| 摘要 |
<p>The invention concerns a heating unit for oil or gas boiler, wherein said heating unit (3) comprises a case (5) lined internally, in a rear zone, with a shell (6), ring-shaped transverse fins (35) are provided between the shell (6) and the case (5) for defining transverse annular channels (36) wherein the fuel gases follow in parallel a transverse path before emerging from the heating unit (3), thereby improving heat exchange between the fuel gases and the water (22) they are meant to heat.</p> |
