Underground heat exchanger and air conditioning system including the same

Abstract

A heat-transfer pipe ( 12 ) is formed so as to extend from a top portion of an outer pipe ( 11 ) and to be bent at a bottom portion of the outer pipe ( 11 ) to return to the top portion, and is arranged such that at least a portion thereof contacts an inner circumferential surface of the outer pipe ( 11 ). The heat-transfer pipe ( 12 ) is configured to allow fluid to be heat-exchanged to flow thereinside in opposite directions in heating operation and cooling operation.

1 . An underground heat exchanger comprising:
 an outer pipe vertically buried under the ground;   a heat-transfer pipe, in which fluid to be heat-exchanged flows, inserted inside the outer pipe; and   a heat medium sealed inside the outer pipe,   wherein a change in phase of the heat medium is used to perform heat exchange with soil, and   the heat-transfer pipe is formed so as to extend from a top portion of the outer pipe and to be bent at a bottom portion of the outer pipe to return to the top portion, and is arranged such that at least a portion thereof positioned inside the outer pipe contacts an inner circumferential surface of the outer pipe to allow the fluid to be heat-exchanged to flow thereinside in opposite directions in heating operation and cooling operation.   
     
     
         2 . The underground heat exchanger of  claim 1 , wherein the heat-transfer pipe is formed such that at least one of a first body portion provided from the top portion to the bottom portion of the outer pipe and a second body portion provided from the bottom portion to the top portion of the outer pipe is in a helical shape, and the helical portion is arranged to contact the inner circumferential surface of the outer pipe. 
     
     
         3 . The underground heat exchanger of  claim 1 , wherein the inner circumferential surface of the outer pipe includes grooves extending in a circumferential direction of the outer pipe. 
     
     
         4 . The underground heat exchanger of  claim 3 , wherein an outer circumferential surface of the heat-transfer pipe includes grooves extending in a circumferential direction of the heat-transfer pipe. 
     
     
         5 . The underground heat exchanger of  claim 3 ,
 wherein the outer pipe is buried under the ground such that a longitudinal direction thereof is in a vertical direction, and   the grooves are formed so as to extend in a horizontal direction.   
     
     
         6 . An air conditioning system, comprising:
 a refrigerant circuit including   the underground heat exchanger of  claim 1 ;   a utilization side heat exchanger;   a compression mechanism;   an expansion mechanism; and   a flow path switching unit for switching a flow direction of refrigerant serving as the fluid to be heat-exchanged,   wherein a switch in the flow direction of the refrigerant inside the refrigerant circuit by the flow path switching unit can switch between heating operation and cooling operation.