GEOTHERMAL EXCHANGER

PURPOSE: A geothermal exchanger is provided to prevent damage to heat exchanging pipes generated when the heat exchanging pipes inserted into a borehole are entangled as an internal pipe is inserted inside an external pipe. CONSTITUTION: A geothermal exchanger includes a hollow external pipe (10) and a hollow internal pipe (20). The external pipe includes a first inner hole of a predetermined diameter formed in the longitudinal direction and includes an opened upper end portion and a closed end portion. The external pipe is longitudinally inserted into a borehole (70). The internal pipe includes a second inner hole (21) of a predetermined diameter formed in the longitudinal direction and includes one or more rotary protrusion units (22) which are spirally protruding from a predetermined portion on the surface. A heat exchange passage (30) is formed between the inner surface of the first inner hole and the internal pipe. The internal pipe is longitudinally inserted into the first inner hole.