Understanding Schmidt Number
The Schmidt number (Sc) is a dimensionless number used in fluid mechanics and mass transfer operations. It is defined as the ratio of momentum diffusivity (kinematic viscosity) to mass diffusivity. It helps to characterize the relative rates of momentum and mass transfer in a fluid.
Factors Influencing Schmidt Number
- Kinematic Viscosity (ν): A measure of a fluid's internal resistance to flow.
- Mass Diffusivity (D): The rate at which particles spread from an area of high concentration to an area of low concentration.
Typical Schmidt Number Values
Different substances exhibit varying Schmidt numbers based on their physical properties:
- Oxygen: Sc ≈ 0.2 - 0.6
- Water: Sc ≈ 1000
- Benzene: Sc ≈ 0.8 - 1.5
- Ethyl Alcohol: Sc ≈ 2.0 - 3.0
Lowest Schmidt Number: Water
Among the options provided, water has the highest Schmidt number, while the lowest is exhibited by oxygen. However, it appears there may have been a misunderstanding in the statement about water being the correct answer.
- Oxygen: Because of its lower viscosity and higher diffusivity, it has the lowest Schmidt number, indicating that momentum transfer occurs much faster relative to mass transfer.
Therefore, the correct answer to the question regarding which substance has the lowest Schmidt number is Oxygen, not water.
Conclusion
In summary, the Schmidt number is crucial for understanding mass transfer phenomena, and oxygen stands out with the lowest value among the given options due to its specific physical properties.