Installed cooler Design Guide

How to Choose the Evaporative Air Coolers

¢ñ. Selection of Air Cooler

Green evaporative air cooler has various products series, including Miracle 
Mobile Series, Demeanor Mobile Series, Wind Marshal Series, Wind Charisma 
Series, Wind Supremo Series, Wind Domination Series, Wind Superior Series and 
Wind Emperor Series (details in catalogue). The case of Miracle Mobile Series 
and Demeanor Mobile Series is made of plastic, with beautiful design, small 
airflow and suitable for residential applications. The case of Wind Marshal 
Series, Wind Charisma Series, Wind Supremo Series and Wind Domination Series is 
also made of plastic, with beautiful design, compact structure, large airflow 
and high cost efficiency. Wind Superior Series and Wind Emperor Series use 
centrifugal fan, with larger airflow and long drive distance than axial one, 
suitable for large areas and commercial applications. Correct selection of air 
cooler should take several points into consideration, including application 
area, people density, heat productivity and place of installation.

¢ò. Using psychrometric chart to confirm air supply temperature

First, confirm the outdoor state point W according to local meteorologic 
conditions, outdoor state from W points along the line in such enthalpy 85% (air 
cooler saturated efficiency.

¢ó. Selection of air cooler quantity

Entire Ventilation

Calculation in theory

Calculate the cooling load, moisture load and airflow of the using room 
according to conventional air conditioning load calculation formula, and then 
calculate the whole cooling capacity that air cooler can provide. And then you 
may decide the quantity and model no. that you want. The total cooling capacity 
of air cooler should be larger than that required by the using room, the margin 
can be 10%. Total cooling capacity of evaporative air cooler can be calculated 
in theory as follows:

Total cooling capacity: S=LρCp{e•£¨tg£­ts£©+tn£­tg}/3600

in which: L------actual air supply capacity of air cooler £¨m3/h£©

ρ------air density of air outlet£¨kg/m3£©
Cp------ air specific heat£¨kJ/kg•K£©
e------saturation efficiency of air cooler, normally in 85%

£¨tg£­ts)------wet-bulb depression£¨¡æ£©
£¨tn£­tg£©------temperature difference between indoor and outdoor£¨¡æ£©
Set ¡÷t1=£¨tg£­ts£©, ¡÷t2=£¨tn£­tg£©, ¡÷t1 should be positive value, ¡÷t2 can be both 
positive or negative value.

Total cooling capacity S=LρCp£¨e•¡÷t1+¡÷t2£©, ρ¡¢Cp¡¢e are constant, we can see that 
total cooling capacity relates to actual air output, wet-bulb depression and 
temperature difference between indoor and outdoor. ¡÷t1 and ¡÷t2 are uncertain 
values and change according to outside environment conditions, so the formula of 
total cooling capacity is only use for qualitative analysis. 
Calculate in experience

Calculate the quantity of air cooler needed in a space according to air changes, 
which is a commonly used method in actual engineering design.

(1) Definition of air changes: air changes (times/hour)=total air output L/ 
(room area S ×the height of air supply outlet or exhaust outlet(take the large 
one H))

(2)Usually, air change is 25¡«30 times/ hour

(3) In some crowd public areas, air change is 30¡«40 times/ hour

(4) In some workshop with heat appliance, air change is 40¡«50/hour

(5) air change can increase properly in some wet areas, and decrease in hot and 
dry areas.
Calculate as follows:

(1) Calculate the areas that needs to be cooled, confirm the height of air 
supply outlet and exhaust outlet and take the large one H

(2) Confirm air change according to actual condition

(3) The volume of cooling space V×air change N, and get the total air supply 
capacity that the space needs.                  

(4) Total air supply capacity divide actual airflow of independent unit L1, and 
get the quantity of air cooler that you need.

¢ô.Design of ventilating duct

1. Basic terms
air flow
calculating method of round duct
L=900§Ýd2v  £¨m3/h£©
d------inner diameter of the duct  £¨m£©
v------speed    £¨m/s£©

calculating method of rectangle duct
L=3600abv   £¨m3/h£©
a¡¢b------the net width and height of cross section of the duct(m)  

Resistance of duct system

The resistance include the friction and local resistance, the formula is as 
follows:
¡÷P=¡÷Pm+¡÷Pj
¡÷P-----total resistance of the system (Pa)
¡÷Pm----- friction resistance (Pa)
¡÷Pj-----local resistance  (Pa)

The calculation of friction resistance 
¡÷Pm=¡÷pm•L
¡÷pm----- on-way resistance (Pa/m) 
L-----length of the duct section (m)

Loss of local resistance 
¡÷Pj=ξ•v2ρ/2
ξ------local resistance coefficient
v------air velocity of the space where local resistance loss 
occurs £¨m/s£©
ρ------air density£¨kg/m3£© 
2. Points for designing Aolan air cooler duct

£¨1£©The material of ducts should be galvanized sheets, or glass steel, plastic, 
aluminum foil sheets, etc.

£¨2£©Grilles or diffusers should be installed at the places where cooling is 
needed. The specification can be decided according to airflow and air speed. The 
material could be aluminum, wood etc., and the type could be selected according 
to actual situations. We recommend Double Deflection Air Grille with 3-6m/s 
airflows speed, and an airflow adjusting valve is recommended.

£¨3£©The dimension of the duct is usually assumed as follows: the wind velocity is 
6-8m/s in the main duct, 4-5 m/s in the branches, and 3-4 m/s at the end.

£¨4£©The design of the duct system is supposed to be economical, low resistance 
and low noise to make the maximum airflow of “Aolan” air cooler. In order to 
reduce the resistance, the curvature radius of the elbow should not be less than 
1.5 times of the width of the elbow.

£¨5£©It is much better to make the duct go straight, avoiding corners and 
branches, to reduce resistance.

£¨6£©Both auto swing air grilles and duct can be used for side discharge air 
coolers.

£¨7£©According to different airflows, the duct should be designed with sections of 
different specifications to be connected together. The reducing ducts should not 
be too many, usually no more than 4 ducts in a whole system, and the length 
is≥2£¨D-d£©.

£¨8£©The connection between duct and air cooler should be hose, with no 
temperature preservation design.
 

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