1.GBH Enterprises, Ltd.Process Engineering Guide: GBHE-PEG-FLO-300Estimation of Pressure Drop in Pipe SystemsInformation contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the information for its own particular purpose. GBHE gives no warranty as to the fitness of this information for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com

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Process Engineering Guide:Estimation of Pressure Drop in Pipe SystemsCONTENTS 0INTRODUCTION/PURPOSE51SCOPE52FIELD OF APPLICATION53DEFINITIONS63.1 units64SOURCES OF DATA65BASIC CONCEPTS75.1 Equation for Pressure Change in a Flowing Fluid 5.2 Static and Stagnation Pressures 5.3 Sonic Flow67 8 10INCOMPRESSIBLE FLOW IN PIPES OF CONSTANT CROSS-SECTION116.1 Straight Circular Pipes 6.2 Ducts of Non-circular Cross-section 6.3 Coils 6.4 General Equation for Incompressible Flow in Pipes of Constant Cross-section11 16 19 20Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 3. 7COMPRESSIBLE FLOW IN PIPES OF CONSTANT CROSS-SECTION7.1 Isothermal Flow 7.2 Adiabatic Flow 7.3 Estimation of Pressure Drop for Adiabatic Flow in Pipes of Constant Cross-section 7.4 Ratio of Isothermal to Adiabatic Pressure Drop8FLOW IN PIPE FITTINGS 8.1 Incompressible Flow 8.2 Compressible Flow9FLOW IN BENDSCHANGES IN CROSS-SECTIONAL AREA 9.1 Incompressible Flow 9.2 Compressible Flow1121 22 29 3233 33 35 389.1 Incompressible Flow in Bends 9.2 Compressible Flow in Bends 1021ORIFICES, NOZZLES AND VENTURIS38 47 48 48 515511.1 Incompressible Flow through an Orifice 56 11.2 Compressible Flow through an Orifice or Nozzle 57 11.3 Venturi Choke Tubes 6112VALVES6412.1 General 12.2 Incompressible Flow in Valves 12.2 Compressible Flow in Valves64 65 76Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 4. 13COMBINING AND DIVIDING FLOW789.1 Incompressible Flow 9.2 Compressible Flow78 8414COMPUTER PROGRAMS FOR FLUID FLOW8615NOMENCLATURE8616REFERENCES90APPENDICESABASIC THERMODYNAMICS92BCOMPRESSIBLE FLOW THROUGH ORIFICES102CTHE TWO-K METHOD FOR FITTING PRESSURE LOSS104Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 5. TABLES 1DEFINITIONS OF FRICTION FACTOR122TYPICAL ROUGHNESS VALUES133HYDRAULIC MEAN DIAMETER FOR DIFFERENT CHANNELS174RATIO OF ISOTHERMAL TO ADIABATIC PRESSURE GRADIENT 325LOSS COEFFICIENTS Kb FOR 90 BENDS386PRESSURE LOSS COEFFICIENTS FOR SINGLE MITRE BENDS40APPROXIMATE BASE LOSS COEFFICIENTS K*b FOR 90 MITRE BENDS42INTERACTION CORRECTION FACTOR FOR COMBINATIONS OF TWO 90 BENDS45LOSS COEFFICIENTS Kb FOR 90 BENDS COMPRESSIBLE FLOW47PRESSURE DROP PARAMETERS FOR DISCS AND ROUND WIRE GAUZES5611CRITICAL PRESSURE RATIOS5812FLOW AND LOSS COEFFICIENTS FOR DURCO PLUG VALVES 6913LOSS COEFFICIENTS FOR DURCO BUTTERFLY VALVES7214LOSS COEFFICIENTS FOR BATLEY BUTTERFLY VALVES7215LOSS COEFFICIENTS FOR SAUNDERS TYPE KB DIAPHRAGM VALVES74VALVE TYPE CONSTANTS C1777891016Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 6. FIGURES 1MOODY CHART - FRICTION FACTOR vs REYNOLDS NUMBER 142SHAPE FACTOR K2 FOR NON-CIRCULAR DUCTS183SECONDARY FLOW PATTERNS IN COILS194FACTOR FOR GAS FLOW IN A PIPE225RELATIONSHIP BETWEEN PRESSURE AND FRICTION FACTOR REQUIRED TO PRODUCE SONIC FLOW AT PIPE OUTLET 256RELATIONSHIP BETWEEN STATIC PRESSURE AND MACH NUMBER267STAGNATION PRESSURE278PRESSURE PLUS MOMENTUM FLUX289COMPARISON OF OVERALL AND TRUE PRESSURE DROP IN FITTINGS37APPROXIMATE LOSS COEFFICIENT FOR 90 CIRCULAR BENDS OF r/d BETWEEN 1.5 AND 2.0 AT LOW REYNOLDS NUMBERS3911OUTLET TANGENT CORRECTION4012MITRE BEND LOSS COEFFICIENTS4113NOTATION FOR COMBINATIONS OF TWO 90 BENDS4414CORRECTION FACTORS FOR 0 COMBINED BENDS4615CORRECTION FACTORS FOR 90 COMBINED BENDS4616CORRECTION FACTORS FOR 180 COMBINED BENDS4717TYPES OF CONTRACTION4910Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 7. 18CONTRACTION5119ENLARGEMEN5220CHANGE IN MACH NUMBER FOR COMPRESSIBLE FLOW THROUGH A SUDDEN ENLARGEMENT5421SCHEMATIC OF FLOW THROUGH AN ORIFICE5522ORIFICE FLOW vs PRESSURE RATIO6023TYPICAL VENTURI CHOKE TUBE6124VENTURI STATIC PRESSURE DROP AT CRITICAL CONDITIONS63VARIATION OF VENTURI PRESSURE DROP WITH FLOWRATE6426VALVES WITH ALMOST LINEAR CHARACTERISTICS6627CHARACTERISTICS OF EQUAL PERCENTAGE VALVES6728BALL VALVE LOSS COEFFICIENTS6829VARIATION OF Cv AND Kv WITH POSITION6930APPROXIMATE EFFECT OF REYNOLDS NUMBER, GATE, PLUG AND BUTTERFLY VALVES7031LOSS COEFFICIENTS FOR BUTTERFLY VALVES7132DIAPHRAGM VALVE LOSS COEFFICIENTS7333APPROXIMATE EFFECT OF REYNOLDS NUMBER, POPPET TYPE AND DIAPHRAGM VALVES7334FULLY OPEN GATE VALVE LOSS COEFFICIENTS7535GATE AND SLUICE VALVE LOSS COEFFICIENTS7536APPROXIMATE LOSS COEFFICIENTS FOR FULLY OPEN GLOBE VALVES7625Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 8. 