Indirect heating of process air through a heat-transfer surface.
Steam, hot water or thermal oil flows inside the exchanger tubes while process air passes across the finned surfaces. Heat is transferred indirectly to the air before it enters the drying system.

Technical Parameter Table 1
| Item | Stainless Steel | Carbon Steel | Aluminum |
| Tube Specification | Φ18×2 | Φ19×2 | — |
| Fin Outside Diameter (mm) | Φ38 | Φ39 | — |
| Fin Thickness (mm) | 0.24 | — | 0.4 |
| Heat-Transfer Area Coefficient | 0.64 | 0.64 | 0.64 |
Technical Parameter Table 2
| Item | Specification |
| Tube Specification | Φ63×3 |
| Fin Outside Diameter (mm) | Φ103 |
| Fin Thickness (mm) | 0.5 |
| Heat-Transfer Area Coefficient | 1.5 |