myklrs

Suction or Vacuum power - Bernoulli

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I was wondering while looking at the Bernoulli schematic if you can produce a strong suction or vacuum at the entry of the schematic? For example: using a 6 inch pvc pipe in the schematic and inserting a 2 inch pipe a couple inches inside of the six inch pipe at the entry area of the schematic. Water would be flowing on the outside of the 2 inch pipe but inside the 6 inch pipe. Would there be a suction or vacuum area so that water would flow through the 2 inch pipe. If so, could I manipulate the schematic (dimensions of the outside pipe through bell reducers or differing the different lengths or areas of the schematic to increase the suction or vacuum power or energy.

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The normal way to use this as a pump is to put an opening where (schematically) the P2 label is; the pressure is lowest there. It's called a Venturi pump or aspirator.

 

The normal way to use this as a pump is to put an opening where (schematically) the P2 label is; the pressure is lowest there. It's called a Venturi pump or aspirator.

 

I should restate my question, it was not very clear. I am trying to produce a strong suction at the circle utilizing the Bernoulli principle in a pipe with in a pipe by reversing the normal water flow in the outer pipe there by producing a strong suction or vacuum for the 2" pipe at the circled area. The total length of pipes with in the pipes is 5 ft. Outer pipe is 6" ID, Bernoulli section pipe is 4" ID, suction pipe is 2" ID. High pressure trash pump: 433 gal/min, 4" intake on pump, 3" discharge on pump. Any thoughts would be appreciated on creating the strongest type of suction or vacuum. Thanks myklrs.

Suction power.bmp

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I should restate my question, it was not very clear. I am trying to produce a strong suction at the circle utilizing the Bernoulli principle in a pipe with in a pipe by reversing the normal water flow in the outer pipe there by producing a strong suction or vacuum for the 2" pipe at the circled area. The total length of pipes with in the pipes is 5 ft. Outer pipe is 6" ID, Bernoulli section pipe is 4" ID, suction pipe is 2" ID. High pressure trash pump: 433 gal/min, 4" intake on pump, 3" discharge on pump. Any thoughts would be appreciated on creating the strongest type of suction or vacuum. Thanks myklrs.

 

You can increase the vacuum (lower the pressure) but not the vacuum power.

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In the hydraulic industry I typically tell people that there's really no such thing as a vacuum, that it's only label for an absence of atmospheric pressure. There really is no 'vacuum power' per se because any work done with a vacuum is actually work done by atmospheric pressure.

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In the hydraulic industry I typically tell people that there's really no such thing as a vacuum, that it's only label for an absence of atmospheric pressure. There really is no 'vacuum power' per se because any work done with a vacuum is actually work done by atmospheric pressure.

 

I have been thinking of your comment and have a few questions or thoughts. I read in an article (research on the Bernoulli Principle) that the restricted area should be 1/2 the size of the inlet diameter. For example: 10" inlet to a 5" restriction. OK, then it mentioned that the restriction should be short. It also mentioned that by inserting a tube in the restricted area acts like a pump by siphoning air pressure into the restriction area increases the fluid flow, 1 atm or 14.7 psi. at sea level.

 

Questions:

 

1) How short should the restriction be, is there a rule of thumb or best ratio for the length of the restriction in relation to the inlet and outlet.

 

2) If you add more than one tube to the restriction area does that increase the flow characteristics. Example: two tubes at 180 degrees apart or 3 tubes at 120 degrees apart.

 

3) Would adding a venturi tube after the Bernoulli Principle section benefit the velocity of the fluid (water) moving through the Bernoulli section.

 

4) Is there a relation for the size of the tube size in the restriction area, how big or small or does it matter.

 

Thanks for any comments, myklrs.

Edited by myklrs

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See http://en.wikipedia.org/wiki/Venturi_effect and http://en.wikipedia.org/wiki/De_Laval_nozzle

 

The restriction can be as short as an orifice but that affects the rate of energy loss. The ratio of energy loss and pressure between the upstream and choked flow sections will limit the venturi effect and the cross sectional area of the venturi will affect this as well. For a given ratio there will be an optimum area for the venturi and it won't matter if it's one big tube or divided into smaller tubes.

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I know I probably did my calculations wrong, but does anyone have an opion on whether this idea would work before I start to build one? thanks myklr.

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Still not clear on some basics of your proposal. Just where is the "circled area" in your diagram? If the flow through the small pipe is in the opposite direction to what you show through the nozzle, and the small pipe is at the left of the diagram before the orifice, then you may increase the flow through the small pipe, which I suppose is your intention, by imparting swirl to the feed, such as by rotating the big pipe. In that case the vortex-wall interaction would collapse the vortex and jet water to the left as the feed flows to the right and through the nozzle. However, the flow through the nozzle might cease. The hydrocyclone relates here.

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Actually I am a gold dredger, I am working on an underwater gold mining system that uses less horse power because it does not break the waters surface. It is very efficient as it traps gold particles on an incline rather than a gravity system with riffles. I have not seen a true 360 degree jet in all my years of mining and I think this is it. Most jet logs are set at a 45 degree angle or there about. This is a true 360 degree suction jet. Thank you for your imput, myklrs.

go look a a gold drege .that is much like what you are doing .

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