Heat Transfer Project By Jacob Shearman

Conduction Example 1 Situation: Marshmallows on metal sticks are touching hot logs on a fire. Log is the hotter object and the object losing heat. Marshmallow is the colder object and the object gaining heat. This is an example of conduction because the marshmallows are directly touching the log. In this image, multiple examples of conduction are present. The immediate example is of the cold marshmallow touching the hot log. The hot log loses heat and the cold marshmallow gains heat until they are in thermal equilibrium. This is what cooks the marshmallow; the marshmallow’s temperature increases dramatically to reach thermal equilibrium with the log because its mass is much smaller than the log, and its heat capacity is much less. Because the marshmallow is touching the log, it is an example of conduction. There are also other examples of conduction in this picture; the marshmallow and the stick, and also the stick and the hand.

Conduction Example 2 Situation: Heat is flowing inside and out of the house via the window. On a summer day outside is hotter and losing heat and inside is cooler and gaining heat. On a winter night outside is cooler and gaining heat and inside is hotter and losing heat. This is an example of conduction because heat is transferred due to the air touching the window. In this image, the differences in conduction between the inside and outside of the house are shown according to the type and time of day. On a summer day, the outside air is hotter and loses its heat. Heat flows from outside through the window and into the house. On a winter day, the inside air is hotter, so the heat flows from the inside to the outside. Heat conducts from the warmer to the cooler side of the window as each molecule excites its neighbor and passes the energy along. Double glazed windows such as the one above are said to retain the house’s inside temperature during the winter as there is a layer of air between each glass panel. Air, being a gas, is a very good insulator and thus reduces the heat flow.

Radiation Example 1 Situation: Sun is radiating down on the earth. The hotter object and the object that is losing heat is the sun. The colder object and the object which is gaining heat is the earth. This is an example of radiation because the earth is being warmed by electromagnetic waves that have traveled through the empty space. This image is depicting global warming. The hot sun is radiating down on the cool earth, and the earth absorbs most of it. This causes the earth to warm. Although the sun is losing heat, continuous chemical reactions occurring on the sun allow the temperature to remain high. The heat from the electromagnetic waves given off by the sun is absorbed by the earth. Some energy is radiated back into space by the earth in the form of infrared waves. However, some of this outgoing infrared radiation is trapped within the earth’s atmosphere by pollutants known as greenhouse gases which are continuously being dumped into earth’s atmosphere. The increasing amount of outgoing radiation trapped by these gases causes the earth to get hotter.

Radiation Example 2 Situation: A jeep is giving off radiant energy.     Radiation Example 2 Situation: A jeep is giving off radiant energy. The car is the hotter object and is losing heat The surroundings are the colder objects and are gaining heat. This is an example of radiation because all objects continually emit radiant energy. This image shows the radiant energy of the jeep given off in various wave lengths. A temperature gauge is shown to the left, as well as a graph above showing wave lengths. The hot car is emitting radiation into its cooler surroundings. Because of this, the car is losing heat and the surroundings, such as the ceiling, are gaining heat. The graphs help to show that objects at lower temperatures emit longer waves than objects with higher temperatures. Also, objects at standard, everyday temperatures emit waves mostly in the longer wave length end of the infrared region – this is shown by the top image.

Convection Example 1 Situation: Land and sea breezes. Day source: Land Night source: Sea Fluid: Air Day fluid motion: Land heats the air, and the warm air rises. Night fluid motion: Sea heats the air, and the warm air rises. In this image, convection currents are shown in the form of land and sea breezes. Land heats and cools faster than sea; therefore, in the day, land is the source of heat, but in the night, the sea is the source of heat. These convection currents of the fluid, which is air, cycle in different directions depending on the stage of day. During the day time, the warm land heats the air above it which consequently rises and then falls as it reaches the cooler sea. At night time, the sea heats up the air above it which causes the hot air to rise; this air then falls as it travels over the cooler land. These cycles are the causes of both land and sea breezes at the coast.

Convection Example 2 Situation: Movement of Earth’s plates. Source: Earth’s outer core Fluid: Molten rock layers Fluid motion: Source heats up rock layers which rise and then cool as they reach surface and drop. These images demonstrate how the earth’s plates move due to convection currents. The currents that occur in the mantle are specifically the convection currents that move the plates; there are also currents occurring in the inner and outer layers. The hot outer layer heats the rock layers closest to it and causes this rock (considered as a fluid despite its viscosity) to rise. As these layers reach the cooler surface, they begin to cool and start to drop back to the outer core. After this, the cycle continues. The rock at the surface which is pushed aside by the hot rising rock drags the lithosphere or plates along with it. This concept is known as slab pull. These currents are; therefore, the cause of our plate movement.

Bibliography Microsoft PowerPoint Clipart and Animation. http://www.atc.army.mil/fac_guide/facilities/images http://www.kidsgeo.com http://corporateportal.ppg.com http://staffwww.fullcoll.edu http://static.photo.net http://www.uoguelph.ca www.energyquest.ca.gov www.physicalgeography.net www.winona.edu

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