8. Fig. Natural Gas Characteristics: Where the equations allowed input, the following was included: Natural Gas Specific Gravity = 0.60. 8—Two-phase-flow patterns in horizontal flow (courtesy of AMEC Paragon). As previously discussed, there are certain conditions under which the various formulas are more applicable. p1 = Pressure incoming (kg/m2) Tulsa, Oklahoma: Natural Gas Processors Suppliers Assn. else
Gas Processors Suppliers Assn.). The formula is applicable if the following conditions are met: There are several notable characteristics associated with pressure drop because of elevation changes in two-phase flow. The volume ratios for the comparisons reduce significantly, particularly at the higher pressure drops where Laminar Flow is less likely. liquid specific gravity relative to water. For laminar flow, where Re is < 2,000, there is little mixing of the flowing fluid, and the flow velocity is parabolic; the Moody friction factor is expressed as f = 64/Re.
They can be described as follows: Fig. Advertising Center This equation would be used to determine the capacity of a pipeline where the flow rates are below the flow where the critical “ReCr” value is 1,549: Qh = 101,990 * D4 * Δh / L ( Q = 8.50273E-06 * D4 * Δh / L ) (Equation 12). The equations are stated next. else 3—Friction-factor chart (courtesy of AMEC Paragon). (Eq. It is not unusual for measured pressure drops in the field to differ by ± 20% from those calculated by any of these models. The solutions to this calculation is plotted vs. the Reynolds number to create a Moody Chart. The Moody friction factor, f, expressed in the previous equations, is a function of the Reynolds number and the roughness of the internal surface of the pipe and is given by Fig. Fig. This page was last edited on 8 June 2015, at 09:38. Equation Reynolds Number: Re = ω D / v. Re = ρ v l / µ. Note 2: Fully Turbulent Flow is normally not encountered with low pressure gas piping. AIChE J. 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).
(With partially turbulent flow, the boundary layer between the flowing gas and the edge wall is similar to laminar flow and only determined by diameter. λ = Pipe Friction Coefficient
9—Horizontal multiphase-flow map (after Griffith).[1]. If the Reynolds number > 2320, you have turbulent flow. lg = Short for Log. Because all are based to some extent on empirical relations, they are limited in accuracy to the data sets from which the relations were designed. This equation would be used to determine the capacity of a pipeline where the flow rates are between the two flows, Qcr, where “ReCr”values are between 4,000 and 1,549: Qh = 2,380.2 * D2.5 * (Δh / L)0.5 ( Q = 0.000725636* D2.5 * (Δh / L)0.5 ) (Equation 11). Engineering Book Store l = Characteristic length, thoe chord of an airfoil, Kinematic Viscosity Table Chart of Liquids. These texts all indicate that the Darcy-Weisbach equation appears to be the most accurate method for determining pressure drop. v = Kinematic Viscosity (m2/s) in diameter (ΔP < 10% of P1).The petroleum engineer will find that the general gas equation and the Weymouth equation are very useful. The gas phase is continuous, and the bulk of the liquid is entrained within the gas. Therefore is the pressure drop along the pipe not constant. With Laminar Flow being dependent on the pipe diameter as well as the velocity, Laminar Flow is more prevalent in smaller pipes than in larger pipes. There is an irregular motion of fluid particles in directions transverse to the direction of the main flow. Calculator is applicable for any natural gas composition. However, this method has been avoided because of the difficulty of determining the value for “f” (friction coefficient). In long pipeline systems, the pressure drop through fittings and valves can often be ignored. Essentially all of the data for pipe sizes 1/4” to 3/4” was deemed to be faulty (between 5 and 100% off). 16)where, The formula for rate of mixture flow is (Eq. Re = ω l / v . Fittings such as elbows, tees and valves represent a significant component of the pressure loss in most pipe systems. Since the steel pipe tables use a whole group of sizes from 0.622 inches (15.80 mm) to 11.938-inches (304.37 mm), the need to examine Polyethylene pipe was determined to be non-essential. The variables associated with the fluid (i.e., liquid, gas, or multiphase) affect the flow. Equations displayed for easy reference. Again, the CV is published for most valves and fittings and can be found in Crane Flow of Fluids,[3] Engineering Data Book,[4] Cameron Hydraulic Data Book,[5] as well as the manufacturer’s technical data. Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read, Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro, Pipeline design consideration and standards, Reynolds number and Moody friction factor, Simplified friction pressure drop approximation for two phase flow, Pressure Drop Because of Changes in Elevation, Pressure drop caused by valves and fittings. The resistance coefficients are in most cases found through practical tests and through vendor specification documents.
A general guideline for application of the formulas is given next. Following table gives typical roughness values in millimeters for commonly used piping materials. Note: Reynolds Number Range: 4.2E+02 to 9.1E+05.
Reasonable estimates of the flow capacities can be determined by using equation 11 between the two critical flow rates and by using equation 12 when the flow rates are below the Re = 1,549 flow rate. (Eq.
7—Compressibility of low-molecular-weight natural gases (courtesy of Natl. 19. (Eq. T1 = Temperature incoming (°C) The Moody friction factor is impacted by the characteristic of the flow in the pipe. With increased gas flow, the total pressure drop may decrease as liquid is removed from uphill segments. Fig. https://petrowiki.org/index.php?title=Pressure_drop_evaluation_along_pipelines&oldid=47170, Copyright 2012-2020, Society of Petroleum Engineers.