central heating vs heat sink

central heating

noun
  • Any of various heating systems in which a central source of heat is used to distribute heat (and sometimes hot water) throughout a building in a controlled manner. 

heat sink

noun
  • A place toward which the heat moves in a system. 

  • An object, system or environment that absorbs and dissipates heat from objects in thermal contact (either direct or radiant) with it. 

  • A material capable of absorbing heat. 

How often have the words central heating and heat sink occurred in a corpus of books? (source: Google Ngram Viewer )