Studies on Aero-Thermal Performance of a Cooling Fan Used in a Narrow Space

Experiment and Numerical Analyses on Time-Averaged Characteristics

*

Hongbin YUAN, Ken-ichi FUNAZAKI, Kazutoyo YAMADA, Takashi SHIMADA

Department of Mechanical Engineering, Iwate University, Ueda 4- 3-5,Morioka, Iwate, 020-8551,Japan

Flow field around an entire stage of an axial cooling fan is analyzed using the three-dimensional unsteady

Reynolds-averaged Navier-Stokes (RANS) equations with Shear Stress Transport (SST) turbulence model, aiming

at the investigation of the cooling performance of the fan. The main focus in this study is on the effect of the

distance between the cooling fan and the surface to be cooled. Detailed flow measurement is also executed using a

slant hot-wire probe to clarify time-resolved flow structure as well as turbulent flow characteristics contained in

the downstream flow of the fan. The numerical results are compared with the experimental data as well as the flow

field in the vicinity of the fan blades. This study reveals the important role of the fan-surface distance in terms of

flow rate and cooling performance.

Key Words: Axial- Cooling Fan, Slant Hot-Wire Anemometer, CFD, Turbulent Flow, Air-Cooled Target

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Fig.1 Experimental Apparatus for Flow Rate Measurement

Fig.2 Schematic of the test section

Fig.3 Wire-fixed coordinate system for slant-type hot-wire probe

Fig.4 Configuration of test tan and hot-wire probe traverse position

Fig.5 Configuration of the calculation domain and grids

Fig.6 Fan characteristics for various gaps

Fig.7 Variations of flow rate with the Gap increase for three axial positions of the fan

Fig.8. Averaged Velocity Distributions by EFD & CFD at Measurement location, (a)

Absolute velocity (b) Axial velocity (c) Circumferential velocity (d) Radial velocity

Fig.11 Limit streamline on suction side of the fan blade

(Left: gap=10; middle: gap=20; Right: gap=30)

T

L

V

Separation

T

L

V

Separation

T

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Flow

(a) (b) View from position E

Fig. 9 Locations of cutting plane (a) Front View (b) Side View

C B D A

Observation

Region

Flow

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out

out

in

in

(a) (b) (c) (d)

Flow

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Casing

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Separation

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Fig.10. Distribution of the axial velocity around blade tip at the observation cutting planes

(a) Plane A (b) Plane B; (c) Plane C; (d) Plane D; (Left: gap=10; Middle: gap=20; Right: gap=30)

Casing