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（℃）
（tn－tg）------temperature difference between indoor and outdoor（℃）
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.