Shallow of outlet is influential to a cooling fan?

Cooling fan cooling principle is to accelerate the cold and hot air circulation, make the cold air came in, hot air outflow, so small outlet, not smooth, it will cause hot air out, the cold wind is also not to, or in the cold wind, so the impact on the cooling fan is a lot of

there is a simple test experiment, a customer took a air purifier to measure its cooling fan air volume, air purifier is at the other end with the hook, the leakage air, so will the air circulation is impeded, finally the result is, cooling air volume of fan monomer, is installed on the air purifier operation of air volume of more than 2 times. That is to say, put on the air purifier, cooling fan of the exhaust air much smaller

so, give a cooling fan design a flow of air duct is helpful for heat dissipation, on the other hand, if the outlet is not unobstructed, blindly increasing speed, increase the cooling fan air volume, but the effect is very small for heat dissipation effect. May cost more missing