Pressure & Flow Calculators
Differential Pressure Calculator
Calculate the differential pressure produced by a flow measurement device for a given flow rate and meter K-factor.
Gas Flow Calculator
Calculate volumetric gas flow rate through a duct or pipe from average velocity and cross-sectional area.
Mach Number Calculator (Combustion Gas)
Calculate the Mach number of combustion gas flow from velocity, gas properties, and temperature.
Mass Flow Rate Calculator
Calculate mass flow rate of a gas from its density and volumetric flow rate.
Orifice Flow Calculator
Calculate volumetric flow rate through a sharp-edged orifice from pressure drop, orifice area, and discharge coefficient.
Pipe Velocity Calculator
Calculate average gas velocity inside a pipe or duct from volumetric flow rate and cross-sectional area.
Pressure Drop Calculator
Calculate frictional pressure drop of gas flowing through a duct or pipe using the Darcy-Weisbach equation.
Reynolds Number Calculator
Calculate the Reynolds number of combustion gas flow to determine laminar, transitional, or turbulent flow regime.
Volumetric Flow Rate Calculator
Calculate the volumetric flow rate of a gas from its mass flow rate and density.
The Fluid Dynamics Behind Moving Combustion Gases
Combustion air, fuel gas, and flue gas all have to physically move through pipes, ducts, and orifices, which brings standard fluid dynamics into combustion engineering — Reynolds number determining flow regime, pressure drop determining fan and blower sizing, and orifice flow determining fuel metering. Nine calculators here cover that flow and pressure math for combustion gas systems.
Popular Pressure & Flow Calculators
Nine tools span flow rate, pressure, and flow characterization:
- Mass Flow Rate Calculator — calculates gas mass flow from volumetric flow and density.
- Pressure Drop Calculator — estimates pressure loss through ducts, pipes, or equipment at a given flow rate.
- Orifice Flow Calculator — calculates flow rate through an orifice from differential pressure and orifice geometry.
- Reynolds Number Calculator — determines whether gas flow is laminar or turbulent based on velocity, density, and viscosity.
- Mach Number Calculator (Combustion Gas) — calculates flow velocity relative to the local speed of sound in hot combustion gas.
Why Reynolds Number Matters for Combustion Gas Ducting
Reynolds number predicts whether gas flow through a duct or pipe will be smooth (laminar) or chaotic (turbulent), and combustion gas systems are almost always solidly in the turbulent regime given typical velocities and duct sizes — which matters because pressure drop calculations use different friction factor relationships for laminar versus turbulent flow. Getting the flow regime right isn't academic: using a laminar-flow assumption on a turbulent system would significantly underestimate the actual pressure drop and undersize the fan or blower needed to move the gas.
Frequently Asked Questions
Why does combustion gas velocity need a Mach number check at all?
Hot combustion gas has a lower local speed of sound than cool air, so velocities that would be perfectly subsonic in cold air can approach compressible flow effects in very hot, high-velocity combustion gas streams, which changes how pressure and flow relate.
Explore More
Need combustion air flow sizing specifically? See the Air & Fuel Calculators, or check stack draft physics in the Flue Gas Calculators.