block heater vs heat sink

block heater

noun
  • An electric heater that heats the engine of a car to ease starting in cold weather. 

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 block heater and heat sink occurred in a corpus of books? (source: Google Ngram Viewer )