Steam properties (screening): saturation
properties are obtained from a small embedded table and linearly
interpolated vs absolute pressure; superheat correction uses
h β hg + Cp(TβTsat)
with Cpβ2.08 kJ/kgΒ·K.
Water enthalpy (screening):hBFW β Cp,wΒ·T
with
Cp,wβ4.186 kJ/kgΒ·K
(pressure effect neglected).
For final sizing, use IAPWS-IF97 steam tables / vendor property
package and include nozzle atomization, evaporation length, and
minimum straight run requirements.
Assumptions / Notes
Designed for desuperheating only (outlet
temperature must be β₯ saturation temperature at steam line
pressure).
BFW pressure should exceed steam pressure by a suitable margin
(often β₯ 2 kg/cmΒ²G) to ensure stable injection and good
atomization (confirm with vendor).
Typical vendor screening guideline for water/steam ratio:
2β15 wt%. Low ratio may cause poor
mixing/temperature control; high ratio may indicate condensing
duty or unsuitable set-point.
Heat losses to surroundings, kinetic energy changes, and
pressure drop across the desuperheater are not included in the
balance.
If the target outlet temperature is close to saturation or
below, a separate
attemperation + partial condensation analysis
is required.
Standards / References
IAPWS-IF97 / standard steam tables for water
and steam properties (recommended for design).