PowerPoint PresentationOutlineTypical Challenges in the Design of Complex Flow SystemsThe technique of Flow Network Modeling (FNM) as incorporated in MacroFlow enables you to analyze many design options accurately in a very short time. MacroFlow is a productivity tool.Real System – Exhaust System of a Dump TruckModeling Options for System DesignWhat is Flow Network Modeling?A Network for a Piping SystemFNM of Complex Flow SystemsAdvantages of the FNM TechniqueLimitations of FNMComplementary Nature of FNM and CFDTime Required to Analyze a Typical SystemThermal Design Process Conventional and EnhancedModified Bernoulli’s EquationFlow ResistanceSlide 17Flow Resistance of a DuctFlow Through an Area ChangeFlow Induced by FansSystem Operating PointOverall Thermal ResistanceHeat Transfer in FNMHeat Transfer in FNM (continued)FNM for System DesignMacroFlowTM A Flow Network Modeling Tool for the Design of Flow SystemsCapabilities of MacroFlowDemonstration of MacroFlowFlow through an “S” ManifoldSlide 30Flow through a “U” ManifoldSlide 32Exhaust System of a Dump Truck – Physical SystemExhaust System – The Design ProblemExhaust System – Flow Network ModelExhaust System – Design CycleLiquid Cooling System for Automatic Test EquipmentATE System – The Design ProblemLiquid Cooling System – Characteristics of One LCMSlide 40Liquid Cooling System – Distribution of Flow rates in One Branch of the ManifoldWhy use MacroFlow?Engineering Applications of MacroFlowClosing RemarksA Flow Network Modeling (FNM) ToolMacroFlowTMfor Improving Productivity ofthe Design of Complex Flow SystemsKanchan M. Kelkar, Ph. D.Principal [email protected]Overview of the Design Process and the Role of FNMTheory of FNMDemonstration of MacroFlowValidation of FNM ResultsApplications and Case studiesHands-on SessionTypical Challenges in the Design of Complex Flow SystemsBlower/Pump SizingFlow BalancingFilter DegradationBypass EffectManifold MaldistributionValve SelectionMinimizing Pressure LossTube Sizingetc.The technique of Flow Network Modeling (FNM) as incorporated in MacroFlow enables you to analyze many design options accurately in a very short time.MacroFlow is a productivity tool.Objective of the PresentationReal System – Exhaust System of a Dump Truck Flow Network Modeling is the only feasible techniqueModeling Options for System DesignHand Calculations (HC)Tedious and very limitedSpreadsheets (SS)System-specific, inflexible, and time intensiveFlow Network Modeling (FNM)Simple, fast, and accurateComputational Fluid Dynamics (CFD)Time intensive for model definition, solution, and postprocessingSuitable for component analysis, not suitable for system-level designWhat is Flow Network Modeling?Flow systems are like electrical circuits.Just as a voltage drop drives a current, a pressure drop creates fluid flow.The flow distribution through different flow paths depends upon their flow resistances.A flow system can be represented as a network of flow resistances. This approach is called Flow Network Modeling (FNM).A Network for a Piping SystemFNM of Complex Flow SystemsA network model of the flow system is constructed by identifying flow paths through filters, screens, bends, tees, blowers/pumps, valves, orifices, etc.The flow resistance relationships can be obtained from handbooks, vendor specs, in-house testing, or CFD analysis.The flow rates, pressures, and temperatures throughout the system are calculated by solving mass, momentum, and energy equations.Advantages of the FNM TechniqueFNM is simple, fast, and accurateSimple because it is modular and object-oriented Fast because it uses overall characteristicsAccurate because characteristics are empirically determinedLimitations of FNMThe flow system must be described in terms of identifiable flow paths with definable resistance characteristics. FNM provides gross (rather than detailed) predictions:FNM solution does not give local velocity vectors, flow separation, reattachment, etc.Detailed temperature distributions, local heat fluxes, etc. are not calculated.Accurate resistance correlations are needed for reliable prediction.Complementary Nature of FNM and CFDFNM allows focused and efficient use of CFDExamine hundreds of design alternatives by FNM (Conceptual Design) and select a few promising designs for CFD analysis (Detailed Design).Use FNM for an entire system and provide boundary conditions for the CFD analysis of a subsystem.Use of CFD at the component level for determining the flow resistances enhances the accuracy of the to the FNM technique.Complementary use of System Analysis and CFD results inA comprehensive set of tools for complex flow systems.Shorter design cycleTime Required to Analyze a Typical SystemSetup Time Run TimeFNM 1 Hour 10 SecondsBy using FNM, you save a substantial amount of design engineer’s timeThermal Design Process Conventional and EnhancedConventionalTest-BasedEnhancedFNM-BasedHCTestingFNM CFD TestingFNM TestingModified Bernoulli’s EquationFor constant density and no gravity head:p1 +  V12/2 = p2 +  V22/2 + LossesThe losses are due to viscous forces, flow separation, expansion/contraction, bends, etc.Losses = K( V2/2) where K is the loss coefficient.Thus, P = P1 - P2 = K(V2/2)12Flow ResistanceP = P1 - P2 = K(V2/2)Q = VA  P = K( Q2) / (2A2)Flow resistance:P /Q = (K Q) / (2A2) (nonlinear)The values of K are available for screens, orifices, bends, expansion/contraction, T-junctions, etc.For electronics cooling, the K values are needed for card arrays, heat sinks, power supplies, etc.Flow ResistanceFlow resistance correlations for various flowgeometries are given in:Idelchik, I.E., Handbook of Hydraulic Resistance, CRC Press, Florida, 1994.Blevins, R.D., Fluid Dynamics Handbook, Krieger Publishing Company, 1984.Miller, D.S., Internal Flow Systems, Gulf Publishing Company, Texas, 1990.Flow Resistance of a DuctFriction factor:f = p (D/L) / (V2/2)Thus, K = f L/DFor duct flows, f is a well-established function of the Reynolds number Re and surface roughness.Re = VD/, where  = viscosity andD = hydraulic diameter = (4)(area)/perimeterD Lp1p2Flow Through an Area Change(The color shows total pressure)For an abrupt expansion:K = (1 - A1/A2)2For an abrupt contraction:K = 0.5 (1 - A2/A1)Flow