What is Laminar Flow and Turbulent Flow?

Super Air Knife

Fluid mechanics is the field that studies the properties of fluids in various states.  There are two areas, fluid statics and fluid dynamics.  Fluid dynamics studies the forces on a fluid, either as a liquid or a gas, during motion.  Osborne Reynolds, an Irish innovator, popularized this dynamic with a dimensionless number, Re. This number determines the state in which the fluid is moving; either laminar flow or turbulent flow.  Equation 1 shows the relationship between the inertial forces of the fluid as compared to the viscous forces.

Equation 1:  Re = V * Dh/u

Re – Reynolds Number (no dimensions)

V – Velocity (feet/sec or meters/sec)

Dh – hydraulic diameter (feet or meters)

u – Kinematic Viscosity (feet^2/sec or meter^2/sec)

The value of Re will mark the region in which the fluid (liquid or gas) is moving.  If the Reynolds number, Re, is below 2300, then it is considered to be laminar (streamline and predictable).  If Re is greater than 4000, then it is considered to be turbulent (chaotic and violent).  The area between these two numbers is the transitional area where you can have eddy currents and some non-linear velocities.  To better show the differences between each state, I have a picture below that shows water flowing from a drain pipe into a channel.  The water is loud and disorderly; traveling in different directions, even upstream.  With the high velocity of water coming out of the drain pipe, the inertial forces are greater than the viscosity of the water.  This indicates turbulent flow with a Reynolds number larger than 4000.  As the water flows into the mouth of the river after the channel, the waves transform from a disorderly mess into a more uniform stream.  This is the transitional region.  A bit further downstream, the stream becomes calm and quiet, flowing in the same direction.  This is laminar flow.  Air is also a fluid, and it will behave in a similar way depending on the Reynolds number.

Turbulent to Laminar Water

Why is this important to know?  In certain applications, one state may be better suited than the other.  For mixing, suspension and heat transfer; turbulent flows are better.  But, when it comes to effective blowing, lower pressure drops and reduced noise levels; laminar flows are better.  In many compressed air applications, the laminar region is the best method to generate a strong force efficiently and quietly.  EXAIR offers a large line of products, including the Super Air Knives and Super Air Nozzles that utilizes that laminar flow for compressed air applications.  If you would like to discuss further how laminar flows could benefit your process, an EXAIR Application Engineer will be happy to help you.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

When Air Flow, Not Force, Makes The Difference

I recently had the pleasure of talking with a CAGI Certified Compressed Air Systems Specialist, who was working with a client to improve energy efficiency in the use of their compressed air. One particular application that was particularly taxing on their system is the use of hose barb fittings (basically, an open blow device) to fold over a cardboard box flap on a packaging line.

We discussed the possibility of trying something out, but the client wanted to look at some data, showing what their expected savings could be. Hose barb fittings are quite common, and they DO focus the flow of a compressed air discharge into a forceful little blast, which is quite effective at folding a box flap.

The client’s main concern was the force applied. In truth, there’s no better way to maximize force than by discharging a compressed gas directly through an open ended device. Excessive force, however, isn’t the only way to solve an application like this, as I proved in a test in our Efficiency Lab.  Here’s what happened:

EXAIR 1″ and 2″ Flat Super Air Nozzles can be fitted with a variety of shims for variable performance.
  • All of them folded the box flap easily.  The Model HP1125 folded it just as far as the hose did in the test I rigged, and with a 37% reduction in compressed air consumption.  The others folded it very nearly as far, with 62% (Model 1122) and 70% (Model HP1126) reductions.
  • Not to mention the drastic reduction in noise levels.

Lastly, I documented it all in a short video:

We field calls all the time from callers wanting to know how much force our Intelligent Compressed Air Products can generate.  Applications like part ejection do indeed require a certain amount of force to, say, move an object in motion from a conveyor belt…that’s just physics.  Most blow off applications (and folding over a flat box flap, for instance,) just need air flow…which engineered products from EXAIR Corporation can handle just fine, and at a fraction of the compressed air use & sound levels associated with open end blowing devices.

