Heat exchanger and air-conditioning apparatus

1. A heat exchanger, in which refrigerant causing disproportionation is used, comprising:

a main heat exchange unit including a plurality of first heat transfer pipes arranged side by side;

a sub-heat exchange unit located below the main heat exchange unit and including a plurality of second heat transfer pipes arranged side by side; and

a relay unit including a plurality of relay passages connecting the plurality of first heat transfer pipes and the plurality of second heat transfer pipes,

each of the plurality of relay passages having one inlet connected to a corresponding one of the plurality of second heat transfer pipes, and a plurality of outlets each connected to a corresponding one of the plurality of first heat transfer pipes,

each of the plurality of relay passages distributing the refrigerant flowing from the one inlet, without merging streams of the refrigerant together, and causing the refrigerant to flow out of the plurality of outlets.

2. The heat exchanger of claim 1 , wherein the relay unit is configured to cause a smaller pressure loss of the refrigerant passing through the relay unit than a pressure loss of the refrigerant passing through the sub-heat exchange unit.

3. The heat exchanger of claim 1 , wherein the relay unit is configured to cause a larger pressure loss of the refrigerant passing through the relay unit than a pressure loss of the refrigerant passing through the main heat exchange unit.

4. The heat exchanger of claim 1 , wherein each of the plurality of relay passages has a passage cross-sectional area equal to or more than a passage cross-sectional area of the corresponding one of the plurality of second heat transfer pipes connected to the one inlet, and equal to or less than a total of passage cross-sectional areas of the plurality of first heat transfer pipes connected to the plurality of outlets.

5. A heat exchanger, in which refrigerant causing disproportionation is used, comprising:

a main heat exchange unit including a plurality of first heat transfer pipes arranged side by side;

a sub-heat exchange unit including a plurality of second heat transfer pipes arranged side by side; and

a relay unit including a plurality of relay passages connecting the plurality of first heat transfer pipes and the plurality of second heat transfer pipes,

each of the plurality of relay passages having one inlet connected to a corresponding one of the plurality of second heat transfer pipes, and a plurality of outlets each connected to a corresponding one of the plurality of first heat transfer pipes,

each of the plurality of relay passages distributing the refrigerant flowing from the one inlet, without merging streams of the refrigerant together, and causing the refrigerant to flow out of the plurality of outlets,

a relationship expressed by 4.3×10 6 ≤L/(d 5 ×N 2 )≤3.0×10 10 being satisfied, where L [m] represents an average passage length of the plurality of relay passages, d [m] represents an average hydraulic equivalent diameter of the plurality of relay passages, and N represents a number of the plurality of relay passages.

6. A heat exchanger, in which refrigerant causing disproportionation is used, comprising:

a main heat exchange unit including a plurality of first heat transfer pipes arranged side by side;

a sub-heat exchange unit including a plurality of second heat transfer pipes arranged side by side; and

a relay unit including a plurality of relay passages connecting the plurality of first heat transfer pipes and the plurality of second heat transfer pipes,

each of the plurality of relay passages having one inlet connected to a corresponding one of the plurality of second heat transfer pipes, and a plurality of outlets each connected to a corresponding one of the plurality of first heat transfer pipes,

each of the plurality of relay passages distributing the refrigerant flowing from the one inlet, without merging streams of the refrigerant together, and causing the refrigerant to flow out of the plurality of outlets,

the main heat exchange unit including a plurality of third heat transfer pipes arranged on a leeward side of the plurality of first heat transfer pipes,

the sub-heat exchange unit including a plurality of fourth heat transfer pipes arranged on a windward side of the plurality of second heat transfer pipes,

each of the plurality of first heat transfer pipes having one end communicating to one of the plurality of outlets, and another end communicating to one of the plurality of third heat transfer pipes,

each of the plurality of second heat transfer pipes having one end communicating to one of the plurality of fourth heat transfer pipes, and another end communicating to the one inlet.

7. The heat exchanger of claim 1 , wherein the refrigerant causing the disproportionation comprises R1123 refrigerant, or a mixed refrigerant containing R1123 refrigerant.

8. An air-conditioning apparatus comprising the heat exchanger of claim 1 ,

wherein, when the heat exchanger acts as an evaporator, each of the plurality of relay passages causes the refrigerant flowing from the one inlet to flow out of the plurality of outlets, and when the heat exchanger acts as a condenser, each of the plurality of relay passages causes the refrigerant flowing from the plurality of outlets to flow out of the one inlet.