Documentation

User Guide: Forced Convection Heat Transfer

Overview:

In this user guide, we explain the simulation process of  forced convective heat transfer in Rasberry Pi (Electronic cooling).

Link to project containing the geometry:

Import tutorial project into workbench

  • As a first step we need to create a new simulation. To create a simulation left click under the Geometries  and then on Create Simulation.
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Create Simulation after importing the geometry
  • Select the simulation model. Click on convective Heat Transfer
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Select the Convective heat transfer simulation model

Topological Entities

  • Its important we create topological entities which can be later easily assigned to boundary conditions
  • we have in total 95 faces
  • Inlet and outlet faces form two topological entities. Left click on them to highlight them and create topological entities as shown below
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Create inlet and outlet topological entities
  • The chip faces are also categorized as topological entities.
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Create Topological entities for chips
  • The bottom surface is categorized as board
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Create a topological entity for the bottom surface
  • All the remaining surfaces are to be categorized as walls. Use the Active box selection to select all the faces and deselect the faces from the previous topological entities ‘walls’
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Create a topological entity for other surfaces as walls

Mesh Generation

  •  Left click on the mesh icon to create a new mesh.
  • Choose the Hex-Dominant parametric (only CFD) Algorithm.
  • Choose the meshing mode as internal
  • Choose the Sizing to be Automatic and the number of processors to be 32 as shown below:
Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
Set up the mesh by selecting the above settings

Boundary Layer refinement

  • Select the  Inflate Boundary layer setting
  • keep the default settings in the dialog box
  • Select all the faces using for boundary layer refinement by using the Active box selection icon and dragging it over the entire volume and deselect the inlet and outlet faces
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Setup the boundary layer refinement for the mesh
  • click on generate mesh to start the meshing

Mesh Inspection

  • The generated mesh is presented below:
Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
Generated mesh for the current geometry
  • Click on generate mesh clip to inspect the internal mesh. Adjust the settings of the normal. Click on generate mesh clip icon.
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Mesh clip generated for inspecting the mesh
  • Zoom in to see the boundary layer refinement
Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
Boundary layer refinement visible on the mesh

Simulation Setup

Model

  • Give the model a gravitation field as shown below:
Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
Set up the gravitational force

Materials

  • Assign the standard air material to the fluid domain as shown below
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Assign the standard air material to the fluid domain

Initial Conditions

Default values for initial condition parameters are usually enough. If these parameters estimated correctly, the solution will converge faster.

Boundary Conditions

  • We need to define boundary conditions for each of the topological entities that have been created.
  • The settings for each of the topological entities are mentioned below
  • Inlet: we give a velocity inlet boundary condition and give a velocity of 0.1 m/s.
  • Outlet:  we give a pressure outlet condition with zero gauge pressure
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Outlet: pressure outlet boundary condition
  • Chip 1: We give a wall boundary condition with fixed temperature as 321K.
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Chip 1: Wall with fixed temperature boundary condition
  • Chip 2: We give a wall boundary condition with fixed temperature as 364K.
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Chip 2: Wall with fixed temperature boundary condition
  • Board: A wall with fixed temperature of 297K
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    board: Wall with fixed temperature boundary condition
  • Walls: The remaining walls are given as zero gradient (adiabatic walls) with no slip boundary condition
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Wall: Adiabatic walls with zero gradient

Numerics

The default settings are usually suitable. Experienced users can use Manual settings for better convergence.

Simulation Control

  • The settings for the simulation control are given below:
Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
Simulation control settings
  • please click on the ‘+’ next to Simulation runs to start a new simulation

Results

  • The convergence plot of the simulation is shown below:
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Convergence plot showing the convergence of all the solution fields
  • Click on Solution fields under Convergence plot and generate a cutting plane to view the temperature.
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Temperature field on the cutting plane
  • The settings of color contours need to be adjusted to get a better perspective. Double click on the temperature scale and change the settings as below:
Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
Adjust the temperature scale settings
  • To view the flow of air through the domain, select the velocity vector. the vector field on the cutting plane is shown below
    Forced Convective Heat Transfer in Rasberry Pi using Simscale. User Tutorial.
    Velocity vectors in the cutting plane

 

 

 

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