Formula for calculating pipeline flow rate and velocity

Thread Content

Knowing the pipe diameter D and the pressure inside the pipe P does not allow us to determine the flow velocity and flow rate of the fluid in the pipe. You imagine there is a valve at the end of the pipe, and inside the closed pipe there is pressure P, but the flow rate inside the pipe is zero. The flow rate in a pipe is not determined by the pressure within the pipe, but rather by the pressure drop gradient along its length. Therefore, it is necessary to specify the length of the pipe as well as the pressure difference at both ends of the pipe in order to calculate the flow velocity and flow rate of the pipe. For pressurized pipe flow, the calculation steps are as follows: 1. Calculate the specific resistance S of the pipe. For old cast iron or steel pipes, the Chezy formula can be used to calculate the specific resistance: s = 0.001736/d^5.3, or use s = 10.3n²/d^5.33. Alternatively, refer to relevant tables for this value ； 2. Determine the head difference H at both ends of the pipe, where H = P/(ρg); H is expressed in meters ； P is the pressure difference between the two ends of the pipe (not the pressure at a specific section); P is expressed in Pa ； 3. Calculate the flow rate Q: Q = (H/sL)^(1/2) 4. Flow velocity V = 4Q/(3.1416d^2). In the formula: Q represents the flow rate, in units of m^3/s ； H – Head difference between the start and end of the pipeline, in m^ ； L – the length from the start to the end of the pipeline, in meters. The relationship between flow rate and pressure in a pipe; the relationship between flow velocity, flow rate, and pressure. Flow velocity: V = C√(RJ) = C√. Flow rate: Q = CA√(RJ) = √. In these formulas, C is the Chezy coefficient of the pipe ； L――Pipe length ； P – Pressure difference across the pipeline ； R – the hydraulic radius of the pipe ； ρ――liquid density ； g――acceleration due to gravity ； S – Friction loss in the pipeline. The relationship between the inner diameter of a pipe and its pressure flow rate – as implied by the question – is the relationship between pressure loss, the inner diameter of the pipe, and the flow rate. If that’s the case, the correct answer is that pressure loss is proportional to the square of the flow rate, and inversely proportional to the 5.33rd power of the inner diameter. In other words, the greater the flow rate, the greater the pressure loss; the larger the pipe diameter, the smaller the pressure loss. This quantitative relationship can be expressed by the following formula: Pressure loss (head loss) formula (resistance square region): h = 10.3 * n^2 * L * Q^2 / d^5.33. Strictly speaking, this is a formula for head loss; pressure loss is obtained by multiplying the head loss by the density of the fluid. In the formula, n represents the roughness of the inner wall of the tube ； L――pipe length ； Q――Traffic ； d – inner diameter of the pipe. Given a water pipe with a pressure of 0.3 Mp, a length of 330, and a diameter of 200, how can the flow velocity and the flow rate per hour be calculated? The pipeline pressure is 0.3 Mp; if the valve is closed, both the water flow rate and volume are zero. (Allowable pressure drop to be specified) Pipe length: 330, pipe diameter: 200; is the unit missing? Is the pipe length 330 meters? Is the inner diameter of the pipe 200 millimeters? These include the presence of valves and elbows, as well as their shape and form. Water pipes are made of materials such as steel and cast iron, and the smoothness of their inner walls varies. So it cannot be calculated. As a rough estimate in engineering terms, the average flow velocity in such systems is around 0.5–1 meter per second. The flow rate per hour can be calculated as follows: 0.2×0.2×0.785×1 (meter/second, the assumed value)×3600 = 113 cubic meters per hour. The pressure drop per meter of pipe can be calculated using the formula ΔP (MPa/m) = 0.0000707×V²÷d^1.3, where V is the average flow