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

5 Important Factors When Selecting an Atomizing Spray Nozzle

The most recent EXAIR Webinar is up and ready to be viewed as an on demand video. This presentation showcases five important factors when selecting an atomizing spray nozzle. Throughout the webinar you will gain several key takeaways that are outside of the five factors as well. If you have a liquid spray application and are not sure where to start, this video has a wealth of information for you. As always, the Application Engineer department is also here and ready to assist as needed. We can walk through any application with you and help right over the phone, through email, or even live chat.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

NEW 1/4″ HollowStream™ Cone Liquid Atomizing Nozzle – IN STOCK And Ready To Ship!

Lately, around the globe, we are all getting a little too used to hearing this from vendors. “Okay, so I have your order for one piece, and that is going to be on hold for 8 weeks until we can get parts in.” At EXAIR, we are able to state our products are in stock and ready to ship same-day on orders received by 2 PM ET that are shipping within the US or Canada. There is no exception when it comes to our brand new 1/4″ NPT HollowStream™ Cone Liquid Atomizing Nozzle.

1/4″ NPT HollowStream Liquid Atomizing Nozzle

Since introducing our first liquid only nozzles (no air required) we have been working to add these hollow cone pattern nozzles add to our liquid spray nozzles (complimenting our full cone spray nozzles). There are six flowrate capacities with a 1/4″ NPT inlet. These capacities will range from .06 GPM (.23 LPM) up to 2.5 GPM (9.45 LPM) flow rates. The HollowStream provides a ring of liquid upon your target that can be used for cooling, cleaning, rinsing, or suppression of dust. By only using the outer ring to cover a similar space as a full cone spray the amount of liquid is reduced. This is all done by a pressurized liquid supply.

Spray Dimensions and Pattern

The small footprint of the nozzle matched with the spray volume and pattern is ideal for tight-fitting areas or areas where manifolds of multiple nozzles are required. The maximum through passage is also large enough to permit some slurries and particulate to pass through when recycling the rinse or wash water is needed.

If you would like to discuss your spray application and determine if the 1/4″ NPT HollowStream Cone Nozzle is right for you, contact us. We look forward to helping you determine the correct product that will make the most efficient use of your resources.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Liquid Spray Nozzles Improve Gummy Candy Production

One of the more popular treats for kids and adults are gummies.  They can be sweet, sour, and in different shapes and colors.  A candy company that makes gummy bears was looking for a better way to spray food-grade oil onto their product.  They contacted EXAIR about our Air Atomizing Spray Nozzles. 

We discussed their setup and process for making the gummy candies; or in this case gummy bears.  The sugary mixture is poured into molds that are coated with corn starch.  The corn starch helps to keep the gummy from sticking to the mold.  Once hardened, the bears will be released from the molds and travel through a stainless-steel spinning drum.  In here, they apply a light food-grade oil onto the bears.  This process will hide the starch and give the candy that glazed and colored feature.  The drum was near 60” (1.52 meters) long and spun at 19 RPM.  The gummy bears would tumble along the length of the drum at a designed production rate of 2000 Kg/hr. (4,400 Lbs./hr.).  They used drip tubes along the top to apply the food-grade oil onto the gummy bears.  They noticed that the color was not as good and the coverage was spotty.  The oil pump was metered in a range of 0.35 – 3 gal/hr. (1.32 – 11.3 l/h).  The temperature inside the drum could reach up to 150oF (65oC), and the viscosity of the food-grade oil ranged between 190 – 400 cps.  In order to get the best results for quality, they had to reduce their production rates to about 1,700 to 1,800 Kg/hr. 

To determine the correct solution, we had to dive a bit more into their application.  The details of the EXAIR Atomizing Nozzles are measured with water as the liquid.  Since they are using an oil at different temperatures, the specific gravity will change slightly.  For their oil, the specific gravity is 0.92 at 20oC and 0.89 at 65oC.  We can use Equation 1 to convert the required flow rate from the food-grade oil to water.

Equation 1:

Q1 = Q2 * SQRT (SG2 / SG1)

Q1 – Flow of water (gph)

Q2 – Flow of oil (gph)

SG1 – Specific Gravity of water

SG2 – Specific Gravity of oil

The Specific Gravity of water is 1.  With the range of specific gravity for the oil, we can calculate the range that is needed as indicated by water.  Then we can make a selection as referenced by our data in the catalog.  Since we want to make sure that we can cover the range of the metered oil pump, we will use the maximum flow rate of 3 gph.  In adding the values, we get the following:

@20oC  Q1 = 3 gph * sqrt(0.92) = 2.88 gph

@65oC  Q1 = 3 gph * sqrt(0.89) = 2.83 gph  

Since the viscosity ranges above 300 cps., I recommended the External Mix Atomizing Nozzles to be mounted along the length of the rotating drum.  The External Mix can handle viscous liquids up to 800 cps.  Unlike the drip method, the EXAIR Liquid Atomizing Spray Nozzles use compressed air to shear the oil into small droplets and to disperse the oil in a wide pattern.  With the smaller particle size, we can get more coverage area which will allow them to use less food-grade oil.  The coverage area on the gummy bears was near 15” (38cm) as they rolled down the drum.  I also recommended the No-Drip option to allow for versatility in their process.  The No-Drip option for the Atomizing Nozzles is a very nice option which will stop the liquid solution from dripping when not in use.  When they needed to apply the oil, they would just turn on the compressed air to the Atomizing Nozzle.  It made it very easy to control.  This was important to reduce excess usage and non-conforming parts. It also keeps the inside of the drum oil free during cleaning cycles.   

EB2010SS

From the data above, I recommended three pieces of the model EB2010SS, No Drip External Mix Wide Angle Flat Fan Pattern.  The spray pattern was 14” (35.6cm) wide to cover part of the 60” (1.52m) length of the drum.  With an estimated 1 gph for each nozzle, we would be able to spray the maximum requirement as calculated above (2.88 gph).  After installation, they were able to get a consistent deep color of the gummy bear at the maximum production rate of 2,000 Kg/hr.  They also noticed that with the fine particle spray, they were able to use less oil.  With the three pieces of the model EB2010SS, they were able to reach maximum production rates with less food-grade oil and reduce scrap rates.

If you have a liquid that you would like to spray evenly, efficiently, and effectively; EXAIR Atomizing Nozzles can do that for you.  You can contact an Application Engineer for help.  For the customer above, they were able to create those gummy treats for kids and adults.  Yummy.

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

Picture: Giant Gummy Bear by Alexas_FotosPixabay licence.