Heat exchanger

A heat exchanger, comprising:

• a hollow heat recovery member having an inner peripheral surface and an outer peripheral surface in an axial direction, and an inflow end face and an outflow end face for a first fluid in a direction perpendicular to the axial direction;
• a first outer cylindrical member having an inflow port and an outflow port for the first fluid, the first outer cylindrical member being fitted to the outer peripheral surface of the heat recovery member;
• a first inner cylindrical member having an inflow port and an outflow port for the first fluid, the first inner cylindrical member being fitted to the inner peripheral surface of the heat recovery member, wherein at least one through hole for introducing the first fluid to the inflow end face of the heat recovery member is provided on an upstream side of the inflow end face of the heat recovery member, based on a flow direction of the first fluid as a reference;
• and
• a second inner cylindrical member having an inflow port and an outflow port for the first fluid, the outflow port being located on a radially inner side of the first inner cylindrical member and on an upstream side of a downstream end portion of the through hole of the first inner cylindrical member, based on the flow direction of the first fluid as a reference;
• wherein an end portion of the first inner cylindrical member on the inflow port side is connected to the first outer cylindrical member and/or the second inner cylindrical member,
• wherein a ratio L4/L3 of a flow direction length L4 from the outflow port of the second inner cylindrical member to a position corresponding to an upstream end portion of a space region between the first outer cylindrical member and the first inner cylindrical member formed on an upstream side of the inflow end face of the heat recovery member, to a flow direction length L3 of the space region is 0.05 to 0.95, based on the flow direction of the first fluid as a reference.