Parrafin Melting - Scale Problems

Hello, 

My simulation consists in melting paraffin inside a heat exchanger using hot water (geometry is bellow). Initial conditions of water inlet temperature at 52?C, flow rate at 1.5l/s and the paraffin initially  at 18?C.

Geometry

My first step was to validate my model with an published article, and using real scale it works but took more than one month simulating to finish. 

Now, I want to reduce the model scale to do all the tests I need. I reduced scale (x,y and z to 0.5) and now I received this error         "Stabilizing temperature to enhance linear solver robustness." and the model is not converging anymore. I attached the summary with the methods used.

Can anyone help me?

 

 

Comments

  • edited October 2019

    Models

    ------

     

    Model Settings

    -----------------------------------------------------------------

    Space 3D

    Time Unsteady, 1st-Order Implicit

    Viscous RNG k-epsilon turbulence model

    Wall Treatment Standard Wall Functions

    RNG Differential Viscosity Model Disabled

    RNG Swirl Dominated Flow Option Disabled

    Heat Transfer Enabled

    Solidification and Melting Enabled

    Radiation None

    Species Disabled

    Coupled Dispersed Phase Disabled

    NOx Pollutants Disabled

    SOx Pollutants Disabled

    Soot Disabled

    Mercury Pollutants Disabled

    Structure Disabled

     

    Material Properties

    -------------------

     

    Material: copper (solid)

     

    Property Units Method Value(s)

    ---------------------------------------------------

    Density kg/m3 constant 8978

    Cp (Specific Heat) j/kg-k constant 381

    Thermal Conductivity w/m-k constant 387.6

     

    Material: parafin (fluid)

     

    Property Units Method Value(s)

    -------------------------------------------------------------

    Density kg/m3 constant 750

    Cp (Specific Heat) j/kg-k constant 2000

    Thermal Conductivity w/m-k constant 0.2

    Viscosity kg/m-s constant 0.008

    Molecular Weight kg/kmol constant 18.0152

    Thermal Expansion Coefficient 1/k constant 0.00259

    Pure Solvent Melting Heat j/kg constant 255000

    Solidus Temperature k constant 314.15

    Liquidus Temperature k constant 317.15

    Speed of Sound m/s none #f

     

    Material: water-liquid (fluid)

     

    Property Units Method Value(s)

    -------------------------------------------------------------

    Density kg/m3 constant 998.2

    Cp (Specific Heat) j/kg-k constant 4182

    Thermal Conductivity w/m-k constant 0.6

    Viscosity kg/m-s constant 0.001003

    Molecular Weight kg/kmol constant 18.0152

    Thermal Expansion Coefficient 1/k constant 0

    Pure Solvent Melting Heat j/kg constant 0

    Solidus Temperature k constant 0

    Liquidus Temperature k constant 0

    Speed of Sound m/s none #f

     

    Cell Zone Conditions

    --------------------

     

    Zones

     

    name id type

    -----------------------

    fin-cooper 11 solid

    tank-pcm 9 fluid

    pipe-water 10 fluid

     

    Setup Conditions

     

    fin-cooper

     

    Condition Value

    ---------------------

    Frame Motion? no

    Mesh Motion? no

     

    tank-pcm

     

    Condition Value

    ---------------------

    Frame Motion? no

    Mesh Motion? no

     

    pipe-water

     

    Condition Value

    ----------------------------

    Material Name water-liquid

    Frame Motion? no

    Mesh Motion? no

     

    Boundary Conditions

    -------------------

     

    Zones

     

    name id type

    ----------------------------------------

    inlet-water 13 mass-flow-inlet

    fin-wall 4 wall

    fin-wall.1 5 wall

    pipe-wall 6 wall

    tank-wall 12 wall

    outlet-water 14 pressure-outlet

    pipe-wall-shadow 16 wall

    fin-wall.1-shadow 15 wall

    fin-wall-shadow 8 wall

     

    Setup Conditions

     

    inlet-water

     

    Condition Value

    ---------------------------------------

    Mass Flow Rate (kg/s) 1.4973

    Total Temperature (k) 325.15

    Direction Specification Method 1

    Turbulent Intensity (%) 1

    Turbulent Viscosity Ratio 5

     

    fin-wall

     

    Condition Value

    -----------------------

    Thermal BC Type 3

     

    fin-wall.1

     

    Condition Value

    -----------------------

    Thermal BC Type 3

     

    pipe-wall

     

    Condition Value

    --------------------------------

    Wall Thickness (m) 0.001

    Thermal BC Type 3

    Wall Motion 0

    Shear Boundary Condition 0

     

    tank-wall

     

    Condition Value

    --------------------------------

    Thermal BC Type 1

    Wall Motion 0

    Shear Boundary Condition 0

     

    outlet-water

     

    Condition Value

    -----------------

     

    pipe-wall-shadow

     

    Condition Value

    --------------------------------

    Wall Thickness (m) 0.001

    Thermal BC Type 3

    Wall Motion 0

    Shear Boundary Condition 0

     

    fin-wall.1-shadow

     

    Condition Value

    --------------------------------

    Thermal BC Type 3

    Wall Motion 0

    Shear Boundary Condition 0

     

    fin-wall-shadow

     

    Condition Value

    --------------------------------

    Thermal BC Type 3

    Wall Motion 0

    Shear Boundary Condition 0

     

    Solver Settings

    ---------------

     

    Equations

     

    Equation Solved

    -------------------

    Flow no

    Turbulence yes

    Energy yes

     

    Numerics

     

    Numeric Enabled

    ---------------------------------------

    Absolute Velocity Formulation yes

     

    Unsteady Calculation Parameters

     

     

    ----------------------------------

    Time Step (s) 40

    Max. Iterations Per Time Step 20

     

    Relaxation

     

    Variable Relaxation Factor

    ----------------------------------------------

    Density 1

    Body Forces 1

    Turbulent Kinetic Energy 0.8

    Turbulent Dissipation Rate 0.8

    Turbulent Viscosity 1

    Liquid Fraction Update 0.9

    Energy 1

     

    Linear Solver

     

    Solver Termination Residual Reduction

    Variable Type Criterion Tolerance

    ------------------------------------------------------------------------

    Flow F-Cycle 0.1

    Turbulent Kinetic Energy Flexible 0.1 0.7

    Turbulent Dissipation Rate Flexible 0.1 0.7

    Energy F-Cycle 0.1

     

    Pressure-Velocity Coupling

     

    Parameter Value

    --------------------------------------------

    Type Coupled

    Pseudo Transient no

    Flow Courant Number 20

    Explicit momentum under-relaxation 0.75

    Explicit pressure under-relaxation 0.75

     

    Discretization Scheme

     

    Variable Scheme

    ------------------------------------------------

    Pressure Second Order

    Momentum Second Order Upwind

    Turbulent Kinetic Energy First Order Upwind

    Turbulent Dissipation Rate First Order Upwind

    Energy Second Order Upwind

     

    Solution Limits

     

    Quantity Limit

    ---------------------------------------

    Minimum Absolute Pressure 1

    Maximum Absolute Pressure 5e+10

    Minimum Temperature 1

    Maximum Temperature 5000

    Minimum Turb. Kinetic Energy 1e-14

    Minimum Turb. Dissipation Rate 1e-20

     

    Maximum Turb. Viscosity Ratio 100000   

  • RobRob UKForum Coordinator
    edited October 2019

    Did you scale the model in Fluent, or geometry?  Is the mass flow rate for the full model or the scaled one? 

  • saifalisaifali Member
    edited November 2019

    Is it possible to share the file

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