Boiler Exhaust Velocity

Reference data and engineering information about boiler exhaust velocity for steam and condensate applications.

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Overview

Engineering reference data for Boiler Exhaust Velocity in steam condensate.

Key Formulas

Steam Quality

$x = \frac{m_v}{m_{total}}$

Mass fraction of vapor in two-phase mixture.

Enthalpy of Wet Steam

$h = h_f + x \cdot h_{fg}$

Specific enthalpy of wet steam.

Flash Steam

$m_{flash} = m_{liquid} \frac{h_f - h_{f2}}{h_{fg2}}$

Steam generated when condensate flashes to lower pressure.

Condensate Load

$m_c = \frac{Q}{h_{fg}}$

Condensate generated by heat transfer.

Variables

Symbol	Description	Unit
$x$	Steam quality	—
$h_f$	Enthalpy of saturated liquid	kJ/kg
$h_{fg}$	Latent heat of vaporization	kJ/kg
$h$	Specific enthalpy	kJ/kg
$Q$	Heat transfer rate	kW

References

Original Source

Recommended Boiler Exhaust Velocity Data

5 rows

Recommended boiler exhaust velocity based on configuration and operating load.
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Ducts at minimum load
Stack at minimum load
Boiler with one-step burner (on - off)
Boiler with two-step burner (high - low)
Boiler with modulating burner

Source: engineeringtoolbox.com

Practical Consideration

To prevent soot accumulation on heat transfer surfaces, the flue gas velocity should generally be maintained above 3.0 - 4.0 m/s (or 9.8 - 13 ft/s).

Source: engineeringtoolbox.com