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flow rate

In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, rate of fluid flow, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol Q (sometimes V̇). The SI unit is cubic metres per second (m3/s). Another unit used is standard cubic centimetres per minute (SCCM).
In hydrometry, it is known as discharge.
In US customary units and imperial units, volumetric flow rate is often expressed as cubic feet per second (ft3/s) or gallons per minute (either US or imperial definitions).
In oceanography, the sverdrup (symbol: Sv, not to be confused with the sievert) is a non-SI metric unit of flow, with 1 Sv equal to 1 million cubic metres per second (260,000,000 US gal/s); it is equivalent to the SI derived unit cubic hectometer per second (symbol: hm3/s or hm3⋅s−1). Named after Harald Sverdrup, it is used almost exclusively in oceanography to measure the volumetric rate of transport of ocean currents.
Volumetric flow rate should not be confused with volumetric flux, as defined by Darcy's law and represented by the symbol q, with units of m3/(m2·s), that is, m·s−1. The integration of a flux over an area gives the volumetric flow rate.

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  1. H

    Glow Worm betacom 24c hot water flow rate.

    I have glow worm 24c combi boiler. The hot water flow rate is next to nothing, at all outlets. Mains water pressure is good. One other problem was the rads getting hot when hot water only. Thinking this must be caused by the diverter valve not working correctly and that the dhw heat...
  2. Chalked

    Flow rate from electric shower

    Can anyone tell me what flow rate to expect from a 9.5kw shower? Got to attend a rental house where the customer is complaining about lack of flow. It could be a blockage in the shower, or head. But would like to measure the rate, in case I need to explain that they will only pass so much. cheers.
  3. B

    Vented vs Unvented in low flow rate flat

    Hi all We currently have a vented system (hot water cylinder, cold water tank above, supplemented by a pump) in our ground floor one bed/one bath flat. We're looking at replacing the system due to age. I've had a couple of quotes from heating engineers who have recommended installing the...
  4. A

    new shower valve has varied flow rate

    Hi, We have fitted a new Watersmith thermostatic bar valve as we couldn't get any hot water from our old shower. Given the fittings were the same we just swapped the valves over. Now it is fitted, I find that I can only get a small flow from the shower and that this is varied from a drizzle...
  5. M

    Low Flow Rate

    My downstairs water supply is about 3L/min. I had the water company out today and they have told me that the pressure at the boundary is 3 bar. I live in a new build property - is it possible that there is some kind of restrictor between he mains supply and my stop valve? Would there be...
  6. T

    Good flow rate low pressure taps

    We have a gravity fed system in our bathroom, both hot and cold fed off the tanks in the loft. We wanted to put more modern taps in. We chose some Bristan single lever taps, designed for pressure down to 0.1bar but the flow rate is really poor. The old Ideal standard ones worked really well...
  7. E

    Question re poor flow rate, measuring flow at stopcock

    Hello, I'm a layperson not in the trade. I hope I'm posting this question to the right place. Thanks for your attention. We are investigating getting a new 32mm mains supply put in by Thames water and re-plumbing internally with 22mm to resolve a poor flow rate in our 1960s house. This will...
  8. J

    Flow rate / regs query

    Hi, not sure if I am in the right place but need a bit of advice please! We recently had a new combi boiler installed, the engineer didn't take flow rate readings and instead relied on the ones he took over a year ago. Is this within regs? I would have thought they needed to do new readings...
  9. N

    Slow/low flow rate to radiators ...I think

    Hi, think we have a flow problem in our central heating....but don't know how to tackle it.. We've an old CH system, which was installed before we moved in 16 years ago...and to be honest not well serviced, but has never let us down. BAXI boiler and expansion tank in loft, that feed a pump and...
  10. S

    Very poor flow rate and pressure on the incoming main

    Hello I ve been to look at a job for a builder i work for. They are converting the back end of a garage into a bathroom. At the moment there is two 50 gallon CWS tanks linked together on the floor in the garage with a submersible pump in it pumping the cold water up to the CWS in the loft. It...
  11. M

    Combi with highest DHW flow rate?

    What's the highest DHW flow rate combi that you know of? I have 25l/min mains and I want to take advantage of that. Was thinking of going unvented but not really worth it in my flat..
  12. M

    Is my water flow rate acceptable

    Hi, we have just moved into a new house and we are not too sure who is responsible for our poor water pressure/flow or whether we have grounds to complain at all, so some help would be greatly appreciated. The developers are still on site, but are now building houses a fair distance from us. we...
  13. M

    Flow rate = pressure?

    Hi all. Is there a calculation to determine pressure form litres per minute??
  14. M

    Water pressure and flow rate?

    Hi all. Out of about 80 boilers I helped install with my previous colleague, not once did we check mains water pressure or flow rate. Do most of you guys actually check this when quoting a job or on installing a boiler to make sure the boiler will operate effectively? Or do you just open up the...
  15. F

    Minimum mains water flow rate

    Hi all. Bumped into a guy who worked for a water supply company the other day and he mentioned that the supply company has a duty to be giving at least 10 litres per minute to a property. Is this true and if so is it true for all of the UK? regards, chris
  16. P

    Shower Pump Not Always Starting - How To Test Flow Rate?

    My daughter has a pumped shower that doesn’t always start without a bit of fiddling. I think the problem is lack of head. How can I test the flow that’s available when pump off, as I believe that the newish Salamander pump needs a min. of 2L per min? Do I test from the shower head end of shower...
  17. N

    Possible Solution To Low Flow rate?

    Hi, I am in the situation where the water pressure at the outside stopcock is 4 Bar with a 30 LPM flow rate. However inside the house I do get 4 bar pressure but through timing how long it takes to fill up a 10 litre bucket I only get 8.2 LMP downstairs and 6.6 upstairs (not sure if this is a...
  18. S

    flow rate

    just browsing around and found this EK C 12kW Electric Combi Boiler for 1 bathroom how can 12kw produce that flow rate when we need 24kw of gas to get similar?
  19. F

    High Flow rate pressure reducer valve

    Hi, I have my presure reducer valve in my kitchen set to 3.5 bar and from that I am geting a flow rate of around 12l per min. I have read on the internet that I should be getting a far higher flow rate from 3.5 bar of presure. Can you let me know what you think? Do you think the presure...
  20. P

    Logic Combi 30 Low DHW Flow Rate

    I have just moved into a property that has an Ideal Logic Combi 30 boiler - installed about two years ago. The DHW flow rate is pitiful - 3 l/min. (Cold from mains is 12 l/min) I've tried setting it to a lower temperature but this doesn't affect the flow rate, only the temperature. We live in...
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