Flash Condenate Lines

Overview

Engineering reference data for Flash Condenate Lines in miscellaneous.

Key Formulas

Unit Conversion

$y = x \cdot k$

Multiply by conversion factor.

Linear Interpolation

$y = y_1 + \frac{(x - x_1)(y_2 - y_1)}{x_2 - x_1}$

Estimate between two known points.

Percentage

$p = \frac{\text{part}}{\text{whole}} \times 100\%$

Part as fraction of whole.

Variables

Symbol	Description	Unit
$x$	Input value	—
$y$	Output value	—
$k$	Conversion factor	—

Application Notes

For condensate line design, account for startup conditions where cold pipes and equipment generate peak condensate. A common engineering rule is that the maximum startup condensate load is approximately twice the maximum operational steam load.

In high-pressure systems with heavy heat exchanger loads, the limiting factor may be the volume of flash steam rather than the liquid condensate itself. Flash steam generation must be calculated to properly size vent lines and condensate receivers.

Worked Example

Consider a heat exchanger operating at 10 bar gauge upstream of the steam trap. The condensate system is vented to atmosphere (0 bar gauge).

Given Steam Properties:

• Initial liquid enthalpy (hil): 781 kJ/kg (at 11 bar abs)
• Final liquid enthalpy (hfl): 418 kJ/kg (at 1 bar abs)
• Enthalpy of evaporation (hfe): 2258 kJ/kg (at 1 bar abs)
• Steam flow rate (ws): 200 kg/h

Calculation:

1. Flash Steam Generated (w%): $w\% = 100 \times \frac{(h_{il} - h_{fl})}{h_{fe}} = 100 \times \frac{(781 - 418)}{2258} \approx 16.1\%$
2. Condensate Load (wc): $w_c = w_s \times \frac{w\%}{100} = 200 \times \frac{16.1}{100} = 32 \text{ kg/h}$

This means 32 kg/h of liquid condensate and a significant volume of flash steam must be handled by the downstream piping and receiver.

References

• Original Source