Humidification Calculations Related To Atomizing Spray Nozzles

I had an application where a customer needed to have a room at 75% relative humidity (RH).  They produced a nylon backing for carpet, and they needed the high RH to reduce the “stickiness” in the gluing process.  Currently they were at 40% RH in a room that was measured at 40ft long by 20ft wide by 20ft high (12.2m long X 6.1m wide X 6.1m high).  They wondered if our Atomizing Nozzles could help him to increase the relative humidity in the room.  I decided to put on my engineering hat to calculate the amount of water that he would need to increase the humidity.

Relative humidity (RH) is the percentage of water vapor as compared to the saturation level at the same temperature.  So, at 100% RH, the ambient air is saturated and cannot hold any more water vapor. You can feel the difference in the Amazon versus Arizona at the same temperature.  With dryer conditions, water can be added to increase the relative humidity; like a humidifier.  With the EXAIR Atomizing Nozzles, we can break liquid water into very small droplets to help increase the humidification rate.  For the customer above, I will have to determine what size and how many Atomizing Nozzles are required.

Equation 1

H = V * ACH * (Wf – Wi) / (v * 7000)

Where:

H – mass flow rate of water, Lbs/hr

V – Volume of room, ft3

ACH – Air changes per hour

Wf – Final Water Content, Grains/lb of dry air

Wi – Initial Water Content, Grains/lb of dry air

v – Specific Volume of Air, ft3/lb

Conversion Constant – 7000 Grains/lb

The customer stated that the room was set to 68oF (20oC), and they used an air handling unit (AHU) that produced 1,600 cfm (44.5 M3/min) of air into the room.  From these factors, we can determine some of the variables above.  For the Air Changes per Hour (ACH), we can use Equation 2.

Equation 2

ACH = 60 * Q / V

Where:

ACH – Air changes per hour

Q – Volumetric flow rate, CFM

V – Volume of room, ft3

The volume of the room is V = 40ft X 20ft X 20ft = 16,000 ft3.  The volumetric flow rate by the AHU is 1,600 ft3/min.  From Equation 2,

ACH = 60 * (1600 ft3/min) / 16,000 ft3

ACH = 6/hr.

In determining the water content values, you can find a chart online to determine the amount of water vapor that is contained in the air at a specific temperature and RH.  At 68oF (20oC), I was able to find the following information:

Wi = 40.58 Grains/lb of dry air at 40% RH

Wf = 76.71 Grains/lb of dry air at 75% RH

v = 14.286 ft3/lb @ 68 deg. F, 1 atm

V = 16,000 ft3

If we plug in the numbers that we have into Equation 1, we can determine how much water that we will need to spray into the air to increase the RH from 40% to 75%.

H = V * ACH * (Wf – Wi) / (v * 7000)

H = 16,000 ft^3 * 6/hr * (76.71 – 40.58 Grains/lb) / (14.286 ft^3/lb * 7000 Grains/lb)

H = 34.68 lb/hr

With my prior line of work in room humidification, we know that there is a lead/lag time between measuring and humidifying.  This may seem complicated, but it is important to get a steady state condition for the Relative Humidity.  To help this customer, I recommend a cycle time of 15 second to turn on and wait 105 seconds to re-measure the RH.  This will help to not over-saturate the room.  As for the location of the Atomizing Nozzles, we want to be near the ceiling to get the most “air” time to vaporize.  We also have to be careful to not allow the water spray to hit any objects or each other as this will cause the water to condense.

To start, I suggested our model AT2010SS No Drip Internal Mix 360o Hollow Circular Pattern.  This type of nozzle helps to extend the settling time of the water droplets; the amount of time that the droplets are suspended in the air.  The orientation of the spray is outward in all direction to increase coverage.  With the No Drip option, it is controlled by the air pressure to open and close the liquid side for spraying.  When the compressed air is turned off, a valve will seal the liquid side to not allow any drips.  It also helps to eliminate the need for any liquid valves next to the Atomizing Nozzles.  When it comes to cycle spraying, the No Drip option works wonderful.

In taking into consideration the flow rate required during operation time, we can calculate the amount of liquid flow required for the Atomizing Nozzle in Equation 3.

