Abstract
High pressure and large flow rate small-sized cooling fans are used for servers in data centers and there is a strong demand to increase its performance because of increase of quantity of heat from servers. Contra-rotating rotors have been adopted for some of high pressure and large flow rate cooling fans to meet the demand. The performance curve of the contra-rotating small-sized cooling fan with 40 mm square casing was investigated by an experimental apparatus and its internal flow condition was clarified by the numerical analysis. The fan static pressure of the front rotor was extremely low and it increased significantly at the rear rotor. The uniform flow was achieved at the inlet of the rear rotor because of the special shape of the casing between the front and rear rotors. On the other hand, the tip leakage flow was large enough to influence on the main flow of the test cooling fan by the design specification of high pressure with compact rotor diameter.
Highlights
Data center has been built because of spread of cloud computing, establishment of ubiquitous networking society and increase of electric parts in machines
The fan static pressure of the rear rotor was high and about 77% of the total fan static pressure was obtained by the rear rotor at the operating flow rate Qo = 0.55 m3/min
The maximum total fan static pressure efficiency obtained at the operating flow rate Qo = 0.55 m3/min−1 was low as ηs = 46.7% because of the design specification of high pressure and large flow rate cooling fan with the 40 mm square casing
Summary
Data center has been built because of spread of cloud computing, establishment of ubiquitous networking society and increase of electric parts in machines. Ravelet et al investigated the effect of the blade loading of counter rotating axial fan on the performance and clarified the different circumferential velocity distributions at off design flow rate for each different blade loading types [12]. There is the strong demand to establish the design method for small-sized axial fans based on the internal flow between the front and rear rotors. The performance characteristics of each front and rear rotor and internal flow condition of the contra-rotating small-sized cooling fan having the spokes are not clarified well. The performance characteristics of each front and rear rotor of contra-rotating small-sized axial fan with 40 mm square casing are. The internal flow conditions of the contra-rotating small-sized cooling fan having spokes are discussed based on the numerical analysis results
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