Simulation of Static Flying Attitudes with Different Heat Transfer Models for a Flying-Height Control Slider with Thermal ProtrusionReport as inadecuate




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Tribology Letters

, Volume 40, Issue 1, pp 31–39

First Online: 16 December 2009Received: 16 June 2009Accepted: 30 November 2009

Abstract

The thermal flying height control TFC, aka dynamic fly height DFH, technique has been recently used in the head disk interface of hard disk drives to obtain a lower head-media spacing. The air bearing cooling effect, i.e., the heat conduction between the slider and the air film, has been incorporated in the numerical thermal–mechanical simulation of the slider’s static performance. However, the heating effect of the viscous dissipation of the air flow has not been considered yet. In this article, both effects are included in the simulation of a flying slider with its flying height controlled by thermal protrusion, and different models for the air bearing cooling are used to obtain the slider’s static flying attitudes. The simulation results directly show that the air bearing cooling is dominant compared with the viscous heating. All of the air bearing cooling models, including a recent one that considers the dependence of the air molecular mean free path on the air temperature, have simulation results close to each other. The largest relative difference in the simulated flying height is less than 9% even when the transducer flying height is lowered to below 2 nm.

KeywordsAir bearings Thermal effects in hydrodynamics Magnetic data recording heads Magnetic data storage List of symbolshSlider–disk spacing

kThermal conductivity of the air

KnKnudsen number

pAir bearing pressure

p0Ambient or reference air pressure

PrPrandtl number

qHeat flux at the slider’s air bearing surface

qconductionConduction heat flux at the slider’s air bearing surface

qviscousViscous dissipation at the slider’s air bearing surface

qCouetteViscous dissipation due to Couette flow at the slider’s air bearing surface

qPoiseuilleViscous dissipation due to Poiseuille flow at the slider’s air bearing surface

qcontConduction heat flux with the rarefaction effect neglected

QJuConduction heat flux in Ju’s model normalized by qcont

QZCConduction heat flux in Zhang’s and Chen’s models normalized by qcont

QZhouConduction heat flux in Zhou’s model normalized by qcont

RSpecific gas constant

TAir bearing temperature

TsTemperature of the slider surface

TdTemperature of the disk surface

T0Ambient or reference air temperature

ULinear velocity of the disk at the slider location in the slider length direction

x, y, zCoordinates for the air bearing in the directions of the slider length, width and height, respectively

Greek symbolsαMomentum accommodation coefficient

γRatio of the specific heat

λMean free path of the air

λ0Reference mean free path of the air molecules at the temperature T0 and pressure P0

μViscosity of the air

ρDensity of the air bearing film

σTThermal accommodation coefficient

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Author: Du Chen - David B. Bogy

Source: https://link.springer.com/







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