Heat Transfer

There are three distinct modes by which heat physically moves. Conduction is direct transfer through matter in contact, from hot to cold, without bulk motion of the material -- quantified by thermal conductivity $K$, defined through the steady-state flow rate $\dfrac{Q}{t}=\dfrac{KA\,\Delta T}{L}$ across a slab of area $A$, thickness $L$, temperature difference $\Delta T$ (Figure 8.11; SI unit W m⁻¹K⁻¹); Table 8.3 shows diamond and silver conduct extremely well while air and cork are extremely poor conductors, which is why cookware uses metals like aluminium and copper. Convection is heat transfer by the actual bulk movement of fluid molecules, driven by density differences created when part of a fluid is heated (illustrated by the sea-breeze/land-breeze cycle, arising from land's lower specific heat than water). Radiation is heat transfer purely by electromagnetic waves, requiring no medium at all …