A.HOW TO CHIOCE AIR FLOW
In order to take away the heat generated by the system or air exchange, it is important to use the fan forced ventilation and select the suitable wind turbine in the system design stage. Should refer to the application environment of the wind power supply, operating conditions, temperature, humidity, corrosion, fan control characteristics, noise, air pressure, wind, etc.. For the use of the fan forced cooling, according to the heat generated by the system and the need to maintain the temperature of the system to do as follows.
Calculate the required air volume of the fan:
Q=2.99W/Tc (Unit: M3/H)
W: Heat dissipated in watts TC: Allowable temperature rise in °C
B. HOW TO CHOICE FAN’S PRESSURE
Equipment designed according to AMCA210 standard, can accurately measure the air volume of the fan and the static pressure and drag system
Flow calculating:
Q=60C/4 D2=M2G/R PN (M3/MIN)
C: Air nozzle coefficient
D: Diameter of nozzle ( M )
R: Air density =1.293
T: Temperature ℃
P: Air pressure (mm H2O)
PN: Differential pressure of air volume (mm H2O)
PS: Air static pressure (m H2O)
G: Gravity acceleration (9.8m/s2 )
Testing max air flow (at 0 pressure ) and Max static pressure (at 0 flow) .
Adjust the fan speed, testing air pressure and air flow, may draw the P-Q curve.。
C. TESTING RESISTANCE OF SYSTEM AND DETERMINE THE WORK POINT OF SYSTEM
When the system is designed to meet the needs of the fan, the fan characteristic curve and the system characteristic curve are selected. Designers need to test out the system of the drag characteristic curve, the system resistance curve and fan characteristic curve of the intersection graph, the air flow volume and the air pressure of the intersection can meet the requirements of air volume and air pressure of the fan cooling system。
D. UNIT CONVERSION TABLE
Air flow ：M3/H= x *1.699 CFM
E. THE NOISE LEVEL TESTING
According to ISO-3845 and ANS112.35 standard, (Background noise is below 15dB)
The testing cooling fan runs in free airflow and a noise meter is Set to 1 meter away from air entrance and at 90degree to the fan in an echo-free room with background noise lower than 15db. The test result is depicted with sound pressure level frequency band In DBAS .
F. BEARING SYSTEM
Bearing is an important part in the evaluation of the performance of the fan, and it is generally used for sleeve bearing and ball bearing. The characteristics of the two kinds of bearings are as follows：
| NO | Project | Sleeve (S) | Ball (B) | Effect |
| 1 | Material | Copper based powder metallurgy | Stainless steel | B than S life long |
| 2 | Friction | Surface contact | Point contact | B than S Heat up less |
| 3 | Sealing property | No Sealing property | With dust cover, sealing performance well | B than S Volatile less |
| 4 | Volatile oil | Volatile | Volatile less | B than S life long |
| 5 | Installation method | Suitable for vertical installation | Fit for any installation | Related to service life |
| 6 | Suitable speed range | Low speed | High speed | Related to service life |
| 7 | Suitable temperature range | 10°—70° | -30°-----75° | Related to service life |
| 8 | Service life | 20000—30000 Hrs | 30000—50000Hrs | B than S life long |
| 9 | Noise | high、Instable | low，Stable | Related to the environment |
| 10 | Cost | LOW | High | Related to the cost |
According to the requirements of the user, the user should select the right fan with different type bearing.
