How to judge a good heat dissipation dc cooling fan?

A lot of people when choosing heat dc cooling fan, I don't know how to choose, are generally not grab a few manufacturers to test can run properly, and then choose the price low. So how are we to distinguish between quality of dc cooling cooling fan? 1. See current: the same speed, the same voltage, the same air. Current small heat dc cooling fan is better. Because the current is smaller, means that the smaller the loss of the cooling fan, which is low consumption, low consumption main reason is that product permeability capability is strong, good motor enameled wire loss, high copper content D lubricating oil of high activity. 2. Listen to noise: same speed, voltage, the smaller the heat dissipation dc cooling fan noise is better, because of the low noise mainly with blades, bearing, oil products, assembly structure and so on. Blade shape design, the better, the air volume will be larger, and the lower the noise; Bearing accuracy is higher, the smaller it with axial friction, collocation is the more accurate size, low noise, of course, also can be jumped over; Low noise, small friction, bearing, shaft core of life will be longer, dc cooling fan, the life also will be longer. 3. Vibration measurement: the same specification and the speed of cooling fan, small vibration of dc cooling fan better heat dissipation, cooling dc cooling fan is a high-speed machine, it must have some vibration, no one can guarantee no vibration, vibration, the smaller is better, the smaller the vibration, the cooling fan operation is more stable, the bearing and the smaller the wastage of the shaft core, also can reduce the volatilization of oil or ball bearing wear, life will be longer, of course. Above some methods of discriminant cooling dc cooling fan is good or bad, of course, the stand or fall of heat dissipation dc cooling fan test is a little bit of a problem, that is why many people choose a, look at the price can be the reason, but these methods is determine heat dc cooling fan effective method of quality.