37TEE JUNCTIONS WITH RIGHT-ANGLED BRANCHES7838TEE JUNCTIONS WITH A DEAD LEG8239TYPES OF 3-LEG JUNCTION8440MODEL FOR COMPRESSIBLE FLOW IN A JUNCTION8541SCHEMATIC OF FLOW THROUGH AN ORIFICE102DOCUMENTS REFERRED TO IN THIS PROCESS ENGINEERING GUIDE105Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 9. 0INTRODUCTION / PURPOSE This Process Engineering Guide is one of a series on fluid flow produced by GBH Enterprises. 1 SCOPE This guide recommends methods for the estimation of pressure drop for the steady state flow of single phase Newtonian liquids and compressible fluids (gases and vapors) in pipe systems. It covers most of the geometries likely to be encountered in normal design cases. Further information on more unusual geometries may be found in Miller [1990]. It does not cover liquids that are non-Newtonian in their behavior, that is, liquids for which, when sheared in laminar flow, the shear stress is not directly proportional to the shear rate. For general information on nonNewtonian behavior see GBHE-PEG-FLO-302. For estimation of the pressure drop for pipeline flow of such fluids see GBHE-PEG-FLO-303 and GBHE-PEG-FLO-304. It does not cover slurries. Slurries with low solids contents may be Newtonian in behavior, but in general most slurries are non-Newtonian. It does not cover pressure drop for two phase gas-liquid flow. It does not cover the gravity driven flow of liquids in partially filled pipes and open channels. Information on this subject can be found in GBHEPEG-FLO-301. It does not cover unsteady fluid flow. An introduction to unsteady state flow (pressure surge) in incompressible systems is given in GBHE-PEGFLO-305. GBHE has access to proprietary computer programs, that may be used to model unsteady state compressible and incompressible flows. The data and methods given in this PEG are suitable for hand calculations, or for incorporation into computer codes.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 10. 2 FIELD OF APPLICATION This guide applies to the process engineering community in GBH Enterprises worldwide. GBHE-PEG-FLO-300 3DEFINITIONS For the purposes of this guide, the following definitions apply: ESDU HTFS3.1Engineering Sciences Data Unit Heat Transfer and Fluid Flow Service. A co-operative research organization, with headquarters at Harwell, UK, involved in research into the fundamentals of heat transfer and two phase flow and the production of design guides and computer programs for the design of industrial heat exchange equipment.Units All equations in this guide are in coherent units unless stated otherwise. Normally, base units for the SI system are used. For example: Length Diameter Time Viscosity-Force Pressure Mass flow Volume flow Temperature -m m s kg.m-1 s-1 (1 kg.m-1 s-1 = 1 N.s.m-2, 1 cP = 10-3 kg.m-1.s-1) N (1 N = 1 kg.m.s-2) N.m-2 (1 bar = 105 N.m-2) kg.s-1 m3.s-1 KUsually, symbols are defined after the equation in which they first occur, and base SI units are given. However, the equations are, in general, equally valid if the individual terms are expressed in any other coherent set of units. Any constants in the equations will then be dimensionless. There are a few equations that include dimensional constants. For these, individual terms must be expressed in the appropriate units, which are indicated with the equations. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 11. A full list of symbols, with the appropriate base SI units, is given in clause 15. 4SOURCES OF DATA The pressure losses through pipe fittings are dependent on the exact geometry of the fitting. Whereas the geometry for straight pipes and bends is readily definable, this is not the case for proprietary items such as valves, where nominally similar items from different manufacturers may have markedly different characteristics. If such components form a significant portion of the total pressure drop, manufacturers data should if possible be used in preference to those contained in this guide.5BASIC CONCEPTS 5.1 Equation for Pressure Change in a Flowing Fluid The change in static pressure during the flow of a fluid in a pipe is the sum of three factors: (a)Pressure change due to change in elevation.