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Home made Vacuum Venturi
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quote:
Originally posted by GrahamLaming:
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.
 
Registered: September 11, 2008Reply With QuoteReport This Post
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Hi Graham.. I want to know what your opinion about my disign "90Degree Venturi"
Thank you
Moshe.

Image90_Degree_Venturi.JPG (47 Kb, 279 downloads)
 
Registered: September 11, 2008Reply With QuoteReport This Post
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Here some more details
Moshe

Image90_Degree_Venturi_Assembly.jpg (42 Kb, 231 downloads)
 
Registered: September 11, 2008Reply With QuoteReport This Post
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Have you tried making it? Did it work? What was your reaon for wanting to make it 90 deg?

You might need a fast high pressure pump to make it work if it can be made to work. Turbulance and fluid impedance might stop it from working.


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. Thank you for your opinion.
I didnt try making this disign.
My reason for wanting to make it 90Deg is some
project that I making now for my college.
I didnt know if it work so if you have any note that can may help me or if you have another solution to make it 90Deg, i am verey glad.
Thank you again.
Moshe.
 
Registered: September 11, 2008Reply With QuoteReport This Post
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make the venturi straight and pipe things to it as needed. Keep bends away from the outlet.


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



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Thought I'd share this with you, it demonstrates the power of a well made venturi, and as a warning to those making a GL Push/Pull reactor. As Graham says, "choose your vessel well". Remember partial vacuums are powerfull.
This is the result of a blocked vent.
 
Location: Suffolk, UK | Registered: November 08, 2006Reply With QuoteReport This Post
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Ventrui question:

Sadly I could not get in touch with James Earl awhile ago and so settled on some PVDF Mazzei injectors. They are good (I think) but still made of plastic and threading them into the metal at best has been squirrelly. (I think you really need thick teflon tape to help them be leak free.) Since these are my first venturis I do not know if the issues I am having with them are Mazzei specific or general issues with venturis.

GENRAL INFO:
I have a push pull set up and the issues I am having are on my small propane/vacuum set up.

I have a vacuum gauge connected right off the suction port of the venturi that I can close off to measure the venturi vaccum and then another Gauge (same brand) on my main processor tank to measure vacuum there.

I am using the harbor freight pump, and Mazzei injector 584. which b100 supply indicates is sized for the HF pumps. As the pump and fittings on my little propane tank are 1", I do have to size the flow down to 3/4" from 1" and back to 1" (after that ball valve.) I don't think that makes a difference but I do not know it doesn't.

QUESTIONS:
1. As the fluids get hotter in my propane tank, I loose suction. I even have a ball valve after the venturi to make variable back pressure and although it works at lower temps, at higher ones it has no effect. Testing with water, I took notes. At room temp, one venturi can produce -28 (hg?) almost -1 atm. at 140f it produces about -15 and at 200F nearly 0. I know this same thing happened with clean Canola Oil, but just at different temps - although I got no suction until the oil at least got warm, but hot, I lost all suction.

Is this typical of all Venturis (James Earl's or just Mazzie's?)



2. Amount (rate?) of Vacuum: I do not have the correct language for this so forgive me for sounding kind of moronic. So although the Venturi above pulls -28 which is quite good, the rate it can pull this vacuum seems kind of limited. I mean that when I apply this great -28 vacuum to the main processor, I only get a some fraction of that vacuum in the tank. I have checked for vacuum leaks and have siliconed any of those, so it appears that is not it. The vacuum slowly rises in the main tank, but I never get to -28. The most I ever got to was -12. Does that mean I have a vacuum leak or is it simply that there is so much head in the tank that the rate and/or volume of vacuum is not enough for the size of processor tank I have? Again is this a Mazzei specific issue, a Doug issue, or a Venturi issue?

2a. Ok, this also in the same vein, but different. I am running a centrifuge to clean my oil. To have it work properly, it has to introduce some air. With the Venturi/vacuum pump reading -28, I apply this vacuum to the centrifuge piping and vacuum drops to 0 (read only at the venturi) - meaning I think that the rate of vacuum is not great enough to keep up with the air that is being introduced. My question: Does this mean there is no pull whatsoever and then just wasting my electricity using my vacuum pump this way? Or there is some good pull - like wind - and can not be measured with a vacuum gauge.

Thanks
Doug
 
Location: Los Angeles | Registered: March 25, 2008Reply With QuoteReport This Post
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Doug,
I am not familiar with the Mazzei venturis but I bet Rick from B100 can help you out there, maybe try and PM him.
I can answer question #2. You have a vacuum leak. The size of the vessel has no bearing on the vacuum pump, just how long it takes to get it pumped down. I pressure tested my reactor with 125 PSI of air and it held for 2 days with no leaks however when I pumped it down to 29Hg it lost the vacuum in a day, so just because it holds positive pressure does not mean it will hold negative pressure. I found that vac leaks are very difficult to find!! It turned out to be the pump seals that were leaking once I valved off the pipe work the vac leak ceased which helped me to narrow it down... I had another leak that appeared once the reactor reached 200F... maybe that's causing the loss of vac when hot?

