Convection is the transfer of heat by the movement of heated particles into an area of cooler particles. You can experience convection when you light a match. The air directly above the lit match is always hotter than the air around the match.

Conduction: Heat transfers into your hands as you hold a hot cup of coffee. Convection: Heat transfers as the barista “steams” cold milk to make hot cocoa. Radiation: Reheating a cold cup of coffee in a microwave oven.

The three types of heat transfer

• Convection.
• Conduction.
• Radiation.

Convection is heat transfer due to a density differential within a fluid. As water’s temperature increases in the presence of a heat source, it will become less dense and rise. As it moves up and away from the heat source, it cools and becomes more dense and sinks.

But in liquids and gases (fluids), a region of lower density will rise and float above the higher density regions due to the influence of gravity. These two concepts, that heat causes a decrease in density and that fluids rise and fall according to density, combine to create the heat-transfer phenomenon of convection.

Deep down at the very bottom of the Atlantic Ocean, geochemist Andrea Koschinsky has found something truly extraordinary: “It’s water,” she says, “but not as we know it.” At over 3 kilometres beneath the surface, sitting atop what could be a huge bubble of magma, it’s the hottest water ever found on Earth.

Any object or substance that is less dense than a fluid will float in that fluid, so hot water rises (floats) in colder water. When fluids are cooled, they contract and therefore become more dense. Any object or substance that is more dense than a fluid will sink in that fluid, so cold water sinks in warmer water.

Using insulating materials is the best way to prevent heat transfer by conduction and convection. Insulating materials are poor conductors of thermal energy and also limit the movement of air in spaces, reducing convection. Insulation slows the rate at which unwanted energy enters the home in the summer.

there is a relatively high temperature gradient and relatively little convective heat transfer. Thus the heat transfer at the base of the trough is to a large extent conduction. When ice forms it gives off heat (latent heat of fusion).