The three ways heat moves and where each one shows up in plumbing and heating.
Heat always moves from hotter to cooler, and it does so in three ways. Knowing them makes radiators, cylinders and insulation make sense.
Conduction is heat passing through a solid by direct contact, as one particle passes energy to the next. It is why a copper pipe quickly feels hot along its length and why metals, being good conductors, are used for heat exchangers.
Convection is heat carried by a moving fluid. Warm water or air rises because it is less dense, cooler fluid sinks to take its place, and the resulting circulation carries heat around. It is the main way a radiator warms a room, by heating the air that then circulates.
Radiation is heat travelling as energy across space without needing anything to carry it, the way you feel warmth from a fire. A radiator gives out some of its heat this way, as direct warmth to objects and people in front of it.
Most plumbing components use all three at once. A hot water cylinder loses heat by conduction through its wall, convection of the air around it and radiation from its surface, which is exactly why a good insulating jacket cuts the losses.
For revision, link each mode to an example: conduction through a pipe, convection round a radiator, radiation off a hot surface. Confirm any values you use against your course material and current guidance.
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