(b)Pressure change due to change in kinetic energy.(c)Pressure change due to frictional effects.The first two of these factors can result in either a pressure loss or a pressure gain, and are known as reversible changes; the pressure change can be reversed by reversing the process. Friction, on the other hand, always results in a fall in pressure in the direction of flow, and is an irreversible change. It is the process whereby mechanical energy is degraded into heat. The basic equation for pressure change for any flowing fluid is:Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 12. Where: g K= =P v z = = = = =acceleration due to gravity (m.s-2) number of velocity heads lost due to friction, or frictional pressure loss coefficient (-) static pressure (N.m-2) velocity of the fluid (m.s-1) elevation of pipe above datum (m) kinetic energy factor (-) density of the fluid (kg.m-3)This equation can be deduced from basic thermodynamics for any fluid. See Appendix A for details of the derivation. The first of the terms on the right hand side of equation 5.1 is the change in pressure due to changes in elevation, the second is the change due to changes in kinetic energy and the third is the change due to frictional losses. The kinetic energy factor, , allows for the effects of a non-uniform velocity profile, as explained in Appendix A. This is important for laminar flow, where the value of for established flow in a straight pipe is equal to 2. However, for established turbulent flow has a value of only about 1.05. In common with most texts on the subject, will in general be omitted from equations in the main body of this document. For most cases where the effects of compressibility are important, the flow is likely to be turbulent. For liquid flows, laminar flow is more of a possibility, and in these cases the methods given should be modified. However, there are few reliable data for laminar flow through fittings. Equation 5.1 applies to all fluids. For an incompressible fluid, the density is constant and the first two terms of equation 5.1 can be integrated directly:For a pipe of constant diameter with an incompressible fluid, v is constant, the second term disappears and the third can be integrated to give:Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 13. For a fitting where the cross sectional area is changing, the third term cannot in general be integrated analytically. It is normal practice in this case to express the loss coefficient for the fitting in terms of the velocity at either the inlet or outlet position.where v r refers to the reference conditions, either the inlet or outlet. Note: In general, the loss coefficient K is not constant, but a function of the Reynolds number. For a compressible fluid, the density is a function of both temperature and pressure, and equation 5.1 cannot be so readily integrated. It is necessary to introduce the equation of state for the fluid to relate the density to temperature and pressure. See Appendix A3. However, the elevation term for gas flow can generally be neglected, so equation 5.1 simplifies to:5.2Static and Stagnation Pressures The term designated by P in the above equations is the static pressure. For a fluid at rest, it is simply the pressure that would be measured by any pressure-measuring device. For a fluid in motion, the static pressure is the pressure measured in a direction normal to the local direction of flow. GBHE-PEG-FLO-3009 If a flowing fluid with a velocity v is brought to rest in a reversible manner, the pressure will rise to the "stagnation pressure" P0. (The term "total pressure" is sometimes used instead of stagnation pressure.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 14. 5.2.1 Incompressible Flow For an incompressible fluid the stagnation pressure is given by:This can be readily seen by applying equation 5.2, omitting the elevation and frictional terms and putting v2 to zero. For an incompressible fluid, the term v2 is known as the "dynamic pressure" or the "velocity pressure", PvSome references work in terms of fluid head rather than pressure, particularly when considering the flow of liquids. A vertical column of liquid exerts a pressure at its base given by:where: g Hs Pg= = ==acceleration due to gravity m.s-2 height of liquid column m static pressure above atmospheric pressure (gauge pressure) N.m-2 liquid density Kg.m-3If this column of liquid is connected at its base to a fluid system, then provided that the fluid is at rest, or the base of the column is parallel to the local direction of flow, the height Hs is a measure of the (gauge) static pressure at the point of attachment, and is termed the "static head". If working in terms of head rather than pressure, the quantity corresponding to the dynamic pressure is the "velocity head" Hv and that corresponding to the stagnation pressure is the "total head" H0.