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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. townfanjon

    Gas flow rate table. .

    Guys , do any of you fine chaps have the figures for 35 mm copper tube flow rates ( 3 , 6 , 9 meters etc etc ) only one I have goes up to 28 mm . Cheers in advance
  2. A

    Vitodenns 050 29kw poor flow rate.

    Hi guys. I'm not familiar with viessmann at all but I'm fitting a bathroom and customer has mentioned poor flow rate from the hot water. The cold is perfectly fine but the hot is really poor. I've checked the cold inlet valve on the boiler and that's fine. I've looked through the manual but...
  3. R

    Flow rate of 20mm MDPE

    Hi Not sure if this is the right forum but i wanted advise on flow rates coming into a house. I have an incoming blue MDPE 20mm pipe that terminates into some kind of connector that goes to 15mm copper. From here into a stop tap and then to the rest of the house. Testing the flow rate at...
  4. T

    Flow rate on Intergas Boiler

    Hi I am thinking about buying a small intergas boiler. The HRE 24/18. It is a 17kw boiler but the house i rent out is a 2 bed terrace. It has a bathroom with bath and a shower over it run off the boiler. My concern is the low Flow rate on this boiler. Has anyone had any issues with it ...
  5. J

    Low flow rate in outside and mains cold tap only. Mains pressure combi system

    Hi, We have been in our house for just over two years, we have always had low pressure in our downstairs cold tap (mixer tap), hot is fine, and also in our outside tap, this branches off the main cold line before it hits the cold side of the tap. (please see images, cold is the right side...
  6. Ted808

    Ferrolli MODENA, 30C, HW flow rate poor.

    Oldish combi, servicing minimum, HW flow rate has decreased, check filter on incomin cold, not much in there, a tiny spec of dirt. I'm thinking heat exchanger scaled up. So, custard wants new boiler for peace of mind. What can I do to ensure that new boiler doesn't have the same issue? Flow rate...
  7. Richard Lindsay

    New boiler flow rate not improved

    Just had a new 35kw boiler installed. Everything working well except that I expected the hot water flow rate to be improved. I had a 20 year old 28kw boiler replaced. The new boiler is rated for 14 litres per min of hot water. I measured the outside tap and get 20 litres per min at 2 bar. The...
  8. M

    poor flow rate for multiple showers

    My sons house has three showers but none seem to be any good water pressure seems ok(2.5bar) but flow rate about 10ltr min but it drops off if a second tap is opened ,the house is 150mtr from the road so a long newish 25mm supply pipe from main supply ( which just to make it a bit more a problem...
  9. S

    Water flow rate calculation - not enough water for 2 showers

    We live in a new build and have a 150l unvented tank attached to an Ideal Logic Heat H15. The house is 4 bed, approx 1500 sqft and has 3 toilets, 1 shower and 1 bath. We don't have excessively long showers, maybe 20 minutes in total for both of us. Sometimes we can get 2 showers but we rush...
  10. W

    What is considered a decent shower flow rate for gravity?

    In litres per minute at say 0.2 bar. Thanks
  11. D

    Incoming mains 3bar flow rate 16litre permin

    3bed house 2 shower 2sink 11rads What size combo boiler please
  12. J

    Pipe size and peak flow rate for converted flats

    Hello everyone, I have a building to be converted to 8 residential flats. It will be 7 one bedroom and 1 two bedroom flats which have one bathroom, one kitchen including washing machine but no dishwasher in each flat. I submitted the application to the water company to add 7 more water meters. I...
  13. Tommy Abdy Collins

    How Can I increase shower drain flow rate

    I have fitted a shower tray using the drain provided which has a 40mm drain. The drain is not coping with the output of water from the shower head. If I fit a larger diameter pipe to the 40mm outlet, will this increase the volume of water being drained? - even though it will start by exiting...
  14. L

    Can anyone help?? New kitchen tap

    Hello, I'm a DIY'er I've bought and fitted a new kitchen mixer tap, hardly anything comes out from either the hot or cold when turned On, just a constant dribble, I've got a combi set up all pipework is run in 15mm, The bath and sink taps are okay, although if the cold tap is running on the bath...
  15. M

    2004 vokera Linea 35he dhw flow rate?

    Hi guys as above does anyone know what the dhw flow rate was on a vokera Linea 35he fitted in 2004. This is the current boiler fitted (I believe, as paperwork does not state capacity and nowhere on the boiler is there a GC number, kw rating or serial number. Aswell as the fact the original...
  16. A

    Loss of flow rate - normal or too much

    Hi, I'm getting quite a big loss in flow rate upstairs compared to downstairs. Here are the details: I'm not getting a great litre per minute of hot water from my combi, I'm getting around 12 lpm (which outputs 18 lpm at maximum). When I looked into it, I'm only getting about 12 lpm of cold...
  17. GQuigley67

    Unvented cylinder reduced flow rate

    When you first open a tap pressure and flow rate is good, it then dies down like a combi would reducing from approx 20 l/min to about 10 l/m. Balanced cold doesn't have this issue, expansion vessel replaced due to being burst, couldn't clean filter in combination valve so temporary bypassed it...
  18. B

    Unvented cylinder flow rate requirements?

    Hi guys. Just a quick question. I've been asked to fit a Worcester Greenstore unvented cylinder but I'm worried flow rate is insufficient. I measured the flow rate at 14 L/PM. It currently comes into the house in 20mm mdpe and goes straight to 15 mm after the stopcock to supply the house. I...
  19. V

    Main Combi HE needing high flow rate to trigger DHW

    Hi everyone - not been on here in ages, but know someone will have some sound advice :-) My Mother has just had her Main Combi 30 HE serviced by her regular guy - Expansion vessel needed recharging and all seem well but after he left I found there was no hot water unless the taps were turned...
  20. J

    oil flow rate measurement

    Hi folks, wondering what people use to measure oil flow can't find any manual measuring equipment?
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