Air amplifier

When the cover is sealed, there is no need (and little ability ) for the external blower (or air amplifier) to try and remove vapor. 

When the cover is loosened, the seal at the top is broken, the air amplifier can remove solvent-laden vapor from the vapor degreaser. 

The proper tool for collection of all fugitive solvent emissions is an air amplifier (air mover powered by compressed air). This device is figuratively shown in use in Figure 4.11, where emissions from all sources around an open-top vapor degreaser are pulled (sucked) into an air... 

An air amplifier (Figure 4.11) performs the function of a fan or blower used in suction mode. Air polluted with solvent from all three types of emissions, and room air, is pulled into a common air stream with the air amplifier. The result is twofold (1) solvent emissions are removed from where workers work and sparks may ignite, and (2) solvent concentrations in air are reduced to below posted exposure limits. 

Since cleaning solvents are heavier than air undisturbed, they don t rise in still air. So one (and probably more] suction point(s) for an air amplifier should be located low in the enclosure/pit/area in which solvents are used (Figure 4.12). 

The orange arrows in Figures 4.12, 4.13, and 4.14 point to those very suitable locations for multiple suction points for an air amplifier. 

It may be that not all of the locations noted above continuously produce solvent fumes. So to conserve resources (solvent, adsorbent bed life, and user attention), sophisticated users are likely to find it economically attractive to couple the air amplifier to an on-line explo-simeter — so that the air amplifier can only extract air when it is polluted with solvent. 

As illustrated in Figures 4.12 to 4.14, there are fugitive emissions emitted from more than one point next to, around, or near the cleaning machine (vapor degreaser or cold cleaner). In other words, the air amplifier may have more than one pickup point (Figure 4.15 ), or more than one air amplifier may be needed to keep the work area sanitary, safe, and hospitable. 

Finally, the most important virme of an air/amplifier is that is offers control of where air is removed from for treatment, when it is removed, at what rate is removed, and what air columns are left undisturbed. 

The reason an air amplifier is used to collect solvent-contaminated air, instead of a fan or blower, is that one can target just the contaminated volume of air for treatment and not the entire shop volume. 

The critical flaw is that every air amplifier (or equivalent ventilation fan) used with solvent vapor degreasers is used (deliberately) to waste money if no air amplifier is in place, the monetary value of escaping solvent is not being wasted . 

But, where solvent vapor is emitted into room air for whatever reason in whatever way, it must be colleaed and removed. That s the reason for use of an air amplifier. 

The essential difference between the air amplifier and the air eductor is in the diameter of the aperture through which the compressed air is expanded. That aperture is called a venturi. An equation which allows calculation of the performance of either device with a venturi is the Bernoulli Equation. ... 

This appears to be an application of Heisenberg s Uncertainty Principle (Ref. 1, Chapter 4.2.3). In the same way that one can t simultaneously measure the position and momentum of a particle, one can t use an air amplifier to collect only the solvent molecules which have escaped beyond the capability of the vapor degreaser to retain them and not pull additional solvent vapor from the throat of the open-top vapor degreaser. Both can t simultaneously be done. 

An air eductor is also known as an eductor-jet pump, an aspirator, a water eductor, a vacuum ejector, and a steam-jet ejector (depending upon what fluid is used as the motive fluid). An air amplifier is also erroneously called an air knife or an air eductor. 

First, direcdy purge solvent vapor from the work chamber into a plenum (duct) which is securely plumbed through an air amplifier into the adsorber bed. 

Normally, use ofventilation devices, such an air amplifiers, is discontinuous — at one high rate during a certain phase of the cleaning cyde, at another lower rate during other phases of the cleaning cyde, and at zero ventilation during off hours. 

Solvent-laden air generally enters the adsorber (pumped by the air amplifier) through a port in the top of the tank . A diffuser spreads the volume of fiow across the entire area of the adsorber bed. 

Solvent retained in the work chamber will either be emitted to the work area when the chamber is opened (so the parts basket can be removed), or pulled from the work chamber by an air amplifier (before the parts basket is removed) and then exhausted into an adsorption bed. There is no third way emit or treat. 

One can t harm the adsorber bed, but the exhaust from it won t be low in solvent concentration. One avoids this situation by using an air amplifier. This device produces air flows up to 15 times that of a small amount of pressurized air. Both the small volume of solvent-rich air and a large volume of clean dry ambient air are entrained by the compressed air flowing through the air nozzle The solvent-rich air is thereby diluted by a factor of 15. Design details are covered in Table 4.2. 

Electric (presumably) power to provide steam (to desorb the adsorption bed), to operate blowers and air amplifiers, to energize pumps, and for general system operation. This utility cost will be variable as the price of power varies greatly by location and time. 

The cost of electric power was estimated as the sum of four terms. The first is the cost to provide the steam flow (in pph) noted in Table 4.11. That value was converted to a requirement for energy as 945 BTU/lb steam, and the conversion factor of 3415 BTU/kilowatt (kW). The second term was the power cost to continually operate the air amplifier, taken to be a 6 HP motor. The third term was the power cost to operate a 3 HP water pump for condensed water and solvent vapor fed to the decanter. The fourth term is a general allocation of 52 kW for miscellaneous and unspecified needs. This value was taken from the reference of Appendix A2, Footnote 12, page 34. Both the third and fourth terms were corrected for the actual capacity of activated carbon using the six-tenth power rule used to estimate capital investment. The sum has the units of kW hours. 

In a device such as an air amplifier or an air eductor, there is no change in elevation (H). So the Bernoulli Equation becomes the equation at above. 

Note the dependence of pressure change on circular channel diameter (D), all else being the same. It s to the fourth power That dependence is how one can design an air amplifier with a large diameter venturi and expect only a small pressure change sufficient to entrain additional air relative to an eductor with a small diameter venturi which would produce a substantial pressure change — a partial vacuum upstream. 

Application of the Bernoulli Equation to the simple apparatus which is an air amplifier implements what is known as the Coanda Effect (named after Romanian aerodynamics pioneer Henri Coanda, who, in 1934, was the first to recognize the practical application of the phenomenon in development of aircraft which would have adequate lift at low air speed). Specifically, in an air amplifier, compressed air expands across a specially configured surface. A high velocity jet is produced. The jet clings to the walls of the surface (the Coanda Effect). A zone of low pressure is created. Available air at a higher pressure is pulled into the zone of lower pressure. The level of low pressure is dependent upon the dimensions of the surface configuration (as predicted by the Bernoulli Equation). 

How air amplifiers may be the most valuable part of a solvent cleaning machine. 

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