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 15. Note: The dynamic pressure Pv is sometimes loosely referred to as the velocity head. 5.2.2 Compressible Flow For a compressible fluid the relation between static and stagnation pressures is more complex, as the density of the fluid changes as it is brought to rest. The stagnation pressure is related to the static pressure by the equation:where: k M= =the isentropic exponent for the fluid in question the Mach number (see 5.3 below)This equation is derived in Appendix A. For a compressible fluid, the dynamic or velocity pressure may be defined either by equation 5.7 above, or as the difference between the stagnation and static pressures.These two definitions are not equivalent, and do not give the same values.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 16. 5.3Sonic FlowIf an incompressible fluid is flowing in a pipe of constant cross section, the pressure gradient down the pipe is constant. For a compressible fluid, on the other hand, as the pressure falls along the pipe so does the density, and the pressure gradient increases with distance down the pipe. If the pressure in a receiver at the downstream end of a pipe is lowered, a point will be reached where the exit velocity from the pipe has reached the sonic velocity. Further reductions in downstream pressure will not result in an increase in mass flowrate down the pipe. Instead, there will be a pressure discontinuity at the exit of the pipe, and the emerging jet will expand down to the pressure in the receiver through a complex series of shocks. The pressure discontinuity is known as a choke. Sonic velocity represents the maximum practical flowrate in normal pipe systems. Sonic velocity will usually only occur at locations where there is an increase in flow area. Thus it can occur at the ends of pipes, at expansions within pipes and at valves, orifices and nozzles in pipes. Following an expansion with a choke, after the shock system the fluid in the larger diameter section will be flowing at a sub-sonic velocity. As it flows along this second pipe the pressure will continue to fall and the fluid will accelerate back towards sonic conditions. It is possible to have more than one choke in a pipe if there are successive increases in flow area, but the first position at which choking occurs dictates the maximum flowrate possible. It is convenient to express the flowrate for high speed compressible flow in terms of the Mach number M, which is the ratio of the fluid velocity to the velocity of sound under the local conditions of temperature and pressure:where: k R T v W Z= = = = = =the isentropic exponent for the fluid in question universal gas constant (= 8314 J. kmole-1.K-1) static temperature (K) fluid velocity (m.s-1) molecular weight of the gas (kg.kmole-1) is the compressibility (correction factor for deviation from ideal gas laws)Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 17. 6INCOMPRESSIBLE FLOW IN PIPES OF CONSTANT CROSS-SECTION6.1Straight Circular Pipes The pressure drop due to friction for steady state flow in a straight pipe of constant diameter can be related to the wall shear stress by the force balance:where: dP f d w dL= = = =Friction pressure drop N.m-2 pipe diameter m wall shear stress N.m-2 increment of pipe length mHence, re-arranging and expressing in terms of the dynamic pressure, as defined by equation 5.7,This equation may also be written in two alternative ways:where K is the frictional pressure loss coefficient. This form corresponds to the last term of equation 5.4.