⤴⤵Convective heat transfer
Have you noticed what happens if you add cold water to a bowl of hot water?
Cold water stands on hot water and to mix hot and cold water you need to stir. As you stir the hot water begins to give off its heat to the cold water, losing some of its heat, while the cold water absorbs some of the heat of the hot water. As a result, all the water in the bowl lowers its temperature compared to the temperature of the water in the bowl at the beginning, before adding cold water.
This process is called convection. Convection is the transfer of heat in fluids – liquids and gases.

Convection is also observed when we turn on the air conditioner to heat the room we are in. It begins to blow warm air, gradually warming the entire space in the room. Why? Because the warm air molecules transfer part of their energy to the air molecules in the room, raising their temperature accordingly.
Everything we have described so far is an example of artificial convection.
There is natural convection, in the nature around us. It is especially important for shaping the weather outside.
Have you noticed in the summertime, when the sun is strong, everything around is heated – sand, earth, asphalt, pool water …. This is because the heat coming from the sun heats the air molecules, transferring some of its energy to other molecules and increasing the temperature of the environment and all objects in it.
What happens with natural convection?
Warm air/gases always rise, as do most warm liquids. Why? Because the molecules in hot air and hot liquids are more active. They have higher energy. They need more space to move and take up more space. Therefore, they have fewer molecules for a certain volume of space (their density is lower). Hot air and hot water (with temperature > 4C) are less dense than cold air and cold water. This is a very important feature of natural convection.

Have you noticed in the summertime that it is always windy on the beach or the dam? This is due to convection. But how does this wind come about?
The land (coast), which is heated by the sun, transfer its heat to the air above it and heats it. When this air heated up, it rises. The air over the water has a lower temperature because the water is cooler than the land. (Water heats up more slowly than the land). Therefore, when the heated air above the land rises, the colder air that was above the water, invades in its place to fill the empty space, which leaves behind the warm air. This phenomenon is called sea breeze (onshore breeze).
All things that heat up faster and cool down faster. At the night the land cools faster than the water in the dam or the sea. Therefore, the air rises above the sea, and the air that was above the land invades the sea and takes its place. This phenomenon is called the land breeze.
This happens every day – in every cycle of the day and night.