Equation 3:

Flow rate: Q = H / (D * T * f)

Where:

Q – Liquid flow rate (gal/hr or GPH)

H – Mass Flow Rate (lbs/hr)

D – Density of Water (8.34 lbs/gal)

T – Span division (no scale)

f – Intermittent Factor (no scale)

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 ACH = 6/hour, the air in the room will change over every 10 minutes.  We want to have a balance between the new air and the existing air.  So, with the time measurement of 15 seconds on and 105 seconds off (2 minutes), we will have 5 humidity checks over the 10 minutes.  We can divide the amount of water to be injected into the room by the span division, T, to cover the time span for check and atomization.  Thus, T = 5.  We will also have to adjust the amount for only running 15 second intervals.  So, the intermittent factor, f, will be 0.0042 (the 15 seconds portion of the hour).

With these values, we get:

Q = (34.68 lbs/hr) / (8.34 lbs/gal * 5 * 0.0042)

Q = 198 gal/hr (GPH)

In the catalog, the model AT2010SS will flow 14.7 GPH (55.7 LPH) of water at 60 PSIG (4.1 Bar) liquid pressure.  If we divide these out, it will tell us how many atomizing nozzles that is needed to humidify the room.

Number of Nozzles: 198 GPH/14.7 GPH = 13.5 or 14 Atomizing Nozzles.

With the above Atomizing Nozzles, the company was able to 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 humidity in your area, you can contact an Application Engineer at EXAIR for help.  We can make it feel like the Amazon.

John Ball
Application Engineer
Email: johnball@exair.com

Big Nozzle, Big Award…Again!

The year was 2016, and it was quite a time for sports fans:

• Team USA dominated at the Summer Olympics in Rio de Janeiro. Swimmer Michael Phelps won five Gold Medals, and gymnast Simone Biles won a Gold Medal on her own, and another for the team event, contributing to the 46 total Gold Medals won by United States Olympians.
• The Chicago Cubs and Cleveland Indians took the World Series to all seven games…and extra innings in Game Seven. That makes it hard to disparage either team, but the Cubs prevailed, winning the Fall Classic for the first time in 108 years.
• World Series heartbreak notwithstanding, Cleveland sports fans were pretty happy a few months earlier when the Cavaliers cinched the NBA Championship in seven games, defeating the heavily favored Golden State Warriors…who beat the Cavs in both of their regular season games that year.

Another big winner (non-sports) that year was EXAIR Corporation’s Model EF5010SS External Mix Narrow Angle Flat Fan Pattern 1/2 NPT Atomizing Spray Nozzle…it won Plant Engineering’s Product of the Year Bronze Medal Award in the Fluid Handling category. Yes, there’s a Compressed Air category, and our products have won a TON of those too…as well as some other categories:

• Material Handling (Line Vacs)
• Maintenance Products (Super Air Nozzles)
• Environmental Health (High Lift Reversible Drum Vac)
• Automation & Controls (EFC Electronic Flow Control)

Anyway, now it’s 2021, and the No-Drip version of that Atomizing Spray Nozzle – Model EF6010SS – has won Plant Engineering’s GOLD Medal Award in the Fluid Handling category. Model EF6010SS offers the same performance as the EF5010SS:

• Liquid flow rates from 141 to 303 gallons per hour (tested with water)
• Flat fan spray dimensions from 15″ wide (6″ from target) to 25″ wide (15″ from target)
• Atomized spray at a distance of up to 35 feet away

And, of course, the No-Drip feature means you can instantly stop liquid flow by shutting off the compressed air supply, up to 180 cycles a minute, if needed. This is a great feature to have to cut down on the cost – and the MESS – associated with overspraying.

Our comprehensive line of Atomizing Spray Nozzles has options for most any liquid that can be sprayed, with a wide range of flow rates and pattern size/shapes. The 1/2 NPT External Mix Narrow Angle Flat Fan model is ideally suited for liquids with higher viscosities where a higher flow rate/thicker coating is needed, as opposed to a humidification or misting application, where a smaller Atomizing Spray Nozzle might be specified. Some current, successfully reported, applications include:

• Snack food provider – applying flavoring to bulk snack materials.
• Commercial bakery – spraying cooking oil onto pans used in a conveyor oven.
• Sporting goods manufacturer – applying adhesive to the tops of skateboard decks to glue the grip tape on.

