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convergenceof natural convection prob. in cfx |
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July 6, 2013, 09:02 |
convergenceof natural convection prob. in cfx
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prakash
Join Date: Jan 2013
Location: mumbai
Posts: 9
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hi..
i m mechanical engg student, and try to simulate a natural convection problem thar is tharmal stratification and conjugate heat transfer in straight pipe in ansys cfx. try to generate temperature gradient across the section, i m fresh in cfx.and dont know much. i have no much time to complete my problem because, plz help me. thanks in advance. prob.: i have a horizontal straight bare pipe length 1m ID, 44mm and OD 56 mm *made of stain less steel). initially filled with 50 degree C, at 160 bar operating. ambient temp is 45C, and inlet 300 C water at 0.002 m/s start entering outlet temperature is average . simulation is carried out for steady state, laminar flow analysis. but it is not meeting desired convergence criteria. convergev=nce required up to RMS 10^-4 . my cfx pre. inputs and boundary conditions are follows "C:\Program Files\ANSYS Inc\v110\CFX\bin\perllib\cfx5solve.pl" Setting up CFX Solver run ... +--------------------------------------------------------------------+ | | | CFX Command Language for Run | LIBRARY: CEL: EXPRESSIONS: cpC = -0.20592 [J kg^-1 K^-3] cpD = 1.75442E-4 [J kg^-1 K^-4] cpA = -6550.39577 [J kg^-1 K^-1] cpB = 81.26306 [J kg^-1 K^-2] cp = cpA+cpB*T+cpC*T^2+cpD*T^3 denB = 1.36311 [kg m^-3 K^-1] denC = -0.0027 [kg m^-3K^-2] denA = 833.93908 [kg m^-3 ] den = denA+denB*T+denC*T^2 kB = 0.02039 [W m^-1 K^-2] kC = -6.1901E-5 [W m^-1 K^-3] kE = -4.99387E-11 [W m^-1 K^-5] kD = 8.74777E-8 [W m^-1 K^-4] kA = -1.87631 [W m^-1 K^-1] k = kA+kB*T+kC*T^2+kD*T^3+kE*T^4 outletTemp = areaAve(T)@REGION:OUTLET visD = -6.68023E-10 [Pa s K^-3] visB = -1.67183E-4 [Pa s K^-1] visC = 5.00487E-7 [Pa s K^-2] visA = 0.02121 [Pa s] visE = 3.34164E-13 [Pa s K^-4] vis = visA+visB*T+visC*T^2+visD*T^3+visE*T^4 END END MATERIAL: ASME SA312 type 316 Material Group = User Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 8000 [kg m^-3] Molar Mass = 55.85 [kg kmol^-1] Option = Value END REFERENCE STATE: Option = Specified Point Reference Temperature = 408.15 [K] END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 500 [J kg^-1 K^-1] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 16.3 [W m^-1 K^-1] END END END MATERIAL: Steel Material Group = CHT Solids,Particle Solids Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 7854 [kg m^-3] Molar Mass = 55.85 [kg kmol^-1] Option = Value END REFERENCE STATE: Option = Automatic END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 4.34E+02 [J kg^-1 K^-1] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 60.5 [W m^-1 K^-1] END END END MATERIAL: Water Material Description = Water (liquid) Material Group = Water Data Option = Pure Substance Thermodynamic State = Liquid PROPERTIES: Option = General Material Thermal Expansivity = 0.001208 [K^-1] ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END DYNAMIC VISCOSITY: Dynamic Viscosity = vis Option = Value END EQUATION OF STATE: Density = den Molar Mass = 18.02 [kg kmol^-1] Option = Value END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = cp Specific Heat Type = Constant Pressure END TABLE GENERATION: Maximum Absolute Pressure = 20 [MPa] Maximum Temperature = 600 [K] Minimum Absolute Pressure = 0 [MPa] Minimum Temperature = 273.15 [K] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = k END END END END FLOW: SOLUTION UNITS: Angle Units = [rad] Length Units = [m] Mass Units = [kg] Solid Angle Units = [sr] Temperature Units = [K] Time Units = [s] END SIMULATION TYPE: Option = Steady State EXTERNAL SOLVER COUPLING: Option = None END END DOMAIN: wall Domain Type = Solid Location = WALL Solids List = Steel BOUNDARY: Domain Interface 1 Side 2 Boundary