Heat Sinks, or HS's, are specialized radiators designed to disperse the excess heat caused by Weaponry, Equipment, and Activity. Each unit typically has several Heat Sinks when necessary, allowing it to disperse any heat generated more quickly. Note that heat sinks do not increase the amount of heat your unit can take, they simply increase the speed at which heat is removed.
There are two kinds of heat sinks: single heat sinks (HS, sometimes SHS) and double heat sinks (DHS). A double heat sink dissipates heat twice as fast as a single heat sink while consuming more space.
Single heat sinks are usually found on certain Inner Sphere 'Mechs. All vehicles in MWLL use single heat sinks as well. Otherwise, all other assets, such as Clan 'Mechs, utilize only double heat sinks.
Heat Sinks are most effective when the unit is Powered Down; also, unit movement speed can affect the rate at which heat is dispersed: the faster its moving, the slower heat dispersion is.
Overheating can cause damage to heat sinks. Damaged heat sinks drastically reduce an asset's ability to shed heat. Continued overheating may destroy a damaged heat sink. While damaged heat sinks can be repaired, destroyed heat sinks cannot.
Heat sinks operate by collecting heat with coolant distributed to heat sources (weapons, engines, myomers, electronics, etc.) and delivering that to a radiator. Because a BattleMech may operate in environments considerably hotter than the interior of the 'Mech, the system includes a heat pump to "force" the heat out of the 'Mech by elevating the temperature of the coolant in some reversible fashion. (The vapor-compression heat pump of home air conditioners is a typical example, but 31st Century BattleMechs may make use of more exotic heat pumps.) Double Heat Sinks, often abbreviated DHS and colloquially also referred to as Freezers throughout the Inner Sphere after their NAIS codename, operate in much the same way and for the same purpose as standard heat sinks. The difference is that a double heat sink offers twice the heat dissipation capacity of a standard heat sink, for the same mass (one ton). Double Heat Sink technology was originally developed during the Star League Era, but was lost during the Succession Wars. However, thanks to the discovery of the Helm Memory Core twenty-two years before the Clan Invasion, the Inner Sphere managed to recreate the DHS - it took up three times as many slots as a Single Heat Sink. The Clans, having never lost the technology, advanced it to the point where it would only take up two slots.