If you’d like to discuss a particular liquid spraying application, I’d love to help…give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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FullStream Liquid Atomizing Nozzles

At EXAIR, we know compressed air, and we’ve been helping customers around the world get the most out of their compressed air systems since 1983. It was only logical that, about ten years ago, we got into using compressed air for liquid atomization.  If you’re looking to spray a liquid in a fine mist with a controllable pattern & flow rate, there are many advantages to using compressed air to atomize it:

• Maximum dispersion
• Optimal, efficient consumption
• Small droplet size

Since their introduction, EXAIR has come to offer 142 distinct models of Air Atomizing Spray Nozzles, and, along the way, we leveraged our engineering, machining, and manufacturing prowess to gain position as an industry leader in liquid spraying.  So much so, that, earlier this year, we introduced a spraying product line that doesn’t require compressed air:  the FullStream Cone Liquid Atomizing Nozzles.  Instead of using the energy of compressed air to effect atomization, these use the energy of the liquid’s pressure and flow to change the continuous stream of liquid flow entering the nozzle into a conical spray as it exits to atmospheric pressure.  Here’s how it works:

While Air Atomizing Spray Nozzles maintain their advantage of a smaller droplet size (ours consistently make droplets under 100 microns in size,) there are clear benefits in certain applications to the FullStream Cone Liquid Atomizing Nozzles:

• Higher liquid flow rates
• Increased liquid coverage
• More compact design

These are all important in applications like quenching, cooling, foam breaking, lubricating, degreasing, and sanitizing.  All stainless steel construction means they’ll stand up to a variety of chemicals…both in what’s being sprayed, and in the environment in which they’re installed.

If you have a liquid that needs sprayed, EXAIR has an engineered solution.  Call an EXAIR Application Engineer today to find out more.

Russ Bowman
Application Engineer
EXAIR Corporation
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How to Pick the Right Atomizing Spray Nozzle

Atomizing spray nozzles atomize fluids with compressed air to create a fine spray in a variety of patterns for a variety of uses. They are commonly used to mark products, paint or coat, cool, reduce dust, lubricate and clean parts.

With the numerous types of Atomizing Nozzles, it can be challenging to sift through all the information. But with a few basic questions you can narrow down the right nozzle type for you and your application:

Are you using a pressurized liquid feed? In some cases, a pressurized liquid source is not available for the nozzle, so you would have to rely on a gravity or siphon fed nozzle. While you lose the complexity of having a liquid pump pressurizing your liquid, you do have a few draw backs. Your siphon height is typically with in 36” so your liquid source has to be fairly close to your nozzle. Siphon fed nozzles are hard to turn off and on, they are best used for applications where you are continuously spraying a low viscosity liquid with a low gph.

What is the viscosity of the fluid? Another deciding factor is the viscosity of the liquid you are spraying. Different nozzles are designed for different viscosity. For example, two of the main nozzle types are internal mix nozzles and external mix nozzles. They function just like they sound, internal mix nozzles mix the compressed air and liquid source inside the nozzle. And because of this they typically can not spray liquids over 300 cP. And because external mix nozzles mix the liquid and air outside the nozzle, they can handle liquids well above 300 cP.

What is the liquid flow rate in gallons per hour(gph)? Another factor in choosing the right nozzle is if your application has a set gph you are looking to achieve. Some nozzles are designed to flow more liquid then others. For example, the external mix nozzles inherently flow more liquid then the internal mix. As there is less restriction on the liquid flow. If you are looking for even higher gph you can source a liquid only atomizing nozzle, its going to give you a large bump in gph. But your droplet size will suffer with the liquid only nozzles.

What droplet size are you looking for? Fine droplet sizes are one of the primary reasons atomizing nozzles are used. Benefits of small droplet sizes include even coating and liquid conservation. Internal mix nozzles will do the best at providing the smallest droplet size possible. While external mix and liquid only will give you larger droplet sizes but they will give you a larger gph some applications need.

Should I use a No-Drip option?  The No-Drip option positively shuts off liquid flow when the    compressed air supply is shut off.  One benefit of this is appreciated in coating applications, where an errant droplet of liquid would mar an otherwise smooth, even coating.  Operationally, though, it also means you can precisely turn the liquid flow on & off, in short, quick bursts, up to 180 times a second.

If you are in the need for a Liquid Nozzle to assist in your facility, please reach out! We have a team of application engineers waiting from 8AM – 5PM EST to help you size and fit a product to your specific application!

Jordan Shouse
Application Engineer

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