What is Flow rate: Definition and 494 Discussions

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).
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. N

    Help with mass flow rate of turbine?

    Homework Statement An turbine expands air at 1300 kPa and 500oC to 100 kPa and 127oC. Air enters the turbine through a 0.2-m2 opening with an average velocity of 50 m/s, and exhausts through a 1-m2 opening. Determine (a) the mass flow rate of air through the turbine Homework Equations PV=RT m...
  2. Hemanth Atthipatla

    Flow rate between two Tee-joints

    does the flow remains constant ... even when length of the two connected tee joints increases ? my thing is ... i want to maintain the same pressure and flow in two different tee joints connected to some length... while doing my experiment practically... (pipe- 10mm dia, legri tee joints,) i got...
  3. M

    How to calculate Air flow rate....?

    Sir, Kindly let me know how to calculate flow rate (cfm or Litre/m) of air flowing through a pipe of 12 mm dia from a reservoir at pressure 7 kg/cm2 to atmosphere. i.e ;- how much volume of compressed air could pass within a minute through a "X"mm dia pipe from a constant pressure (7 kg/cm2)...
  4. Charles CL

    Volumetric flow rate of bubble out of the straw

    Homework Statement Imagine that you are blowing air through a straw in a cup of water and the root of the straw was connected through a rectangular box with empty base and every side of the rectangular box was cut into "teeth" shape. Bubbles will come out from the teeth of the rectangular box...
  5. Kate L

    Equation of Continuity - Flow rate through an artery

    I'm really confused by this question, as it is different than the examples we did in class. I've compared my answer with a few classmates and I'm getting a different one, so I'm not sure if I've done it wrong or if they have. I'd really just like to know if I am on the right track! Thank you :)...
  6. Z

    How to Calculate Pump Shaft Torque from Flow Rate, RPM, and Diameter?

    Attempting to determine the torque on the shaft of a pump. Known values are flow rate, RPM, and shaft diameter. 1. What other values are needed to make the calculation? 2. What is the equation I can use for this?
  7. A

    Calculating Volume Flow Rate of Olive Oil at a Processing Plant

    Homework Statement At a processing plant, olive oil of density 875 kg/m3 flows in a horizontal section of hose that constricts from a diameter of 2.92 cm to a diameter of 1.20 cm. Assume steady, ideal flow. What is the volume flow rate if the change in pressure between the two sections of hose...
  8. B

    Increasing Flow rate through system

    Hi, I'm building an experimental set-up for some heat exchanger I'm trying to analyze, I want to maximize the flow through this little piece. I have a stable temperature bath, (see picture) that has an evacuation valve on the bottom. I only took introduction to Fluid Dynamics (found it amazing...
  9. gracepentinio

    How to design flow rate of a lubrication system?

    I am currently designing a lubrication system which uses a positive displacement gear pump. So how can I get the flow rate of a lubrication system? i don't know which equation to use. thank you so much.
  10. Carlko26

    Turbocharger: Mass flow rate and pressure ratio

    Hello everyone, i am currently dimensioning a compression system using a vehicle turbocharger and need to find a way to relate the pressure ratio of the compressor and the mass flow rate. (flows trough compressor and turbine are of course separated) For the turbine, one can use Stodola's...
  11. T

    Shouldn't pressure loss quadruple if flow rate doubles?

    I've always been taught that in a piping system (only water), if the flow rate doubles, then pressure loss quadruples. But when using the Darcy-Weisbach equation I often find that it is closer to triple. Playing around with viscosity and temperature I've never been able to bring the ratio higher...
  12. A

    Reduce mass flow rate may increase air velocity?

    Hi, I used a blower to flow air across an open duct through a nozzle. By using a gate valve, the mass flow rates were controlled. I took measurement in 3 different locations along the ducts. But, why by decreasing the mass flow rate, the air velocity was increased? It is just happened for the...
  13. B

    Mass of one component in two component w/feed flowrate

    Homework Statement Basically I'm given a feed flowrate - 70,000 gal/day I know the weight percent is 35% and the component is Triethylene Glycol - density - 1.255g/ml Homework EquationsThe Attempt at a Solution So i did this 70,000 gal/day * .35 * (.0378mL/1gal)* 1.255g/mL = g of Triethylene...
  14. G

    Pressure and Flow Rate in a Tank

    Homework Statement A tank of cross-sectional area A is initially filled with fluid of density ρ and viscosity μ to height hi. The pressure above the fluid in the tank is atmospheric, Patm. At the base of the tank there are two pipes, which are both open to teh atmosphere, such that fluid...
  15. T

    Does a pump have a maximum flow rate for a given system?