Type = INTERFACE Location = Primitive 2D A BOUNDARY CONDITIONS: HEAT TRANSFER: Option = Conservative Interface Flux END END END BOUNDARY: wall Default Boundary Type = WALL Location = OUTERSURFACE,Primitive 2D C,Primitive 2D D BOUNDARY CONDITIONS: HEAT TRANSFER: Heat Transfer Coefficient = 10 [W m^-2 K^-1] Option = Heat Transfer Coefficient Outside Temperature = 320.15 [K] END END END DOMAIN MODELS: DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END END INITIALISATION: Option = Automatic INITIAL CONDITIONS: TEMPERATURE: Option = Automatic with Value Temperature = 323.15 [K] END END END SOLID MODELS: HEAT TRANSFER MODEL: Option = Thermal Energy END THERMAL RADIATION MODEL: Option = None END END END DOMAIN: water Coord Frame = Coord 0 Domain Type = Fluid Fluids List = Water Location = WATER BOUNDARY: Domain Interface 1 Side 1 1 Boundary Type = INTERFACE Location = Primitive 2D B BOUNDARY CONDITIONS: HEAT TRANSFER: Option = Conservative Interface Flux END WALL INFLUENCE ON FLOW: Option = No Slip END END END BOUNDARY: INLET Boundary Type = INLET Location = INLET BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = 573.15 [K] END MASS AND MOMENTUM: Normal Speed = 0.002 [m s^-1] Option = Normal Speed END END END BOUNDARY: OUTLET Boundary Type = OPENING Location = OUTLET BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = outletTemp END MASS AND MOMENTUM: Option = Static Pressure for Entrainment Relative Pressure = 0 [Pa] END END END DOMAIN MODELS: BUOYANCY MODEL: Buoyancy Reference Density = 891.48 [kg m^-3] Buoyancy Reference Temperature = 456 [K] Gravity X Component = 0 [m s^-2] Gravity Y Component = -9.81 [m s^-2] Gravity Z Component = 0 [m s^-2] Option = Buoyant BUOYANCY REFERENCE LOCATION: Option = Automatic END END DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END REFERENCE PRESSURE: Reference Pressure = 0 [MPa] END END FLUID MODELS: COMBUSTION MODEL: Option = None END HEAT TRANSFER MODEL: Option = Thermal Energy END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Option = Laminar END END INITIALISATION: Option = Automatic INITIAL CONDITIONS: Velocity Type = Cartesian CARTESIAN VELOCITY COMPONENTS: Option = Automatic END STATIC PRESSURE: Option = Automatic END TEMPERATURE: Option = Automatic with Value Temperature = 323.15 [K] END END END END DOMAIN INTERFACE: Domain Interface 1 Boundary List1 = Domain Interface 1 Side 1 1 Boundary List2 = Domain Interface 1 Side 2 Interface Type = Fluid Solid INTERFACE MODELS: Option = General Connection FRAME CHANGE: Option = None END PITCH CHANGE: Option = None END END MESH CONNECTION: Option = GGI END END OUTPUT CONTROL: RESULTS: File Compression Level = Default Option = Standard END END SOLVER CONTROL: ADVECTION SCHEME: Option = High Resolution END CONVERGENCE CONTROL: Maximum Number of Iterations = 2000 Physical Timescale = 2 [s] Solid Timescale Control = Auto Timescale Timescale Control = Physical Timescale END CONVERGENCE CRITERIA: Residual Target = 0.0001 Residual Type = RMS END DYNAMIC MODEL CONTROL: Global Dynamic Model Control = Off END END END COMMAND FILE: Version = 11.0 Results Version = 11.0 END EXECUTION CONTROL: INTERPOLATOR STEP CONTROL: Runtime Priority = Standard EXECUTABLE SELECTION: Double Precision = Off END MEMORY CONTROL: Memory Allocation Factor = 1.0 END END PARALLEL HOST LIBRARY: HOST DEFINITION: kewat Host Architecture String = intel_p3.sse_winnt5.1 Installation Root = C:\Program Files\ANSYS Inc\v%v\CFX END END PARTITIONER STEP CONTROL: Multidomain Option = Independent Partitioning Runtime Priority = Standard EXECUTABLE SELECTION: Use Large Problem Partitioner = Off END MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARTITIONING TYPE: MeTiS Type = k-way Option = MeTiS Partition Size Rule = Automatic END END RUN DEFINITION: Definition File = D:\M.Tech\trail 3rd_at anb45c and \ Highresuation\trail_3rd.def Interpolate Initial Values = Off Run Mode = Full END SOLVER STEP CONTROL: Runtime Priority = Standard EXECUTABLE SELECTION: Double