Air speed and cooling. Let's break down the confusion.

Written by: Nancy Vander Byl

Air speed and cooling. Let's break down the confusion.

Published Jul 13 





Here is a typical statement about air speed and cooling.


"Ideally, the air over the cow while lying down should be able to reach a wind speed of 2m/sec or more to keep cows cool and provide them with fresh air. Research shows a 1.1 THI reduction per 0.44 m/s wind speed. Fans capable of producing a wind speed of 2.2 -3.1 m/s may reduce the THI by 5.5 - 7.7 points, especially under high relative humidity conditions."


WHAT?!?!?


Professionals in the ventilation industry tend to make the discussion about air speed confusing with speeds in all different measurements.


A wise man once said, "If you confuse, you lose." 


Let's clear up the confusion and break down the statement.


“Ideally, the air over the cow while lying down should be able to reach a wind speed of 2m/sec or more to keep cows cool and provide them with fresh air.”


I’m going to break it down to both mph and km/h to give some commonality and context. Let’s start with this m/sec measurement. Google is great at converting. The formula is below the calculation if you would prefer to figure it out manually.


Air speed and cooling. Let's break down the confusion.


So now we know what 2m/s is. It’s either 4.47mph or 7.2km/h.


Let's look at the next part of that statement.


"Research shows a 1.1 THI reduction per 0.44 m/s wind speed."


Air speed and cooling. Let's break down the confusion.

Now we know that for every 1mph or 1.5 km/h, we can bring the THI in the barn down by 1.1 points. 


But what is THI?


THI or temperature-humidity index. 


Is a measure that accounts for the combined effects of environmental temperature and relative humidity on cattle/livestock to assess the risk of heat stress and prevent significant adverse effects.

· When THI is less than 67, the cows are comfortable (Green Zone)

· When THI exceeds 68, cows are likely to begin experiencing heat stress (Yellow Zone)

· When THI exceeds 72, cow's milk production is seriously affected. (Mustard Yellow Zone)

· When THI rises above 80, very significant losses in milk production are likely. (Pink Zone)

· When THI rises above, 90 cows show signs of severe stress and may ultimately die. (Purple Zone)


Here's a THI chart. I like this one because the temperature is in C° and F°, and it's very clearly color-coded. It also gives you valuable information about how heat stress can impact respiration rates and rectal temperatures.

Air speed and cooling. Let's break down the confusion.


We will take the temperature on the left and the % Humidity across the top, and we will slide our fingers along the row and column until they intersect. Let's work a couple out.


Example 1

· The temperature is 28°C/82°F
· The humidity is 70%
· The THI is 77

A THI of 77 is considered mild-moderate stress. Respiration rate and body temperature will increase, and cattle health and production will begin to suffer.


Let's do another.


Example 2

· The temperature is 32°C/90°F
· The humidity is 50%
· The THI is 81

A THI of 81 is considered moderate-severe, respiration rate exceeds 85 BPM (breaths/minute), and body temperature exceeds 104°F. Reproduction levels are significantly impacted at this level, as are production and overall cattle health.


Let’s look at the next part of that statement.


“Fans capable of producing a wind speed of 2.2 -3.1 m/s, may reduce the
THI by 5.5 - 7.7 points, especially under high relative humidity conditions.”
THI by 5.5 - 7.7 points, especially under high relative humidity conditions.”


Time to get google to help with more calculations.


Air speed and cooling. Let's break down the confusion.



According to the calculations…


2.2m/sec is 7.92km/h, can lower THI by 5.5 and 3.1m/s is11.16km/h can lower THI by 7.7

2.2m/sec is 4.921mph, which can lower THI by 5.5, and 3.1m/s is 6.934mph can lower THI by 7.7.



Let's go back and use the THIs we worked out earlier.


Example 1 –


Temperature is 28°C/82°F, humidity 70% = THI 77

THI 77, Airspeed 2.2m/s, reduction of 5.5 = THI 71.5 (The cow is still suffering mild to moderate heat stress)

THI 77, Airspeed 3.1m/s, reduction of 7.7 = THI 69.3 (The cow is still suffering mild heat stress)


Example 2 –


Temperature is 32°C/90°F, humidity 50% = THI 81

THI 81, Airspeed 2.2m/s, reduction of 5.5 = THI 75.5 (The cow is still suffering mild to moderate heat stress)

THI 81, Airspeed 3.1m/s, reduction of 7.7 = THI 73.3 (The cow is still suffering mild to moderate heat stress)


Hang on a second.


