mantle. The earth’s crust spreads at mid-ocean ridges by 2-3 cm per year.

oceanic convection
Northern Atlantic cold water sinks. This pulls in warmer water from the Gulf Stream. This heat transfer phenomenon determines how warm or cool European climates will be.

Fresh water is less dense than salt water. As Greenland’s ice fields recede more fresh water enters the North Atlantic possibly impacting normal oceanic convection patterns.

Oceanic Convection
forced convection
Forced Convection
  • Forced Convection is not due to the natural forces of buoyancy induced by heating.
  • Instead, there is a external force that causes the fluid to convect, such as a fan or a pump.
convection ovens
Convection Ovens

A fan circulates the air so hot air is not trapped at the top of the oven. More cookies can be baked at one time and all will cook at the same rate.

ceiling fans
www.sleekhome.comCeiling Fans

In both hot and cold weather, ceiling fans are useful for circulating air to force convection.

Rooms with high ceilings are a problem during the winter as the hot air rises and moves away from the floor area.

heat transfer from radiation
Heat Transfer from Radiation
  • All matter that has thermal energy will emit infrared electromagnetic radiation.
  • We can feel this when we put our hands close to a fire.
  • This type of heat transfer requires no medium. Electromagnetic radiation travels at the speed of light through a vacuum.

http://www.newt.com

http://www.charlesandhudson.com

infrared radiation
Infrared Radiation

All objects with thermal energy emit Infrared Radiation (even ice)

Infrared radiation is invisible to our eyes but we can feel it as heat

Nasa.gov

the sun s energy is transferred to earth by electromagnetic waves
The Sun’s energy is transferred to earth by electromagnetic waves
  • Visible Light
  • Infrared radiation
  • Ultraviolet (UV)

http://www.foxnews.com

electromagnetic spectrum of waves
Electromagnetic Spectrum of Waves

http://www.hermes-program.gr

slide37
Ionizing radiation causes matter to ionize (can rip an electron off an atom)
  • Ionizing radiation carries more energy than those waves with larger wavelengths.
  • The sun’s UV waves are those responsible for burning and skin cancer.
  • Infrared is non-ionizing radiation.

Non-ionizing radiation is everywhere and is considered to not be harmful.

laws of thermodynamics
Laws of Thermodynamics

Zeroth Law:

If two objects are in thermal equilibrium with a third object, then they are also in thermal equilibrium with each other.

Thermal equilibrium means an objects temperature, pressure, and volume are not changing.

slide39
http://www.cafemakers.com

A cooling cup of coffee is NOT in thermal equilibrium with the room.

slide40
/www.wentapottery.com

If two cups of coffee are at thermal equilibrium with the room, then the two cups are in thermal equilibrium with each other.

The two cups of coffee have the same temperature.

If the two cups are put in contact with each other no heat will flow.

slide41
First Law of Thermodynamics:

(The good news!)

Energy is Conserved. Energy can not be destroyed.

In an isolated system, the total energy stays the same.

Energy can be converted from one form to another.

Thermal Energy can be converted into another form of energy!

what is entropy
What is Entropy?

Entropy = total disorder of an object/system

Disorder is the sum of the thermal energy plus the physical disorder.

Entropy always increases with time!

examples of increasing entropy
Wikipedia.com

www.wiley.com

Examples of increasing entropy

Playing “52 pick up”

slide44
+

Heat, light, ash, particulates, gases

+

Heat, light, ash, particulates, gases

Direction

Is possible

Direction

Is impossible

slide46
The Second Law of Thermodynamics:

(The bad news!)

An isolated system gets more disordered with time.

Entropy always increases with time.

what does this mean to us
What does this mean to us?
  • It is impossible to construct an engine that converts all its thermal energy into useful work. The exhaust must be hotter than the incoming air.
  • 100% efficiency is impossible –there must be some unusable energy because entropy must increase.
  • We’re going to get old and die
  • The house is going to need cleaning again!
why is 100 efficiency theoretically impossible
Why is 100% efficiency theoretically impossible?
  • If machine operates in a cycle, some energy must be used to reset the machine.
  • Parts of machine will absorb some of the heat.
  • Exhaust must be hotter than incoming air, due to 2nd law. This hot exhaust represents wasted energy.

http://commons.wikimedia.org

doing work on a fluid
Doing work on a Fluid

When a fluid is compressed, work is done on the fluid.

This work/energy is converted into thermal energy within the fluid.

Each molecule has more kinetic energy so the temperature of the fluid increases.

fire piston
www.grannysstore.comFire Piston

As air is rapidly compressed, it can reach 400-500 degrees, allowing tinder to ignite.

The compressed air is the heat source as well as the oxygen needed to ignite the tinder.

Fire piston are thought to be prehistoric fire starting devices, used in South East Asia and South Pacific.

For more info see:

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

slide51
The modern match evolved during the 1800’s. Prior to 1900, fires had to be maintained or started by creating heat through friction.

Many people used flintlock guns.

The Bow and Drill used by Native Americans

Wikipedia.com

http://wildwoodsurvival.com

but fluids can do work on surroundings
But fluids can do work on surroundings
  • A compressed gas will experience an increase in pressure (as well as an increase in temperature if compression is fast).
  • When a pressurized gas expands it’s thermal energy decreases because it is doing work (it is exerting forces as it expands).
    • Ex. Air escaping from a bicycle tire feels cold.
heat engines
Heat Engines

A cycling machine/engine that converts thermal energy into mechanical energy (also known as work)

Examples:

4-stroke engine (OTTO Cycle)

Steam Engines

Stirling Engine

combustion can be used to energize a fluid
Combustion can be used to energize a fluid
  • Fuel source
  • Oxygen
  • Heat

http://www.fs.fed.us

steam engine invented in 1712
Steam Engine invented in 1712
  • Using combustion and water to create steam.
  • External Combustion
  • Used to pump water, power ferries, trains, & factories.
  • Demand for coal rises
  • Ushers in the Industrial Revolution

HowStuffWorks

slide56
A boiler is used to heat water to create steam. This high pressure fluid in turn does work on the pistons.

