Heat exchanger

A heat exchanger, comprising:

• a hollow pillar shaped honeycomb structure having partition walls, an inner peripheral wall, and an outer peripheral wall, the partition walls defining a plurality of cells to form flow paths for a first fluid, each of the cells extending from an inflow end face to an outflow end face;
• a first outer cylinder arranged to be in contact with the outer peripheral wall of the hollow pillar shaped honeycomb structure;
• a first inner cylinder having an inflow port and an outflow port for the first fluid, the first inner cylinder being arranged such that a part of an outer peripheral surface of the first inner cylinder is in contact with the inner peripheral wall of the hollow pillar shaped honeycomb structure;
• a second inner cylinder having an inflow port and an outflow port for the first fluid, the outflow port being arranged so as to be spaced on a radially inner side of the inner peripheral wall of the hollow pillar shaped honeycomb structure;
• and
• an on-off valve arranged on a side of the outflow port of the first inner cylinder,
• wherein the inflow port of the first inner cylinder is arranged at a predetermined position that is downstream from the inflow end face so as to be closer to the outflow end face than the inflow end face in an axial direction of the hollow pillar shaped honeycomb structure, and the inflow end face of the first inner cylinder is fixed to the inner peripheral wall of the hollow pillar shaped honeycomb structure at the predetermined position;
• wherein the outflow port of the second inner cylinder is positioned closer to the outflow end face than the inflow end face in the axial direction of the hollow pillar shaped honeycomb structure;
• and
• wherein the outflow port of the second inner cylinder has a diameter and the inflow port of the first inner cylinder has a diameter such that the diameter of the outflow port of the second inner cylinder is smaller than the diameter of the inflow port of the first inner cylinder.