Heat exchanger configured to accelerate discharge of liquid refrigerant from lowest heat exchange section

A heat exchanger comprising:

• a plurality of flat tubes;
• a first header-collecting pipe connected to an end of each of the flat tubes;
• a second header-collecting pipe connected to the other end of each of the flat tubes;
• and a plurality of fins joined to the flat tubes, the heat exchanger provided in a refrigerant circuit which is configured to perform a refrigerating cycle, and causing a refrigerant to exchange heat with air, wherein
• the first header-collecting pipe and the second header-collecting pipe are in an upright position,
• a plurality of heat exchange sections are arranged one above the other, each heat exchange section being constituted by adjacent flat tubes,
• the first header-collecting pipe includes therein one communicating space which communicates with the flat tubes of all of the heat exchange sections,
• the second header-collecting pipe includes therein subspaces, each of the subspaces fluidly connected to a different one of the heat exchange sections, each of the subspaces communicating with the flat tubes constituting the corresponding one of the heat exchange sections,
• the heat exchanger further includes a discharge accelerator which accelerates discharge of the refrigerant in a liquid state from a lower portion of the heat exchange section which is the lowermost heat exchange section during defrosting in which the refrigerant in a high-pressure gas state is introduced from the one communicating space to the flat tubes in order to melt frost having formed on the fins, and
• the discharge accelerator is formed by an auxiliary gas pipe which, along with a gas connection pipe, is external to said first and second header-collecting pipes,
• the auxiliary gas pipe is configured to introduce the gas refrigerant into the first header-collecting pipe at a bottom portion of the one communicating space in proximity to the flat tubes constituting the lower portion of the lowermost heat exchange section during the defrosting,
• the auxiliary gas pipe has an end connected to a portion of the first header-collecting pipe that is located below an end of the gas connection pipe connected to the first header-collecting pipe,
• the end of the gas connection pipe and the end of the auxiliary gas pipe that are connected to the first header-collecting pipe open in the one communicating space communicating with the flat tubes of all of the heat exchange sections,
• a plurality of auxiliary heat exchange sections are arranged, each of the auxiliary heat exchange sections corresponding to a different one of the heat exchange sections, each of the auxiliary heat exchange sections being constituted by adjacent flat tubes,
• the flat tubes constituting each of the auxiliary heat exchange sections is smaller in number than the flat tubes constituting each of the heat exchange sections,
• the auxiliary heat exchange sections are each in series connection to a corresponding one of the heat exchange sections,
• all of the auxiliary heat exchange sections are located below all of the heat exchange sections,
• the direction of the refrigerant flowing through the auxiliary heat exchange sections is opposite the direction of the refrigerant flowing through the flat tubes constituting the heat exchange sections, and
• all of the flat tubes in the heat exchanger belong to either one of the plurality of heat exchange sections or one of the plurality of auxiliary heat exchange sections.