Two-Phase Flow There are no precise formulas for calculating orifice area for twophase flow. The common convention is to calculate the area required for the gas flow as if there were no liquid present and the area required for the liquid flow as if there were no gas present. The two areas are then added …
Read More…Category: Relief Valve Sizing
Relief Valve Sizing – Flow Rate for Liquids
Conventional Valve, Balanced-Bellows Valve, or Pilot-Operated Valve The corresponding equations for liquid flow are the following: Note that a preliminary orifice size must be determined in order to calculate Reynolds number. If the viscosity correction is significant, it may be necessary to iterate to get a final size.
Read More…Relief Valve Sizing – Flow Rate for Gas
The flow rate for gas through a given orifice area or the area required for a given flow rate is obtained by:
Read More…Relief Valve Sizing – Effects of Back-Pressure
Back-pressure can affect either the set pressure or the capacity of a relief valve. The set pressure is the pressure at which the relief valve begins to open. Capacity is the maximum flow rate that the relief valve will relieve. The set pressure for a conventional relief valve increases directly with back-pressure. Conventional valves can …
Read More…Relief Valve Sizing – Critical Flow
The flow of a compressible fluid through an orifice is limited by critical flow. Critical flow is also referred to as choked flow, sonic flow, or Mach 1. It can occur at a restriction in a line such as a relief valve orifice or a choke, where piping goes from a small branch into a …
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