CHT: Electronics Enclosure Cooling Optimisation

Simulation setup

Internal forced convection with conjugate heat transfer, solid conduction and fluid convection solved together. All cases share the same boundary conditions; only fan placement, venting, and heat sink geometry change. All cases are run at basic mesh settings for quick evaluation.

Case matrix

Each case changes one variable. Cases 01-04 ran at 10 W / 5 W to validate fan approach. Full 25 W / 10 W design load applied from Case 04B onward.

Fan blows air directly into the enclosure from the front. Chip reaches 57.4 °C, power block 49.0 °C, both well within limit at 10 W load. Establishes the reference geometry and result for all comparisons.

Baseline geometry, external inlet fan

Temperature cut, chip 57.4 °C, power block 49.0 °C

Flow trajectories, inlet fan drives air over components

A reducer shroud concentrates inlet airflow directly onto the chip heat sink. The chip improves to 48.3 °C, but the power block rises to 51.1 °C as the shroud restricts flow reaching that region. Packaging cost is also higher. Rejected as the primary path, the tradeoff between components is the wrong direction.

Reducer shroud concentrates inlet flow

Temperature cut, chip 48.3 °C, power block rises to 51.1 °C

Flow trajectories, shroud channels air to heat sink, bypasses power block

Fan pulls air out of the enclosure instead of pushing it in. The chip reaches 118.8 °C, 34 °C above the limit at only half the design load. Hot exhaust recirculates over the chip before it can exit. Immediately rejected.

Outlet fan geometry

Temperature cut, chip 118.8 °C (34 °C over limit at 10 W)

Flow trajectories, hot air recirculates over chip before exiting

Fan moved inside the enclosure. Chip drops to 50.9 °C and power block to 41.7 °C, the best combined result so far. Internal placement confirmed as the correct direction. The fan approach is selected; attention now shifts to whether it holds at full 25 W load.

Temperature cut, chip 50.9 °C, power block 41.7 °C

Chip and heat sink surface temperatures

Flow trajectories, internal fan drives clean air over chip and power block

Same internal fan configuration as Case 04 but at the real design load: 25 W chip / 10 W power block. The chip rises to 99.8 °C, over the 85 °C limit. The fan placement is correct; the solid Al block heat sink is insufficient at full load. A finned heat sink is needed.

Fluid temperature field, at 25 W the solid block heat sink cannot keep pace (chip 99.8 °C)

An upper vent is opened to allow hot air to escape directly. The chip drops to 84.4 °C, just within the 85 °C target. However, the open aperture creates an uncontrolled dust ingress path. Rejected despite meeting the thermal target.

Temperature cut, chip 84.4 °C (meets limit but only just)

Flow trajectories, hot air exits through upper vent, but vent is open to dust

A rear exhaust fan is added alongside the internal fan to increase total airflow. The chip worsens to 95.4 °C, worse than Case 04B with no second fan. The rear exhaust fan pulls air away from the heat sink before it can absorb heat from the chip. More fans, worse result.

Temperature cut, chip 95.4 °C (worse than 04B despite added fan)

Flow trajectories, rear fan pulls flow away before it reaches the chip heat sink

The solid Al block is replaced with a finned heat sink: 50 × 50 mm base, 40 mm tall, 14 fins at 1 mm thick with 3.3 mm gaps. The chip drops to 50.9 °C. But the power block rises to 84.1 °C, right at the limit. The finned heat sink draws more airflow to the chip region, leaving less for the power block. Chip is no longer the bottleneck.

Temperature cut, chip 50.9 °C, power block 84.1 °C (at limit)

Velocity cut, high-speed airflow through fins, less reaching power block

Flow trajectories, fins pull flow; power block region is under-served

A side-mounted cross-flow external inlet fan is added to deliver fresh air directly to the power block region. The internal fan and finned heat sink continue to manage the chip independently. Both components meet the 85 °C target with clear margin: chip 61.1 °C, power block 60.0 °C.

Final geometry, optimised heat sink + cross-flow inlet fan

Temperature cut, chip 61.1 °C, power block 60.0 °C

Fluid temperature, balanced thermal distribution across enclosure

Velocity cut, dual fan airflow covering both thermal zones

Flow trajectories, cross-flow fan delivers fresh air directly to power block region

Case 08 meets the 85 °C target. The table below captures the most impactful next steps if power density increases or design constraints tighten.