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Home made Vacuum Venturi
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quote:

May I add my compliments to those who have spoken before me? That is some beautiful work!


Yes, Jim, without question that should be on show at the National Gallery in London.
 
Location: New Zealand | Registered: August 15, 2006Reply With QuoteReport This Post
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Attached are some pictures of the venturi Jamesrl made for me -- the 1" diameter one. Just got it plumbed in this morning, and ran a batch.



what is the flow rate and pressure of your pump?


mathematical elegance -- desired result achieved with minimal complication
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post
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what is the flow rate and pressure of your pump?


Hi Ant,

It was made to run on the famous HF pump, rated at 330gall./hour, not sure at what pressure.

Jim
 
Location: Suffolk, UK | Registered: November 08, 2006Reply With QuoteReport This Post
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around 25 litres a minute? That is slow for three quarter inch piping. I thought my 40 litres a minute pump was slow and restrict the outlet to at least 15mm to speed up the stream as it enters the tank. I`m still experimenting.


mathematical elegance -- desired result achieved with minimal complication
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post
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The throat of the venturi is 8mm, quite an increase in the flow velocity.
I haven't tried restricting the out let in an experiment, but I have put my thumb over the out let and messed about like that. It does have an affect on the efficiency of the venturi.

Jim.
 
Location: Suffolk, UK | Registered: November 08, 2006Reply With QuoteReport This Post
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Here is my naff sketch of my lego venturi. A properly drawn up one should follow thank's to GL's willingness to do one of his lovely diagrams for our benefit.

The 22mm coupler on the inlet connetcts to my inch bsp hydraulic hose using a standard adaptor fitting. Using a similar adaptor the 22mm connector on the outlet side connects to an inch bsp stainless pipe weleded into the side of my tank. The foot of 15mm pipe passes through the 22mm connector and the inch bsp pipe to enter the tank. The inch bsp pipe extends inside the tank but the 15mmm pipe extends beyond it. The pipe is welded in at an angle to encourage swirl.

The copper pipe fittings are all of the end feed type. Silver solder is used to join them as the greater mechanical strength it offers is needed with my heavy hose. This is also why most of the venturi outlet is inside the tank beyond the mounting point on the inch bsp pipe; to reduce leverage forces and improve mechanical stability.

It works well enough to draw in meth at about 3 litres per min with my 40litre per min rated pump. I think with oil the pump runs more like 30lpm in practice; so a ten to one mixing ratio seems to be what is happening. It costs two or three quid in parts plus another couple of quid for a stick of silver solder. Or four for two sticks if you are rusty lol. Either way under a tenner including the propane is very cheap for a venturi that works. £30 would normally be considered cheap and custom jobs in stainless can run you nearly £200.


mathematical elegance -- desired result achieved with minimal complication


ImageMy_Lego_Venturi.jpg (28 Kb, 829 downloads) lego venturi
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post



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Hi Ant

I used a similar scheme to make my venturi except I used a 22mm T...

See here

Cheers

Nick


Free collection of waste cooking oil in the Nottingahm area http://wastevegoil.co.uk
 
Location: Nottingham UK | Registered: December 14, 2005Reply With QuoteReport This Post
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Yes it is similar although you have chosen a different stratagy for the outlet side without a narrow inlet if that makes sense.

22mm won't work on my low flow rate pump. I took one of Graham's handbeaten 22mm venturis and beat it down further to a 10mm throat with an 8mm side tube. It worked a bit but not as well as the lego one and the lego is much easier and quicker to make. With a higher flow rate pump it would be different of course.

What flow rate and pressure is your pump at? How well did the venturi work?

were you using it as a meth injector or as an in tank mixing eductor? The latter would explain the different nozzle stratagy. I might try it myself for that.


mathematical elegance -- desired result achieved with minimal complication
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post
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Hi Ant

I have one of Graham's masterpieces (serial No 002) on my preheat/drying tank. I use it to draw air into the oil stream, which it does very well.

