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What is heat transfer by direct contact?

Melissa Norris

in Online Courses

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Nicholas Rivera on November 5, 2018

When a cold object and a hot object are in direct contact (touching) the heat is transferred by thermal conduction. Normally, heat transfer processes are classified as thermal conduction, radiative transfer or convection. The transfer of heat through the thermal conduction is the direct transfer of kinetic energy from one molecule to the nearby molecule. Because the temperature is directly proportional to the kinetic energy, the interactions between neighboring particles exchange energy and the exchange of energy gradually works it way from the high-temperature regions to lower temperature regions. The process of the temperature becoming the same is called thermal equilibrium. Convective heat transfer occurs in fluids. If a gas, liquid, or other liquids, changes in density of the fluid change the buoyancy and will cause fluid to flow (a process called convection) and the heat contained in the warmer fluid is transferred to a new location by the physical movement of fluids. Radiative transfer occurs when a hot object radiates electromagnetic energy. While the sun is an obvious source of electromagnetic energy, it is also generated in smaller quantities by any object. The most hot objects radiate more electromagnetic energy and the cooler objects absorb. This radiative transfer is important, but not as remarkable as the other two. Occurs between objects that are in direct contact or not, but it tends to be so small as to not be important of the objects that are touching.


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