There are two important concepts, required to understand the essentials of how air cooling works and why cooling mechanisms are designed the way they are. The two concepts are thermal conductivity and thermal capacity. The thermal conductivity is the measurement of the thermal resistance of a material, i.e. how well it transports thermal energy. Thermal capacity is actually the measurement of how much thermal energy a material can absorb. The thermal capacity doesnät really matter much when discussing cooling, it is only important when determining how much time it will take for a cooling flange to get hot. A higher thermal capacity enables the flange to last longer before getting hot.