velocity (m/s) and d is the inner diameter of the pipe. Given that the inner diameter of the pipe is 10 mm, the inlet pressure is 14 MPa, the outlet pressure is at normal atmospheric pressure, and the gas is argon, it is possible to calculate the flow rate What is the formula for calculation? It seems there are fewer requirements; the friction coefficient between the gas and the pipe walls, as well as the length of the pipe, need to be known. Q=ν*r^2*3.14*3600 ； (The relationship between flow rate and velocity) R=(λ/D)*(ν^2*γ/2g) ； (Frictional resistance derivation formula) P=RL ； (Mechanical equilibrium formula) Q – flow rate (h/m3) ； ν-velocity (m/s) ； r - Pipe radius (m) ； D - Pipe diameter (m) ； P-Pressure (kg/m2) ； R- Duct friction loss (kg/m2) ； L-Pipe length (m) ； g-gravitational acceleration=9.8. Pressure can be converted to Pa, with 1 Pa = 1/9.81 (kg/m2). Using the given values, these three equations are combined to form a system of equations; by solving this system, the flow rate Q can be determined. There is a small issue with the second formula as well; λ and Y are not labeled. λ might be the friction coefficient of the pipe wall, while Y represents the length of the pipe. Please check relevant materials again. If you know the pressure and the area of the pipe, how can you calculate the flow rate? (For an air pipe with a cross-sectional area of 0.0176 square meters and a pressure of 9 kilograms, what is the flow rate per hour?) ) There are multiple formulas: Q=ν*r^2*3.14*3600 ；           D=Q*4/(ν*3.14*3600) ；           P=RL ； R=(λ/D)*(ν^2*γ/2g). Q-Flow rate (h/m3) ； ν-velocity (m/s) ； r - Pipe radius (m) ； D - Pipe diameter (m) ； P-Pressure (kg/m2) ； R- Duct friction loss (kg/m2) ； L-Pipe length (m) ； g-gravitational acceleration=9.8. Pressure can be converted to Pa; 1 Pa = 1/9.81 (kg/m2). There is a problem with your question. Condition is missing. Low flow rate, or frictional resistance. Can the flow rate be calculated if the outlet pressure and the cross-sectional area of the pipe are known? Knowing the exhaust pressure (Pa) at the pipe outlet and the pipe cross-sectional area (S), can the flow rate be calculated? (Density = air density) It’s okay. Knowing the pressure (Pa) allows one to determine the resistance of the pipe: according to Bernoulli’s equation, the pressure difference equals the fluid density multiplied by Hf. By substituting this into ρU²/2 + P1 = ρhf, it is possible to calculate the flow velocity U, where ρ is the fluid density and U² is the square of the velocity. P1 is the pressure inside the pipe, and hf is the resistance parameter. Finally: flow velocity (m/s) × pipe cross-sectional area (m2) = flow rate (cubic meters per second). The premise for these calculations is that the pressure in question is the pressure within a straight pipe, and the other end of the straight pipe must be open to the atmosphere.  The pipeline pressure is 0.5 Mp, the length is 3000 meters, and the diameter is 200. How can the flow velocity and flow rate be calculated? The pressure at the start of the pipeline is 0.5 Mpa; what is the pressure at the end of the pipeline? The pressure at both ends of the pipe is needed to calculate the flow velocity and flow rate.  Insufficient data for the topic; pipe flow rate does not depend on pressure, but rather on the pressure gradient. You should specify the conditions: what are the pressures at both the beginning and the end of the pipeline in order to carry out the calculation? If the pressure at the start of the pipeline is 0.5 Mp, then you need to provide the pressure at the end of the pipeline as well.  