Tag: mathing

Tools Of The Trade: The Rotameter

Published on by Brian FarnoLeave a comment
EXAIR’s Free Efficiency Lab

One of the free services we offer to customers here at EXAIR is our Efficiency Lab. In case you are not familiar here is a brief synopsis. Speak with an Application Engineer about your existing compressed air blowoff/point of use product and that you would like to know how much air it consumes. Fill out the brief survey and send the product you use in to our facility. Let us perform tests on calibrated test equipment to determine the force, flow, and noise level. We will then issue you a report that states what the EXAIR model would best be suited (if applicable) as well as how much compressed air you will be able to save. Order the recommendation and start saving money.

To do these evaluations, we have to have calibrated equipment that is reliable and capable of handling vast range of products we may receive in. For this, we could use a Digital Flowmeter, in some cases that is what has to be done due to large flow rates. For the majority of these though we go old school. We utilize a piece of equipment called a rotameter.

A rotameter pairs nicely with a calibrated pressure gauge as well.
The float can be seen with graduated marks for readings. The taper of the chamber is not easily seen with the naked eye.

This is a device that is designed to measure the flow rate of a fluid within a closed tube. The inside diameter of the tube is varied which causes the float within the meter to raise or lower.  They are calibrated for a specific gas at a given pressure and temperature, most are calibrated for atmospheric conditions, 14.7 psi (1.014 Bar). The meter must be mounted vertically and this is not always best suited for industrial environments.

When testing products the compressed air within the meter is pressurized which means we have to correct the reading for the given pressure, if the temperature is outside of the calibration temp then we must also perform that correction. We do this using a table provided by the manufacturer of the meter or by using the calculations shown to get exact values that may be in between the pressures in the table.

Pressure Correction Table

 

This will allow us to then multiply the Correction Factor by the meter reading and calculate our corrected flow for the point of use device at a given operating pressure and temperature.

Temperature correction table

Knowing where the values that are measured and calculated come from add validity to the reports and understanding all of the variables that go into reading like this helps to better validate the cost savings that can be seen.

In a pinch, for a field estimation, we can also use these Correction Factors and determine an approximate consumption rate of a device that has been measured at a pressure such as our cataloged 80 psig (5.5 Bar). This can often be done on the fly to help determine the flowrates currently on a system. This can be helpful when troubleshooting, giving estimated simple ROIs, and help justify results and reasons for future purchases of engineered solutions.

If you want to discuss the Efficiency Lab or any of the math behind our calculations, contact any Application Engineer, we can all help out.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Leaks and Why They Matter

Published on by Brian FarnoLeave a comment

Leaks can be discussed quite frequently around industrial environments. These can be refrigerant leaks, water leaks, gas leaks, even information leaks. All of these leaks have one thing in common, they all cost the company money in the end. I often think about several classic cartoons when I hear about leaks being fixed as they are found. They can become a little overwhelming like the “Squirrel” from the movie Ice Age 2.

1 – Ice Age 2 – Scrat – Mission Impossible

When it comes down to it, not many leaks create good results, that is why I want to take a second and educate on the costs your facility may be seeing from compressed air leaks. The leaks within an industrial environment can often account for up to 30% of the total compressed air generated.

So let’s take a look at that, the cost of compressed air is derived from the kWh cost the facility pays to the utility company. Here in the Midwest the average cost is around $0.08 / kWh. The equation to convert this to cost per cubic foot of compressed air is shown below. This formula assumes that the compressor generates four standard cubic feet of compressed air per horsepower of compressor. Again this is an industry acceptable assumption.

The size of a leak will determine how much compressed air is wasted, most of these leaks are not even to the audible range for the human ear which leads them to be undetected for long periods of time. A leak that is equivalent to a 1/16″ diameter orifice can result in an annual loss of more than $836.50 USD. While the scale of this number when compared to the annual revenue of a company may be small, the fact remains that this single leak would more than likely not be the only one. This isn’t the only way leaks will cost money though.

Leaks can also generate false demand which can result in pressure drops on a system. When the pressure on a production line drops this could result in unscheduled shutdowns. Often, when a pressure drop is observed the quick answer is to increase the header pressure which causes even more energy to be utilized and even more compressed air will be pushed out of these leaks. That increase in system pressure comes at a price as well. When increasing a system pressure by 2 psi the compressor will consume an additional percent of total input power. This again will hit the bottom line and result in lower efficiency of operation for the facility.

