We can convert this to m 2 by dividing by 1,000,000 for more convenient results, getting 0.000490875 m 2.
What is the flow rate of the water? First, we calculate the cross-section area to be (25/2)^2 This equation is applicable to liquids whereas for gaseous substances some additional information is required to perform the calculations.Įxample 1: A round pipe has a diameter of 25 mm and water is running through it with a velocity of 10 m/s. The mass flow rate ṁ is the flow of mass m through a surface per unit time t, therefore the formula for mass flow rate, given the volumetric flow rate, is ṁ = Q * ρ where ρ (Greek lower-case letter rho) is the volumetric density of the substance. The equation can be transformed in a straightforward way to allow for solving for the cross-section area or velocity. In the case of a round pipe the cross-sectional area is the inner diameter divided by 2 times π while if it is rectangular the area is the inner width times the inner height. The resulting Q is the volumetric flow rate. Therefore, the formula for flow rate ( Q), also known as "discharge rate" expressed in terms of the flow area ( A) and its velocity ( v) is the so-called discharge equation: The volumetric flow rate of a stream of liquid or gas is equal to the flow velocity multiplied by its cross-sectional area. It should be noted that the Poiseuille formula for calculating a pipe's flow rate through pressure does not work so well for gases where additional information is required for an accurate computation. The graph illustrates a general case where that applies. Mineral oils, however, are somewhat compressible, so beware of using the formula for such cases.Īn example application is if one has manometers measuring the pressure of the fluid or gas at the start an the end of the section of piping that the flow rate is to be calculated for. Water is a good example of an incompressible fluid, and so is any hydraulic fluid.
In the Poiseuille equation (p 1 - p 2) = Δp is the pressure difference between the ends of the pipe (pressure drop), μ is the dynamic viscosity of the fluid, L and R are the length and radius of the pipe segment in question, and π is the constant Pi ≈ 3.14159 to the fifth significant digit. To calculate flow rate from pressure the formula is expressed as such: Flow rate formula via pressure differenceįlow rate calculation using pressure is done via the Hagen–Poiseuille equation which describes the pressure drop due to the fluid viscosity. The second one is if we know the fluid velocity. The first one is if we know the pressure difference (pressure drop) between the two points for which we want to estimate the flow. There are two main approaches to calculating the flow rate Q which is equivalent to the difference in volume divided by the difference in time (Δv / Δt). The output metrics are automatically adjusted for your convenience. Output units for mass flow rate include: kg/h, kg/mins, kg/s, tonnes/h, lb/h, lb/min, lb/s, tons/h. Some of the output units include: m 3/h, m 3/min, m 3/s, l/h, l/min, l/s, ft 3/h, ft 3/min, ft 3/s, yd 3/h, yd 3/min, yd 3/s, gallons per hour, gallons per minute. The output is in either imperial or metric units, depending on your selection. are accepted) in order to calculate the flow rate. In flow velocity mode one needs to know the flow velocity of the gas or fluid (feet per second, meters per second, km/h, etc.
If the substance is a liquid and its volumetric density is known the calculator will also output the mass flow rate (more information is required to calculate it for gases and it is currently not supported). This pipe flow rate calculator calculates the volumetric flow rate ( discharge rate) a gas or fluid (liquid) going through a round or rectangular pipe of known dimensions.
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