Evaporative Cooling Concept

As the name implies, evaporative cooling works by evaporating water into the air stream. This principle is best illustrated in a personal way by chilling effect that you feel when you come out of a swimming pool and a wind  blows across your body!  The chilling effect is caused by the evaporation process of the water drying quickly from your body. The same thing happens when you sweat.  A “cool breeze” is just air flowing over your body evaporating the sweat.  It is nature’s way of keeping us cool during hot weather or physical exertion.

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Evaporative cooling is the use of this evaporation process to cool the air passing through a wetted cooling media.  The cooling media could be as simple as a wet cloth. In fact, this process has been used for hundreds (if not thousands) of years.  Hanging a wet cloth over an open window cools the air passing through the cloth.

In technical terms, temperature is measured in two important ways that relate to evaporative cooling. These are “dry bulb” and “wet bulb” temperatures expressed in degrees Fahrenheit or Celsius. There are several other measurements that reflect the amount of moisture in the air; these are “dewpoint”,  “absolute humidity” and “relative humidity”. The following brief explanation of these measurements will help in the understanding of this process.

Temperature Reduction Chart

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Ambient Dry Bulb Temperature (0C) Ambient Relative Humidity
10% 20% 30% 40% 50% 60% 70% 80% 90%
10 2.9 4 4.6 5.4 6.3 7.2 8 8.5 9.4
15 6.5 8.1 8.5 10 10.6 11.5 12.5 13.2 14.2
20 10.1 10.4 12.8 13.7 15 16.1 17.2 18.1 19
25 13.8 15.2 17 18.2 19.4 20.5 21.6 22.8 24
30 16.6 18.8 20 22.1 23.5 24.9 26 27.2 28.8
35 20 24 24.2 26 28.1 29.9 31 32.2 33.4
40 23 28.1 29 30.5 32.2 33.7 N/A N/A N/A
45 25.7 29 32 34.2 N/A N/A N/A N/A N/A
50 29 32.5 35.6 N/A N/A N/A N/A N/A N/A
 

Dry Bulb: The ambient (surrounding air) temperature taken with a thermometer .

Wet Bulb: The lowest temperature level of the air that can be reached by evaporatively cooling the air.

Wet Bulb Depression: The difference between the Dry Bulb and Wet Bulb temperatures. I.E. if Dry Bulb is 100 degrees (f) and the Wet Bulb is 70 degrees (f), the Web Bulb Depression is 30 degrees (f). The Wet Bulb Depression depends upon the efficiency of the cooling media and depth of cooling media used.

Cooling Efficiency: The percent of the temperature drop across the media compared to the Wet Bulb Depression. I.E. if the Wet Bulb Depression is 30 degrees (f) (as in the above example) and the actual temperature drop measured across the cooling media is 27 degrees (f), the cooling efficiency of the media is 90%. (27/30 = .90). The cooling efficiency is also referred to as “Saturation Efficiency” because it refers to the amount of moisture that is packed into the air. 100% Saturation Efficiency would indicate a temperature drop of 30 degrees (f) in the above example of wet bulb depression.

Dewpoint: The temperature at which moisture begins to form on a slick surface indicating 100% saturation of the air with moisture. That is how the dew gets on the grass in the morning. The dry bulb air temperature drops to the wet bulb temperature level.

Absolute humidity: Actual measurement of water vapour in the air.

Relative humidity: The percent of moisture in the air compared to the amount of moisture the air could contain. This is the most common reading to be reported in the weather reports. The report of “100 degrees and 12% relative humidity (RH)” is the same as all the above examples. Using the analogy of a glass half filled with water means the glass is 50% full. It could hold an additional 50% at which point it would start to overflow if more water was added.

Evaporation Rate: The rate at which water is absorbed into the air passing through the cooling media. For practical purposes, this rate is measured in gallons of water per hour (or minute).

Cooling Media: The Evaporative Cooling Pad, made of cellulose paper is engineered from cross-sectional specially treated flute media capable of absorbing and retaining water to provide the maximum cooling efficiencies. The cellulose media is treated with stiffening and rot-resisting agents to increase its useful life. The geometry of the cellulose media provides cooling without any water carryover as long as the air velocity through the pads is less than the recommended maximum.

Cooling equipment
Evapoler can be used in all kinds of cooling equipment rooms. It is the most energy-saving and economical cooling way.

Net Bar
In public place such as net bar, if we always use conventional aircon, 80%-90% of indoor air will circulate and become muddy. However, if we use Evapoler air cooler, the indoor air can not only be cooled down, but also keep fresh.

