There are a great many applications that require a spray (as opposed to a stream) of liquid. Certain droplet sizes, and flow rates, are beneficial for certain applications. For example, if you’re fighting a fire, you want as high of a flow rate as possible – the more water you douse the fire with, the quicker it goes out. You also want a fairly large droplet size, since a mist would tend to evaporate instead of extinguishing the flames.
Pressure washers also benefit from higher (though not near as high as fire hose) flow rates, and droplet sizes. You want an appreciable flow rate, because that means high velocity, and good sized droplets combine that velocity with their relative mass to “blast” away dirt and detritus from the surface.
Medicine delivery devices, like asthma inhalers, are designed to produce mid-sized droplets, but pretty low (and controlled) flows. The droplets need to be small enough to efficiently spread the medicine through the breathing passages, but large enough to where they won’t evaporate before they ‘plant’ on the nasal & bronchial membranes to get absorbed.
These are examples of “liquid-only” nozzles…no other media or means of force are used to effect the spraying action. Most of the time, the droplet sizes in these applications are measured in hundreds of microns, which “liquid-only” nozzles are ideally suited to generate. Other applications, however, call for much smaller droplet sizes…such as those only attainable through atomization.
Small droplet size is key to cost effectiveness in many applications:
Think about expensive coatings…the smaller the droplet size, the better and more even the coverage, and the less you have to spray (and pay) out.
Or humidification…smaller droplet size means more stays airborne, for longer, and in a larger space.
Petroleum based lubricants, by their nature, only require a thin layer for best results. Smaller droplets make as even and thin of a layer as possible.
Dust control is much more effective with smaller droplet sizes, since the longer the mist lingers in the air, the more dust particles the individual droplets will adhere to…and then drop with them to the surface. This also prevents getting the surface of the material any wetter than it has to be.
If you’d like to discuss a liquid spraying application, I’d love to hear from you. Call me.
Russ Bowman Application Engineer EXAIR Corporation Visit us on the Web Follow me on Twitter Like us on Facebook
Eliminate drips to conserve valuable liquids and improve product finishes! EXAIR’s patented No Drip Atomizing Nozzle provides the same great performance as the the standard atomizing nozzles with the added benefit of positive liquid flow stoppage when the compressed air is shut off.
The No Drip option eliminates the occurrence of post spray liquid flow that results in unwanted drips that can mar a finish on painted or coated surfaces. Also, excess liquid loss is minimized saving on expensive materials like chemicals or coatings. When the compressed air is shut-off, the No Drip nozzle positively seals off the flow, eliminating the chance for a drip or lost liquid. Only one compressed air line is needed, as the line to combine and atomize the liquid also provides the no drip operation and control.
The Internal Mix type operates under the principle that the air and liquid come together and mix ‘internal’ to the nozzle. This type provides the finest atomization and smallest droplet size. The Internal Mix type of nozzle can be used with liquids up to 300 cP in viscosity. Both the air and liquid sides are pressure fed. The No drip Internal Mix Atomizing Nozzles are best for pressure fed applications not requiring independent air and liquid control.
The No Drip Atomizing Nozzles are available in (3) sizes – 1/8, 1/4, and 1/2 NPT – to provide a wide range of flow rates and pattern sizes. The No Drip feature does not impact the flow rates compared to the standard models. Minimum air pressure operation is 30 PSIG for the 1/4 and 1/2 NPT, and just 20 PSIG for the 1/8 NPT models.
Like the standard Internal Mix Atomizing Nozzles, spray patterns include narrow and wide angle round, flat fan, deflected flat fan and a 360° hollow circular pattern offering a wide selection to best meet the application needs.
Operation at up to 180 spray cycles per minute is possible. Air and Liquid Caps can be switched out to change the pattern and flow rates.
No post spray drip
Easily used with EFC
Minimizes air and liquid consumption
All stainless steel construction
Interchangeable liquid and air caps
If you need an Atomizing Spray Nozzle or any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
The patented (no longer patent pending) EXAIR No-Drip Atomizing Spray Nozzles have been nominated and are a finalist in the Flow Control 2016 Innovation Awards. The No Drip Atomizing Nozzles are just a portion of the entire Liquid Atomizing Nozzle products that EXAIR Offers. The No-Drip’s patented liquid shut off valve design eliminates the need for a separate pilot air line to positively shut off liquid flow ensuring there are no drips or excess flow from the nozzle. These are ideal when dealing with fine surface finishes, costly liquids, or intermittent spraying needs. The nozzles are offered in both pressure fed liquid and siphon fed liquid versions.
For the pressure fed version, the nozzle will require both compressed air and a pressurized liquid source. Both pressures can be adjusted independently giving a large spectrum of adjustment to fine tune the spray pattern and droplet sizes. The siphon fed nozzles can draw liquid up to 36″ vertically or be gravity fed up to 18″ overhead. This makes installation quick and easy when a pressurized liquid source, or liquid pump is not at hand.
The No-Drip Atomizing Spray Nozzles have also proven themselves in many applications, you can even read about a few of them here on our blog, links below.
