I think he correct term to fill in the blank would be heat sink. The CPU might be covered by a heat sink, which dissipates the heat generated by the chip. A heat sink is any device or a substance that absorbs heat generated or from the heat reservoir. For a device, it would be one that has a fan or a peltier device in order to keep a system having a cool temperature. This is done to protect a system from any damage due to excess heat. This protect any device from overheating. A CPU surely have this device because it should be kept cool to protect the chips inside it.
