Gravitational capillary viscometer for low-temperature liquids

Area of Science:

• Cryogenic fluid dynamics
• Materials science and engineering

Background:

• Accurate viscosity measurements of subcooled liquefied gases are critical for aerospace applications.
• Existing data and correlations for liquid oxygen viscosity are incomplete and lack precision in certain density regimes.

Purpose of the Study:

• To develop and validate a novel pressurized gravitational capillary viscometer for subcooled liquefied gases.
• To obtain precise absolute viscosity measurements for liquid oxygen.

Main Methods:

• A novel viscometer design utilizing a coiled capillary and capacitive liquid-level sensors was employed.
• Helium gas was used to create a liquid level difference and pressurize reservoirs, enabling gravity-driven flow measurements.
• Absolute viscosity was determined by measuring flow rates through the capillary under controlled pressure and temperature conditions.

Main Results:

• The viscometer achieved an absolute viscosity measurement uncertainty of 1% at a 95.5% confidence level.
• Viscosity data for liquid oxygen were successfully acquired across a pressure range of 0.15 to 1.0 MPa and temperatures from the boiling point to near the freezing point.
• The generated viscosity data are demonstrated to be superior to existing published data and correlations for subcooled liquid oxygen.

Conclusions:

• The developed viscometer is a reliable instrument for precise viscosity measurements of cryogenic liquids.
• The new viscosity data for liquid oxygen fill a critical gap in the available literature.
• This work provides essential, high-quality data for advancing aerospace engineering and cryogenic fluid management.