Some of the reasons the EXAIR No-Drip Atomizing Nozzles were selected for these applications are the patented no-drip valve, their ability to atomize liquids to a range of 22-71 micron droplet size, the ability to fit into a tight space as well as the many spray pattern options. These features have ranked the nozzles as a finalist in Flow Control’s 2016 Innovation Awards.
We are very grateful if you choose to vote for our nozzle at the link below. Please vote.
I had an application where a customer needed to have a room at 80% relative humidity (RH). They produced a nylon backing for carpet, and they needed the high RH to reduce the “stickiness” in the process. Currently he was at 40% RH in a room that was sized at 40ft long by 20ft wide by 20ft high (12.2m long X 6.1m wide X 6.1m high). He wondered if our Atomizing Nozzles could help him. I decided to put on my engineering hat to calculate the amount of water that he would need to increase the moisture content. Other markets that would require higher RH in their ambient air are wood working, dust control, laboratories, and High Voltage applications.
Relative humidity (RH) is the percentage of water vapor as compared to saturation at the same temperature. So, at 100% RH, the ambient air cannot hold any more water. With our atomizing nozzles, we can atomize the water droplets to a very small droplet to help increase the absorption rate into ambient air. This will increase the RH of a room, but I will have to determine what size and how many.
The equation that I use is as follows, Equation 1:
Imperial Units S.I. Units
H = V * RAC * (Wf – Wi) / (v * 7000) Imperial H = V * RAC * (Wf – Wi) / (v * 997.9) Metric
H – mass flow rate of water, Lbs/hr H – mass flow rate of water, Kg/hr
V – Volume of Section, ft^3 V – Volume of Section, m^3
RAC – Room Air Changes, No. per hour RAC – Room Air Changes, No. per hour
Wf – Final Water Content, Grains/lb of dry air Wf – Final Water Content, Grams/Kg of dry air
Wi – Initial Water Content, Grains/lb of dry air Wi – Initial Water Content, Grams/Kg of dry air
v – Specific Volume of Air, ft^3/lb v – Specific Volume of Air, m^3/Kg
The customer stated that the room is at 68 deg. F (20 deg C). The humidity sensor is +/- 5%; so, when the RH in the room gets to 75%, it will kick on their system. They also use a standard HVAC unit to heat and cool the room. From these factors, we can determine some of the variables above. With the water content, you can find a chart online to determine the amount of water vapor that is contained in air at a specific temperature and RH. At 68 deg. F (20 deg. C), I was able to find the following information:
Imperial Units S.I. Units
Wi = 43 Grains/lb of dry air at 40% RH Wi = 6.1 Grams/Kg of dry air at 40% RH
Wi = 80.5 Grains/lb of dry air at 75% RH Wi = 11.5 Grams/Kg of dry air at 75% RH
Wf = 85.5 Grains/lb of dry air at 80% RH Wf = 12.2 Grams/Kg of dry air at 80% RH
v = 13.35 ft^3/lb @ 68 deg. F, 1 atm v = 0.8334 M^3/Kg at 20 deg. C, 1 bar (absolute)
V = 40ft X 20ft X 20ft = 16,000 ft^3 V = 12.2m X 6.1m X 6.1m = 454 m^3
Another factor is the number of air changes in that room. With the HVAC system, it will turn on and off to heat and cool the air. Some fresh air is brought in during this cycle. With a typical system, the room air will change between 2 – 4 times an hour. So, RAC = 4/hour (worse case). (Other locations may have scrubber systems, continuous air flow systems, etc. and the RAC will be greater).
If we plug in the numbers that we have, we can determine how much water that we will need to spray into the air to increase the RH from 40% to 80%.
Now that we know the rate of water to put into the ambient air, we have to look at the set up. With the settling time of the water droplets and the location of the humidity sensor, we will have a lead/lag problem. To help in this situation, I would recommend to turn on the Atomizing Nozzles for 10 – 15 seconds, and wait 2 minutes to re-measure the RH. This will help to not over saturate the room. As for the location of the Atomizing Nozzles, you have to make sure that the spray does not contact any structure or other atomizing spray patterns. This will cause the water to condense and either coat a structure or create rain. To help with the entire system, I suggested our No Drip External Mix Wide Angle Flat Fan Pattern Atomizing Nozzle. This will eliminate a water valve at each Atomizing Nozzle. When the air pressure is turned off to stop spraying, the No Drip Atomizing Nozzle will seal and not allow any water to drip. To also help with consistent RH in the room, the EB2030SS was my choice. The spray range helps to cover the area especially with multiple units operating.
To determine the number of Atomizing Nozzles, we want to look at the time determination with the controller and the intermittence of operation. With the RAC = 4/hour, the air in the room will change over every 15 minutes. We want to have a balance between the new air and the existing air. So, with the time measurement of 2 minutes off and 15 seconds on, we will have 6 humidity checks over 15 minutes. We can divide the amount of water to be injected into the room by 6 to cover that time span. Also, we have to factor in that we will not be running the Atomizing Nozzle for the continuous hour. We will have to adjust the amount for only running for 15 seconds. So, the intermittent factor will be 0.0042 (the 15 seconds portion of the hour).
