Condensate Lines and Flash Steam

Flash steam produced by hot water and condensate

In general condensate lines are designed to handle start-up conditions where huge amounts of steam condensate in cold pipes and heating equipment. As a rule of thumb the maximum condensate load is often twice the maximum steam load during operation.

Within certain circumstances, especially in high pressure steam systems with heavy load heat exchangers, the generated flash steam may be the limitation of the condensate lines.

The flash steam generated can be expressed as

w_% = 100 (h_il - h_fl) / h_fe         (1)

where

w_% = ratio of flash steam generated (%)

h_il = initial liquid enthalpy (kJ/kg)

h_fl = final liquid enthalpy (kJ/kg)

h_fe = enthalpy of evaporation (kJ/kg)

The condensate load can be expressed as

w_c = w_s w_% / 100         (2)

where

w_c = condensate load (kg/h)

w_s = steam flow rate (kg/h)

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