We tested several venturis at Graham's a few weeks back and the one we're talking about would draw liquid at about 4 litres per minute, but only at a head of less than 3 feet or so. I actually don't use it for injecting methoxide, I do that the conventional way before the pump. The pump is a Clark CEB102, basically the brass bodied version of the infamous HF pump - 33 litres/min.

It's becoming increasingly clear that you don't need to be scared of constricting the bore to form the venturi throat when you have a low flow rate pump. It's the pressure difference across the device that counts so I will try one to your dimensions. I'm also looking forward to trying one of Jamesrl's works of art, dimensioned to suit the HF type pump. I'll report back on the outcome.

Cheers

Nick


Free collection of waste cooking oil in the Nottingahm area http://wastevegoil.co.uk
 
Location: Nottingham UK | Registered: December 14, 2005Reply With QuoteReport This Post
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It's becoming increasingly clear that you don't need to be scared of constricting the bore to form the venturi throat when you have a low flow rate pump. It's the pressure difference across the device that counts so I will try one to your dimensions.



In fact I find the narrow constrictions are needed to get the local fluid velocity that is an important element in the design. For a given flow rate pump that has enough head pressure to cope with the loading of the constriction then the narrower pipes and jets will increase suction by speeding up the flow of fluid over the surfaces.

As I understand it, this surface fluid flow is the basic mechanism governed by the Bournelli equation that describes how low pressure zones are created. I'm a bit hazy on the exact details.

I intend to build another even thinner venturi using 4mm and 6mm fittings, instead of the 8mm and 10mm, if I can get them. I have been pointed towards refrigeration air con type places as a source. Time will tell


mathematical elegance -- desired result achieved with minimal complication
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post
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I intend to build another even thinner venturi using 4mm and 6mm fittings,


Hi Ant,

I've just been down that road whilst making an eductor for RickdaTeck, I took the nozzle down to 5mm. Drew it down from 15mm, well you now me, have hammer will bash, anyway the back pressure was so great I had to go round tightening up joins that have never leaked before.

I checked to see how far it would squirt, over 50ft, wow, but of cause there's a down side, the total volume going through was very low.

I see the constriction in a venturi as a compromise between through put of oil and preformance of the venturi, and I've made a few.

Using the same pump and varying the venturi design I got from 30sec/ltr to 2.8sec/ltr.

Which one is best for our process? you tell me.

Jim.
 
Location: Suffolk, UK | Registered: November 08, 2006Reply With QuoteReport This Post
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Traditionally we would say 30 seconds is better. Slow introduction of meth to aid complet and even mixing with all the oil.

Others have gone for fast introduction of meth with powerful mixing stratagies of one kind or another. Both approaches work. It's all about the mixing. Getting all the meth in contact with all the oil.

Which is the best given venturi depends on the pump. I want more positive lift more than I want faster meth introduction. The current venturi will lift the meth from floor level sometimes but ocasionally needs the tub lifting a bit. Not hard or risky but slightly dissatisfying. I also want a fast enough exit stream to drive an eductor.

The turbulant mixing zone of the venturi outlet tube changes things a bit and may allow for faster meth addition, still with even and complete mixing.

In my case I have around a ten to one mixing ration. I think up to five to one would be fine if I can do it. Faster than that and the meth is less evenly distributed to begin with; roughly speaking.

As I said it depends on what achives this for a given pump. I'm not sure throughput would be a problem with my particular pump. At 20 odd bar nothing seems to slow it down so far. Hopefully the silver solder will stem any tendency to leak. I can only try it and see what happens.


mathematical elegance -- desired result achieved with minimal complication
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post



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Here is the good pic courtesy of Graham. I would have used an unequal tee with an 8mm side branch if I could have found one.


mathematical elegance -- desired result achieved with minimal complication


Imageants_venturi.gif (9 Kb, 2487 downloads) Nice diagram
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post
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Hi Ant,

That is the basic design of my Supa-Dupa Venturi for Hi-output pumps, 90ltr/min plus.
The only difference is the anlges and soothness of transition.

