# Gas pipe discharge flow rate calculator

## calculation of gas outflow from the pipe or through the valve

Gas pipe discharge flow rate calculator can be used for flow rate or pipe diameter calculation of gas flow exiting from pipe, reservoir to atmosphere, other pipe or reservoir. It can be used for all two and three atomic ideal gases including air, nitrogen, carbon dioxide and others. Calculator can be used for flow through pipes with or without valves and fittings in the pipe line.

With gas discharge calculator you can calculate maximum flow rate for known pressure difference and pipe diameter, or you can calculate pipe diameter for known flow rate and pressure drop. Based on the known pressure difference (head loss) between one point of flow stream at the start of pipe or in front of the valve, to the outside point (like atmosphere), or after the valve with known inside pipe diameter, mass flow rate and volume flow rate is calculated. Calculator is for steady flow with constant pressures in one point of stream line. For flow rate calculation modified Darcy formula is used:

where is:

*w*- discharge mass flow rate [kg/s]*Y*- expansion factor [ - ]*d*- internal pipe diameter [mm]*Δ p*- pressure drop [Pa]*ρ*- density [kg/m^{3}]*K*- resistance coefficient [ - ]

Friction coefficient is also calculated, using Colebrook-White formula:

where is:

*f*- friction factor [ - ]*k*- pipe roughness [mm]*D*- internal pipe diameter [mm]*Re*- Reynolds number [ - ]

Reynolds number and expansion factor also calculated and results are presented. Resistance factor K for valves and fittings, if they are existing in the system should be known and entered for calculation. Calculator is checking if flow is choked or not and choked flow status is presented and flow rate is calculated at choked conditions.