| 摘要 |
An EGR cooler is provided which is satisfactorily applicable to a diesel engine with no substantial lowering in performance. With respect to the EGR cooler which is provided with tubes 3 and a shell 1 enclosing the tubes 3, cooling water 9 being supplied to and discharged from the shell 1, exhaust gas 10 being guided from a diesel engine into the tubes 3 to be heat exchanged with the cooling water 9, an inner periphery of each of the tubes 3 is formed with three streaks of spiral protrusions 12, 13 and 14 running without crossing and with phases peripherally shifted to each other, a pitch P ratio (P/D) of each of the spiral protrusions 12, 13 and 14 to an inner diameter D of each of the tubes 3 being 2.0-4.0, a ridge height H ratio (H/D) of each of the spiral protrusions 12, 13 and 14 to the inner diameter D of each of the tubes 3 being 0.1-0.2. |
