Unit 6(text):

IR camera

Various cups

Logger Pro temp sensors

Heat: three mode of transfer

Radiation: needs no medium, can be reflected (white, mirrored surfaces), more efficient at high temperatures (red hot), e.g. solar radiation from the sun to us, 8 light minutes away, through a vacuum.

You also know this as albedo: (recall Albus Dumbledore-white beard). Clouds and ice have high albedo (reflect radiation), ocean water and soil have low albedo. You can feel thermal radiation (infrared) and can see visible radiation (light), ultraviolet radiation burns your skin (reflect with clothes or white sunscreen). Geckos and some snakes can see in the infrared. Bees see in the ultraviolet (not "ultra-violent")

Conduction: (contact), air over warm earth, picks up heat (thermal energy) by contact then rises into the atmosphere to be cooled. You also know about conduction if you touch something hot, or want to stay warm when it is cold outside. Air is a good insulator, so anything that traps air can insulate from conduction. The ultimate insulator is a vacuum. Most insulators of heat are also insulators of electricity. Question: to touch something hot would you wrap your hands in a cloth or aluminum foil? Which would you use to touch something electrical? Insulators include styrofoam (air pockets in plastic), rubber, thermal garments and "pink panther" home insulation. Also soy insulation used here at the elab, and in your green homes. Conductors include copper, silver, platinum, gold and aluminum, which is why wires are made of these.

Convection: (mass in motion), dependent on density differences, cause of all wind, weather, storms, and heat transfer to space.

Cool fact: There is no convection in space, since there is no effective up or down, so all computers on the space station need fans to push away heat.

Global warming: driven by change in albedo (radiation) and carbon dioxide (insulation)

Energy use: energy efficiency is in its infancy-you could change this

Building insulation

Hot water insulation

HVAC

Housing

Industry

Transportation

Energy flow can be measured by decay rates (k), or the rate at which energy moves from hot to cold.

Example: hot water heater

Hot initial temp: 50°C (30° above room temp, the final temp)

Later temp: 40°C (20° above room temp)

Outside temp: 20°C

time to decay from 50°C->40°C = 2 hours (7200 seconds)

Goal: calculate k, the thermal decay constant for this hot water heater

ln(20/30) = 0.4

0.4/7200 = 5.5 ee-5 (0.000055)

this is the value for k