Predicting enhanced mass flow rates in gas microchannels using nonkinetic models

Area of Science:

• Fluid dynamics
• Microfluidics
• Rarefied gas dynamics

Background:

• Enhanced mass flow rates are observed in pressure-driven rarefied gas flows through microchannels.
• Existing nonkinetic models struggle to accurately predict these phenomena across all flow regimes.

Purpose of the Study:

• To theoretically predict enhanced mass flow rates in microchannels using nonkinetic approaches.
• To interpret the Knudsen minimum phenomenon in gas flow dynamics.
• To evaluate different nonkinetic models against experimental data.

Main Methods:

• Utilized mechanically consistent volume-diffusion hydrodynamic equations for analytical solutions.
• Analyzed experimental data on subatmospheric pressure-dependent viscosity.
• Investigated pressure-dependent viscosity exponent, slip-velocity, and volume diffusion models.

Main Results:

• A single momentum diffusion model with pressure-dependent viscosity failed to match experimental data.
• The volume diffusion model provided a comprehensive explanation for the Knudsen minimum.
• The volume diffusion model achieved excellent agreement with experimental data up to a Knudsen number of 5.

Conclusions:

• Volume diffusion is a critical transport mechanism for understanding rarefied gas flow in microchannels.
• The volume diffusion model offers a physically sound interpretation of experimental observations, including the Knudsen minimum.
• This approach accurately predicts gas flow rates across a wide range of Knudsen numbers, extending into the transition regime.