What is the meaning of molecular flow?

the flow of a rarefied gas (of molecules, atoms, ions, or electrons) during which the properties of the flow depend significantly on the random motion of the molecules, in contrast to flows where the gas is considered to be a continuous medium.

What are the differences between continuum flow and free molecule flow?

Continuum flow is that flow that approaches zero Knudsen number. It can be achieved when the mean free path of a fluid molecule is tiny, or the section is enormous. Free molecular flow is a type of flow in which the mean free path of the gas molecule is larger than the chamber.

What is free molecular heating?

Free Molecular heating occurs in very low density gases where the mean free path of the gas molecules is large compared to the distance between the surfaces. The Knudsen number is the ratio of the mean free path and the effective length between surfaces.

At what pressure does molecular flow occur?

What prevails is molecular flow. In this case, the mean free path is significantly greater than the diameter of the flow channel. In molecular flow, the product of pressure and component diameter is approximately ≤ 1.3 · 10-2 hPa cm.

What do you understand by mean free path?

mean free path, average distance an object will move between collisions. The actual distance a particle, such as a molecule in a gas, will move before a collision, called free path, cannot generally be given because its calculation would require knowledge of the path of every particle in the region.

What is molecular flow rate?

From Wikipedia, the free encyclopedia. Free molecular flow describes the fluid dynamics of gas where the mean free path of the molecules is larger than the size of the chamber or of the object under test. For tubes/objects of the size of several cm, this means pressures well below 10−3 mbar.

What is concept of continuum?

A continuum is an area that can keep being divided and divided infinitely; no individual particles. It is a simplification that makes it possible to investigate the movement of matter on scales larger than the distances between particles.

What is the mean free path of air?

The constant μ is the mean free path and is the average (mean) distance traveled by a molecule between collisions. The mean free path of an oxygen gas molecule under a pressure of 1 atmosphere at 0° C is about 6 × 10-6 cm (2 × 10−6 inch).

What causes gas to flow?

When a collision occurs between molecules they will move off in whatever direction that collision causes. When a molecule of gas hits a surface it will reside there for a small fraction of a second and then release and move away, but in a completely random direction.

What is mean free path of electrons in metals?

In a pure metal a finite free path is caused by the thermal vibrations of the lattice and is of the same order as the average wavelength of the sound waves in the metal, which is large compared with the interatomic distance and is increased by lowering the temperature.

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