How to post-process heat flow?

This article shows practical ways to visualize, quantify, and report heat flow results in Simcenter 3D.

Introduction

Studying heat flows helps you:
  • Understand how energy moves through the model and system.
  • Verify that the model behaves as intended: energy in ≈ energy out at steady state.
  • Detect and fix modeling and system issues such as missing contacts, wrong boundary conditions, and mesh problems.

Key terms

  • Heat load (W): heat added via surface heat flux, temperature, or volumetric source. Positive is into the body.
  • Heat flux (W/m²): heat flow through a conductor between two nodes. Positive from node A to node B as ordered by conductor definition.

Before you solve

  1. Request the right outputs. In the Thermal Output Request, on the Thermal page, select:
    • Conductive Heat Fluxes — vector field used for vector/contour plots; represents heat passing through elements per unit area in a given direction.
    • Convective Heat Fluxes — scalar field on 2D/shell elements; includes all convective fluxes to or from a surface. It includes but is not restricted to Convection to Environment and Thermal Coupling - Convection.
    • Total Loads and Fluxes — combined applied overall loads and fluxes from all sources, such as thermal boundary conditions, radiative fluxes, and orbital fluxes.
      Note:
      This result set does not include heat loads or heat fluxes resulting from constraints defined in the solution.
  2. Create a Report simulation object.
  3. Create named groups for all boundaries and regions you will analyze: sources, sinks, and interfaces.

Tools in Simcenter 3D to post - process heat flows

  • Post-Processing Navigator:
    • Vector or contour plots of heat load or flux to visualize heat-flow paths. Create separate plots for radiative/environmental loads when included in the solution.
    • Identify Results to list values per node or element; export to CSV.
    • Result Variable with a Result Probe to define derived quantities and evaluate them.
  • Simulation Navigator:
    • Report simulation object to generate tabular outputs for different solution data.

Selection guide

Choose the right Simcenter 3D tool to quantify or visualize heat flow for a given task.
If you need Use this How Output When to use
Combined applied loads from all sources (element view) Total Heat Load - Elemental Plot Total Heat Load. Visual plot Quick review of where heat is applied.
Combined overall fluxes from all sources (element view) Total Heat Flux - Elemental Plot Total Heat Flux. Visual plot Quick view of where flux leaves/enters.
Heat load (Q) on a surface from flux Convective/Conductive Heat Flux + Identify Results Plot convective or conductive heat flux, use Identify Results on the surface to get average flux. Multiply the average heat flux on the surface area: Scalar, manual calculation Fast estimate when you only need one surface’s Q.
Directional heat flux (radial/axial) on a surface Conductive Heat Flux + Identify Results Plot the conductive heat flux, W/m², in the X, Y, or Z direction. Use the Identify Results to obtain the weighted average values for the x, y, and z conductive fluxes over the selected regions. Visual + Scalar Component checks and cylindrical directions.
Weighted averages/HTC/custom metrics on a surface Result Variable + Result Prob Use Result Variable to create a new variable for HTC or heat flux. Create a Result Probe (average, max, ...) on the surface. In Results Probe, set Combined Value to Integral and Weighted Average By to Area to get heat load (W) from heat flux (W/m2. Scalar Repeatable extraction with saved probes.
Applied load or flux on a region. Report - Per Region Add a Per Region report with selected Heat Load or Heat Flux options. CSV and HTML with the time history over the run. Review what was applied to each region (not a transfer between A→B). Displays average, maximum, and minimum values.
Heat in and out between element groups Report - Heat Maps Add a Heat Maps report.
Note:
The Heat Maps report cannot be combined with another report.
 CSV and HTML with the time history over the run. Review detailed conductive, radiative, and convective heat flows between specific element groups.
Heat between two surfaces/regions (A→B) Report - Between Regions Add a Between Regions report with Primary = Region/Surface A, Secondary = Region/Surface B.
Note:
You obtain a radiative heat flow if any elements of the two regions share a view factor between them, and a conductive heat flow if there are any direct conductive thermal couplings.
 CSV and HTML with the time history over the run. Net interface transfer. Recommended when the mesh is non-conforming at the interface. Useful for model reduction.
Heat flow from a region to the environment (fluid or space) Report - Between Regions Add a Between Regions report with Primary = Region/Surface A and the Override Secondary Region option set to either Fluid Ambient or Radiative Ambient. If you want both, you’ll need to create 2 reports.
Note:
To get the heat flow towards the environment with the report, the surfaces need to be connected to the fluid/radiative ambient nodes.
 CSV and HTML with the time history over the run. Environment transfer; works with non-conforming meshes.
Per-ambient heat flows (multiple environment temperatures) Report - Between Regions (explicit sinks) Create sinks per ambient: 0D nodes when HTC known, or 1D ducts when HTC computed. Create thermal couplings from the model surfaces to the sink elements. Create the Between Regions report by selecting the sinked elements as the secondary region to get per-ambient heat flows. CSV + HTML (time history) Different areas see different ambient temperatures.
Heat into the Non-Geometric Element (NGE) Report - Between Regions Select the region connected to the NGE as a Primary region and set Secondary Region Override to NGE. CSV + HTML (time history) Sinks are modeled as NGEs.
Have the NGE flow appear in the log’s heat-balance summary. Use 0D temperature element Replace NGE with 0D element + Temperature constraint. <simulation name-solution name>.log When you need it in the heat-balance table.
Heat flows into temperature constraints Log file summary Read the end-of-run heat-balance summary for flows into temperature BCs. <simulation name-solution name>.log Cross-check against probes/reports at steady state.
Heat flow across thermal coupling Advanced Control with the DISPLAY BC DATA SUMMARY or PLOT BC SUMMARY advanced parameter Add the advanced parameter and read the thermal coupling data in the boundary condition data summary or the HTML file. <simulation name-solution name>.bcdata or <simulation name-solution name>_data.html Inspect each thermal coupling’s heat flow and direction—positive when the Tpimary>Tsecondary.
Note:
  • When creating a Heat Map report, only certain entity types are allowed—select bodies for conduction and surfaces for Linear Thermal Couplings; by adding a null surface coat (2D shell) to the faces and selecting the 3D body elements together with the 2D coat elements, the report aggregates them as a single component in the table.
  • Create one report object per region or region pair.