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Thermal · Fluids · CFD · System Design

Aircraft Environmental Control System

A preliminary avionics-cooling ECS developed from first-principles sizing through robust design selection, off-design performance analysis, and independent three-dimensional CFD validation.

Engineering Problem

Design a preliminary environmental control system for an aircraft avionics/electronics compartment using a closed recirculating-air loop and a separate external cooling-air stream through an air-to-air heat exchanger.

System-Level Workflow

  • Developed a traceable avionics thermal-load model and required cooling-airflow calculation.
  • Modeled duct friction, fitting losses, heat-exchanger resistance, fan power, and fan heat addition.
  • Sized the heat exchanger using an effectiveness-NTU approach.
  • Performed multi-parameter sensitivity studies, a 50-case robust-design sweep, and off-design operating-envelope analysis.
  • Independently validated the selected duct network with 3D CFD and a controlled mesh-refinement study.
32.395°CFinal nominal zone temperature
39.205°CCombined stressed-condition zone temperature
0.795°CWorst-case thermal margin to 40°C limit
CFD streamlines through the selected ECS duct network
3D CFD flow trajectories through the selected long-radius duct network.

CFD Validation

Static pressure contour in ECS duct
Static-pressure field used to evaluate duct-network pressure loss.
Velocity magnitude contour in ECS duct
Velocity-magnitude contours highlighting acceleration and redistribution through the bends.
26.83 PaFinest-mesh CFD duct pressure drop
2.57%Difference between two finest meshes
11.9%Approx. aerodynamic sizing margin

Robust Design Result

The final design intentionally retained a conservative analytical pressure-loss basis for fan sizing even though CFD predicted lower losses for the idealized smooth long-radius geometry. The selected configuration also preserved positive thermal reserve and could tolerate approximately 20.7% additional avionics load at the baseline external condition before reaching the zone-temperature limit.

Engineering Takeaway

The project became a complete preliminary design workflow rather than a single calculation: first-principles sizing, integrated modeling, sensitivity analysis, robust configuration selection, off-design evaluation, and independent CFD validation all informed the final design freeze.

Full technical report
The complete report contains the thermal model, duct sizing, fan and heat-exchanger calculations, sensitivity studies, robust-design sweep, operating envelope, CFD validation, and final validation matrix.

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