In heat flow {conduction, heat}|, collisions among molecules can transfer translational random kinetic energy.
materials
Fluids are good heat conductors, because molecules move freely. Metals are good heat conductors, because electrons move freely. Diamonds have high thermal conductivity, because crystal vibrations transfer heat.
area
Conductive-heat flow rate increases as contact area increases. Adding fins to surfaces or roughing up surfaces increases surface area and conducts heat better.
temperature
Conductive-heat flow rate increases as temperature difference increases. At room temperature, good conductor, such as metal, feels cool to touch, because heat moves quickly away from warmer human body. Poor conductor, such as plastic or wool, feels neither cool nor warm. Steering wheel covers and seat covers reduce heat conductivity.
In heat flow {convection, heat}|, mass can move in another mass, as hotter fluid at lower density rises and cooler fluid at higher density falls or as masses mix, flow, or blow. Convection is non-random motion that transfers heat by mass movement. Convective-heat flow rate increases as temperature difference increases. Blowing on something to cool it uses convection. Radiators use convection.
Electromagnetic-radiation emission or absorption {radiation, heat}| can transfer heat.
fire
Fire is electromagnetic radiation, emitting infrared and visible light from excited atoms in hot gas. Other objects can absorb radiation energy from fire and become hotter.
infrared
Heat radiation is typically infrared radiation. Infrared radiation is high in materials above 100 degrees Celsius.
color
White or shiny surfaces do not absorb radiation well, reflect radiation back into themselves at surfaces, and do not radiate at all frequencies well. Black surfaces absorb radiation well, do not reflect radiation back into themselves at surfaces, and radiate at all frequencies well.
Ideal objects {black body} can emit maximum heat radiation and have Planck distribution of radiation wavelengths and energies {black-body radiation}|.
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Date Modified: 2022.0225