24V DC Cooling Fan how to judge?

1. Choose Select brand means choosing a good quality fan from the "24V DC Cooling Fan" brand, so that the DC fan is important to guarantee the quality.
2. "24V DC Cooling Fan" bearing up choice because bearings are divided into two kinds of ball bearings and bearing oil. Ball bearing long life, low noise, but the price is very expensive requirements. Oil-bearing ball bearing service life is shorter than 1/3, may be some noise (over one year) in use for some time, but the price is cheap. After more understanding since we can choose, but if any ball fan and oil prices "24V DC Cooling Fan" almost the price, it indicates that it is the old ball bearing products do not buy or eliminated. And push for new manufacturers of bearings (except clear that the oil-bearing outer) will not exceed the life of the ball bearing, and there will be noise in the future use.