Precision = Off END MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARALLEL ENVIRONMENT: Number of Processes = 1 Start Method = Serial END END END +--------------------------------------------------------------------+ | | | Solver | | | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | | | ANSYS CFX Solver 11.0 | | | | Version 2007.01.15-19.20 Mon Jan 15 19:24:21 GMTST 2007 | | | | Executable Attributes | | | | single-int32-32bit-novc6-optimised-supfort-noprof-nospag-lcomp | | | | Copyright 1996-2007 ANSYS Europe Ltd. | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | Job Information | +--------------------------------------------------------------------+ Run mode: serial run Host computer: KEWAT Job started: Fri Jul 05 16:29:28 2013 +--------------------------------------------------------------------+ | Memory Allocated for Run (Actual usage may be less) | +--------------------------------------------------------------------+ Data Type Kwords Words/Node Words/Elem Kbytes Bytes/Node Real 101526.5 211.91 222.18 396587.9 847.63 Integer 51398.6 107.28 112.48 200775.9 429.12 Character 2864.8 5.98 6.27 2797.7 5.98 Logical 65.0 0.14 0.14 253.9 0.54 Double 1208.0 2.52 2.64 9437.5 20.17 +--------------------------------------------------------------------+ | ****** Notice ****** | | Wall Heat Transfer Coefficient written to the results file uses | | "Wall Adjacent Temperature" for the bulk temperature. If you want | | to override the bulk temperature then set the expert parameter | | "tbulk for htc = <value>" | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | Mesh Statistics | +--------------------------------------------------------------------+ Domain Name : water Total Number of Nodes = 398177 Total Number of Elements = 389760 Total Number of Hexahedrons = 389760 Total Number of Faces = 16224 Minimum Orthogonality Angle [degrees] = 71.6 OK Maximum Aspect Ratio = 54.4 OK Maximum Mesh Expansion Factor = 1.5 OK Domain Name : wall Total Number of Nodes = 80928 Total Number of Elements = 67200 Total Number of Hexahedrons = 67200 Total Number of Faces = 27360 Minimum Orthogonality Angle [degrees] = 86.9 OK Maximum Aspect Ratio = 4.4 OK Maximum Mesh Expansion Factor = 1.2 OK Global Statistics : Global Number of Nodes = 479105 Global Number of Elements = 456960 Total Number of Hexahedrons = 456960 Global Number of Faces = 43584 Minimum Orthogonality Angle [degrees] = 71.6 OK Maximum Aspect Ratio = 54.4 OK Maximum Mesh Expansion Factor = 1.5 OK Domain Interface Name : Domain Interface 1 Non-overlap area fraction on side 1 = 0.00E+00 Non-overlap area fraction on side 2 = 0.00E+00 +--------------------------------------------------------------------+ | Buoyancy Reference Information | +--------------------------------------------------------------------+ Domain Group: water Buoyancy has been activated. The absolute pressure will include hydrostatic pressure contribution, using the following reference coordinates: (-1.71162E-11,-3.77106E-12,-1.00000E+00). +--------------------------------------------------------------------+ | Average Scale Information | +--------------------------------------------------------------------+ Domain Name : water Global Length = 1.1488E-01 Minimum Extent = 4.4000E-02 Maximum Extent = 1.0000E+00 Density = 9.9248E+02 Dynamic Viscosity = 5.5002E-04 Velocity = 2.0000E-03 Advection Time = 5.7441E+01 Reynolds Number = 4.1460E+02 Thermal Conductivity = 6.5603E-01 Specific Heat Capacity at Constant Pressure = 4.1267E+03 Prandtl Number = 3.4598E+00 Domain Name : wall Global Length = 9.7951E-02 Minimum Extent = 5.6000E-02 Maximum Extent = 1.0000E+00 Density = 7.8540E+03 Thermal Conductivity = 6.0500E+01 Specific Heat Capacity at Constant Pressure = 4.3400E+02 Thermal Diffusivity = 1.7749E-05 Average Timescale = 5.4056E+02 Minimum Timescale = 1.7669E+02 Maximum Timescale = 5.6341E+04 I need urs expert comment. waiting for the reply.. plz help again thanx.. |
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