If you’d like to find out how EXAIR Corporation can help save you money on compressed air consumption, and ear plugs, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
Visit us on the Web
Follow me on Twitter
Like us on Facebook

 

 

 

Air! image courtesy of Barney Moss  Creative Commons License

EXAIR’s Efficiency Lab can Help With your Energy Audit, Quantify Savings and Provide an ROI

I recently received an inquiry from a customer to test their current air guns through our Efficiency Lab service. According to the operators, the handheld blow gun they were purchasing from a commercial retailer was too loud and complaints were rolling in.  They were also hoping to save some compressed air in the process as they were performing an energy audit at the same time.

Commercial Air Gun w/ Cross Cut Hole
Commercial Air Gun w/ Cross Cut Hole

Cross Cut Hole Nozzle
Cross Cut Hole Nozzle

The gun they sent in looked fairly similar to our Precision Safety Air Gun but it did not have an engineered nozzle on the tip of it.   Instead, it was simply a cross cut hole in a piece of material.   The air inlet to the gun was a 1/4″ NPT just like our Precision Safety Air Gun, the extension on the gun was slightly longer, the only significant variance I saw was the tip.

EXAIR Model 1410SS-CS
EXAIR Model 1410SS-CS

The Model 1110SS Nao Super Air Nozzle and Chip Shield
The Model 1110SS Nao Super Air Nozzle and Chip Shield

To try and get as much information as possible I measured the O.D. and I.D. of the extension, the hole size was approximately .140″.  I measured the extension on our Precision Safety Air Gun just to see what is different, it came in at the same size.  So, I flow tested the competitive blow gun with their tip on it and came up with air consumption of 12.69 SCFM, noise level of 92 dBA at 3′ away, and a blowing force of 11.5 oz at 80 psig.   I then measured the same attributes of EXAIR’s model 1410SS-CS Precision Safety Air Gun at 80 psig inlet pressure.  The model 1410SS-CS measured 8.3 SCFM, gave 8.1 ozs of working force, and only produced a 75 dBA sound level from 3′ away.

The sound level reduction was a total of 17 dBA which is below the OSHA standard for allowable noise level exposure, as well as reduced their air consumption by 4.39 SCFM.  That is almost a 35% reduction in their compressed air usage per gun replaced.  After seeing these levels of reduction the customer had more than enough information to provide management with in order to replace the blow guns not just for noise level reduction but also because it will reduce air use and save money. A clear supportive role in their energy audit.

If you would like to discuss how EXAIR can provide some free force, flow, and noise level testing for your facility, please contact an Application Engineer or check out the Efficiency Lab page on our site.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

Super Air Nozzles Are a Better Solution for an Application

Granular brick residue blow off 2

Earlier this morning I took a call from a production facility here in the U.S. with a specific application need.  In this facility, bricks are made via automated processes, and during one stage of production a residue remains which affects future product progression.

To combat the residue accumulation, airguns were mounted in place with the triggers zip tied and controlled by an adjacent solenoid.  Using 1/4″ NPT nozzles of unknown origin, these air guns remove the build up of small granular dirt along the edge of the bricks. An image of this setup can be seen above.

While the solution provided some relief, the compressed air use was deemed excessive and the noise level too high.  The end user in this case contacted EXAIR for a more efficient and more quiet solution.

Due to the size of the existing nozzles, and the desire of the end user to only replace the nozzle portion of the setup, our recommendation was to use model 1100 or model 1126 Super Air Nozzles.  Based on prior experience, I recommended to test each style of nozzle to determine which will provide the better result.

The customer responded in turn. “Not a problem.  We have other applications that need this same type of upgrade.  I’m sure we’ll use them both and be calling you again.”

Solving problems and upgrading existing solutions is what EXAIR products are designed to do.  If you have an application you’d like to discuss, contact an Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE