Note: Reynolds Number Range: 1.1E+03 to 4.1E+05. Assumptions: no work performed, steady-state flow, and f = constant as a function of the length. We set the pipe friction number as a constant and calculate it with the input-data. 8. Above the critical transition region, the NFPA/IFGC calculation, the Sptizglass calculation, and the NFPA/IFGC tables provide reasonable and more conservative estimates of the gas flow capacities of these pipelines in these applications. The characteristics of the vertical flow regimes are shown in Fig. Fluid Power Equipment. else Equations displayed for easy reference. If the pressure drop in a pipeline is less than 40% of P 1, then our Darcy-Weisbach incompressible flow calculation may be more accurate than the Weymouth or Panhandles for a short pipe or low flow. The pressure, temperature, and elevation at Point A. document.write('~~'); All computations performed used 0.6 as the specific gravity. The inside diameters of each of these pipes is different. (kg/m2) Where: Qh = Flow Rate based on pipe diameter, design Δh and Pipe length – CuFt/Hr (M3/hr). https://petrowiki.org/index.php?title=Pressure_drop_evaluation_along_pipelines&oldid=47170, Copyright 2012-2020, Society of Petroleum Engineers. Natural Gas Characteristics: Where the equations allowed input, the following was included: Natural Gas Specific Gravity = 0.60. (NGPSA) Engineering Data Book[4] and Ingersoll-Rand’s Cameron Hydraulic Data Book[5] are also good sources of references for the information. 5—Effective viscosity of an oil/water mixture (courtesy of AMEC Paragon). The North American Combustion Handbook (3rd Edition – 1986) places the specific gravity of natural gas between 0.59 and 0.64. The values in the NFPA/IFGC tables were also compared; it should be noted here that the low pressure gas equations and the tables in both the NFPA 54 and IFGC codes are the same. Gas Processors Suppliers Assn.). The straightforward capacity factor for gas is (0.65/0.60)0.5; this equates to 1.04 (and approximately 1.06 when “f” is considered). compressibility factor for gas, dimensionless. Disclaimer There are several equations and tables for determining the flow in natural gas pipes and the pressure drops associated with those flows, or vise versa. (m). According to both Coelho and Pinho and Petroleum Refining and Natural Gas Processing, the transition between Partially Turbulent Flow and Fully Turbulent Flow occurs where the results of the two equations intersect; the higher value of “f” is used. = Pressure Drop (kg/m2) In low gas/liquid flow, the flow in uphill segments can be liquid "full" at low flow rates. To determine the fluid (liquid or gas) pressure drop along a pipe or pipe component, the following calculations, in the following order. // --> In other words, the calculated head loss caused by fluid passing through a gate valve is expressed as an additional length of pipe that is added to the actual length of pipe in calculating pressure drop.All of the equivalent lengths caused by the valves and fittings within a pipe segment would be added together to compute the pressure drop for the pipe segment. Note: Perfectly smooth pipes will have a roughness of zero. Engineering Videos 6)where. The velocity distribution of turbulent flow is more uniform across the pipe diameter than in laminar flow. k = Absolute Roughness (mm) [3] The Natural Gas Processors Suppliers Assn. Previous articles in this series were used to evaluate various equations used for determining the pressure drop in high pressure natural gas lines. The liquid moves at a fairly uniform velocity while the bubbles move up through the liquid at differing velocities, which are dictated by the size of the bubbles. | Contact | Privacy Policy, Home }, Fluid Flow Table of Contents The classic equation for Reynolds number is: Re = ρ V D /μ (Equation 2), μ = gas dynamic viscosity – 6.98311E-06 lbm/ft/sec (0.010392 centipoise). It is expressed as (Eq. 23). 4 can be used for the viscosity of crude oil, Fig. 3—Friction-factor chart (courtesy of AMEC Paragon). Fig. p2 = Pressure leaving (kg/m2) To assist in the calculation, when density is broken down (into the perfect gas law equation) and velocity is broken down (as a function of flow and density), and then substituted in the classic Reynolds number equation, the following equation can be derived: Re = 4 Qst 29 Sg Pst / (μ π D Tst) (Equation 3), Where: Qst = Gas Flow rate at Standard Conditions, 29 = molecular weight of air, 28.9647 lb/lbmol (28.9647 g/gmol), Pst = standard gas pressure – 14.696 psia (101.325 kPa), = Universal gas constant, 1545.349 lbf ft/(lbmol °R) [8314.41 J/(kmol °K)], Tst = Standard gas temperature, 518.67°R (288.15°K). p = Density (kg/m3) Calculation is based on the isothermal gas pressure drop calculation formula. specific gravity of liquid relative to water (water = 1). ρ = Density of fluid (kg/m3) For turbulent flow, where Re > 4,000, there is complete mixing of the flow, and the flow velocity has a uniform profile; f depends on Re and the relative roughness (Є/D). 18)where. The comparisons were set up for each of the following: given inlet pressure, given ending pressure, distance in feet, pipe diameter (actual), and pipe interior surface roughness (where considered). 17)where, The density of the mixture is given by (Eq. Since “f” =0.0413 at Re = 4,000 and “f” = 0.32 at Re = 2,000, the safe alternative would be to hold the value of “f” at 0.0413between Re = 4,000 and Re = 1,549 (where 64/Re = 0.0413). 8)where, The Hazen-Williams equation, which is applicable only for water in turbulent flow at 60°F, expresses head loss as (Eq. D = internal diameter of the pipe – inches (mm). The “f” value drops to 0.032 at “Re” being 2,000, and it quickly rises to 0.064 at “Re” being 1,000. 16 provides an approximate solution for friction pressure drop in two-phase-flow problems that meet the assumptions stated. Determine Pressure drop in circular pipes: Δp = Pressure Drop (Pa or kg / m-s 2) The volume ratios for the comparisons reduce significantly, particularly at the higher pressure drops where Laminar Flow is less likely. Essentially all of the data for pipe sizes 1/4” to 3/4” was deemed to be faulty (between 5 and 100% off). There is an irregular motion of fluid particles in directions transverse to the direction of the main flow. Help with editing, Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. New York City: Crane Manufacturing Co. Engineering Data Book, ninth edition. Fig. Eq. It is also valid for gases if the pressure drop is less than 40% of the upstream pressure. Fig. and Loomis,A.W. (Results compared to Darcy). 20)where. The solutions to this calculation is plotted vs. the Reynolds number to create a Moody Chart. Re = Reynolds number As in real piping system, losses of energy are existing and energy is being added to or taken from the fluid (using pumps and turbines) these must be included in the Bernoulli equation. ~~

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