Commercial Places such as Supermarkets
In big commercial places, Evapoler Air Coolers can circulate the inside air and supply consumers with fresh air, making a healthy and comfortable public environment.

Cooling Communication Room and Station
Evapoler Air Coolers can be used in kinds of communication rooms. It is the most energy-saving and economical cooling way.

Spot Cooling
If it is no need to cool all space, Evapoler Air Coolers can be designed to just offer spot cooling and energy is saved.

Humidifying
For textile industry, especially in hot summer, it not only needs to cool the workshop, but also needs to keep some humidity in the workshop. By installing Evaporative Air Coolers, these two problems are resolved.

Food Processing Industry
For food processing industry, Evapoler Air Coolers can help shorten cool time of the food, improve production efficiency and product quality.

Green Houses
Evaporative Air Coolers can be the best choice for the flowers plants as they can supply the flowers with the most natural cool air which is good for the flowers” growth.

Kitchen 
Evapoler Air Coolers can be used in big kitchens of hotels, restaurants,etc. to help exhaust the waste gas and supply cooks a good and cool working environment.

Supply Fresh Air
In electronics industry, workers often feel terrible in hot summer day. By installing Evaporative Air Coolers, it can supply workers in a cool and clean environment.

How many evaporative coolers you should install ?

Ventilation frequecy for different area.

Normal environnment Crowded environment With heat equipment High temperature and serious pollution
25-30 times/hour 30-40 times/hour 40-50 times/hour 50-60times/hour

How should you choose evaporative cooler?

  1. Normal priority choose Series A 18000~20000 m3/h cooler,it suit any place.
  2. For Industrial,workshop,warehouse,big noise place you can choose Series B 18000~20000 m3/h or 30000 m3/h .

How choose evaporative cooler quantity for your place ?

N–quantity coolers
S–area need cooling down
n–ventilation frequency
v=S*h(the height of wind)
V–volume need cooling down
h–the height of wind
Q–cooler airflow

Formula as below

  1. quantity coolers N =(V*n)/Q
  2. Ventilation frequency n =(Q*N)/V

For example
If you need cooling down the factory area 1000 M2, height 4M (assuming the factory does not have heat equipment) ,there the ventilation frequency should be 25-30 times/h,and you choose 18000 M3/h cooler .
so V=1000*4=4000M3
     N=(4000*30)/18000=6.6(so you should install 7 pcs coolers.)

Temperature Reduction Chartworking

Ambient Dry Bulb Temperature (0C) Ambient Relative Humidity
10% 20% 30% 40% 50% 60% 70% 80% 90%
10 2.9 4 4.6 5.4 6.3 7.2 8 8.5 9.4
15 6.5 8.1 8.5 10 10.6 11.5 12.5 13.2 14.2
20 10.1 10.4 12.8 13.7 15 16.1 17.2 18.1 19
25 13.8 15.2 17 18.2 19.4 20.5 21.6 22.8 24
30 16.6 18.8 20 22.1 23.5 24.9 26 27.2 28.8
35 20 24 24.2 26 28.1 29.9 31 32.2 33.4
40 23 28.1 29 30.5 32.2 33.7 N/A N/A N/A
45 25.7 29 32 34.2 N/A N/A N/A N/A N/A
50 29 32.5 35.6 N/A N/A N/A N/A N/A N/A

Comparison

Evaporative air cooler is not an air conditioner, as it does not use a compressor and Freon gas. We could not expect an Evaporative Air Cooler to deliver the kind of coolness as refrigerated air conditioner does. However, compared with air conditioner the advantages of the Evaporative Air Cooler are:

  • Low purchasing cost
  • Low power consumption
  • Low installation cost
  • Low maintenance cost
  • Green, energy-saving, eco-friendly
  • Windows and doors can be kept open
  • Multifunctional: Air cooling, ventilation, humidification, purifier
  • Widely used in indoor and outdoor applications

COMPARISON WITH OTHER COOLING AND AIR CONDITIONING SYSTEM :

TYPE Evapoler Air Conditioning Centrifugal Fan
Capacity 18000 CMH 2 ton 18000 CMH
Power 1.1 kw 2.1 kw 3.8 kw
Covered Area 2000 sqft 2000 sqft 2000 sqft
Air Change per hour 30 0 30
No. of Machines Required 1 5 1
Total kw 1.1 10.5 3.8
Electricity Unit Consumption per year(10 hrs, 365 days) 4015 38325 13870
Cost in Rupees when electricity price Rs.7.00 per unit Rs. 28105 Rs. 268275.00 Rs. 97090.00
% cost with reference to referigerative aircon 10.48% 100% 36.19%