evaporative cooling pads

Forum: Plastic Evaporative Cooling Pads

Published on: 09/06/2012
Author/s : Dr. Mike Czarick and Dr. Brian D. Fairchild (University of Georgia)
Figure 1. Evaporative cooling system with plastic pads. Little has changed when it comes to poultry house evaporative cooling pads over the last 30 years. Yes, there have been some relatively minor changes in things such as flute angles (45° X 15° vs. 30° X 30°), edge coatings, and pad thickness (6" vs. 4"), but for the most part the traditional paper pad looks and cools about t...
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Dr Asad Abbas Malik Dr Asad Abbas Malik
DVM, M.Phill Animal Nutrition
September 6, 2012

very well done, very informative knowledge about plastic evaporative cooling pads. Thank you for sharing.

Reply
Waqar Waqar
CEO
September 6, 2012
Dear Dr Fairchild & dr Czarick
This scribe ,during IPE Altana expo,four years hence, saw bricks as evaporative coolers from some company in South America, who claimed it is being used there to advantage for its cheapness,easy washibility. I has the wicking property and retains the moisture for a long time due to its mass and hence can be used during wet weather without too much dropping of water and does not increase humidity as does the paper/cellulose pad. Though,perhaps it may have a negative point that the surface area per square foot to evaporate water may not be compatible to paper pad.
For my information pls,that have you ever studied that material for evaporation in your University for which I have a high regards

Waqar,The Automation Company Pakistan
Reply
September 7, 2012

Dear Dr. Brian,

Thank you very much for throwing more light on the pros & cons on the performance of the two pad materials through research and fine analysis of the results. We too replaced some of our paper pads just because of its strength, durability and ease of cleaning. With this knowledge, we may be able to analyze the performances and would help us to understand differences of performances.

D.C.Hettiarachchi - Sri Lanka

Reply
Dr. Mike Czarick Dr. Mike Czarick
Agricultural Engineer
September 7, 2012
Brick pads can produce some level of evaporative cooling, but it will be less than traditional paper pads. How much less depends on a variety of factors such as air speed through the pad, outside temperature, relative humidity, and amount of water placed on the pad. The reason that a paper pad will produce more cooling basically comes down to surface area. A paper pad typically has at least 10 times the surface area of a "brick" pad.

Another thing to keep in mind that the humidity a pad produces is proportional to cooling produced by a pad. For every 1 C cooling an evaporative cooling pad will increase the Rh 5%. This is true for ANY pad or fogging system. The reason a brick pad produces less rh is that it is producing less cooling. 5 C less cooling....25% less humidity. You cannot get the same level of cooling without producing the same level of Rh.

Hope this helps.

mike czarick
Reply
Waqar Waqar
CEO
September 12, 2012
I thank you for your valuable comments. Appreciate how much research you have done on all aspects of ventilation and their effects on birds. Specially valuable with the advent of totally closed environmental houses where lack of perfect technical knowledge means total disaster.
The poultry tips on ventilation from Georgia University are like ventilation pearls for poultry industry. We, in Pakistan poultry community, admire you people.

Thanks again for taking time to reply.

Waqar : The Automation Company Pakistan

Reply
Dr. Mike Czarick Dr. Mike Czarick
Agricultural Engineer
September 13, 2012

It is always nice to hear from our friends in Pakistan. Please let us know if we can every be of assistance.

Mike Czarick

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July 17, 2014
Hi Mr. CZARICK

I am a mechanical engineer with some expertise in fluid dynamics and ventilation. I am using plastic cooling pads and I read your article here and the other copy in poultry housing tips.

You have mentioned "Since the pad was designed to have the similar air flow/static pressure characteristics of traditional paper pads...", but I checked pressure drop of cellulosic pads and plastic pads and the plastic pads pressure drop is significantly lower (Plastic pad manufacturer claims the system will have at least 30% less energy due to lower pressure drop). It means with same amount of fans, the air speed should be higher in plastic pads.

This can change the meaning of the results that you have reported dramatically, if it is true. Because, if the air speed is higher, it means there is more air exchange in the house and the parameters are not all the same for comparison. With more air, the temperature difference in house could be less with same amount of heat transferred from birds to air. Also, the air with less humidity takes more heat from birds without getting warmer. So, generally speaking, the term "Less heat taken from the birds" can be false.

But the question is how can we measure the amount of heat energy taken from the birds? The answer is to form a virtual control surface around the hall as I explain below:

Consider a surface is covered the hall and we measure the amount of energy goes in and energy goes out, the difference is the amount of heat rejected from birds' body plus some neglectable other losses. How to calculate the amount of energy? By air enthalpy, not temperature. If we multiply average air speed (m/s) at pads (which is easily measurable) and multiply it to pad area, we will have the amount of air goes inside the house (in m3/s). By measuring air temperature and Rh, we can read the enthalpy of air in kJ/kg. multiplying these two by air density (kg/m3) will give us the amount of energy flow per second :

Airflow (m3/s) x Air Density (kg/m3)= Air mass flow rate (kg/s)
Air mass flow rate (kg/s) x Input Air Enthalpy (kJ/kg)= Energy flow in (kJ/s)

as we can consider air to be in compressible at this speed and pressure and we neglect the small change in air density because of temperature change we will have:

Air mass flow rate (kg/s) x Input Air Enthalpy (kJ/kg)= Energy flow out (kJ/s)

Energy taken from birds (kJ/s)=Energy flow out - energy flow in

If we can measure this data, it would be a meaningful result and a prominent job. We can finally see the real result of the battle between cellulosic pads and plastic pads.

