| 4Ó by 6Ó Cards |
| TodayÕs assignment | ||
| Name, SID – legible penmanship | ||
| What worked | ||
| What didnÕt and needs clarification | ||
| NATS 101 |
| Lecture 4 Temperature, Heat Transfer |
| What is Temperature? |
| Microscopic View | |
| Energy due to random jiggling of molecules | |
| Related to average molecular speed; 500 m/s (=1100 mph) at room temperature for air |
| Temperature and Density |
| Consider volume of air | |
| If air is warmed: | |
| The molecules will move faster, have ÒstrongerÓ collisions, and tend to become spaced farther apart | |
| Volume increases, so density decreases | |
| Warmer ó less dense |
| Temperature Scales |
| Fahrenheit (oF) - relative | |
| US public standard | |
| Celsius (oC) - relative | |
| Freezing point 0oC | |
| Boiling point 100oC | |
| oC= 5/9 (oF-32) | |
| Kelvin (K) - absolute | |
| K= oC+273 |
| What is Heat? |
| Heat-Energy in the process of being transferred from a warmer object to a cooler object | |
| Consider a pot of water on a hot burner. | |
| Consider the following questions: |
| Heat Transfer Questions |
| What causes theÉ | |
| Pan bottom and handle to get warmer? | |
| Top of the water to become warmer? | |
| Water temperature to not exceed 100oC? | |
| Region away from side of pan to feel warm? |
| Conduction |
| Heat transfer due to collision of molecules. | |
| Conduction warms the bottom of the pan! | |
| Conductivity - rate of heat transfer across a 1 cm thick slab of material if one side is kept 1oC warmer than the other | |
| Cheap Experiment: Touch your chair! |
| Heat Conductivity |
| Convection |
| Heat transfer due to vertical exchange of mass | |
| Occurs in fluids (liquids, gases) because of gravity | |
| Warm, buoyant air rises - Cool, dense air sinks | |
| Convection warms top of liquid! |
| Convection Movies |
| 2D Convection Tank Animation E | |
| 2D Convection Model Ra=10**6 | |
| 2D Convection Model Ra=10**7 IC1 | |
| 2D Convection Model Ra=10**7 IC2 | |
| 3D Rayleigh-Benard Convection Model E | |
| Last hour movie of clouds and moist convection | |
| over Catalina mountains |
| Energy States and Water Phases |
| Latent Heat |
| Heat Transfer Questions |
| What causes theÉ | |
| Pan bottom and handle to get warmer? | |
| Top of the water to become warmer? | |
| Water temperature to not exceed 100oC? | |
| Region away from side of pan to feel warm? |
| Modes of Heat Transfer |
| Take Home Concepts |
| Heat-Energy transfer due to temperature differences | |
| Three modes of heat transfer | |
| Conduction – molecule to molecule | |
| Convection – transport of fluid | |
| Radiation – electromagnetic waves | |
| Latent Heat – energy of phase changes |
| Reading Assignment |
| Ahrens | |
| Pages 30-34 | |
| Problems 2.7, 2.9 | |