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 18. where: C n= =a friction factor a constant, whose value depends on the form taken by the friction factor.Unfortunately, there is no general agreement on the form that the friction factor should take. Table 1 shows the forms quoted in several sources commonly used in GBH Enterprises. The 4th column of Table 1 shows the relationship between the value of the friction factor in laminar flow, C lam and the Reynolds number Re. The Reynolds number for flow in a circular pipe is defined as:where:The mass flux G is defined as the mass flow per unit cross sectional area. TABLE 1DEFINITIONS OF FRICTION FACTORRefinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 19. It is obviously essential that, when a friction factor is quoted, the form used should be clearly understood. An easy way to determine the form used is to look at the variation of friction factor with Reynolds number for laminar flow, as given in the last column of Table 1. This guide, to maintain continuity with V/CP/17 and P/CP/4, uses the Moody form of the friction factor. Thus the frictional pressure drop for straight pipe flow is given by:The friction factor is a function of the Reynolds number, Re, and the relative roughness, /d, where is the absolute roughness of the inside surface of the pipe and d is the pipe inside diameter. Suggested values of for some typical pipe materials are given in Table 2. Note: Different sources may quote different values for the same material.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 20. TABLE 2TYPICAL ROUGHNESS VALUESA useful way of presenting friction factors is the Moody Chart, which shows the friction factor as a function of the Reynolds number for a range of values of relative roughness (Figure 1). Figure 1 is based on the Moody definition of friction factor. Different sources may be based on different definitions of friction factor: they will have different scales for the vertical axis, but may still refer to the chart as a "Moody Chart".Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 21. FIGURE 1MOODY CHART - FRICTION FACTOR vs REYNOLDS NUMBERRefinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 22. Note: For laminar flow, the friction factor is independent of roughness, and is given by:Equation 6.5 applies in the laminar flow region, up to a Reynolds number of about 2100. For turbulent flow, the Moody chart is a plot of the Colebrook-White equation:This equation was derived from a systematic analysis of experimental data taken on a range of smooth and artificially roughened pipes. The Colebrook-White equation has the disadvantage that it cannot be solved directly, as the friction factor appears on both sides of the equation. Several equations that give the friction factor explicitly have been developed. V/CP/17 and Miller [1990] suggest the following equation, which agrees with the Colebrook-White equation to within 2%:Equations 6.6 and 6.7 apply for Reynolds numbers above about 4000. Between 2100 and 4000, the transition region, the friction factor is uncertain, and depends amongst other things on the upstream flow conditions and also the past history of the flow; hysteresis effects may occur. This region should be avoided for design if possible. If calculations are required for this region, the recommendation is to interpolate between the laminar value at Re = 2100 and the turbulent value at Re = 4000. The pressure drop in a pipe is sensitive to the pipe diameter. Equation 6.4 may be written as:Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 23. where: A F= =pipe cross-sectional area (m2) mass flowrate (kg.s-1)For a rough pipe at high Reynolds number, the friction factor is independent of Reynolds number, and thus the pressure drop varies inversely with the fifth power of the pipe diameter. For a smooth pipe, the friction factor is reasonably represented by the Blasius equation:Hence, as the Reynolds number for a given mass flow is inversely proportional to the diameter, for a smooth pipe the pressure drop varies inversely with the diameter to the power 4.75. For laminar flow, the friction factor varies as the inverse of the Reynolds number, and thus the pressure drop is inversely proportional to the diameter raised to the power 4. It is given by Poiseuilles equation:Poiseuilles equation can be derived theoretically; details are given in standard text books. See, for example, Coulson & Richardson. It can also be deduced from equations 6.4 and 6.5, thus demonstrating a theoretical basis for equation 6.5. Hence, it is essential that the actual internal diameter of the pipe be used when calculating pressure drops. A 10% reduction in pipe diameter results in a 52 to 70% increase in pressure drop, even assuming no change in the relative roughness. If the reduction is due to fouling, the relative roughness could increase significantly, and the overall effect on pressure drop be even higher. Note: The thickness of a heavy duty plastic lining in a pipe may be 4 mm, reducing the bore by 8 mm, which is approximately 10% for a 3" nominal bore pipe.