The present invention relates to a method and a means for applying a heat exchanger in a drill hole (2) in rock, loose soils or the like for the purpose of heat recovery or storage, achieving a more efficient heat transfer between the defining surface (4) of the drill hole and a heating medium contained in the heat exchanger, wherein at least one heat-exchanging element (1) is lowered into the drill hole (2) and expanded in substantially radial direction so that the heat-exchanging element (1) is thus caused at least partially to be substantially in contact with the defining surface (4) of the drill hole.