If you hear that distinct hiss of compressed air leaks when you are walking through your facility, or even if you don’t hear the his and you know that a leak detection action plan is not being practiced and want to find out the best ways to get one in place, contact us. We are always willing to help you determine how to lower the leaks in your facility as well as reduce the system pressure required to keep your lines up and running by implementing engineered solutions at the point of use.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

1 – Ice Age 2 – Mission Impossible Scrat – retrieve from YouTube – https://www.youtube.com/watch?v=S-HniegbnFs

 

Laminar Flow and Digital Flowmeters: An Explanation On How To Achieve Laminar Flow

Published on by Brian FarnoLeave a comment

When I see turbulent flow vs. laminar flow I vaguely remember my fluid dynamics class at the University of Cincinnati.  A lot of times when one thinks about the flow of a liquid or compressed gas within a pipe they want to believe that it is always going to be laminar flow. This, however, is not true and there is quite a bit of science that goes into this.  Rather than me start with Reynolds number and go through flow within pipes I have found this amazing video from a Mechanical Engineering Professor in California. Luckily for us, they bookmarked some of the major sections. Watch from around the 12:00 mark until around the 20:00 mark. This is the good stuff.

The difference between entrance flow, turbulent flow and laminar flow is shown ideally at around the 20:00 mark.  This length of piping that is required in order to achieve laminar flow is one of the main reasons our Digital Flowmeters are required to be installed within a rigid straight section of pipe that has no fittings or bends for 30 diameters in length of the pipe upstream with 5 diameters of pipe in length downstream.

This is so the meter is able to measure the flow of compressed air at the most accurate location due to the fully developed laminar flow. As long as the pipe is straight and does not change diameter, temperature, or have fittings within it then the mass, velocity, Q value all stay the same.  The only variable that will change is the pressure over the length of the pipe when it is given a considerable length.

Another great visualization of laminar vs. turbulent flow, check out this great video.

 

If you would like to discuss the laminar and turbulent flow please contact an Application Engineer.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

1 -Fluid Mechanics: Viscous Flow in Pipes, Laminar Pipe Flow Characteristics (16 of 34) – CPPMechEngTutorials – https://www.youtube.com/watch?v=rQcZIcEa960

2 – Why Laminar Flow is AWESOME – Smarter Every Day 208 – SmarterEveryDay – https://www.youtube.com/watch?v=y7Hyc3MRKno

 

 

Applying a Vortex Tube and Adjusting Temperature

Published on by Brian FarnoLeave a comment

Throughout my tenure with EXAIR there are may days where I have tested different operating pressure, volumetric flow rates, back pressures, lengths of discharge tubing, generator compression, and even some new inquiries with cold air distribution all on a vortex tube.  These all spawn from great conversations with existing customers or potential customers on different ways to apply and applications for vortex tubes.

Many of the conversations start in the same spot… How exactly does this vortex tube work, and how do I get the most out of it?  Well, the answer is never the same as every application has some variation.  I like to start with a good idea of the area, temperatures, and features of exactly what we are trying to cool down.  The next step is learning how fast this needs to be done.  That all helps determine whether we are going to be looking at a small, medium, or large vortex tube and which cooling capacity to choose.   After determining these factors the explanation on how to adjust the vortex tube to meet the needs of the application begins.

This video below is a great example of how a vortex tube is adjusted and what the effects of the cold fraction have and just how easy it is to adjust.  This adjustment combined with varying the air pressure gives great versatility within a single vortex tube.

The table below showcases the test points that we have cataloged for performance values.  As the video illustrates, by adjusting the cold fraction lower, meaning less volumetric flow of air is coming out of the cold side and more is exhausting out the hot side, the colder the temperature gets.

EXAIR Vortex Tube Performance Chart

This chart helps to determine the best case scenario of performance for the vortex tube.  Then the discussion leads to delivery of the cold or hot air onto the target.  That is where the material covered in these two blogs, Blog 1, Blog 2 comes into play and we get to start using some math.  (Yes I realize the blogs are from 2016, the good news is the math hasn’t changed and Thermodynamics hasn’t either.)  This then leads to a final decision on which model of vortex tube will best suit the application or maybe if a different products such as a Super Air Amplifier (See Tyler Daniel’s Air Amplifier Cooling Video here.)is all that is needed.

Where this all boils down to is, if you have any questions on how to apply a vortex tube or other spot cooling product, please contact us.  When we get to discuss applications that get extremely detailed it makes us appreciate all the testing and experience we have gained over the years.  Also, it helps to build on those experiences because no two applications are exactly the same.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF