Heat transfer — Engineering, 14–17 years
Heat transfer explains how thermal energy moves by contact, moving fluids or radiation, and how engineers control that movement.
Three ways heat moves
Heat moves from a warmer place to a cooler one. Conduction passes energy through touching matter, convection carries it in moving liquids or gases, and radiation travels as electromagnetic waves, even through empty space.
The problem of unwanted heat
A phone must lose heat without becoming too hot, while a house should keep winter warmth inside. Engineers study heat transfer because ignoring it can waste energy, damage components or make people uncomfortable.
Why a metal spoon heats
Leave a metal spoon in hot tea and its handle soon feels warm. Energy conducts from the tea into the bowl, then through the metal to the handle; metal transfers heat readily, so the change is easy to notice.
Cold is not a substance
People often say that cold flows into a warm object, because a cold hand feels as if it receives cold from a surface. The useful picture is the reverse: thermal energy leaves the warmer object and enters the cooler one.
Controlling heat in real designs
Insulation in a coat or building slows conduction, while a radiator uses moving air to spread heat by convection. Solar ovens and spacecraft also use surfaces that absorb or reflect radiation, depending on whether they need to gain or lose heat.
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