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Thermal Analysis
Thermal Analysis
We ran an initial thermal simulation to identify the temperature range and hotspots in a simplified PCB stator model under passive air convection.
The model featured a 4-layer PCB stator (outer diameter 152.4 mm, inner diameter 25 mm), sandwiched between two 6061 aluminum rotors, with a 1mm air gap. A stainless steel shaft (8 mm diameter) passed through the stator’s center.
Simulation Setup:
Stator: 600W heat source
Rotors: 9500 RPM rotating regions
Environment: 30℃ air, standard atmospheric conditions
Assumptions: No conduction or radiation, passive convection only, steady state, axial airflow at 0.5 m/s
The results showed extremely high temperatures — up to 648 K, concentrated near the stator’s inner diameter. This confirmed the need for rotor perforations near the core to improve airflow and cooling.
Rotor Performance Analysis
Rotor Performance Analysis
Before finalizing the rotor design, we tested how the system responded to lower heat sources using SolidWorks Flow Simulation, with the same boundary conditions as before. We tracked:
Maximum stator temperature
Average heat transfer coefficient
Air velocity
We ran cases at 50W, 100W, 150W, 250W, and 600W heat loss, with the results shown in the table
Even with reduced heat sources, temperatures were still too high. The only case where the temperature reached an acceptable level (129.5°C) required reducing the heat source to just 100W — far too low for actual operation.
This also highlighted two key issues:
Air velocity was too low, limiting convective cooling.
Heat transfer coefficient was too small, indicating poor airflow around the stator.
This confirmed the need for perforated rotors to boost airflow and heat dissipation near the stator.
Rotor Design Analysis
Rotor Design Analysis
Four different rotor designs were modeled and evaluated for their thermal performance using SolidWorks Flow Simulation with the same assumptions as before and with a 600 W heat source. The results were the following:
J1
J2
J3
J4
The four rotor designs were able to significantly increase the average heat transfer coefficient (21.8-26.1W/m²K) and slightly increase fluid velocities (8.6-11.2 m/s) in comparison to the plain disk rotor. Based on this data, the best-performing rotor is Rotor 3 (J3), due to it achieving the lowest maximum temperature (552.423°C).
Despite reaching a reasonable heat transfer coefficient value, the table above still showed temperatures exceeding the desired maximum. This led to further optimizations of the rotor design to further decrease the maximum temperature, eventually leading to design SD, shown in below.
J3
J3
Number of Holes: 18
Hole Diameter: 2.5 mm
Total Hole Area: 91 mm^2
SD
SD
Number of Holes: 30
Hole Diameter: 5mm
Total Hole Area: 589 mm^2
As can be seen, the optimized rotor provided a higher average heat transfer coefficient and a lower maximum stator temperature. Even though simulated system temperatures were still very high, this improvement was significant.
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