A device for converting a liquid into vapor includes an enclosure, a heating surface with a downward slope arranged in the enclosure, and a liquid inlet port connected to an upper portion of the heating surface so that a liquid introduced from the liquid inlet port flows on the heating surface. The device also includes a vapor outlet port formed through a wall of the enclosure. The heating surface includes a heat transfer pipe configured to allow the flowing of a heat transfer fluid to heat the heating surface, and a corner piece including a U-shaped cross-section with a semi-circular portion arranged around the heat transfer pipe and an upper portion forming an opening on the enclosure.