For pressurized pipe flow, the formula and steps for calculating the flow rate are as follows: 1. Calculate the specific resistance S of the pipe. For old cast iron or steel pipes, the Shchelikhov formula can be used: s = 0.001736/d^5.3, or s = 10.3n^2/d^5.33 (where n is the roughness coefficient of the pipe’s inner wall and d is the inner diameter of the pipe in meters); alternatively, relevant tables can be consulted ； 2. Determine the head difference ΔH between the two ends of the pipe; when pipes of equal diameter are arranged horizontally, ΔH = ΔP/(ρg), where H is in meters ； ΔP is the pressure difference between the two ends of the pipe (not the pressure at a particular section); ΔP is expressed in Pa. ρ is the density of water, with ρ = 1000 kg/m^3 ； g=9.8 N/kg3. Calculate the flow rate Q: Q = (ΔH/sL)^(1/2). The flow velocity V is given by V=4Q/(3.1416d^2). In these formulas, Q represents the flow rate, in units of m^3/s ； H — Head difference between the start and end of the pipeline, in meters ； L — the length from the start to the end of the pipeline, in meters. ^It denotes the exponentiation operation; d^2 represents the square of the pipe diameter ； d^5.33 represents 5.33 cubic units of the pipe diameter. 3.1416 is pi rounded to 4 decimal places. The flow rate, pressure, and pipe diameter (i.e., the internal diameter area) are related to the flow volume. The diameter of the main pipe remains constant at DN200 (you should specify the internal diameter of the pipe rather than its nominal diameter); the flow rate in the main pipe also stays constant at 150 tons per hour. Energy losses during transportation through the pipe are negligible, so they are not taken into account. The flow rate at the exit of the main pipe is also 150 tons, meaning that the flow rate when transporting fluid into a tank is 150 tons. If the diameter and flow rate of the main pipeline remain unchanged (i.e., the pressure stays constant), the flow rate of fluid through each of the three storage tanks will be 150/3 tons, which is 50 tons. It is necessary to ensure that the diameters of the three branch pipes are equal, and that the sum of the cross-sectional areas of the inner diameters of these three branch pipes is equal to or greater than the cross-sectional area of the inner diameter of the main pipe. Method for calculating flow velocity: In the first case, pressure is not involved; knowing two of the three values – pipe diameter, flow velocity, and flow rate – it is possible to derive a formula using geometric principles: V = 4000Q/3.14D². In the second case, pressure and pipe diameter, as well as the length of the pipe, are known. Here, pressure refers to the pressure difference between the two ends of the pipe. The calculation is as follows: Pipe friction loss S = 10.3n²/d⁵.³³, where n is the roughness coefficient of the pipe’s inner surface, and d is the inner diameter of the pipe, expressed in meters ； Head difference H = P/(ρg), where P is the pressure difference between the two ends of the pipe ； ρ —— liquid density ； g——acceleration due to gravity ； The flow rate Q=^(0.5), where H is the head difference between the two ends of the pipe, in meters ； L —— Pipe length, in meters ； Q —— flow rate, in m^3/s. The pipe flow velocity V = 4Q/(3.1416d^2), where V is the flow velocity in m/s, and Q and d have the same meanings as above. Formula for calculating pipeline flow rate: 600 cubic meters of water, DN90 pipe – how to calculate the flow velocity per second? A. The cross-sectional areas for pipe diameters of DN15, DN25, and DN50 are as follows: DN15: 152*3.14/4 = 176.625 square millimeters, which is equivalent to 0.0177 square decimeters.  DN25: 252*3.14/4=490.625 square millimeters, which is equivalent to 0.0491 square decimeters.  DN50: 502*3.14/4=1962.5 square millimeters, which is equivalent to 0.1963 square decimeters.  Assuming the flow velocity in the pipe is V=4 meters per second, which is equivalent to V=40 decimeters per second, and given that 1 liter equals 1 cubic decimeter, the flow rate in the pipe is calculated as (cross-sectional area times flow velocity). For a DN15 pipe, the flow rate Q=0.0177*40=0.708 liters per second, which is equivalent to 2.55 cubic meters per hour.  DN25 pipe: Flow rate Q=0.0491*40=1.964 liters/second, which is equivalent to 7.07 cubic meters per hour.  