Parrafin Melting - Scale Problems

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  • Last Post 29 November 2019
CarolineFarias posted this 12 October 2019

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?

 

 

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CarolineFarias posted this 12 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   

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rwoolhou posted this 14 October 2019

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

saifali posted this 29 November 2019

Is it possible to share the file

s96aif

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