Heat exchange unit for refrigerant circuit

The present invention relates to a heat exchange unit (1) for making the flow passage of a refrigerant circuit in an air conditioning system of a vehicle bidirectional. The air-conditioning system is formed so as to perform an operation combining a refrigerator mode and a heat pump mode, and the heat exchange unit (1) is formed to have multiple passes, wherein the flow direction of the refrigerant changes depending on operational mode. A first heat exchange unit (1) formed of multiple passes includes header pipes (2, 3), flow paths respectively allocated to the passes, and a means for dividing the internal space of at least one of the header pipes (2, 3) into independent regions. The first path of the heat exchange unit (1) is formed with a larger flow cross section and a larger heat exchange surface than the last pass. A second heat exchange unit (1) has a refrigerant passage opening (4) formed with a connection block (28) for connecting to a refrigerant line (27), wherein a short-circuit line (29) is arranged between the header pipe (2) and the connection block (28) as an additional fluid connection part with the refrigerant passage opening (4). Also, the present invention relates to a device for dividing the internal space of the header pipes (2, 3) of the heat exchange unit (1). Arranged inside the header pipes (2, 3) is at least one moveable separating element (13, 13'), which is formed depending on a principle of differential pressure, and opens or closes the opening according to its alignment and the pressure difference applied to it in the header pipes (2, 3).