Characteristics of heat transfer in small disk enclosures at high rotation speeds

Experimental results are reported on heat transfer in small disk enclosures (DEs) containing several 5.25-inch-diameter disks and two symmetrical brushless DC motors mounted on a spindle. Windage loss decreases with disk diameter, and the ratio of windage loss in the 5.25-inch-diameter disk to that in 10.5-inch-diameter disks is 1/16. Air flow over the disk surface is probably turbulent at rotation speeds of more than 5400 RPM. The windage loss dominates the total at rotation loss speeds of more than 5400 RPM. An effective forced convection suppresses the temperature increase of the DE to less than 5 degrees C, due to the higher thermal conductivity of the DE surface. High track densities of more than 100 tracks/mm are feasible as a result of the low thermal off-tracking, less than 0.3 mu m, and the small deviation in head positioning, less than 0.5 mu m. These low values arise from the thermally and mechanically symmetrical DE structure and a ceramic positioner with high stiffness.<
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