What if you don't have 7-11 km/h or 5-8 mph in the stall? What if you have 3.2 km/h or 2mph? How does that affect the calculation?



"Research shows a 1.1 THI reduction per 0.44 m/s wind speed."


Using this statement as the bases of our calculation, let's figure out how many THI points we can lower with an air speed of 2mph in every stall.


Air speed and cooling. Let's break down the confusion.


0.894 ÷ 0.44m/s = will result in a THI reduction of 2.03, let's say 2.


Taking that THI from Example 1 of 77 to 75 offers little to no relief. 


So you can have a barn full of fans, but if they aren’t producing a significant amount of airspeed, they offer little to no relief from the heat.



Now you are armed with the information you need to assess the conditions in your barn.

1. Grab a wind speed meter, (about $30 on Amazon)
2. Check the airspeed in several stalls around the barn and average them out for your air speed.
3. Take your average temperature data or your real-time data to calculate your THI

How many points can you lower your THI with the air speed in your stalls?

Are your cattle still heat-stressed?


These calculations highlight the importance of airspeed for cooling, but even more than that, it shows that evaporative cooling needs to be added to the equation for relief from severe heat stress.


That's why systems like Core Cool, which add water to the equation, can offer significantly more cooling than a system with airspeed alone.


Water is becoming an increasingly valuable resource on farms today. Cooling systems that use large amounts of water to cool cows can solve heat stress issues but often create other problems the producer or manager has to deal with. Wastewater fills manure pits, and pumping it out onto fields is costly and time-consuming. Then on sweltering days, a cow's water consumption can double. On the days the cows need water the most, the cooling system consumes massive amounts of water, putting stress and strain on your supply, and creating another management issue.


The Core Cool System provides the same amount of cooling as systems that use 40 to 70% more water. Research conducted at the University of Georgia by Dr. John Bernard proved this.


At UGA, Dr. John Bernard and his team compared the 2 systems, ours and the one they were already using that was a large droplet soaking the cow's skin system. 


Here are the results at a glance.

· There were no differences in body temperature (average 102.39 ◦ F),
· respiration rate (57.6 breaths/min), or
· Milk yield (77.8 lb/d) of the cows.
· Water use was much lower (5,624 L/d) for the early Core Cool System compared with the control system (9,008 L/d).
· The dry matter content of the sand was similar for both systems (93.7 and 94.5 for control and Core Cool systems, respectively).
· During the trial, the temperature ranged from 68 to 86 ◦ F, and relative humidity ranged from 55 to 98%


Click the link for the entire research document - 

Since the study Core Cool Systems has put many hours of research and development into making the system more effective and efficient.


· The EC motor provides incredible energy savings.
· Internal variable speed control for variable speed cooling without a VFD.
· The air shaper provides a focused, spiraling air flow
· The unique blade design, powerful motor and more combine to provide  5mph/8km/h at 80ft/24 meters.
· The intelligent water cooling uses less than ½ gallon/2liters per cow per hour.


Creating a system that considers and utilizes every element required to achieve cooling, maintain core body temperature and keep cows feeling comfortable and cool all year. Not just on the hottest days but during those spring and fall days when we can experience temperature variances of 10–20° over the day.


Remember, cows love consistency, and when we give it to them, they can get the most out of everything we offer them, maximizing productivity and performance and boosting your bottom line.



P.S. Here is that original statement in plain English


mph

Ideally, the air speed in the stall where the cow is laying down should be 4.5mph or greater to keep cows cool and provide them with fresh air. Research shows that THI can be reduced by 1.1 for every 1mph of airspeed. Fans capable of producing 5-7mph may reduce the THI by 5.5 – 7.7 points, especially under high relative humidity.


Km/h

Ideally, the air speed in the stall where the cow is laying down should be 7 km/h or greater to keep cows cool and provide them with fresh air. Research shows that THI can be reduced by 1.1 for every 1.5 km/h of airspeed. Fans capable of producing 7-11 km/h may reduce the THI by 5.5 – 7.7 points, especially under high relative humidity. 

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