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 24. The main difficulty in calculating friction losses in straight pipes is the uncertainty in selecting a value for the pipe roughness. Consider, for example, water at 20C flowing at 2 m/s in a mild steel pipe of diameter 0.1 m. The Reynolds number in this case is 2x10 5. Table 6.2 suggests three different values for the roughness of carbon steel, corresponding to the conditions slightly corroded, moderate rust layer and badly corroded. The values are 0.05, 0.25 and 1.0 mm respectively. Using these values, the friction factors at Re = 2x105 are 0.19. 0.275 and 0.38 respectively. There is thus a factor of two between the extremes of calculated pressure drop. 6.2Ducts of Non-circular Cross-sectionThe friction factors given in Figure 1 or equations 6.5 to 6.7 may be used for calculating pressure drops in non-circular straight ducts with the following adjustments. (a) The Reynolds number should be calculated based on the true mass flux through the duct, i.e. the actual mass flowrate divided by the cross sectional area for flow, but the characteristic dimension used in the Reynolds number should be the hydraulic mean diameter de:(b) The friction factor based on the above Reynolds number should be corrected by a factor K2 to allow for geometric effects (see below)(c) The pressure drop is then given by equation 6.4, with the diameter d replaced by the hydraulic mean diameter de. Table 3 shows the definition of hydraulic mean diameter for some common non-circular channels. Note that for a circular cross-section, the hydraulic mean diameter equates to the actual diameter.Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 25. TABLE 3 HYDRAULIC MEAN DIAMETER FOR DIFFERENT CHANNELSFigures 2a to 2d show the values of K2 for the cross-sections given in Table 3. Note the following points: (1)K2 is independent of Reynolds number for laminar flow, and nearly independent for turbulent flow, and is taken as independent for all Reynolds numbers.(2)In general, the effects of K2 are greater for laminar flow than for turbulent flow. For the concentric annulus and the rectangle, K2 is unity for turbulent flow.(3)The values of K2 for turbulent flow apply to hydraulically smooth surfaces. No information is available on the effects of roughness in these geometries. In the absence of any data, assume that the value of K2 will apply equally to rough tubes, where the relative roughness is the ratio of the absolute roughness to the equivalent diameter.(4)For other ducts having shapes which depart significantly from circular or rectangular cross sections, consult section 8.3.4 of Miller [1990].Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 26. FIGURE 26.3SHAPE FACTOR K2 FOR NON-CIRCULAR DUCTSCoilsSingle phase flow in helically coiled tubes differs from that in straight tubes because of the effects of centrifugal force on the fluid. This is greatest on the fastest moving fluid at the centre of the tube; as a result, a secondary flow pattern is set up, with two recirculation systems (see Figure 3).Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 27. FIGURE 3SECONDARY FLOW PATTERNS IN COILSThis secondary flow system tends to stabilize laminar flow, increasing the transition Reynolds number between laminar and turbulent flow. The recommended transition Reynolds number is given in HTFS Handbook [HTFS 1976].where: d D Rec= = =pipe internal diameter (m) diameter of helix (m) transition Reynolds numberRefinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 28. The secondary flow, by increasing the dissipation of turbulent energy, increases the friction factor above that for straight pipe flow. The following equations for friction factor in coiled pipes, taken from HTFS 1976, are recommended. Note: These equations have been changed from their original form to allow for the different definition of friction factor used in this guide from that in HTFS Handbook. For laminar flow, the friction factor is a function of the Dean number, DN, defined as:Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com 29. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com