    Hi everyone, I am an electrical engineering student and in my free time, I make educational youtube videos about electronics. (youtube.com/SolidStateWorkshop). I'm working on a video right now about transistors. To help explain their operation, I am attempting to use a hydraulic circuit...
  16. J

    Calculate Remaining Anesthetic Time: Mass Flow Rate Question

    Homework Statement A patient, on an anesthetic, is hooked up with only 18 mg of the anesthetic remaining. If the current flow is 12 mg/h and the dentist needs to increase the flow to 20.0 mg/h within two minutes, then how long will it take for the anesthetic to run out? Homework Equations...
  17. W

    Can force be expressed as mass flow rate times velocity

    I know that F=ma which give the units of kg.m/s/s (in SI units) but can force also be expressed as mass flow rate times velocity which also has the same units? Example: water coming out a hose or gas coming out a spray can?
  18. gillmitch92

    Calculating percentage change in flow rate through a valve

    < Mentor Note -- thread moved to HH from the technical forums, so no HH Template is shown > The max flow rate through a control valve with an equal percentage characteristic is 10 m3/h. If the valve has a rangeability ratio of 50:1 and is subjected to a constant differential pressure, calculate...
  19. A

    What is the procedure to calculate flow coefficient?

    I want to calculate the flow rate from flow coefficient (cv ) ,so i need the testing methodology and procedure .please give an idea to clarify my doubts.
  20. T

    Why Does Flow Rate Remain Constant When Reducing Orifice Size in a Water Tank?

    So we all know that due to the conservation of volume flow rate, reducing the diameter of a hose pipe would increase the velocity of the water flow.(A*V is conserved) But when the are of an orifice near the bottom of a water tank is reduced the velocity remains the same! Does anyone know why...
  21. daPope

    Have mass flow rate, want superficial vapour velocity

    Hi guys, quick simple question. Lets say I have a pipe separated into 3 sectoins (all horizontal), all have the same flow areas. In the first section it is all liquid water. I know the mass flow rate in this. In the second section the water is heated. And I can work out the steam quality...
  22. A

    Calculating Radiator & Coolant Flow Rate

    if anyone can please tell me is there any specific method for calculating radiator size and coolant flow rate for an engine...
  23. S

    Calculate Mass Flow rate of cooling water through condenser?

    I have a condenser with a mass flow rate of 60kg/s, an initial point 1: P=50kPa, Quality = 95% and a final point 2: P = 50kPa that is saturated liquid. cooling water flows through the condenser with a mass flow rate of m(dot) and has a delta temperature of 15 degrees Celsius. how do i...
  24. F

    Increasing flow rate makes pressure drops larger

    hello In venturi meters, orifice plate meters and generally when there is a neck, constriction at a point in a pipe there is, at that point, a drop in pressure and an increase in velocity, so that the whole energy is preserved (theoretically) my question is, why if we increase the flow rate...
  25. J

    Formulas for flow rate through orifice

    I am in need of a formula to calculate mass flow rate of liquids through a known orifice size and known pressure/secondary pressure. I need to do this for multiple liquids and I know the specific gravity for each liquid. can anyone help with this formula.
  26. moenste

    Mechanics -- Converting volumetric flow rate to nozzle velocity

    Homework Statement A hose with a nozzle 80 mm in diameter ejects a horizontal stream of water at a reate of 0.044 m3 s-1. With what velocity will the water leave the nozzle? What will be the force exerted on a vertical wall situated close to the nozzle and at right-angles to the stream of...
  27. C

    Fluid dynamics, mass flow rate

    I've Attached the question and my answer to question 1 to task 3 and guidance if I've done it right? Or any guidance?
  28. danielng245

    Please help calculate flowrate frm blower to push water down

    How to calculate how much flowrate from blower i can push water pool 2,75m*1,8m down by 1,25m in 1 sec? Note : Blower Pressure 0.03 bar - 0.035 bar There is an empty room above the water pool with dimension of 2.75m*1.8m*1.7m This process happen in a closed chamber...
  29. S

    Flow Rate, Velocity and Pressure relationship

    Hello everyone, I'm new to this forum and this is my first post so go easy! I have an engineering problem which I am uncertain as to how to solve. I am trying to design a basic ballast system for pumping seawater. The idea is to use compressed air to evacuate the water through a series of...
  30. S

    Effect Pressure In Main tube due to outlets

    I had to detect a Leakage in my pipe ,and i am really confused whether the Darcy Weisbach or Hagen-poiseuille equation will be satisfied by the current criteria ,as described below: I have a main tube with ends A and B and various outlets,suppose n outlets are present between A and B , I have...
  31. P

    Is the mass flow rate in a regenerative vapor power cycle constant?

    Does the mass flow rate differ depending on whether it's after the feedwater heaters or before the turbines or is it just constant throughout the entire system?
  32. U

    Finding volumetric flow rate from pressure?

    Hello everyone, I am quite new to Fluid dynamics, so I would like to ask for your help. Is it possible to calculate volumetric flow rate from the instantaneous pressure? We need to know the flow rate of the air entering the cylinder in the engine due to the suction pressure. It is required to...
  33. cajamarcus

    How can I calculate the vacuum pressure in Y-junction?

    Hi, even though it seems so simple; I can't solve this since a few days and it's driving me crazy. Flow gets inside the tube from point 1, it will create a vacuum, which will let a secondary flow inlet from point 2. Both flows will mix inside the tube, and get out of the junction from point...
  34. Suresh Gadekar

    Does a Pressure Regulator Maintain Equal Flow Rates at Inlet and Outlet?