In taking into consideration the flow rate required during operation time, we can calculate the amount of flow required for the Atomizing Nozzle as in Equation 2.
Imperial UnitsSI Units
Flow rate: Q = H / (D * T * f) Flow rate: Q = H / (D * T * f)
Mass Flow Rate: H = 29.1 lbs/hr Mass Flow Rate: H = 13.3 Kg/hr
Density of Water: D = 8.34 lbs/gal Density of Water: D = 1 Kg/L
Span division of time: T = 6 Span division of time: T=6
Intermittent Factor: f = 0.0042 Intermittent Factor: f = 0.0042
In the catalog, the model EB2030SS will flow 14.0 GPH (53.0 LPH) at 40 PSIG (2.8 Bar) water pressure. This would be in the compressed air pressure range of 50 PSIG (3.4 Bar) to 95 PSIG (6.5 Bar). If we divide these out, it will tell us how many atomizing nozzles that is needed to humidify the room.
Imperial: 138.5 GPH/14.0 GPH = 9.9 or 10 Atomizing Nozzles.
SI units: 527.8 LPH/53.0 LPH = 9.9 or 10 Atomizing Nozzles.
The last thing to determine is the amount of time that would be required to maintain the 80% RH when the controller calls for more humidification. At 75% RH, we can use Equation 1 to determine the amount required to reach 80%. As we plug in the initial Water Content, Wi, at 75% RH as 80.5 Grains/lb of dry air (11.5 Grams/Kg of dry air), we will get an H value of 3.42 lb/hr (1.55 Kg/hr). With each Atomizing Nozzle putting out 14.0 GPH (53.0 LPH) of water, we can determine the time to atomize the 3.42 lbs (1.53 Kg) of water during the operational time. The control will be much better as the air is changing with the new incoming air and the existing air. Thus, we have in Equation 3:
Imperial UnitsSI Units
Time (sec): T = 3600 * m/ (N * Qa * D) Time (sec): T = 3600 * m/ (N * Qa * D)
Mass of water: m = 3.42 lb Mass of water: m= 1.53 Kg
Density of Water: D = 8.34 lb/gal Density of Water: D = 1 Kg/L
T = 3600 * 3.42 lb / (10 * 14 GPH * 8.34 lb/gal) T = 3600 * 1.55 Kg / (10 * 53 LPH * 1 Kg/L)
T = 10.5 seconds T = 10.5 seconds
With some other humidification devices like steam generators, companies have to capitalize the system. With the Atomizing Nozzles, my customer was able to keep the cost down and control the RH at a high level for his manufacturing process. In turn, he was able to increase productivity and reduce downtime. If you need to increase the level of moisture in an area, you can always contact one of the Application Engineers at EXAIR for help.
As EXAIR Atomizing Nozzles become more popular with our customers, we are getting a lot of interesting questions that folks have regarding the nozzles themselves and the information that we provide so the customer can make an informed decision.
One set of questions has to do with the flow rate information presented in our technical data for the Atomizing Nozzles. The question is, “What is the fluid that is being used to derive your flow data given in the charts?” That answer would be plain old water (H2O). The next question that comes is, “What if my fluid has a higher viscosity? How do I figure out the flow rate that will apply to that?”
The answer is that you will not know until you actually perform a test with your specific material. However, if you apply some simple logic to the question, a higher viscosity fluid is going to flow less than water through an Atomizing Nozzle. So, to compensate, you can select an Atomizing Nozzle size which has a higher water flow rate in order to compensate for a thicker fluid. A chart for viscosity of common fluids can be accessed here.
You do have options in terms of which style of Atomizing Nozzle you choose for the application. For example, fluids that have viscosity up to 200 centipoise can work well with either a siphon type or an internal mix type Atomizing Nozzle (an internal mix type can work with viscosity up to 300 centipoise). The siphon nozzle option is for applications where the fluid is not pressurized but is available from a nearby container (this can also be set up to be gravity fed type depending on the height of the fluid in relation to the nozzle). The internal mix nozzle is used when the applied liquid can be pressurized by a pump or perhaps by a pressure pot.
For applications where the fluid is over 300 centipoise, an external mix Atomizing Nozzle is the suggested product to use. Because the air and the pressurized fluid mix out in front of the nozzle, the liquid is not subject to the back pressure present upon it in an internal mix nozzle configuration. Therefore, the liquid pressure and air pressure are completely independent. This means a much higher pressure can be used on the high viscosity fluid to push it through the nozzle and be atomized.
The variety of nozzles available with different configurations, flow rates, spray patterns and abilities can be a little difficult to navigate without some help. That is expressly why we are here. To help customers determine what they need in this range of product.
If you have been considering an Atomizing Nozzle for an application, please let us know if you have any questions or just want to talk things over to make sure you are headed in the right direction. We are here to help make the decision an easy one.