Power Plant · Flow
Desuperheater Spray-Water Flow
Spray-water flow needed to cool superheated steam to a target outlet temperature, from an exact mass-and-energy balance using IAPWS-IF97 enthalpies of steam and compressed spray water.
Verified against published standard
Steam and spray
Leave empty to use the inlet pressure.
Enter the inputs and press Calculate.
About This Calculation
A desuperheater cools superheated steam by injecting feedwater. The spray flow follows from mass and energy balance across the mixing section, so a precise answer needs real steam and compressed-water enthalpies rather than a constant specific heat. The result also shows the remaining superheat margin above saturation.
Frequently Asked Questions
Why must outlet superheat stay above saturation?
If spray does not fully evaporate, water droplets can erode and thermally shock downstream piping and valves; practice is to keep roughly 10–15 °C margin, but follow the manufacturer.
Does spray pressure matter?
Slightly: spray enthalpy is that of compressed liquid at its own pressure and temperature, and it must also exceed the steam pressure to inject.
Why must the spray water pressure exceed the steam pressure?
Water can only be injected if its pressure is above that of the steam. Feedwater taken from the boiler feed pump discharge is normally at a much higher pressure, which is why the spray pressure input is separate from the steam pressure.
Does the calculation include pressure drop across the desuperheater?
It uses the outlet pressure you give, or the inlet pressure if you leave it blank. For a typical spray-type desuperheater the pressure drop is small and has little effect on the enthalpy balance.