Sorry I don't have more input for ya!
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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Thanks. Vacuum leak was what I was worried about. So far to find the ones I had, get some kind of vacuum going, shut everything down and listen very closely to all joints. Hey, I have a crappy stethoscope from a halloween costume... it couldn't hurt.

Doug
 
Location: Los Angeles | Registered: March 25, 2008Reply With QuoteReport This Post
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If you have any techy wiz mates they may be able to put together an ultrasonic ear for you. It detects the, inaudible to us, whistle of leaks. Or train your dog lol.


mathematical elegance -- desired result achieved with minimal complication
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post
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Have you tried to pressure test it? If not pressurize it and use soapy water in a spray bottle to check all your joints, you will see bubbles from even the smallest of leaks...
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post



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Here is another simple to build venturi from Johno.

http://www.biodieselpictures.com/viewtopic.php?p=1307#1307

Simple construction, a brass compression fitting drilled out so the copper tubing can slide through mounted in a black TEE. Johno calls it an eductor because it is planned to be used both as eductor and venturi like the one discussed here:

http://biodiesel.infopop.cc/eve/forums/a/tpc/f/919605551/m/7251052182




Happy New Year Everyone!

Imagejohnos_venturi.jpg (20 Kb, 575 downloads)
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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quote:
I am using the harbor freight pump, and Mazzei injector 584. which b100 supply indicates is sized for the HF pumps. As the pump and fittings on my little propane tank are 1", I do have to size the flow down to 3/4" from 1" and back to 1" (after that ball valve.) I don't think that makes a difference but I do not know it doesn't.


Sizing it down to 3/4" will not make any difference. The testing I did indicated that you could plumb the output of the harbor freight pump with 1/2" pipe and not see any reduction in flow rates, so 3/4" will be fine. Plumbing on the input side of the pump needs to be at least 3/4" to avoid restrictions that can cause cavitation (more precisely it could cause the methanol to boil in the pump).
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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Aloha Rick da Tech

For the brass compression fitting would it be possible to use a brass hose barb instead? Say 1/2" NPT and 3/8" hose barb?

pb


quote:
Originally posted by Murphy: In short, this place is like a multi-dimensional bull$hit detector on steroids
 
Location: In the Pacific Somewhere | Registered: January 25, 2008Reply With QuoteReport This Post
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I'd say yes as long as the end of the nozzle is near the center of the TEE. The size of the hole through the hose barb is important. JohnO an I have been doing experiments using the HF pump. Different pumps will tune out to different size jets.

I tried a similar hose barb and it works for me with an HF pump. I think mine would have worked better for me if I had cut one barbs off to bring the end of the barb closer to the center of the side port in the tee.

Edit - It would work on my style, not JohnO's style. The end of the jet needs to be near the center of the TEE. In my style I thread the inside of a 3/4" pipe with 1/2" threads and screw a compression fitting in it so that it sits inside the TEE. The picture shows the compressing fitting with the nut still on, but I took it off and drilled it out to 1/4" before putting it on the processor.

This message has been edited. Last edited by: RickDaTech,
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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Ok just to make sure the 1/4" hole is it measured or is it just whatever the size of a 1/4" drill bit is. I am sure it does not have to be that precise but I was just curious.


quote:
Originally posted by Murphy: In short, this place is like a multi-dimensional bull$hit detector on steroids
 
Location: In the Pacific Somewhere | Registered: January 25, 2008Reply With QuoteReport This Post
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In the picture above I used a 1/2" npt x 1/4" compression fitting. The compression fitting has a ledge in it that the tubing buts up against. I used a 1/4" drill to remove that ledge and make it a smooth bore thru. I used a hand drill so I'm sure the hole was a little bit over sized and out of round. I don't think a few thousandths make any difference. In fact I think it will work just fine anywhere from 0.200" to 0.300" Above 0.300" the venturi does not draw well. Below 0.200" and the flow rate starts to drop off dramatically.
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post



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I'm sure this question has already been asked somewhere in the currently 21 pages of this thread, but my eyes are burning with fatigue from a sudden shift change from night shift to day shift (I'm reaaaaaly tired), so I'll just ask it anyway & risk looking lazy for not having read the entire thread yet.

From the Penberthy link found on page 2, I searched the left hand margin list for the word venturi, but coudn't find it listed. I punched "venturi" into their search engine & the first result was this PDF:


http://www.penberthy-online.com/faq/FAQ_05_Intuitive_Je...=r&cq=&id=487f5bc033

About 1/3 of the way down the text, Penberthy states that "jet pumps are are occassionally (but incorrectly) called Venturi pumps".

Is the subject of this thread actually about jet pumps, or about Venturis?

I'm sure there's some technical difference between the two, but I'm a welder, not a process engineer, so I'm hoping someone here might have an answer that a layman like myself can actually understand.

Thanx!
 
Registered: September 26, 2005Reply With QuoteReport This Post
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The Penberthy site may have changed since the link was posted.

The information is there. look in the left hand column for "pumping liquids with liquids" Then look in the main frame for "Typical Applications" then you'll see how the site is set up.

Jet pumps have a venturi as a major component.
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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