Page 36 - Digital Book Bilingual Perpindahan Kalor

Convection

Convection is a process of heat transfer

that is accompanied by the transfer of
mass or the movement of the particles of

the medium. Convection occurs only in
substances whose atoms or molecules can

move freely. Such substances are fluids,
which include liquids and gases.

For example, when water in a pan is heated, the part of the water that

receives heat first is the portion in contact with the pan, especially at
the bottom. However, over time the entire water becomes hot due to the

flow of water molecules from the bottom to the top. This flow pushes
the cooler water at the top downward, causing it to be heated as well.

There are two types of convection :

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The equation that relates several quantities affecting the rate of heat
transfer by convection is shown below:

where:
H = rate of heat transfer (J s⁻¹)

h = convective heat transfer coefficient (J s⁻¹ m⁻² K⁻¹)
A = surface area (m²)
ΔT = temperature difference (K)

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