Fill out the form to download

Required field
Required field
Not a valid email address
Required field
Required field
  • Set up your own cloud-native simulation in minutes.

  • Documentation

    Validation Case: RF Electronics Package Cooling

    This study aims at validating the CHT v2 and CHT (IBM) solvers. A peer-reviewed publication of R.Boukhanouf\(^1\) focusing on thermal analyses and cooling of a Radio Frequency (RF) electronics package has been used as the basis for this validation case. Reasonable assumptions and approximations have been made to bridge uncertainty in the publication.

    The validation study involves qualitative and quantitative comparisons between SimScale and the commercial CFD code FloTHERM involving:

    • temperature, and
    • velocity vectors


    The battery pack was modeled using the CAD tool Onshape. Necessary assumptions were made to overcome missing/inconsistent geometric data:

    the model from the publication was reversed engineered to be used in this validation case
    Figure 1: A 1:1 model (right image) reverse-engineered from measurements and images provided in the publication (left image).

    The model contains the following parts:

    • DC Shelf
      • Upper Copper mount for DC component
    • DC Shelf components
      • DC component with 15 \(W\) Heat Rating
      • Thermal via circuit built into RF4 PCB
      • Solder layer
      • Thermal insulating material (TIM)
    • RF Shelf
      • Upper Copper mount for RF components
    • RF components
      • Three RF components with 60 \(W\) , 0.5 \(W\), 0.5 \(W\) Heat Ratings
      • Aluminium RF4 PCB
      • Dielectric substrate to insulate components from each other
      • Solder layer
      • Thermal insulating material (TIM)
    • Heat sink: Finned Heat Exchanger  
    • Aluminium Enclosure Box
    • Fan: Air delivery 11 \(m^3 \over \ h\) at 40 \(^o C\)

    Analysis Type and Mesh

    Tool Type: OpenFOAMⓇ

    Analysis Type: Incompressible, steady-state analysis with the Conjugate Heat Transfer v2 (CHT v2) and Conjugate Heat Transfer (IBM) solvers.

    Mesh and Element Types:

    The Standard mesher algorithm with tetrahedral and hexahedral cells was used to generate the mesh for the CHTv2 runs. Meanwhile, CHT (IBM) uses cartesian meshes:

    ibm and chtv2 meshes validation case heat sink
    Figure 2: Three-dimensional CHTv2 unstructured mesh containing tetrahedral and hexahedral elements created with the Standard algorithm (left) and cartesian mesh created for a CHT (IBM) simulation (right)

    A mesh sensitivity analysis has been carried out to determine the dependence of the CHTv2 solver temperature predictions on the mesh:

    Mesh CountMesh TypeTC@DC Component \([°C]\)TC@RF1 Component
    TC@RF2 Component
    TC@RF3 Component
    Mesh 13.4M cells, 1M nodesStandard106.72148.8588.2588.25
    Mesh 24.4M cells, 1.2M nodesStandard105.95148.6587.7587.75
    Absolute TC deviation (Mesh2-Mesh1)0.770.20.50.5
    % TC deviation (Mesh2-Mesh1)0.73%0.13%0.57%0.57%
    Table 1: The results of the mesh sensitivity analysis after the area-averaged temperatures of the package components have been compared.

    TC stands for the Temperature in Celsius degrees. The values in the table are area-averaged values over the respective components.

    It is indicated that the temperature deviation between Mesh 1 and Mesh 2 was found to be within 1% for all the package components:

    deviation between meshes to decide the most appropriate set for the validation case
    Figure 3: Based on the mesh sensitivity analysis, the fine mesh (Mesh 2) has been used for all comparisons.

