What are the 4 factors affecting the performance of evaporative cooling pad?


The evaporative pad cooling system has the characteristics of green, safety, energy saving, environmental protection and economic energy saving.

Evaporative cooling pad combined with greenhouse exhaust fan this efficient cooling method is widely used in poultry breeding, animal husbandry, greenhouse planting, gardening flower planting, industrial production and other places.

There are many factors that affect the cooling effect of evaporative cooling pad.

Many users will ask whether the circulating water used for evaporative pad is better with ice water?

In some customers’ return visits, we found that some customers like to use deep well water or add ice cubes in the water tank of cooling pad.

Customers believe that the low water temperature of honeycomb cooling pad can greatly improve the cooling effect.

In fact, this can not improve the cooling effect of the cooling pad, and it is not economic.


After a lot of research, Mike Czarick of the University of Georgia put 30 5-pound (2.27-kg) bags of ice into a water tank of cooling pad in a chicken coop to test this fact.

Record the outdoor temperature, indoor temperature and water temperature every 10 seconds from a few minutes before the fan pad system starts operation until the water temperature approaches normal.As shown below

Adding ice to the water had no noticeable effect on the temperature of the air entering the room. Whether the water temperature is 77 ° F /25 ° C or 52 ° F /11 ° C, the air entering the room is always about 77 ° F /25 ° C.

Why is that? In fact, the cooling of the evaporative pad is because water evaporates through the surface of the pad and carries away heat, thereby lowering the temperature of the air.

The more water evaporates the more heat it takes with it, the more the air cools.

The water evaporates and takes away much more heat than the temperature of the water rises.

The data shows that evaporating 1L of water will take 2425kJ heat away, but 1L of water will only take 4.19kJ heat away if the temperature rises by 1℃, so when the water temperature drops by 40℃, it will only take 167.6kJ more heat away, which is only about 6.9% more than the heat absorbed by evaporation.

Therefore, the effect of using cold water as circulating water on the evaporative pad is extremely limited.

And with the cost of cold water and ice, it’s not economical.

Normal temperature water can achieve very good results, but also can be recycled to reduce water waste.


Would the evaporation efficiency be better if the wind speed through the evaporative pad was faster?

Some customers in the design of evaporative cooler pads, hope to increase the wind speed through the pads, and thought that the effect will be better.

However, the higher the wind speed, the less sufficient the heat exchange between air and water, and the worse the cooling efficiency. The wind speed is too large, easy to affect the life of swamp cooler pad, and cause greater pressure loss. It will also make the water out of the surface of the pad directly into the room, causing the indoor humidity to rise, and the ground near the evaporative air cooler to become wet.

So whether a slower wind speed is conducive to better evaporation? The smaller the wind speed, the larger the padding area required to be configured, which takes up too much of the envelope area.;

Therefore, considering the factors of economy, service life and practicability, it is recommended that the evaporative cooling pad wind speed is 1.25-1.8m /s for the thickness of 100 mm, and 1.8-2.5m/s for the evap cooler pad with a thickness of 150 mm.


Structure of evaporative cooling pad (Angle size, thickness of evaporative cooling pad)

The structure of the evaporative pad will also affect its cooling effect. The main parameters of the pad structure include height H, width W, thickness D, and the combination Angle α and β of the cooling pad paper.


At present, the domestic (China) general use of thickness D is 150mm or 100mm evaporative cooling pad, models are 5090 and 7090 and 6090 or 7060, the combination Angle is α45°, β45° and α15°, β45°

The different combination Angle will affect the cooling efficiency and pressure drop of the evap pad.

The following figure compares the cooling effect and pressure drop of 7090 and 7060 evaporative pad under different wind speeds.


It can be seen that the faster the wind passing through the pad, the lower the cooling efficiency, but the higher the pressure drop.

Under the same wind speed, the cooling efficiency of 7090 is higher than that of 7060, but the pressure drop formed is larger.

The cooling efficiency of evaporative cooling pad of different structure is different, and the pressure drop is also different.

The negative pressure directly affects the working efficiency of the fan and the configuration of the number of fans.

Especially high-density livestock and poultry houses, the pressure drop in the house is very large during longitudinal ventilation, and the pressure drop is one of the factors that must be considered when configuring environmental control equipment.

Cooling efficiency is an important index to evaluate the cooling effect of evaporative cooling pad, and its calculation formula is as follows:

η=(Tdb-Ti )/(Tdb-Twb)x100%

Where: η – cooling efficiency (%);

Tdb – air dry bulb temperature before cooling (℃);

Twb – wet bulb temperature of air before cooling (℃);

Ti – Air dry bulb temperature after cooling (℃).

The quantity of fan and cooling pad should be matched.

In the fan pad cooling system, when we determine the number of fans according to the total amount of indoor air change, how to determine the area of water curtain is particularly important.

If the area of the evaporative cooling pad is not enough, the wind speed through the pad is too fast, it will make the water from the surface directly into the room, causing the indoor humidity to rise, and the ground near the air cooler to become wet.

If the area of water curtain paper is too large, the wind speed through cooling pad is too slow, the evaporation rate will slow down, and the temperature drop effect is not obvious.

How to determine the area of evaporative cooling pad?

We generally calculate according to the following formula.

Cooling pad area = hourly exhaust air volume ÷ curtain wind speed

(1.25-1.8m /s for thickness of 100 mm, and 1.8-2.5m/s for thickness of 150 mm)

There are many factors that affect the cooling effect of evaporative cooling pad.

In addition to the analysis of water temperature, cooling pad wind speed, pad structure and area, and cleanliness and other factors are very important for the cooling efficiency.

Besides, regular maintenance of the cooling pad is also required.

On the maintenance of water cooling pad and other common problems to deal with, we will continue to explain oh in the following article.

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