We complete the technical notes for proper sizing of the DN of a valve with the following types of fluid: saturated steam, subsonic and sonic gases and vapors.

D) Saturated steam
with the following formula:

where:

  • G = flow rate in Kg / h
  • C = 1 + 0.0013 (t1 - t2)
  • t1 = saturated steam temperature @ P1 pressure
  • t2 = saturated steam temperature @ P2 pressure
  • P1 = upstream absolute pressure in kPa
  • P2 = downstream absolute pressure in kPa
  • DP = pressure drop in kPa (P1-P2)

E) Gas and vapors

For these fluids, we have to distinguish two flow regimes: subsonic and sonic.

Subsonic regime


where:

and when do not reach the critical pressure ratio

when the flow reaches the speed of sound.

Flow rate:

where:

  • Q = flow rate in Nm3 / h @ 0°C
  • r = density in kg / dm3 @ 0°C and atmospheric pressure
  • P2 = downstream absolute pressure in kPa
  • DP = pressure drop in KPa
  • T = absolute temperature upstream in °K

Mass flow:

where:

  • W = flow rate in kg / h
  • r = density in kg / dm3 @ 0°C and atmospheric pressure
  • P2 = downstream absolute pressure in kPa
  • DP = pressure drop in KPa
  • T1 = absolute temperature upstream in °K

Sonic regime

and reaching or exceeding the critical pressure ratio

ie the flow reaches the speed of sound

Flow rate:

where:

  • Q = flow rate in Nm3 / h @ 0°C
  • r = density in kg / dm3 @ 0°C and atmospheric pressure
  • P1 = upstream absolute pressure in kPa
  • T = upstream absolute temperature in °K

Mass Flow:

where:

  • W = flow rate in kg / h
  • r = density in kg / dm3 @ 0°C and atmospheric pressure
  • P1 = upstream absolute pressure in kPa
  • T1 = upstream absolute temperature in °K

The technical notes indicated above are a summary of the general theory of fluid thermodynamics.
Our technicians are available to select and properly calculate the suitable control valve.


Posted in: Technical Library