Flash Steam Generation - SI-units
When condensate leaves the steam traps - flash steam is generated. Amount of flash steam generated at different pressures - kN/m2.
The amount of flash steam generated depend on the steam pressure - the pressure in the condensate before it leaves the condensate trap - and the condensate pressure after the trap - the pressure in the condensate return pipe lines.
The table below indicates the ratio of flash steam generated at different pressures before and after the condensate trap.
| Percent Flash Steam of Condensate (%) | |||||||
|---|---|---|---|---|---|---|---|
| Absolute Pressure before the condensate trap (kN/m2) | Temperature (oC) | Absolute Pressure after the condensate trap (kN/m2) | |||||
| 400 | 260 | 170 | 101.33 | 65 | 35 | ||
| 1500 | 198.3 | 11.3 | 14.0 | 16.4 | 18.9 | 20.4 | 23.2 |
| 1150 | 186.0 | 8.7 | 11.5 | 13.9 | 16.5 | 18.4 | 20.9 |
| 800 | 170.4 | 5.5 | 8.2 | 10.8 | 13.4 | 15.4 | 17.9 |
| 650 | 162.4 | 3.7 | 6.5 | 9.1 | 11.8 | 13.7 | 16.3 |
| 500 | 151.8 | 1.6 | 4.6 | 7.1 | 9.8 | 11.8 | 14.4 |
| 400 | 143.6 | 3.0 | 5.5 | 8.3 | 10.3 | 12.9 | |
| 260 | 128.7 | 2.6 | 5.4 | 7.5 | 10.2 | ||
| 170 | 115.2 | 2.8 | 5.0 | 7.7 | |||
| 101.33 | 100 | 2.2 | 4.9 | ||||
Example - Generated Flash Steam
A condensate system is vented to the surroundings and the pressure in the condensate system after the condensate traps is 101.33 kN/m2. The absolute steam pressure before the condensate trap is 1150 kN/m2.
According the table above 16.5% of the condensate will evaporate as flash steam after the trap.
Note! Without any flash recovery system the energy in the flash steam will be lost to the surroundings.