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Date : Wednesday, April 21, 2010
Time : 9:35 AM
Title : Conduction Convection and Radiation
Time : 9:35 AM
Title : Conduction Convection and Radiation
Conduction is the transfer of heat by direct contact of particles of matter.Heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from one atom to another.Heat conduction is directly analogous to diffusion of particles into a fluid, in the situation where there are no fluid currents. This type of heat diffusion differs from mass diffusion in behavior, only in as much as it can occur in solids, whereas mass diffusion is mostly limited to fluids.
Conduction
Convection is the transfer of thermal energy by the movement of molecules from one part of the material to another.There are two types of convective heat transfer
Natural convection: when the fluid motion is caused by buoyancy forces that result from the density variations due to variations of temperature in the fluid. For example, in the absence of an external source, when the mass of the fluid is in contact with a hot surface, its molecules separate and scatter, causing the mass of fluid to become less dense. When this happens, the fluid is displaced vertically or horizontally while the cooler fluid gets denser and the fluid sinks. Thus the hotter volume transfers heat towards the cooler volume of that fluid.[3]
Forced convection: when the fluid is forced to flow over the surface by external source such as fans and pumps, creating an artificially induced convection current.[4]
Internal and external flow can also classify convection. Internal flow occurs when the fluid is enclosed by a solid boundary such as a flow through a pipe. An external flow occurs when the fluid extends indefinitely without encountering a solid surface. Both of these convections, either natural or forced, can be internal or external because they are independent of each other.[citation needed]
Convection
Radiation is the transfer of heat energy through empty space.No medium is necessary for radiation to occur, for it is transferred through electromagnetic waves; radiation works even in and through a perfect vacuum. The energy from the Sun travels through the vacuum of space before warming the earth.
Radiation
http://en.wikipedia.org/wiki/Heat_transfer
Done by syahirah dayana
Conduction
Convection is the transfer of thermal energy by the movement of molecules from one part of the material to another.There are two types of convective heat transfer
Natural convection: when the fluid motion is caused by buoyancy forces that result from the density variations due to variations of temperature in the fluid. For example, in the absence of an external source, when the mass of the fluid is in contact with a hot surface, its molecules separate and scatter, causing the mass of fluid to become less dense. When this happens, the fluid is displaced vertically or horizontally while the cooler fluid gets denser and the fluid sinks. Thus the hotter volume transfers heat towards the cooler volume of that fluid.[3]
Forced convection: when the fluid is forced to flow over the surface by external source such as fans and pumps, creating an artificially induced convection current.[4]
Internal and external flow can also classify convection. Internal flow occurs when the fluid is enclosed by a solid boundary such as a flow through a pipe. An external flow occurs when the fluid extends indefinitely without encountering a solid surface. Both of these convections, either natural or forced, can be internal or external because they are independent of each other.[citation needed]
Convection
Radiation is the transfer of heat energy through empty space.No medium is necessary for radiation to occur, for it is transferred through electromagnetic waves; radiation works even in and through a perfect vacuum. The energy from the Sun travels through the vacuum of space before warming the earth.
Radiation
http://en.wikipedia.org/wiki/Heat_transfer
Done by syahirah dayana