Abstract: A plurality of heat-exchange tubes 30 each including a flat pipe including a groove 36 and wavelike depression-and-projection portions 33, 34 are arranged in parallel in such a manner that each of respective longitudinal directions thereof is a vertical direction, and a heat exchange medium is made to flow from an inlet 31 at each lower portion to an outlet 32 at each upper portion. Guide walls 43, 44 are provided in a shell 40, and exhaust gas is made to flow an inlet 41 at an upper portion to an outlet 42 at a lower portion, thereby making the exhaust gas meander in flow paths 46a to 46d and a space between the plurality of heat-exchange tubes 30.

Abstract: A plurality of flat tubes formed as a tube having notches by linearly cutting upper and lower parts from a hollow flat circular doughnut shape are stacked to structure a tube laminate. It is attached to a case so that a notch aligns with the notch and faces upward by an exhaust inflow end plate and that a notch aligns with the notch and faces downward by an exhaust outflow end plate. A cutoff valve is provided at an exhaust outflow end of an exhaust communication tube passing through the center of the tube laminate by heat insulation. While an internal combustion engine is warming up, the cutoff valve is closed to cause the exhaust to flow in gaps of the respective flat tubes from upward to downward as a whole and also a heat exchange medium is caused to flow in the respective flat tubes from downward to upward as a whole to have heat exchanged between the exhaust and the heat exchange medium to recover the exhaust heat.

Abstract: A plurality of flat tubes formed as a tube having notches by linearly cutting upper and lower parts from a hollow flat circular doughnut shape are stacked to structure a tube laminate. It is attached to a case so that a notch aligns with the notch and faces upward by an exhaust inflow end plate and that a notch aligns with the notch and faces downward by an exhaust outflow end plate. A cutoff valve is provided at an exhaust outflow end of an exhaust communication tube passing through the center of the tube laminate by heat insulation. While an internal combustion engine is warming up, the cutoff valve is closed to cause the exhaust to flow in gaps of the respective flat tubes from upward to downward as a whole and also a heat exchange medium is caused to flow in the respective flat tubes from downward to upward as a whole to have heat exchanged between the exhaust and the heat exchange medium to recover the exhaust heat.