Working fluid (steam) is heated through a heat exchanger. Fuel is external to working fluid.

About 6% efficient

HowStuffWorks

http://science.howstuffworks.com/steam1.htm

Click for animation

coal and steam powered factory
Coal and Steam Powered Factory

Briggs and Stratton Website

stirling engine 1816
Stirling Engine - 1816
  • Closed Cycle – working fluid is contained within the system
  • Highest efficiency possible
  • Higher capital costs
  • Heat Source and Heat Sink needed
slide59
The Power Piston lags the Displacer by 90o

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

gasoline engines
Gasoline Engines
  • Internal Combustion – burning takes place inside the engine
  • Based on a four-stroke combustion cycle called the

Otto Cycle:

    • Intake
    • Compression
    • Combustion
    • Exhaust

http://auto.howstuffworks.com/engine1.htm

Click for animation

diesel engine 1876
Diesel Engine - 1876

Diesel engines do not have spark plugs because similar to the fire piston, the compression of the gas and air mixture is great enough to automatically ignite the fuel.

Gas is injected into cylinder after air is compressed. This allows for greater compression, and higher efficiency.

http://auto.howstuffworks.com/diesel1.htm

Click for animation

biodiesel
BioDiesel
  • Made from plant or animal oils
  • Chemically treated so that BioDiesel won’t solidify at low temperatures or clog fuel lines
  • Very simply chemistry

Make Magazine Vol#3

efficiency of engines
Efficiency of Engines
  • IC Engine is only 20-30% efficient
  • Diesel is more efficient due to the greater compression rate and ability to extract more work out of the fuel
why 100 efficiency is impossible
Why 100% efficiency is impossible?
  • At least some of the energy must be passed on to heat a low-temperature energy sink
  • This is due to the 2nd Law of Thermodynamics – Entropy must increase!
  • Engine needs to be reset.
  • Engine parts will absorb some of the heat energy.
early cars employed three technologies
Early cars employed three technologies
  • Steam powered
  • Electric battery powered
  • Gasoline and Diesel powered

Stanley Steam Car 1912

steam cars
Steam Cars
  • Heavy
  • Slow to heat up and start
  • Required carrying both fuel and water

http://www.steamcar.net/my-85.html

first electric vehicles ev
First electric vehicles (EV)
  • Edison worked on battery storage believing that electricity would power future cars
  • In 1900, roughly a third of all vehicles sold are EVs
  • EVs were marketed to women and for urban areas

Thomas Edison circa 1900

Morrison’s 4-horse power EV with a range of 50 miles.

Circa 1888

early electric vehicles
Early electric vehicles

Waverley Automobile Co.

Detroit Electric Carriage - 1912

early gas powered cars
Early Gas powered cars

Karl Benz was the first to commercialize a gas powered motorwagon in 1885

why did evs and steamers fade away
Why did EVs and Steamers fade away?
  • Gasoline and Diesel have high energy densities
  • Oil found in Texas
  • Greatest need for cars and trucks was in rural areas, therefore long range was needed.
  • Steamers too heavy on unpaved roads
  • Gas powered cars started quickly
  • Henry Ford perfected the assembly-line, making his cars the most affordable
why was gasoline the chosen fuel source for the automobile
Why was gasoline the chosen fuel source for the automobile?
  • Gasoline has 1000X the energy as an equal weight of batteries.
  • Gasoline has 4.5X more energy per gallon than liquid hydrogen.
  • Gasoline has 2X the energy of coal for the same weight
  • Gas has slightly less energy per volume as veggie oil
  • Gasoline combines with Oxygen when it burns. The Oxygen is free and does not have to be carried.
slide73
Huntington Beach 1928

Beaumont, Texas on Spindletop Hill

refrigeration a vapor compression cycle
Refrigeration:A vapor compression cycle

Heat flows into fluid

The Evaporator

Heat leaves the fluid, heating the kitchen floor and condensing the fluid.

slide76
The compressor on the bottom compresses the working fluid raising its temperature.

In the condenser coils, heat leaves the fluid and enters the room. This condenses the fluid into a liquid.

When allowed to expand, the temperature of the liquid drops dramatically. This cold fluid absorbs heat from the inside of the refrigerator, causing the fluid to evaporate and turn back into a gas.

http://www.lpappliances.com

which law of thermodynamics does the following video demonstrate
Which law of Thermodynamics does the following video demonstrate?

http://www.youtube.com/watch?v=U82eWptFxSs

internal combustion vs external combustion
Internal Combustion vs. External Combustion

External Combustion – the fluid doing the work (working fluid) is heated externally.

Internal Combustion – the fluid doing the work is heated by burning a fuel internally inside a cylinder pushing down on a piston

Major Plus

  • Pros of IC
    • electric starter, so easier and quick to start up
  • Cons of IC
    • By-products of combustion in exhaust gases
  • Pros of EC
    • Fuel can be anything
  • Cons of EC
    • Slow to start
    • Heat exchanger needed
    • If steam is the working fluid:
      • Boiler needed
      • Water freezes at low temperatures
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