    Is flow rate at inlet of pressure regulator ( not relief valve) equal to flow rate at outlet ?
  35. C

    Calculating Flow Rate for CO2 Cylinders System

    Hello guys, I need to calculate the flow rate for the following system. 2 lines of CO2 cyclinders at 60 bar. Each line (1/2'') goes to a 1/2'' PSV valve. Downstream the 2 PSV the line are collected together into 1'' pipe. The two PSV are identical and as per datasheet they have the following...
  36. P

    Calculate Flow Rate of Sand in Inclined System

    Hi. First of all, I should mention that I'm quite a novice in both physics and engineering. Let's consider an hourglass (or a silo) that is inclined at a constant angle. I'm unsure of how to calculate the necessary diameter of an orifice for a given mass or volume of granular matter to...
  37. Y

    Compressed nitrogen v flow rate question

    Currently i have a system using bulk argon and i am changing to nitrogen. To trial this i am going to use cylinders of OFN(oxygen free nitrogen). how do i caculate how many cylinders i need based on a flow rate of 16 liters/min. Thanks
  38. M

    Volume flow rate and mass flow rate

    Hello there, so I have answered my question from fluid systems but the answer doesn't look right ;/ and I have no idea what have I done wrong. Can you please check and correct where it's wrong ? ;) here is the question: A pipe contains a gradually tapering section in which its diameter decreases...
  39. L

    Mass flow rate for compressible flow

    I am confused about the relation of mass flow rate with different mach numbers in a compressible flow. In wikipedia (http://en.wikipedia.org/wiki/Choked_flow), I read the following: "Although the gas velocity reaches a maximum and becomes choked, the mass flow rate is not choked. The mass flow...
  40. B

    Water vs. water/glycol flow rates

    I'm trying to get a rough idea of how flow rate through a round, sharp edged orifice is affected when a fluid is water/glycol versus pain water. In this circumstance, it's 30% water, 55% Dihydroxydiethyl Glycol and 15% Polyalkylene Glycol. I don't need exact numbers at this point, just a...
  41. A

    Flow Rate in Pipe: Q, v, A Explained

    Hi, I have a question regarding the flow rate in a pipe. According to the general rule the flow rate is: Q = v * A where Q [m3/s] v [m/s] A [m2] So according to this formula the flow rate depends only on the inner area of the pipe and the velocity of the fluid and does...
  42. J

    PV=nRT to PQ=ṁRT where Q - volumetric flow rate?

    Homework Statement Hello, I have really hard time to express the gas law PV=nRT to PQ=ṁRT where Q is volumetric flow rate and ṁ- mass flow rate. Is it possible ? Teacher told me, it is ... Homework EquationsThe Attempt at a Solution
  43. S

    Water flow rate (or pressure) drop question

    Hi, I'm not sure if I'm posting in the right spot but I'm going to guess this is an easy question for you all. I'm going to give as much detail as I can, maybe too much.. My 2 family house condo has a single 2" or 3" water supply from the street. It is split to supply the first floor and...
  44. A

    Estimate pipe diameter based on flow rate

    I'm designing a testing unit where I need to estimate the smallest diameter of a short complex pipe (around 1 meter, three bends and some diameter viariations). Since the pipe is being cooled down in a water bath after production, my idea is to force water with a known pressure in one end of the...
  45. elementHTTP

    Mass flow rate, conveyor screw calculations and books

    I am interested in mass flow rate in conveyor screw transportation http://www.colormaxsystems.com/wp-content/uploads/2013/11/5-screws-300x222.jpg any recommended book,engineering guides ?
  46. J

    Calculating Max Flow Rate Through Pipe System

    Is it possible to calculate the max flow rate (gals/m) achievable through a given piping system with only the following variables? - 4" SDR 11 HDPE pipe (3.633" ID) - 28,000 feet of pipe from source to destination - 90' of elevation change from source to destination - destination is another...
  47. D

    How do i work out a flow rate?

    Hi I need to work out a flow rate of a fire hydrant in Liters per second. I know the pressure is 3.5bar and the pipe diameter is 100mm Any help would be appreciated Thanks
  48. N

    Pump and nozzle output flow rate

    If I have a pump of 50psi and 2L/min flow rate and it is connected to a nozzle. The nozzle catalogue specs for example shows that : 40psi = 0.5L/min 50psi = 0.6L/min 60psi = 0.7L/min Is flow rate at the nozzle output 0.6L/min? Regardless of the pump flow rate, as long as pressure are same...
  49. E

    Calculate Volumic Flow Rate for Air (kg/s) at 1 bar, 20 - 50°C

    Hey guys, can some of ou help me with this question: I need to calculate the volumic flow rate for air by using the ideal gas law. Things i know from the assignment: molarmass = 28,96 kg/kmol Pressure = 1 bar mass flow = 2 kg/s t in = 20 degrees celcius t out = 50 degrees celcius (sorry for bad...
  50. A

    Confused about Volumetric Flow Rate & Valves?

    I'm new here, and I have a question that might be easy but really confuses me. Does the volumetric flow rate of incompressible fluid change across a valve?. Based on my analysis, no it can not change since the mass is conserved, and since it's incompressible fluid. I know that the velocity will...
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