Following are the factors in coils that will enhance or affect the duty of the exchanger. The following are given for some types of fins.
FIN TYPOLOGY CORRUGATION FACTOR FRICTION FACTOR
| FIN TYPOLOGY | CORRUGATION FACTOR | FRICTION FACTOR |
| SMOOTH | 1.0 | 1.0 |
| PYRAMID | 0.95 | 0.95 |
| CORRUGATED | 1.15 | 1.25 |
| WINDOWED | 1.35 | 1.45 |
| LOUVERED | 1.45 | 1.55 |
The following factors are given for some types of tubes.
| TUBE TYPOLOGY | COEF.FACTOR TUBE SIDE | CORR. FACTOR FRICTION FACTOR |
| SMOOTH | 1.0 | 1.0 |
| MICROFIN | 1.1 | 1.2 |
| CORRUGATED | 1.25 | 1.35 |
| HERRING BONE | 1.4 | 1.5 |
Another important factor is the “security factor” which is used to set the surface you want to use.
For example let’s say we want to use the 80% of the surface area. In such case, we would write it as 0,8 because 1 would be equal to 100% of the surface.