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
Twitter: @EXAIR_jb

Photo: Forest by janeb13Pixabay License

Air Atomizing Nozzles for Blue Jean Manufacturing

Acid washed Jeans

I wrote an earlier blog on how a blue jean manufacturer used EXAIR Air Operated Conveyors to help transport pumice stones into washers for stonewashed jeans.  You can find it here, “The EXAIR Air Operated Conveyors with stonewashed jeans.”  This same company contacted EXAIR again for another application.  With great customer service and thousands of products in stock, this customer stated it was an easy decision to come back to us.  This time it was for a spraying application.  I was happy to help them again.

Beside stone-washing, there are other ways to give that “worn out” look to blue jeans.  In this operation, they would scuff areas on the denim material with sandpaper.  To brighten that area, they would manually spray Potassium Permanganate over the jeans.  This reaction would fade the blue in the scuffed areas during the washing cycle.  They wanted to automate this process and move away from the manual operation (reference photo above).  So, I recommended our Air Atomizing Nozzles.

No Drip Atomizing Family

To tell you about EXAIR Air Atomizing Nozzles, they use compressed air to shear liquid into very fine particles.  The smaller the particles, the more surface area is produced.  Thus, less liquid material is required which will save money on the expense of the liquid.  EXAIR offers three different body sizes in NPT or BSP conversions; 1/8”, 1/4”, and 1/2”.  They are made from stainless steel for corrosion resistance.  We have an Internal Mix and an External Mix for use with pressurized liquid, and a Siphon Fed for open containers.

With each body style, we have a variety of liquid caps for different flow amounts, and an assortment of air caps to direct the fine mist.  For the Atomizing Nozzles, EXAIR can offer a No-Drip option and brackets.  The No-Drip option will stop liquid flow when the compressed air is turned off which will not allow the liquid to drip from the nozzle.  The brackets fit snugly around the body to support the Atomizing Nozzles for precise spraying.

For this application, I recommended the model AW9010SS.  This is a 1/8” NPT No-Drip Internal mix Atomizing Nozzle with a wide-angle round pattern.  The liquid flow rate fit their application with a maximum of 3.5 GPH (13.2 LPH).  The wide spray angle was able to cover the patterns on the denim material.  The potassium permanganate was delivered to the Atomizing Nozzle with a liquid pump, and with the No-Drip Option, they could start and stop spraying accurately and quickly with a simple compressed air solenoid valve.  Also, the model AW9010SS is a durable lightweight nozzle; and with the model 901786 bracket, the Atomizing Nozzles were easily mounted to the end of a robot arm for automation.

The EXAIR Atomizing Nozzles were able to replace the manual operation.  The amount of liquid material that this denim manufacturer was able to save was near 20%.  Depending on the expense of the fluid that you use, this can be quite a savings.  Also, they found that the “worn” areas were more consistent with accurate spraying and an even amount of potassium permanganate.

And as an added note with the safety issues in spraying potassium permanganate, the Atomizing Nozzles were a more effective way to reduce the hazard as a substitution control.  The operator with personal protective equipment, or PPE, is the least effective way for controlling occupational hazards.  The automated system with EXAIR Atomizing Nozzles was able to remove the operator from the hazard.

If you have a liquid that you would like to spray evenly, efficiently, and effectively; EXAIR Atomizing Nozzles can do that for you.  As with the customer above with the Air Operated Conveyors or Atomizing Nozzles, the quality of the products and the great customer service was what caused this customer to use EXAIR.  If you would like to experience the EXAIR way, you can contact an Application Engineer.  We will be happy to help you.

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

 

Photo: Stonewash Jeans by realworkhardPixabay License.

EXAIR Atomizing Spray Nozzles for Coating, Cleaning, Cooling

A recent customer in the automation / tool making industry had a need to spray a mold release agent onto some specialized tooling. Originally, the customer had planned to use some sort of pressurized sprayer. After some initial tests to prove the concept, the customer found that the moving mechanical parts of the sprayer became fouled by the release agent. And cleaning the internal parts was not easy to do.

No Drip Atomizing Nozzle
No Drip Atomizing Nozzle

In their search for a more permanent solution, the customer came across EXAIR Atomizing Nozzles. After going through some application type questions to narrow the focus down to one model, we determined that the customer would be best served by model AF1010SS (Internal Mix, Flat Fan Pattern Atomizing Nozzle). The customer had a couple of questions about the nozzle in order test the product.

