Experimental and CFD investigation of heat transfer in high-power avionics equipment

Abstract

Reliable thermal verification of high-power-density avionics is challenging because densely packed circuit boards and narrow cooling passages complicate detailed modeling and experimental validation. This study evaluates the thermal performance of an avionics enclosure using an integrated SpaceClaim–Icepak workflow combining CAD simplification with conjugate computational fluid dynamics (CFD). Thermally noncritical geometric details were removed while preserving key heat-transfer features, and a 9.5-million-cell mesh was generated with grid independence confirmed within 0.2 °C. Forced convection from two intake fans, conduction through the aluminum housing, and flow redistribution by an air-control plate were modeled using the Zero-Equation turbulence model with temperature-dependent properties. Experimental validation was performed in a climatic chamber at 43 °C and approximately sea-level pressure. All evaluated components remained below allowable junction-temperature limits. Predicted hot-spot locations agreed well with measurements, with an RMSE of 4.1 °C and a maximum deviation of 6.2 °C. Boundary-layer analysis of the 8 mm inter-CCA gaps showed that the local Nusselt number varied by a factor of 3.7, while the velocity-to-thermal boundary-layer thickness ratio ranged from approximately 0.43 to 2.19, compared with an equilibrium reference value of approximately 0.89 for air. These results demonstrate strongly non-equilibrium local heat-transfer behavior and support preliminary thermal screening and relative design comparison under the tested condition.