Felix Hu

Felix Hu

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VacDry Low-Temperature Vacuum Dryer

VacDry: Low-Temperature Vacuum Dryer for Delicate Clothes

UC Berkeley Spark Program | 2024-2025 | Berkeley, CA

Team: David Li Yongye Hu Eric Pham Alex Li Shaojie Wang Show all

Mechatronics Engineer

Hit 20-minute drying at 40 C and 50 dBA; validated through 10 continuous 1-hour operation cycles with no pressure loss.

  • SolidWorks
  • Ansys Fluent
  • FMEA
  • 3D printing
  • Vacuum systems
Case Type Hardware product prototype
Technical Center Vacuum-system design, CFD-backed experiments, FMEA, leak isolation
Outcome Hit 20-minute drying at 40 C and 50 dBA; validated through 10 continuous 1-hour operation cycles with no pressure loss.
Ownership Led mechanical design and prototype development from concept through testable hardware.

Hardest engineering problem: A rotating drive-shaft penetration kept breaking vacuum reliability until the failure mode was removed with a magnetically coupled drive.

Overview

VacDry was a self-initiated hardware product prototype targeting a specific gap in home drying: delicate fabrics are damaged by heat, conventional cycles are slow, and apartment-friendly machines need lower noise. The target spec was deliberately concrete: dry at 40 C, finish in about 20 minutes, and stay around 50 dBA.

My Role

I led mechanical design and prototype development from concept to testable hardware. My work covered CAD, packaging, vacuum chamber design, CFD-supported operating assumptions, FMEA-driven reliability improvements, fabrication, and subsystem integration across pump, heater, sensor, and drive mechanisms.

Key Results

  • Built a working prototype that reached the target 20-minute drying cycle at 40 C and 50 dBA.
  • Validated reliability through 10 continuous 1-hour operation cycles with no pressure loss or failures.
  • Used physical experiments to tune drying curves and shorten drying time by about 30% from earlier settings.
  • Converted FMEA findings into concrete reliability upgrades for a consumer-facing safety case.

System Architecture

VacDry vacuum system and instrumentation architecture with chamber, gasket, textile roller, heater, pump, magnetic coupling, sensors, and validation gate
The physical system view makes the prototype boundary explicit: chamber, textile motion, heat, pump path, sealing line, magnetic coupling, and measurements all fed the validation gate. This is prototype validation, not a production-certification claim.
VacDry validation and debugging architecture diagram
VacDry was organized as a product-shaped validation stack: target spec, simulation, physical experiment, risk analysis, and vacuum-leak diagnosis all fed the prototype decision loop.

Drying System

Vacuum chamber, low-temperature heat source, air/vapor management, sensors, and rotating textile support.

Reliability System

Pressure hold, gasket integrity, sensor plausibility, thermal redundancy, and user-facing safety risks.

Validation System

CFD assumptions were checked against physical drying curves and repeated one-hour operation cycles.

Instrumentation / Reliability Architecture

VacDry was less code-centered than the robotics projects, so the architecture emphasis is on instrumentation and validation rather than a large firmware stack. The publishable story is how pressure, temperature, noise, cycle time, and drying performance were measured together so the prototype could be judged as a consumer machine rather than a lab mechanism.

Flow boundary: the page treats pump, heater, chamber seal, textile rotation, and sensors as a prototype validation system. It does not claim a certified or production-ready appliance.

Control / Simulation Methodology

The method stack was intentionally layered. CFD gave a low-cost way to explore operating parameters before fabrication, experiments closed the gap between simulation and real drying behavior, and FMEA translated engineering risks into a reliability story that would matter for a consumer product.

MethodWhat it answeredWhy it mattered
CFDExpected flow and operating behavior before expensive iteration.Reduced blind mechanical redesign.
Physical testsActual drying curve and pressure behavior.Closed the model-to-prototype gap.
FMEAConsumer-facing failure modes across pump, heater, and roller subsystems.Turned safety into design requirements.

Validation & Debugging

VacDry vacuum leak debugging decision tree
The leak fix was a root-cause isolation loop: pressure-hold behavior ruled out pump-down assumptions, localization narrowed the leak, and magnetic coupling removed the shaft penetration failure mode.

The hardest issue was a recurring vacuum leak. I diagnosed it with a pressure-rise isolation process and ultrasonic localization, then traced the root cause to the rotating drive-shaft penetration. Instead of trying to improve the dynamic seal, I replaced the failure mode with a magnetically coupled drive so the rotating shaft no longer penetrated the vacuum chamber.

Validation gateMeasurementPublic result
Drying targetCycle time and operating temperature.20-minute drying at 40 C.
Noise targetAcoustic level during operation.About 50 dBA.
Pressure reliabilityRepeated one-hour operation cycles.10 continuous cycles with no pressure loss or failure.
Risk controlFMEA findings across pump, heater, and rolling subsystems.Pressure alarm, gasket improvement, sensor plausibility checks, and redundant temperature sensing.

The final validation gate was not only a single successful dry cycle: the prototype ran 10 continuous one-hour operation cycles without pressure loss or failure.

What I Would Improve

I would make the next version more instrumented from day one: pressure, humidity, textile mass, chamber temperature, and acoustic readings should be logged together so each design change has a measured effect on the product target. I would also separate the vacuum sealing test rig from the drying rig so leak fixes can be isolated before the full machine is assembled.