Cryocooler Project Presentation

Jul 29, 2024

Cryocooler Project Presentation Notes

Introduction

  • Sponsored by Squarespace
  • Homemade cryocooler capable of making liquid nitrogen
  • Temperature details:
    • Liquid nitrogen: -196 °C or -320 °F
    • Demonstration of superconductor levitation

Cryocooler Construction

  • Built entirely from salvaged parts of old window AC units and electronic components
    • No fancy Stirling cryocoolers used

Components Used

  • Standard Refrigeration components
  • Same machine as previous video for producing liquid methane, with modifications.

Basic Operation

  • Process overview:

    1. Gases are compressed
    2. Heat is removed via a radiator
    3. High-pressure gas travels through a counterflow heat exchanger
    4. A capillary tube throttles the flow, dropping the gas pressure and temperature
    5. The cold gas cools the incoming high-pressure gas
  • Joule-Thomson Effect: Causes the temperature drop during gas expansion.

  • Cycle repeats creating a positive feedback loop, achieving extremely low temperatures.

    • Lowest temperature achieved: -180 °C
    • High-pressure side reaches about 400 PSI (28 bar).

Gas Mixture Used

  • Combination of propane, ethylene, methane, argon, and nitrogen.
  • Achieved low temperatures using only argon and propane, though less efficiently.

Liquid Nitrogen Production

  • Low-pressure gas enters a tank fed with high-pressure nitrogen from another compressor.
  • Liquid nitrogen begins condensing at around -150 °C when pressure is 400-450 PSI.
  • Liquid is discharged through a motorized needle valve.

Design Improvements & Changes

  • Previous issues encountered with a liquid methane holding tank explosion.
  • Rebuilt the tank with proper end caps and insulation.
  • Challenges with thermal inertia and insulation causing temperature drops to only -68 °C.

Tank Modifications

  • Tried smaller tanks and different insulation techniques (foam, rubber) leading to better performance down to -172 °C.
  • Liquid capture efficiency improved by minimizing thermal losses.

Liquid Nitrogen Collection

  • Used a rotary compressor for nitrogen gas transfer; switched to a fridge compressor for better performance.
  • Successful operations resulted in approximately 108 grams of liquid nitrogen captured.

Thermodynamic Analysis

  • Observed mass drops due to evaporation without proper insulation.
  • Demonstrated the "laden Frost effect" for heat transfer slowing down.
  • Tested superconductivity with YBCO and measured resistance changes when cooled.

Conclusion

  • System consumes 1,400 watts, producing 130 cc of liquid nitrogen per hour.
  • Future optimizations expected to improve yield to 200-300 cc/h.
  • Future videos planned for extracting nitrogen from air using pressure swing absorption.
  • Will explore oxygen liquefaction with safety precautions noted due to fire hazards.

Final Thoughts

  • Thanks for watching, hope viewers enjoy the demonstration.