Heat exchanger

A heat exchanger, comprising:

• a hollow pillar shaped honeycomb structure having an inner peripheral wall, an outer peripheral wall and partition walls each disposed between the inner peripheral wall and the 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 cylindrical member fitted to a surface of the outer peripheral wall of the pillar shaped honeycomb structure;
• a second cylindrical member fitted to a surface of the inner peripheral wall of the pillar shaped honeycomb structure;
• a cylindrical guide member having a portion, the portion being disposed on a radially inner side of the second cylindrical member with a distance so as to form the flow path for the first fluid;
• an upstream cylindrical member connecting an upstream end of the first cylindrical member to an upstream side of the guide member;
• and
• a downstream cylindrical member connected to a downstream end of the first cylindrical member,
• wherein the guide member comprises an inclined portion that inclines to its downstream side;
• and
• wherein a communication port for directing the first fluid flowing on an inner peripheral side of the guide member to a space between an inner peripheral side of the second cylindrical member and an outer peripheral side of the guide member is provided between a tip of the inclined portion of the guide member and the second cylindrical member or at the inclined portion of the guide member.