Module Spacing Investigation

This investigation is an experiment in SimScale to investigate the relationship of 3 variables to the function of a single module in a channel. These variables vary from baseline values. The simulation project can be found at Cell Test

• Spacing between cells in x

  • Baseline of 31.5mm

  • Varies by increments of 2mm

  • Investigated between 23.5mm and 43.5mm

• Spacing between cells in y

  • Baseline of 31.5mm

  • Varies by increments of 2mm

  • Investigated between 23.5mm and 43.5mm

• Inlet air velocity

  • Baseline of 1 m/s

  • Varies by increments of 0.5m/s

  • Investigated between 0.5m/s and 4m/s

  • Velocity of air being blown by “fans” through module

Due to a limited number of yearly processor hours on SimScale for free members, we will initially simulate these variables independent of one another, i.e. the simulations investigating spacing of cells in y will always have an x value of 31.5mm and an air inlet velocity

Simulation Geometries

Naming Convention

Simulation Geometries refer to the available simulation geometries in the “Geometries” section of the SimScale project. A typical simulation geometry consists of a set of dimension digits separated from a revision digit by underscores, e.g. “31.5x29.5_Rd0”. 31.5 represents the spacing in the x axis in mm, perpendicular to the air flow direction. The second digit, in this case 29.5, represents the spacing in the y axis in mm, parallel to the air flow direction. The third digit represents the number of rounds of processing the geometry has underwent, starting at a zero index.

Currently, all geometries have been processed one time. All simulations currently use Rd0.

Parts

This section describes the parts in the geometry.

• Flow Region

The flow region represents the volume of air to be simulated.

• Tube
  

  

  The tube represents the confined space in which the air flow is simulated

• Cell Holders
  

  

  The cell holders are simplified cell holders based off of Jeyoung’s module design, simplified for easier simulation (removing threads and mounting holes, fillets)

• Cells
  

  

  The cells are an array of cylinders approximating the size and shape of a 21700 lithium-ion battery cell, with spacing as described by the geometry name.

Simulation

The simulation model we use in this investigation is the Conjugate Heat Transfer Model, which simulates heat transfer between fluid and solids. In this case, we simulate the heat transfer between cells and air.

Naming Convention

The naming convention for simulations is similar to that of geometries. Names consists of spatial digits separated by an airflow digit by underscores. The third digit represents the inlet air velocity. (e.g. 31.5x31.5_1)

Setup Steps

1. Select a geometry that has not yet been simulated and select “Create Simulation”. Choose Conjugate Heat Transfer, and name the simulation accordingly to the geometry and intake velocity combination which corresponds to the simulation.
   Ensure the turbulence model is k-omega SST, the time dependency is steady-state, and radiation is switched off (Radiation does not have a very significant impact on final results at lower temperatures, and takes extra core hours).

   

   
   

2. Enable gravity under the Model tab
   

   

3. Begin setting materials under the Materials tab.

   1. The flow region should use air as its material
      

      

   2. The cell holders and tunnel should use PET as its material, as the Cell holders are printed with PETG filament.

   3. The cells will require you to create a custom material called Cell, created by assigning the cells to an arbitrary material, then altering the properties of the material. It shall have the properties listed in Table 1.
      

      

4. Initial Conditions

   1. Set temperature to 25 degrees Celsius, to correspond with SATP

5. Boundary Conditions

   1. Set the inlet velocity to be the specified inlet velocity, in the positive Y direction. The inlet shall be the wall of the flow domain that is the most negative in y. Set the inlet temperature to 25 degrees Celsius, to correspond with SATP.
      

      

   2. Set the outlet pressure to be 1.013e+5, so as to correspond to SATP (Should be this by default). The outlet shall be the face of the flow domain opposite to the inlet
      

      

6. Power Zones
   In the Advanced Concepts section of the simulations tab, open Power Sources and create an absolute power source with a value of 0.125W, calculated from the internal resistance of a Molicel m50a, and a current draw of 5A. Assign all of the cells to the power source.
   

   

7. Meshing
   Create a new mesh with the name of the simulation geometry, and a mesh fineness of 4. Leave all other settings as default. Prior to running the simulation, the mesh will automatically generate.
   

   

8. Run simulation
   

   

9. Wait.
   

   
   
   
   s

Table 1: Cell Material Properties