Am I right about this issue?
Reply
Dr. Mike Czarick Dr. Mike Czarick
Agricultural Engineer
July 17, 2014
To analyze an evaporative cooling pad you need both a static pressure curve AND a cooling efficiency curve. You mention that a plastic pad has a lower static pressure drop but did it have the same cooling efficiency...at the same surface velocity. Secondly how much the air exchange rate would change depends on exactly the static pressure was decreased. The fact is that a 30% decrease in pressure could have a minimal effect on air exchange rates.
Reply
July 17, 2014
Thank you very much for your fast reply, I agree with you that we need both curves for predicting the results, but in test condition we should test all the parameters, including air speed. The effect of less pressure drop on the amount of air flow depends on the fan performance curves. I just checked the pressure drop curves of the pads, The pressure drop of cellulosic pads at air speed of 1.5 m/s is about 33 Pa (Monters CelDek 5090-150mm *1), for plastic pad it is 11Pa (Hewitech AK150 Coolnet *2). It is one third, not 30% less. I guess the 30% is overal performance, combined of airspeed , performance, pressure drop and others). And this amount is considerable.

There are two reasons that I commented here, firstly, I have checked the air speed in two adjutant egg-layer houses, one with Cellulosic pad and one with Plastic pads. The air flow rate was at least 50% more in plastic pads with the same configuration. It is a significant amount. Consider that cellulosic pads cools down the air by 10 degrees and plastic pads by 8 degrees, the amount of energy taken from air in one second in one square meter of each pad would be 10xQ for cellulosic one and 8x1.5xQ. (Q is an arbitrary constant) If I am correct.

Secondly, here in Turkey, we have very bad water condition with high TDS, the formation of scales on cellulosic pads makes the air passing holes or flutes narrower and the pressure drop will increase with time, but as it can be seen in your pictures of one year old plastic pads, the scale does not affect the curved air passages. it means that after two or three years of operation, the amount of airflow in cellulosic pads will decrease significantly. As far as I know, Air flow is also important for ammonia removal and providing fresh air for the birds. I have installed plastic pads in two farms one year ago, and I am waiting for one more year to check the results again after this period to see if there is a considerable change or not.

What I want to say is that i doubt that the current acquired data is enough to judge the plastic pads are less than cellulosic ones. Of course you have much more experience than me in this field, I want to know your opinion which is very valuable for me.

Kindest Regards,
Pouya

*1- http://www.munters.com/upload/Related%20product%20files/Celdek%205090-15%20English.pdf
*2-http://www.hewitech.de/fileadmin/hewitech/redaktuer/pdf/HewitechCoolPad_Eng.pdf
Reply
Dr. Mike Czarick Dr. Mike Czarick
Agricultural Engineer
July 17, 2014
In the U.S. (and most of the world) we use a 15 cm Celdek 45 X 15 flute angle pad. The static pressure drop at 1.5 m/sec is 10 Pa which is basically the same as the hewitech plastic pad (what we saw/measured in the field). Their is no difference in pressure drop at the same velocity therefore there would be basically no difference in fan performance. The cooling efficiency of the Celdek 45 X 15 pad is in fact higher than the plastic pad which would result in a reduction in air cooling.
Reply
July 17, 2014
Thank you for your information and your time.
Reply
Dr. Mike Czarick Dr. Mike Czarick
Agricultural Engineer
July 17, 2014
my pleasure. I enjoyed your thoughtful questions.
Reply
eddie tan eddie tan
CEO
September 18, 2014
can a bamboo that weave in the form of cooling pads replace the paper / plastic evaporative cooling pads ?
Reply
January 2, 2015
Hi Dr. CZARICK,

I have a question again, did you continue the test for the second year, when both cellulosic and plastic pads are used for 1 year?

Sincerely,
Pouya
Reply
bhaskar rao bhaskar rao
Agriculturist
March 4, 2015
Sir,
Wanted to have the relative humidity and temperature data during hot humid months inside the greenhouse which has a plastic evaporative cooling pad compared to the ambient. Has this system been employed in the Middle East ( gulf countries) for agricultural/livestock production. Here in Bahrain we do have high humidity & high temperature during June to August/sept, so how far will this plastic pad be effective.
Reply
November 16, 2020
The high humidity climate like gulf countries is not efficient to use the Evap. cooling system al all. I know it is too late to respond but I felt that I have to clarify this information.
Greenhouse Environment control specialist.
KFU
Reply
Dr. Mike Czarick Dr. Mike Czarick
Agricultural Engineer
March 4, 2015
The plastic pad will cool similarly to a traditional paper pad. Since a plastic pad has a slightly lower cooling efficiency it will produce slightly less cooling with slightly less humidity.
Reply
bhaskar rao bhaskar rao
Agriculturist
March 4, 2015
Dr . Mike, is this the explanation to my Query. I need a more detailed response & would love to have more members discuss it.
Reply
mojtaba abedini mojtaba abedini
Student
May 24, 2015
hi pleas send me method of Removal of odor from the cooling pad
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