Vapor-jet pumps

Water vapor pumps Oil vapor jet pumps Mercury vapor jet pumps... 

Mercury diffusion and vapor-jet pumps are less sensitive to air ingress than oil diffusion pumps. The oxidation of the hot mercury caused by the air ingress is negligible in regard to the operating characteristics of the pump when compared with the mercury loss in the forepump line. 

Vacuum pump, diffusion pump (DP) A compression-type vacuum pump that operates by the collision of heavy vapor molecules with the gas molecules to be pumped, giving the gas molecules a preferential velocity toward the high pressure stages of the pump. Also called a Diff pump or Vapor jet pump. 

Vapor jet pump (vacuum technology) A kinetic pump where the gas molecules are entrained in a jet of fluid vapor. See also Diffusion pump. 

Fig. 4. (a) Multistage diffusion pump (b) insert A, jet spray, where closed circles indicate gas molecules and open circles indicate vapor-jet molecules P. ... 

Pumps where the pumping effect is based mainly on the diffusion of gases into a gas-free high speed vapor jet (vapor pumps)... 

Sixties, mercury as the medium was almost completely replaced by oil. To obtain as high a vapor stream velocity as possible, he allowed the vapor stream to emanate from a nozzle with supersonic speed. The pump fluid vapor, which constitutes the vapor jet, is condensed at the cooled wall of the pump housing, whereas the fransported gas is further compressed, usually in one or more succeeding stages, before it is removed by the backing pump. The compression ratios, which can be obtained with fluid entrainment pumps, are very high if there is a pressure of 10 mbar at the inlet port of the fluid-entrainment pump and a backing pressure of 10 2 mbar, the pumped gas is compressed by a factor of 10 ... 

Included in the class of fluid-entrainment pumps are not only pumps that use a fast-streaming vapor as the pump fluid, but also liquid jet pumps. The simplest and cheapest vacuum pumps are water jet pumps. As in a vapor pump (see Fig. 2.46 or 2.51), the liquid stream is first released from a nozzle and then, because of turbulence, mixes with the pumped gas in the mixing chamber. Finally, the movement of the water - gas mixture is slowed down in a Venturi tube. The ultimate total pressure in a container that is pumped by a water jet pump is determined by the vapor pressure of the water and, for example, at a water temperature of 15 °C amounts te about 17 mbar. 

Figure 9. Design of the dye laser amplifier. Ultrafast laser pulses are amplified roughly 10,000 times by seven passes through a dye jet pumped by a copper vapor laser.

Doms M, Muller J. Design, fabrication, and characterization of a micro vapor-jet vacuum pump. Journal of Fluids Engineering 2007, 129, 1339-1345. 

Doms M, Muller J (2007) A micromachined vapor-jet vacuum pump. Transducers 2007 -international solid-state sensors, actuators and microsystems conference... 

The basic principle of a diffusion pump can be explained with a simple single-stage mercury diffusion pump (see Fig. 7.21). On the system side of the pump (at about 10 2 to 10 3 torr, or better), gas molecules wander around, limited by their mean free path and collisions with other molecules. The lowest section of this diffusion pump is an electric heater that brings the diffusion pump liquid up to its vapor pressure temperature. The vapors of the diffusion pump liquid are vented up a central chimney where, at the top, they are expelled out of vapor jets at supersonic speeds (up to 1000 ft/sec). Below these jets is a constant rain of the pumping fluid (mercury or low vapor-pressure oil) on the gases within the vacuum system. Using momentum transfer/ gas molecules are physically knocked to the bottom of the pump, where they are trapped by the vapor jets from above. Finally, they are collected in a sufficient quantity to be drawn out by the auxiliary (mechanical) pump. 

Jet pumps are used to remove air, gases, or vapors from condensers and vacuum equipment, and the steam jets can be connected in series or parallel to handle larger amounts of gas or to develop a greater vacuum. The capacity of steam-jet ejectors is usually reported as pounds per hour instead of on a volume basis. Far design purposes, it is often necessary to make a rough estimate of die steam requirements for various ejector capacities and conditions. The data given in Table 3 can be used for this purpose. 

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