In 1885, Scottish chemist and physicist Sir James Dewar (1842–1923) at the Royal Institution in London invented the Dewar Vacuum Flask (commonly known today as the Thermos flask).
Dewar designed a double-walled silvered glass vessel evacuated to high vacuum ($< 10^{-5}\,\text{Torr}$), eliminating thermal conduction, convection, and radiation to store cryogenic liquid gases ($\text{O}_2, \text{N}_2, \text{H}_2, \text{He}$) for weeks.
Physical Principles of Vacuum Insulation¶
Dewar addressed the three fundamental mechanisms of thermodynamic heat transfer:
- Evacuated Vacuum Gap: Removing air between the double glass walls eliminated heat transfer by thermal conduction and fluid convection.
- Silvered Internal Mirrors: Coating inner glass surfaces with thin silver mirror films reflected infrared thermal radiation ($P = \sigma A T^4$), reducing radiative heat absorption by $95\%$.
- Narrow Neck Support: Minimizing glass neck contact area suppressed solid conductive heat leakage.
Impact on Low-Temperature Quantum Physics¶
Dewar used his vacuum flask to liquefy hydrogen gas ($20.28\,\text{K}$) in 1898 and solidify hydrogen ($14.01\,\text{K}$) in 1899.
Dewar’s vacuum flasks enabled Heike Kamerlingh Onnes in 1908 to liquefy helium ($4.2\,\text{K}$) and discover Superconductivity (1911), serving as the universal thermal shield for modern NMR medical MRIs, dilution refrigerators, and superconducting quantum computers.
Key Takeaways¶
- Year: 1885
- Key Figure: Sir James Dewar (Scottish Chemist & Physicist)
- Core Discovery: Invented the Dewar Vacuum Flask, conquering conductive, convective, and radiative thermal heat loss.
- Cryogenic Milestone: Enabled continuous storage of liquefied gases near absolute zero ($T < 20\,\text{K}$).
- Quantum Relevance: Universal thermal isolation container for superconducting quantum processors and dilution refrigerators.