3 Pipe Flow Rate
Shari Alvine
We regularly get asked about the water flow capacity of different pipe sizes, and which is the best roof drain for a specific pipe size. Unfortunately, recommendations aren't that straightforward because you also need to account for water pressure, material friction and more.
That said, we put together the following tables to serve as general guides for estimating a pipe's water flow capacity through a pipe or roof drain. If you have questions, please call our Drain Wizard at 800-635-0384.
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. 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).
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 first one is if we know the pressure difference (pressure drop) between the two points for which we want to estimate the flow. The second one is if we know the fluid velocity. Both are covered below.
An 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. The graph illustrates a general case where that applies.
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 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. This equation is applicable to liquids whereas for gaseous substances some additional information is required to perform the calculations. The above formulas are the ones employed in this flow rate calculator.
Example 2: A rectangular pipe has a height of 2cm and width of 4cm and a gas running through it at a speed of 15 m/s. What is the discharge rate of this pipe? First, we find the cross-section area via the formula for the area of a rectangle which is simply 2 4 = 8 cm2 or 0.0008 m2. To find the flow rate Q, we multiply 0.0008 by 15 to get 0.012 cubic meters per second. To get litres per second we simply need to multiply by 1,000 to get 12 l/s. If we wanted to get liters per hour, we can further multiply by 3600 to get 43,200 litres per hour.
If you'd like to cite this online calculator resource and information as provided on the page, you can use the following citation:
Georgiev G.Z., "Flow Rate Calculator", [online] Available at: -flow-rate-calculator.php URL [Accessed Date: 26 Jul, 2024].
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Pipe flow rate control is a crucial aspect of any fluid transport system, as it ensures optimal efficiency and prevents damage to equipment. Valves are commonly used to control flow rate, with the assistance of a differential pressure gauge. Flow rate adjustment is done by adjusting the valves in the pipeline that control an orifice plate, which can be monitored using a differential pressure gauge. Diaphragm type differential pressure instruments are commonly used to control flow rates, with selection based on service and range. These gauges provide accurate and reliable measurements of differential pressure, which can be used to calculate flow rates using the Bernoulli equation.
By using differential pressure gauges to monitor flow rate monitoring and control, operators can ensure the efficient and safe operation of their fluid transport systems. Flow rate control using valves and differential pressure gauges is a widely used method for optimizing system performance and preventing issues in fluid transport systems. Proper selection, installation, calibration, and maintenance of differential pressure gauges are critical to ensure accurate measurements and precise control of flow rates.
Can anybody help with and hvac revit model I have been working on, having real trouble sizing ducts and pipes and everything on supply line is coming back flow rate 0. I deally it be great if sum one could look at the file I have a give few ideas because I've tired everything and need help badly. Living and working remotely from home in Ireland Ireland
Your terminal families (air terminals, radiators, coils etc) need to have the correct classification of connectors in them (Exhaust, Supply, Hydronic Supply) etc with flow configuration set as Preset, and with a flow parameter associated to them. The value of the flow parameter transfers to the connector then to the pipe or duct and should totalise up through the system if everything is correctly connected.
I have just uploaded my hvac model ! be great if you could take a look at it because ive tried everything and still getting problems with flow rates and sizing ducts. if you could have a look at it that would be great.
On the supply system your open bellmouths at FCs are seen as open ends and have no assigned flow - you'll need to add an air terminal to them (e.g. make a wiremesh grille family or even just a dummy terminal).
You also have the "enable analysis for closed loop....." active, which is fine as long as your loops conform to the conditions stated in the dialogue box. If your system doesn't meet these criteria then you need to split the loops at the plantroom end and calculate flows and returns as separate systems.
Thanks a million for your help, something I thought id never be able to do but I finally got flow rates to both return and supply ducts to size which I have been trying for weeks. Although I have one or two more problems that I wondering if you have any ideas, I cannot size any of my pipes even after I edited FC unit family which I linked both connections for flow and return Supply as in and Return as out and condensate out and when I try to use system inspect tool it doesn't give me an option to check flow rate probably because flow rate at 0. Also in screen shot two having issues deleting spaces out my model tried everything but they still remain in hidden view.
I have to say that because of your help I'm beginning to feel confident about get a working model finished and submitted in May , I'm am very grateful for your valuable input as I have been trying everything to make things work watching LinkedIn tutorials working every hour to make this work and I feel I'm getting a better understanding on how things work from your help, as tutors and online training videos explain how to model but when things go wrong there's little or no help. I tired creating a space Schedule before but because I deleted zones and spaces from "project Browser " no spaces show up but still in hidden view they remain and need them completely deleted. In the Mechanical settings I disabled analysis for closed loop hydronic piping networks but still getting errors when pipe sizing, I even changed all mech equipment to preset and supply to in return to out and linking both connections which have been used but still getting same problems. Also I have query regarding what you do if you don't have information for Revit Mech families AHU, FCU ,Boilers Chillers regarding Flow rates, pressure drops, air flow rates because all these families are set to 0 and sometimes I make my own up which is problem messing up model. I have in some cases go on to manufacturing websites and see if I can get crucial spec that help model but I don't know if this helps my design from screen shots of spec on FCU and what I entered in parameters section design. I have attached latest copy of my model to this email.
Firstly, I notice that you have a pump in both the flow (supply) and return pipes - this would be highly unusual in reality (in fact I've never done this). Because the loops are closed circuits, the water which is pumped through the flow (supply) must come back along the return, so you only need one heating pump and one chilled water pump.
Pipe sizing also works BUT you will get an error (below) - this is caused by the fact that when Revit increases the pipe sizes the Pipe Accessories don't auto-resize so it tries to insert tapers, but there may not be space to do so. Also at certain combinations of pipe fittings (e.g. a tee with a bend on the branch very close to the tee) the increased size of the components means there is not enough space for them so Revit has to break those connections and then you need to move the pipes further apart and remake the connections.
I have to say thanks for all your valuable input into helping me with my model, the ducts are sizing pipes are sizing and my model are beginning to take shape. if you only realize the hours I put into trying to make it work and nearly through in the towel, so I am very grateful and appreciate all your help. There was just one or two questions I wanted to ask you about my model:
I noticed all ducts and pipes are sizing and getting flow rates but for some reason the system inspect tool will not let my check the supply or return and same with all pipes even through there sizing and presume for the ducts its cause its not connected up correctly which I think could be I just made up figure in the ahu for flow rate as didn't have one
The solution seems to be to use trial and error pretty much by breaking and remaking connections until the inspector shows. This might assist: -products/learn-explore/caas/screencast/Main/Details/d58...
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