    Simulation Setup

    Fluid Material:

    • Air
      • Dynamic viscosity \((\mu)\) = 1.83e-5 \(m^2 \over\ s\)
      • Specific heat = 1004 \(J \over\ (kg \times\ K)\)

    Solid Materials:
    The table highlights the materials and thermal conductivity values used for each component of the RF electronics package:

    ComponentMaterialThermal conductivity \(W \over \ (m \times \ K) \)
    Enclosure BoxAluminum180
    RF & DC shelvesCopper385
    Solder layerTin50
    Thermal via circuit(Derived)22 (Derived)
    TIMSil Pad® and Gap Pad®2
    Dielectric SubstrateDielectric material0.6
    PCB Aluminum 180
    Table 2: Properties of the solid materials

    The RF components have been modeled as using the thermal resistance network and therefore are not assigned any material properties.

    The Heat Ratings and Thermal Resistance values used are respectively as follows:

    • RF1: 15 \(W\), 0.7 \(^o C \over \ W\) 
    • RF2: 0.5 \(W\), 0.8 \(^o C \over \ W\)  
    • RF3: 0.5 \(W\), 0.8 \(^o C \over \ W\) 
    • DC: 60 \(W\), 0.78 \(^o C \over \ W\)

    Boundary Conditions:

    • Natural convection inlet-outlet with an ambient temperature of 40 \(^o C\)
    • Fan as a momentum source with a velocity of 1.85 \(m \over \ s\)
    • Thermal Resistance Network: Star Network Resistance Model
    • DC Component:
      • Resistance: 0.78 \(K \over \ W\)
      • Power Source: 15 \(W\)
    • RF1 Component:
      • Resistance: 0.7 \(K \over \ W\)
      • Power Source: 60 \(W\)
    • RF2 Component:
      • Resistance: 0.8 \(K \over \ W\)
      • Power Source: 0.5 \(W\)
    • RF2 Component:
      • Resistance: 0.8 \(K \over \ W\)
      • Power Source: 0.5 \(W\)
    • No-slip walls
    • Coupled contact interfaces

    Result Comparison

    Convergence below 1e-3 has been achieved. Calculated physical quantities such as inlet pressure, outlet velocity, and cell average temperatures have also been allowed to converge to stable values.

    The validation of the SimScale’s CHTv2 has been carried out by qualitatively comparing temperatures and velocities with the reference results\(^1\). The reference results have been produced with the commercial CFD code Flotherm. All post-processing was done in SimScale’s online post-processor:

    FloTHERM and simscale results chtv2 cht ibm
    Figure 4: Qualitative comparison of the temperature distribution between FloTHERM (left), CHT IBM (center), and CHTv2 (right)

    Another section was compared between the two:

    temperature distribution on package mid-section for qualitative comparison of results between the validation and SimScale
    Figure 5: This comparison shows temperature distribution at the package mid-section between the FloTHERM (left), CHT IBM (center) and CHTv2 (right) solvers.

    A quantitative comparison of the velocity field shows a good match between the two solvers:

    velocity vectors comparison flowtherm simscale
    Figure 6: FloTHERM (left), CHT IBM (center), and CHTv2 (right) showcase consistency when it comes to the velocity vectors, to both direction and magnitude.

    Except from the qualitative comparison, a quantitative study was performed:

    CHT (IBM) \([°C]\)CHT v2
    TC deviation (CHT IBM – FloTHERM) \([°C]\)TC deviation (CHTv2 – FloTHERM) \([°C]\)
    TC@DC Component10198.46105.95-2.544.95
    TC@RF1 Component 137.85133.77148.65-4.0810.8
    Table 3: A qualitative comparison of area-averaged temperatures on the package components has been performed.
    comparison of temperature between literature and SimScale results
    Figure 7: Quantitative temperature comparison on the electronic components

    From Table 3 and Figure 7 above, the DC and RF1 component temperatures are within 5% and 8% of the reference FloTHERM results respectively.

    This deviation could be traced down to two possible factors:

    • The publication does not clarify how the thermal resistance has been implemented (top/board/side). 
    • Temperature measurement type in the paper.

    Overall, The study shows a moderately good agreement between the temperature predictions from the two CFD solvers.


    If you still encounter problems validating you simulation, then please post the issue on our forum or contact us.

    Last updated: September 8th, 2023