Re: Venturi Tube
Dear Shenjie,
Your idea of using a venturi eductor as an air mover for a combined vacuum system and pressure system is not new.
However, the combination of a vacuum- and a pressure system with one air mover is complicated.
A vacuum system creates a changing mass flow of air, related to the created vacuum by a varying material flow.
The pressure system, fed with the vacuum related and changing airflow, requires a constant mass flow of air.
The result is that a high vacuum causes a low air mass flow in the pressure system, where a blockage may be induced.
At the same time, the pressure ratio over the compressor (eductor/venturi) is becoming very high:
Pressure ratio = outlet pressure/inlet pressure = (discharge pressure+1)/(1-vacuum)
Moreover, the conveying air mass flow is influenced by the compressor (eductor/venturi) pressure-flow curve.
Designing an eductor/venturi system requires the balancing of all these parameters
-vacuum
-pressure
- air flow in vacuum system
-airflow in pressure system
-SLR in vacuum system
-SLR in pressure system
-Flow-vacuum/pressure curve of eductor/venturi
-Sub critical nozzle or critical nozzle (If your 3.0 barg air supply is a single compressor, the nozzle should be sub critical, otherwise the compressor must be venting compressed air and a subcritical nozzle limits the conveying power.)
-An eductor/venturi can create very low temperatures at the pickup point.
-An eductor/venturi system has a very low energetic efficiency
A system, whereby the eductor is gravity fed, does not have all these complications (apart from the very low energetic efficiency)
A system, whereby the venturi is applied as a vacuum source is also possible and is often used in the petro chemical plants (stem driven vacuum eductors) for conveying catalyst.
The low energetic efficiency also limits the application to low conveying pressures and therefore to low conveying rates and short distances.
Have a look at:
http://www.foxvalve.com/
Success
Teus ■
Teus
Re: Venturi Tube
Teus,
Thanks for your reply.
Shenjie ■
Shenjie Tel:+86(0)20 83553890,83550361 Fax: +86(0)20 83542314 [email]sj@chinabulk.com[/email] [url=http://www.chinabulk.com]Sino-Auto Technology[/url]
Venturi-Eductor
Dear Shenjie,
To transfer 5 t/h pp-pellets 30 m into a silo is not very difficult if you have enough air (around 600 to 850 m3/h at 3 bar g) available. For your application I would recommend to choose an 100 or 125 mm pipe or hose.
If you need further information don´t hesitate to contact me.
Best regards
Klaus Schneider
KS-Engineering GmbH, Cologne, Germany
www.enviro-engineering.de ■
Re: Venturi Tube
Dear Mr Schneider,
I made an indicative conveying calculation for the required 5 t/hr pp-pellets of unknown properties.
I made the calculation, based on your advised air flow and pipe diameter.
For a gravity fed eductor installation, I found a workable solution with a sub critical nozzle.
However, Mr Shenjie is asking for an installation, whereby the pp-pellets are vacuum conveyed over a distance of 10 m and then pressure conveyed over a distance of 20 m vertical.
In this situation, we have 3 airflows:
1)a suction airflow with 5 tph pp-pellets
2)a pressure air flow with 5 tph pp-pellets
3)a compressor airflow
In this configuration, the pressure air flow = suction air flow + compressor air flow.
The suction airflow is depending on the vacuum at the venturi (eductor intake) and therefore varies with the material flow.
When the pressure at the nozzle outlet in the eductor becomes higher than 1 bar(a), due to the required conveying pressure, the vacuum has already stopped.
Not being experienced in the application of venturi-eductors, I doubt whether the required installation can be designed in such a way that a stable conveying system results.
Very much interested to your opinion.
Have a nice day
Teus
Attachments
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Teus
Ejector Using Coanda-Effect
Dear Mr. Tuinenburg,
Sorry for the long delay. You are right with almost all of your concern. Don´t worry about that.
I guess that yiu never have seen a coanda or ring-gap ejectors. There is only a short suctionpart (made from aluminium for pp-pellets) with connection(hose) to the airsupply.
Therefore you can eliminate the10 m suction part. Of course, you need high pressure air as I said in my first response.
Best regards
Klaus Schneider
Originally Posted by Teus Tuinenburg
I made an indicative conveying calculation for the required 5 t/hr pp-pellets of unknown properties.
I made the calculation, based on your advised air flow and pipe diameter.
For a gravity fed eductor installation, I found a workable solution with a sub critical nozzle.
However, Mr Shenjie is asking for an installation, whereby the pp-pellets are vacuum conveyed over a distance of 10 m and then pressure conveyed over a distance of 20 m vertical.
In this situation, we have 3 airflows:
1)a suction airflow with 5 tph pp-pellets
2)a pressure air flow with 5 tph pp-pellets
3)a compressor airflow
In this configuration, the pressure air flow = suction air flow + compressor air flow.
The suction airflow is depending on the vacuum at the venturi (eductor intake) and therefore varies with the material flow.
When the pressure at the nozzle outlet in the eductor becomes higher than 1 bar(a), due to the required conveying pressure, the vacuum has already stopped.
Not being experienced in the application of venturi-eductors, I doubt whether the required installation can be designed in such a way that a stable conveying system results.
Very much interested to your opinion.
Have a nice day
Teus
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Venturi Tube
I have 3.0 Barg air supply. I need to suck PP pellet from a bulk trailer to the top of a silo.
Condition as below:
Capacity: 5 tons/h
Horizontal: 10 meter
Vertical: 20 meter
Bends: 2
Can I use a venturi tube fixed at one leg of the silo, a 10 meter flexible pipe with a sucking nozzle installed at the inlet, 20 meter hard pipe from the outlet to top of the silo?
Who has experiance for similar configuration?
Thanks! ■
Shenjie Tel:+86(0)20 83553890,83550361 Fax: +86(0)20 83542314 [email]sj@chinabulk.com[/email] [url=http://www.chinabulk.com]Sino-Auto Technology[/url]