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Heat Transfers Conduction, Convection and Radiation

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Katy Feldhahn

on 16 June 2015

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Transcript of Heat Transfers Conduction, Convection and Radiation

Heat and thermodynamics
Emily B, Elisabeth, Katy, Emily C, Laura, Nolan, Charlie, Spencer, Hayes, Simone, Luke
Entropy
Heat Transfers, Conduction, Convection and Radiation
Thermodynamic
Energy Transfer and Efficiency
New Mug Design
Mind Maps
Specific Heat of Coffee Cup
Cooling Curve
Heat Transfers
Radiation
What is
Convection
?
Conduction
Portrayal of hot water in convection...
Portrayal of cold water in convection...
Mind Map
Have you ever heard someone say "Heat rises"?
Convection is the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.
*Fluids are liquid and gases
http://www.cleanvideosearch.com/media/action/yt/watch?videoId=7xWWowXtuvA
Here is a more clear depiction of the warm water rising and the cold water descending.
In the following video you will see an experiment showing convection currents with only the use of a bucket of ice and a bucket of hot water below a fish tank filled with room temperature water and two different colors of food dye.
Everyday Convection
In ordinary heat transfer on the Earth, it is difficult to quantify the effects of convection since it inherently depends upon small nonuniformities in an otherwise fairly homogeneous medium. In modeling things like the cooling of the human body, we usually just lump it in with conduction.
Conduction is heat transfer by means of molecular agitation within a material without any motion of the material as a whole. If one end of a metal rod is at a higher temperature, then energy will be transferred down the rod toward the colder end because the higher speed particles will collide with the slower ones with a net transfer of energy to the slower ones
Ma * Ca * Qa = Mc * Cc * Qc
The transfer of heat is normally from a high temperature object to a lower temperature object. \Heat transfer changes the internal energy of both systems involved according to the First Law of Thermodynamics.


Thermal Radiation is energy transfer by the emission of electromagnetic waves which carry energy away from the emitting object.
Efficiency
Stefan-Boltzmann Law
Carnot Efficiency : (TH - TC)/ TH X 100
Reversible processes with no change in entropy are efficient.
Efficiency (%) = (useful power out / total power in) X 100
Q/t=kA(T hot-T cold)/d
Radiation Calculation
The sun at 5800K and a hot campfire at 800K give off radiation at a rate proportional to the 4th power of the temperature.
0th Law of Thermodynamics
Second Law of Thermodynamics
Multiplicity of A System
gives right behavior for combining two systems. Entropy of combined systems = the sum of their entropies, but the multiplicity = product of their multiplicities. The fact that the logarithm of the product of two multiplicities is the sum of their individual logarithms gives the proper kind of combination of entropies. The multiplicity for ordinary collections of matter is inconveniently large, on the order of Avogadro's number, so using the logarithm of the multiplicity as entropy is convenient.
Disorder
If we conduct an experiment to find the specific heat of a metal dropped in water, then by using all of these physics laws can we create a new mug?
Disorder Example:
For a glass of water the number of molecules is astronomical. The jumble of ice chips may look more disordered in comparison to the glass of water which looks uniform and homogeneous. But the ice chips place limits on the number of ways the molecules can be arranged. The water molecules in the glass of water can be arranged in many more ways; they have greater "multiplicity" and therefore greater entropy.
S= Q/T
First Law of Thermodynamics
U= Q - W
WE conducted our own experiment to show heat convection currents and the difference between pouring hot water (90 degrees Fahrenheit) into lukewarm water and pouring cold water (40 degrees Fahrenheit) into lukewarm water, and how coffee particles travel when dropped in the mixture.
U= thermal energy
Q= heat
W= work done
work done increases internal energy
Constant Pressure
W= P V
Non-Constant Pressure
New Design
Three layer mug made with ceramic on the inside and outside with a layer of anti-heat gel in the middle of the ceramic to keep your hands from getting burnt from the liquid inside.
Marketing
Survey Results
What is an Energy Transfer
Also known as an 'energy exchange', energy transfer from one system to another is said to occur when an amount of energy crosses the boundary between them. This in turn increases the energy content of one system while decreasing the energy content of the other system by the same amount.
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