Thermal Analysis in CAE

Definition & Context

Thermal analysis solves the heat-conduction equation to predict temperature distribution and heat flux, accounting for the three heat-transfer modes: conduction (Fourier's law, driven by thermal conductivity k), convection (Newton's law of cooling with film coefficient h), and radiation (Stefan–Boltzmann, ∝ emissivity × T⁴).

Studies are steady-state (final equilibrium temperatures) or transient (temperature vs time, needing specific heat and density). Results feed thermal-stress analysis, where temperature fields are mapped onto a structural model to compute thermal expansion stresses. Conjugate heat transfer (CHT) couples solid conduction with fluid convection in a single CFD solve.

Why It Matters

Electronics, engines, LED luminaires, and building envelopes all fail thermally before they fail structurally. Predicting hot-spots and thermal cycling lets engineers size heat sinks, choose materials, and avoid solder-joint fatigue or warping.

The accuracy of a thermal model lives in its boundary conditions, which are often the least certain inputs: convection film coefficients (h) can vary by an order of magnitude between natural and forced convection, and radiation matters far more than intuition suggests at high temperature because it scales with the fourth power of absolute temperature. For that reason engineers frequently couple thermal to other physics — conjugate heat transfer (CHT) to compute h from a real airflow instead of guessing it, and thermal-stress mapping to turn the temperature field into expansion stresses — rather than trusting a standalone conduction solve with assumed coefficients.

Best Practices

• Get film coefficients right — convection h is often the dominant uncertainty; use correlations or CHT rather than guessing.
• Include radiation for high-temperature or vacuum problems where it dominates.
• For transient runs, verify the time step resolves the thermal time constant of the smallest feature.
• Map thermal results to a structural model to capture thermal-expansion stress in constrained assemblies.
• Validate against a measured temperature or a hand calculation of total heat dissipated.

Common Pitfalls

• Neglecting radiation on hot bodies, badly under-predicting cooling.
• Using a single guessed convection coefficient for a complex flow field.
• Ignoring contact thermal resistance at bolted/pressed interfaces.
• Steady-state assumptions on a duty cycle that never reaches equilibrium.

Sources & Further Reading

• Autodesk — Thermal simulation
• Siemens — Heat transfer simulation

Related Concepts

• CFD Fundamentals — conjugate heat transfer supplies real film coefficients
• Finite Element Analysis — thermal fields map to thermal-stress FEA
• Fatigue Analysis — thermal cycling drives solder/joint fatigue

Enterprise Production Implementation & GstarCAD 2027 Workflow

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