DN50 pipe: Flow rate Q=0.1963*40=7.852 liters/second, which is equivalent to 28.27 cubic meters per hour.  Note: A flow velocity must be specified in order to calculate the flow rate; the above calculation is based on 4 m/s. B. It’s 600 cubic meters per hour, right! Volume flow rate Q = 600 cubic meters per hour = 0.167 m^3/s. Flow velocity V = 4Q/(3.1416D^2) = 4*0.167/(3.1416*0.090^2) = 26.25 m/s. The flow velocity is very high! It might be 600 cubic meters per day. In that case: Flow rate Q = 600 cubic meters/day = 0.00694 m^3/s. Velocity V = 4Q / (3.1416 * D^2) = 4 * 0.00694 / (3.1416 * 0.090^2) = 1.09 m/s. This velocity is within the normal range. The calculation of pipeline flow rate requires analysis on a case-by-case basis. 1. If the average flow velocity V and the cross-sectional area A of a pressurized pipe flow are known, then the flow rate Q = VA. 2. If the hydraulic gradient J, cross-sectional area A, hydraulic radius R, and Chezy coefficient C of a pressurized flow are known, then the flow rate Q = CA√(R/J), where J = (H1 – H2)/L; H1 and H2 represent the head pressures at the beginning and end of the pipe respectively, and L is the length of the pipe. 3. If the specific resistance s, length L, and head H of a pressurized pipe are known, then the flow rate is Q = √(s·L·H).
4. For a pressurized pipe where both frictional head loss and local head loss occur, the flow rate is:
Q = VA = A√(2gH)/√(1 + ζ + λL/d)
Where: A – cross-sectional area of the pipe ； H——Head of water available for use in the pipeline ； ζ——local resistance coefficient of the pipeline ； λ —— the friction coefficient along the pipeline ； L—Pipe length ； d——Inner diameter of the pipe. 5. For building water supply pipes, the flow rate q is not only related to the inner diameter d of the pipe but also to the head loss per unit length of the pipe (hydraulic gradient) i. The specific relationship can be derived as follows: The hydraulic gradient of a pipe can be calculated using the Shcheklov formula: i = 0.00107V^2/d^1.3. The flow rate q in the pipe is given by q = (πd^2/4)V. By eliminating the velocity V from these two equations, we obtain: q = 24d^2.65√i (where i is in units of m/m), or q = 7.59d^2.65√i (where i is in units of kPa/m). Once the diameter of the pipe, the pressure, and the velocity are known, the pipe flow rate can be calculated. In practical engineering applications, the pressure in water pipes is usually between 0.1–0.6 MPa, while the velocity of water flowing through the pipes is between 1–3 meters per second; 1.5 meters per second is often used as a typical value. Flow rate = Cross-sectional area of the pipe × Flow velocity = 0.002827 × Diameter of the pipe² × Flow velocity (m³/h)²: squared. Diameter unit: mm. Diameter = sqrt(353.68 × Flow rate / Flow velocity). sqrt: square root. The formula for saturated steam is the same as that for water; however, the flow velocity is generally taken to be 20–40 meters per second.  If an accurate calculation is required, one must first assume a flow velocity; then, using the viscosity, density of water, and pipe diameter, the Reynolds number is calculated. From this Reynolds number, the friction factor along the pipe is determined. The equivalent pipe lengths for various pipe fittings in the pipeline—such as tees, elbows, valves, and reducers—are obtained from tables. Finally, the total pressure loss in the pipeline is calculated by multiplying the friction factor by the total length of the pipeline (including the equivalent pipe lengths). The actual flow velocity is then determined using Bernoulli’s principle. This process is repeated using the actual flow velocity until the two values become close to each other (an iterative method). Therefore, in practice, very few people calculate it this way; generally, different flow velocities are chosen based on the magnitude of the pressure difference, and the calculation is done according to the method described at the beginning.