PURPOSE: To permit to maximize heat exchanging efficiency by a simple constitution by a method wherein a multitude of pipes, whose both ends are cut, is arranged so as to form a substantially truncated conical tubular shape and both ends of the group of pipes are fixed and positioned so as to be opened in a suction part and an exhaust part respectively.

CONSTITUTION: A multitude of pipes 2A is arranged so as to form a substantially truncated conical tubular shape as a whole in a condition that they are neighbored mutually and is fixed and held at position near both ends in the axial direction of the tube through partitioning plates 10, 10 to constitute a heat exchanging element 2. Short tubular bodies 3, 4 are arranged and fixed at both axial ends of a cylindrical case 1 having substantially the same diameter as the meximum diameter of the element 2 in the coaxial condition with the case 1, thereby forming suction and exhaust sections 3A, 3B, 4A, 4B which are defined into inner and outer sections respectively. The element 2 is fixed and supported in the case 1 under a condition that both ends of the group of pipes 2A are opened at the suction section 3A in one end of the cylindrical case 1 and at the exhaust section 4B in the other end of the cylindrical case 1.