  1. Is it possible to disassemble the nozzle and clean it completely? The answer is yes, the Atomizing Nozzles can be completely disassembled to allow for cleaning, maintenance or replacement of worn parts.
  2. Are the nozzles solvent resistant? The answer is also yes; the Atomizing Nozzles are made of AISI303 type stainless steel and can be cleaned with any normal solvent based cleaner.

Earlier in this article, I mentioned that we went through some application type questions. Here is a list of general questions that we normally ask a customer about their application in order to determine which in our selection would be best suited.

  1. What is the volume of liquid flow (G/Hr) needed for the application?
  2. What is the viscosity (cP) of the liquid being applied?
  3. What are the required spray pattern, size and shape required?
  4. Is the liquid under pressure (by pump or pressure pot)? If so, what is the liquid pressure?
    1. Side note: we have options for non-pressurized liquid by using our siphon fed nozzles.

If you have an application where you have a liquid that needs to be applied in atomized form to a target, or perhaps a humidification application, please give EXAIR Atomizing Nozzles your consideration.

Jordan Shouse
Application Engineer

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Twitter: @EXAIR_JS

EXAIR Siphon Fed Air Atomizing Nozzles: Overview

In today’s market, the cost of consumable products are on the rise; especially with paints, oils, and yes, even the cost of water.  You can help alleviate some of that cost by being more effective when spraying these liquids.

The EXAIR Atomizing Nozzles can accomplish this by using compressed air to shear the liquid into small micron-sized droplets.  By reducing the diameter of a particle by half, this will multiply the number of droplets by eight.  This will increase the surface area and coverage of the droplets; thus, requiring less material in your application.  EXAIR manufactures three families of Atomizing Nozzles; Internal Mix, External Mix, and the Siphon Fed.  In this blog, I will cover the Siphon Fed Atomizing Nozzles that EXAIR manufactures.

When no liquid pressure is available, the Siphon Fed Atomizing Nozzles will create a vacuum to draw the liquid into the nozzle.  This action is done by the unique design of the air cap.  As the velocity of the air passes through the air cap, a low pressure is created by a venturi.  The Siphon Fed Atomizing Nozzles can draw liquid from a suction height of 36” (91 cm), or it can be gravity fed from 18” (46 cm) away.  They are manufactured from stainless steel for durability and corrosion resistance.  The Siphon Fed models can spray viscous fluids up to 200 centipoise, and are used in many applications like washing, coating, cooling, quenching, and dust control.

EXAIR carries three different body sizes in 1/8” NPT, ¼” NPT, and ½” NPT ports; so, you can create a light mist or a monsoon.  The maximum liquid flow rate through each body size is controlled by the air cap and liquid cap.  A unique feature of the EXAIR Atomizing Nozzle is that the caps are easily interchangeable for each body size to modify the spray patterns, control the amount of fluid, and reduce any downtime if cleaning is required.  Here is a video that shows how this can be done:

The amount of liquid to be applied is easily adjusted by the siphon height, the inlet pressure, and the liquid adjusting stem.  So, you can dial in the exact amount of fluid required for your process to eliminate any excess waste. They are very compact and easy to install.  We carry mounting brackets for each size to allow for easy mounting and positioning.   Versatility is very important in saving, applying, and spraying costly fluids; and, the Siphon Fed Atomizing Nozzle has it.

Siphon Fed No Drip Option

To help reduce waste even more, EXAIR has a No Drip option.  This patented design is used to keep the expensive liquid from dripping out of the Atomizing Nozzles.  When the compressed air is turned off, a valve inside the body will create a seal on the liquid side.  For delicate applications, the No Drip options will eliminate unwanted drips that can ruin the finish of your product.  This option also enhances the function of the Siphon Fed Atomizing Nozzle for intermittent processes.  It will keep the liquid inside the body of the nozzle; so, when air pressure is applied, the Atomizing Nozzle will give an instant spray.

The minimum air pressure required to open the No Drip valve is 30 PSIG (2.1 bar) for the ¼” NPT and the ½” NPT port sizes, and 20 PSIG (1.4 bar) for the 1/8” port size.  Unlike some manufacturers, there is no need to run a separate compressed air line to operate the no drip function.  The Siphon Fed Atomizing Nozzle with the No Drip option is compact, efficient, and precise without any drips.

If you need to maximize the liquid dispersion and minimize liquid consumption, the EXAIR Atomizing Nozzles are the products to use.  Instead of researching the requirements for liquid pumps or pressure pots, the Siphon Fed Atomizing Nozzle can draw the liquid through the feed line and start spraying.  It can help reduce the cost of your project as well as save you money on your consumable products.  If you have an application involving liquid spraying, an Application Engineer at EXAIR can help determine the correct model for you.

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