Underground heat exchanger and air conditioning system including the same

Abstract

An outer pipe ( 11 ), which is buried under the ground, is provided, and a heat transfer pipe ( 12 ), in which heat exchange fluid flows, is inserted into the outer pipe ( 11 ). A heat medium ( 13 ) is sealed in the outer pipe ( 11 ). At least a part of the heat transfer pipe ( 12 ) is formed by a flat body ( 12 e , . . . ) that is formed by a flat pipe ( 12 e, 14 ) or a composite pipe ( 15 ) in which a plurality of pipes ( 15 a ) are arranged in a flat shape. A flat side of the flat body ( 12 e , . . . ) contacts an inner peripheral surface of the outer pipe ( 11 ).

1 . An underground heat exchanger, comprising:
 an outer pipe ( 11 ) that is buried under a ground;   a heat-transfer pipe ( 12 ) which is inserted into the outer pipe ( 11 ), and in which heat exchange fluid flows; and   a heat medium ( 13 ) that is sealed in the outer pipe ( 11 ), where   the underground heat exchanger exchanges heat with soil by using a change in phase of the heat medium ( 13 ), wherein   at least a part of the heat-transfer pipe ( 12 ) is formed by a flat body ( 12   e , . . . ) that is foamed by a flat pipe ( 12   e ,  14 ) or a composite pipe ( 15 ) in which a plurality of pipes ( 15   a ) are arranged in a flat shape, and   a flat side of the flat body ( 12   e , . . . ) contacts an inner peripheral surface of the outer pipe ( 11 ).   
     
     
         2 . The underground heat exchanger of  claim 1 , wherein
 the heat-transfer pipe ( 12 ) is formed so as to extend from a top of the outer pipe ( 11 ) and to be bent at a bottom of the outer pipe ( 11 ) to return to the top.   
     
     
         3 . The underground heat exchanger of  claim 1 , wherein
 the heat-transfer pipe ( 12 ) includes a first main body portion ( 12   d ) extending from a top to a bottom of the outer pipe ( 11 ), and a second main body portion ( 12   e ) extending from the bottom to the top of the outer pipe ( 11 ), and   at least one of the first and second main body portions ( 12   d ,  12   e ) is formed in a helical shape, and a portion having the helical shape is the flat body ( 12   e , . . . ).   
     
     
         4 . The underground heat exchanger of  claim 3 , wherein
 a plurality of grooves ( 12   f ), which extend in a direction of gravity in an installed state, are formed in an outer peripheral surface of the heat-transfer pipe ( 12 ).   
     
     
         5 . The underground heat exchanger of  claim 1 , wherein
 a groove ( 11   a ) extending in a circumferential direction of the outer pipe ( 11 ) is formed in the inner peripheral surface of the outer pipe ( 11 ).   
     
     
         6 . The underground heat exchanger of  claim 5 , wherein
 the groove ( 11   a ) of the outer pipe ( 11 ) is formed so as to extend in a horizontal direction in an installed state.   
     
     
         7 . An air conditioning system, comprising:
 a refrigerant circuit ( 2 ) including the underground heat exchanger ( 10 ) of  claim 1 , a utilization-side heat exchanger ( 5 ), a compression mechanism ( 3 ), an expansion mechanism ( 6 ), and a flow path switching portion ( 4 ) that switches a direction in which a refrigerant as the heat exchange fluid flows, wherein   the air conditioning system is configured to be capable of switching between a heating operation and a cooling operation by switching the direction in which the refrigerant flows in the refrigerant circuit ( 2 ) by the flow path switching portion ( 4 ).