Remember, you can always change the units, so don't worry if you need to work in gallons/minute or liters/hour. We've found out that the volumetric flow rate is 0.4909 ft³/s. Let's pick 10 ft/s.Īnd there it is, the first part of the calculations is done: the tool has worked as a volumetric flow rate calculator. Let's choose a pipe with an internal diameter of 3 inches.Įnter the average velocity of the flow. In every other case, you can type the area value directly into the calculator (you can use our comprehensive area calculator to help you). If the cross-section is a circle or square/ rectangle, you'll find that option on the list. Input the measurements needed to compute cross-sectional area. For this example, we'd like to know the flow rate of water in a circular pipe, so we will select the circular (full) option. Now that you know what the flow rate is, let's check it out with a simple example:įirst, select a shape from the drop-down list. Mass flow rate = m / t = ρ × V / t = ρ × Volumetric flow rate = ρ × A × v To find the mass flow rate formula, we need to remind ourselves of the density definition first:Īs the mass flow rate is the mass of a substance passing per unit of time, we can write the formula as: The equation can be rearranged to find the formula for pipe velocity. Volumetric flow rate for cylindrical pipe = π × (d/2)² × v where d is the pipe diameter Most pipes are cylindrical, so the formula for volumetric flow rate will look as follows: So, the volumetric flow rate formula boils down to: Substituting the above formula to the equation from the flow rate definition, we obtain:Īs l / t is the volume length divided by time, you can see that it's just the flow velocity. If our pipe is circular, it's just the formula for cylinder volume. Where A is a cross-sectional area of the fluid, and l is the width of a given portion of the fluid. You can first calculate the volume of a portion of the fluid in a channel as: The volumetric flow rate formula may be written in the alternative (read: way more useful) form. Mass flow rate formula: Mass flow rate = ρ × Volumetric flow rate = ρ × A × v Where A - cross-sectional area, v - flow velocity Volumetric flow rate formula: Volumetric flow rate = A × v Also, the hydrostatic pressure and buoyancy calculators may be helpful. If you're interested in fluid mechanics, you should also have a look at the Bernoulli equation calculator to determine the speed and pressure of an incompressible fluid. Mass flow rate is commonly used in the specifications of fans and turbines, amongst other things. It is an essential measure when purifying water in a wastewater plant. This time it's not the volume, but mass of a substance that passes through a given cross-sectional area per unit of time. Volumetric flow rate = V / t = Volume / timeĪnother related concept is mass flow rate, sometimes called mass flux or mass current.
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It's usually represented by the symbol Q (sometimes V̇ - V with a dot)
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The volumetric flow rate can be defined as the volume of a given fluid that passes through a given cross-sectional area per unit of time. When we talk about flow rate, you most likely picture the concept of volumetric flow rate (also known as rate of liquid flow, volume flow rate or volume velocity).