## 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

## Another Spray Nozzle, Another Award

EXAIR Corporation’s Research & Development team often finds themselves at odds with our Marketing department, who thinks R&D, through their constant introduction of new ideas & products, is trying to turn our catalog into something resembling a phone book.

I do not believe that is their aim or intention, though (and to be fair, Marketing doesn’t either.)  Honestly, we just want to help folks in a wide range of industries solve problems.  And a diverse range of engineered compressed air products is our tried-and-true, successful method for doing so.

Over the past few years, EXAIR has worked hard on expanding our line of Atomizing Spray Nozzles with different sizes, flow rates, and spray patterns to meet most any need for a fine, controllable liquid spray.  Most recently, our efforts were rewarded when our Model AT5010SS 1/2 NPT 360° Hollow Circular Pattern Atomizing Spray Nozzle earned recognition by Plant Engineering as a 2018 Product of the Year, in the Fluid Handling category.

If you need to spray liquid over a large area, this is the spray nozzle you’re looking for.  It can cover a 13 foot diameter with up to 150 gallons per hour.

EXAIR Corporation offers a wide variety of Liquid Atomizing Nozzles, enough to fill a phonebook where we’re certain to have one that fits your spraying needs.  To find out more, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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## EXAIR External Mix Atomizing Nozzles – For Use with Viscous Fluids and High Flow Rates

EXAIR’s Atomizing Spray Nozzles are used to atomize fluids in a wide range of different spray patterns. They utilize a small amount of compressed air which mixes with the liquid supply to create a fine mist of atomized liquid. EXAIR manufactures Atomizing Spray Nozzles in (3) different varieties: Internal Mix, External Mix, and Siphon Fed. For this blog, I’m going to focus on just the External Mix variety.

On all External Mix Atomizing Nozzles the volume of liquid is easily adjusted by adjusting the valve stem on the standard Atomizing Nozzle, or by regulating the liquid pressure (the only option with the No-Drip style). Increasing the liquid pressure will result in an increased liquid flow rate.

The External Mix nozzles have the highest flow rates and can be used with liquids with a viscosity greater than 300 centipoise (cP). Since the air and liquid are mixing just outside of the nozzle, thicker liquids have a lesser chance of clogging in the nozzle. Both the liquid stream and the air stream will come into contact with each other just outside both the air and liquid caps. The compressed air breaks the liquid up into very small particles, allowing you to use much less liquid than a liquid only nozzle.

This makes them very effective in applications that utilize expensive paints, oils, or other liquids. Rather than wasting the expensive materials, the nozzle can be set to precisely dispense only what is necessary to achieve a successful application. The External Mix Atomizing Nozzle is available in the standard configuration as well as the No-Drip style.

The No-Drip Atomizing Nozzle is used in a variety of applications where any liquid dripping from the nozzle after the air supply has shut off would cause a problem. This is common in painting applications where any paint dripping would affect the quality.

The External Mix Atomizing Nozzle is available in (3) different sizes: 1/8” NPT, ¼” NPT, and ½” NPT. If your application could benefit from utilizing the fine atomized spray of liquid look no further than EXAIR’s Atomizing Nozzles. With all sizes and configurations available from stock, we can get one out to you quickly!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com

## EXAIR’s Huge Variety of Air Nozzles is Like an Equalizer for your Application

Many of us are familiar with what an equalizer (EQ) looks like and what it does. Unfortunately, sometimes they get a bad rap from so-called audiophiles, which in my opinion are defined individuals who spent so much money on their equipment they can’t afford to buy any music to play!  Typically, they insist that tone controls must be set to flat because the sound recording engineers mastering the music have already equalized the recording to perfection and if you need to attenuate or cut certain frequencies it is an indicator of poor-quality equipment, and that is simply is not true!

Let’s consider some of the reasons why an equalizer makes sense and, in my opinion, an absolute necessity. The objects and materials in the room will change the sound reproduction characteristics of any speaker system.  If you have large floor standing speakers positioned in the corners of the room, sitting directly on wood floors the speakers are now “acoustically coupled” with the floor and the walls.   On the other hand, if you move the speakers away from the wall and/or place them on spikes or stands (isolating them for the floor) you would have “acoustically de-coupled” the speakers from the walls and floor, which will reduce the bass or low-frequency loudness. This all affects the perceived loudness and/or quality of the music we want to listen too.

This is where the graphic equalizer shines, no need to move the speakers around or use speaker stands or spikes.  An equalizer will allow you to increase or decrease the loudness of multiple frequencies.  You can completely customize your sound to suit your tastes, overcome issues with your listening room acoustics, the speakers you are listening with or even anomalies with the music recording.

Like adjusting an equalizer to suit your room acoustics, speaker size and/or speaker frequency response, EXAIR understands that the need for many different options gives you the necessary adjustments for a successful application.  A few sizes of Air Nozzle, Air Jet or High Force Air Nozzles will not solve every application with the highest efficiency or effectiveness.  EXAIR’s air nozzle variety allows you to produce maximum effectiveness based upon the air pressure and air volume you have available.  Whether you need a strong blast or a gentle breeze, if you have tricky mounting positions or remote applications, EXAIR has the largest selection to choose from and solve your production problem.

We clearly state compressed air volume requirements in SCFM (Standard Cubic Feet per Minute) at a given operating pressure in PSI (Pounds per Square Inch), force at 12” from the compressed air outlet and the sound loudness in dBA at 3′ from the nozzle. These details provide the starting point for selecting the best air nozzle.

When you are looking for expert advice on safe, quiet, efficient, and engineered point of use compressed air products give us a call.   We would enjoy hearing from you!

Steve Harrison
Application Engineer
Send me an email
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