A master piece in simplicity, well done.

Jim.
 
Location: Suffolk, UK | Registered: November 08, 2006Reply With QuoteReport This Post
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Hi Ant.....thanks for the plan from store bought stuff. I do have one question. What is the purpose of the (output side) 22mm:15mm reducer with internl stops filed off? It looks (from this pic) that it would not be required at all.

Anypne try this with Non-metric fittings (like 1/2, 3/4, 1" copper pipe sweat fittings)?


Newbie
 
Registered: March 13, 2005Reply With QuoteReport This Post
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Thank you gents. The output 22mm adaptor is purely to fit to the adaptor not shown that goes from 22mm compression to inch bsp female threaded. I have an inch bsp male threaded inlet on my tank. The 15mm tube passes inside that and into the tank.

I have just got some quarter inch (6mm) to half inch reducer that will mate with 8mm and 15mm metric adaptors with a bit of push and solder. sometime in the next week or so I hope to try my next generation lego venturi. I have two designs in mind and am not sure how each one will work. The both use a quarter inch female with qurter inch pipe soldered in for the outlet jet and a qurter inch female without the pipe for the inlet jet. I would also consider an 8mm fitting for the inlet jet.

The basic difference is that one design would use a 15mm tee as in my first attempt; the other an 8mm tee joining only the small ends of the reducers.

Both designs will need a steel or stainless inch bsp shell for mechanical strength. I have found this a slight problem with the current design due to the mechanical loading of the inch bsp hydraulic hose.


mathematical elegance -- desired result achieved with minimal complication
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post
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Another Home made venturi this time for the Pitbull pump.

Dont forget. If you would like a venturi for the GL Ecosystem just PM me.

Jim.

ImagePitbull_Venturi.JPG (34 Kb, 654 downloads)
 
Location: Suffolk, UK | Registered: November 08, 2006Reply With QuoteReport This Post
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Graham,
what do you think about ading a small vacuum pump to your design.
The pump should draw a light vacuum from the headspace of the destillate container through a separate moisture trap.
Vent should be closed.
The light vacuum could lower the boiling point of the methanol and you will use less energy to keep the BD/Byproduct at the temperature needed for destillation.
I think, this could be another step in the evolution of your system.

vy 73 Dieter
 
Location: Germany | Registered: January 11, 2007Reply With QuoteReport This Post



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Hi Dieter.

The vacuum pump seems good in theory, but in practise it is difficult to make a benefit with it.

The light vacuum will cause the boiling point to lower, which will cause the vacuum to be reduced by more vapour, so you will need to pump more.

As you pump, the temperature of the liquid will drop, caused by usage of latent heat of vaporisation of the methanol, so you will need to make a stronger vacuum, unless you add more heat.

In fact, using a vacuum pump uses more energy, because the vacuum pump will have an efficiency perhaps 40%.

Provided your insulation is good, normal atmospheric distillation works well, and the venturi allows you to recover methanol even from 25C, because we are not using boiling, but evaporation, and at atmospheric pressure, so no problems of pressure/vacuum vessel design, and no moving parts apart from the liquid pump.


Rover 75 + Skoda Fabia on B100
http://www.graham-laming.com

Bicycle on G100 12,000 miles p.a. ( http://uk.virginmoneygiving.com/GrahamLaming )
 
Location: UK | Registered: December 04, 2005Reply With QuoteReport This Post
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Hi Graham,
thanks for ur reply.
I`m happy to hear, that you are not affected by the flooding.
...
You are right and I think I didnt understood your design to the end :-)
The best points are the lack of moving parts except the pump and the simple design.
Ading a vacuum pump would make the things more complicated and will not ad a real benefit.

Thanks for ur explanation, I will build my processor with your design and learn more.

have a nice day &
vy 73 Dieter
 
Location: Germany | Registered: January 11, 2007Reply With QuoteReport This Post
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