Effect of Humidity on the Nanoscale Heat Transfer at the Head-Media Interface

2019 ◽  
Author(s):  
Qilong Cheng ◽  
Yuan Ma ◽  
David Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Heat Dissipation ◽  
Hard Disk Drives ◽  
Water Layer ◽  
Rate Of Change ◽  
Nanoscale Heat Transfer ◽  
The Media ◽  
Bearing Design ◽  
The Heat Transfer Coefficient

Abstract In hard disk drives (HDD), the head-media spacing has decreased to less than 10 nm. Across this nanoscale gap, the heat transfer between the head and media may affect the air-bearing design, lubricant transfer and contact issues. Thus, understanding the heat transfer mechanism is very important to magnetic recording, especially for Heat Assisted Magnetic Recording (HAMR). In this paper, the heat transfer between a head and a static media is studied. In particular, the effect of humidity on the nanoscale heat transfer between a head and a static media is studied experimentally. From the transient and steady data of the experiments, it is proposed that the dynamic response of head protrusion is faster than heat dissipation. Also, a layer of water is assumed to form between the head and the media under high humidity. The water-layer affects the spacing and the heat transfer coefficient across the interface. In the near-contact regime, namely when the clearance is less than 2 nm or so, the protrusion interacts with the water-layer on the media, resulting in a lower rate of change of cooling.

Numerical and Experimental Investigation of Nanoscale Heat Transfer in the Head-Media Interface During Static Touchdown

2019 ◽  
Author(s):  
Siddhesh V. Sakhalkar ◽  
Qilong Cheng ◽  
Yuan Ma ◽  
Amin Ghafari ◽  
David B. Bogy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Magnetic Recording ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drives ◽  
Nanoscale Heat Transfer ◽  
Fly Height ◽  
Head Temperature

Abstract With minimum fly height of less than 10 nm in contemporary hard-disk drives, understanding nanoscale heat transfer at the head-media interface is crucial for developing reliable head and media designs. Particularly, with the emergence of Heat-Assisted Magnetic Recording (HAMR) and Microwave-Assisted Magnetic Recording (MAMR), head failure due to overheating has become an increasing concern. There is a need to develop a methodology to use theoretical curves for spacing-dependent nanoscale heat transfer coefficient to predict head and media temperatures in actual hard disk drives. In this study, we present a numerical model to simulate the head and media temperature profiles during static touchdown and compare our results with experiments performed with a magnetic head on a silicon wafer. As the head approaches touchdown with increasing TFC power, the phonon conduction heat transfer coefficient between the head and the substrate increases exponentially, causing a drop in the head temperature vs TFC power curve. Our model shows that the introduction of van der Waals forces between the head and the substrate causes a steeper drop in the head temperature curve and ensures a good quantitative match with experimental results.

Disk Protrusion Measurement in a Back-Heating Study for Heat Assisted Magnetic Recording

2020 ◽  
Author(s):  
Shaomin Xiong ◽  
Robert Smith ◽  
Erhard Schreck
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Local Heating ◽  
Hard Disk Drives ◽  
Detection Sensitivity ◽  
Experimental Setup ◽  
Heat Assisted Magnetic Recording ◽  
Management Scheme ◽  
The Media ◽  
Disk Spacing

Abstract Heat assisted magnetic recording (HAMR) is a promising technology for the next generation hard disk drives (HDDs). Understanding the heat transfer at nanoscales and implementing a proper thermal management scheme become very critical as a few heat sources and energy delivery components are compactly integrated in a HAMR drive. Recently, a back-heating experimental setup is used to study heat transfer behavior. It is found that the detection of head disk contact and head disk spacing control become more complicated in this experimental setup because the local heating generates a protrusion on the media surface. In this paper, we demonstrate a method to enhance the contact detection sensitivity significantly by modulating the head disk spacing. It shows that a light contact between the head TFC protrusion and media protrusion can be effectively detected. Thereafter, the media protrusion can be measured and the head disk spacing can be well set.

Numerical and Experimental Investigation of Nanoscale Heat Transfer Between a Flying Head Over a Rotating Disk

2020 ◽  
Author(s):  
Siddhesh V. Sakhalkar ◽  
Qilong Cheng ◽  
David B. Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Adhesion Force ◽  
Hard Disk Drives ◽  
Rotating Disk ◽  
Recording Head ◽  
Disk Interface ◽  
Nanoscale Heat Transfer ◽  
Magnetic Recording Head ◽  
Fly Height

Abstract With the minimum fly height less than 10 nm in contemporary hard-disk drives, understanding nanoscale heat transfer at the head-disk interface (HDI) is crucial for developing reliable head and media designs. While flying at near-contact, the fly height and spacing dependent nanoscale heat transfer are significantly affected by interfacial forces in the HDI (such as adhesion force, contact force etc.). Moreover, with the emergence of technologies such as Heat-Assisted Magnetic Recording and Microwave-Assisted Magnetic Recording, head failure due to overheating has become an increasing concern. In this study, we present a numerical model to simulate the head temperature profile and the head-disk spacing for a flying head over a spinning disk and compare our results with touchdown experiments performed with a magnetic recording head flying over a rotating Al-Mg disk. In order to accurately predict the fly height and heat transfer at near-contact, we incorporate asperity based adhesion and contact models, air & phonon conduction heat transfer, friction heating and the effect of disk temperature rise in our model. Our results show that the incorporation of adhesion force between the head and the disk causes a reduction in the fly height, leading to a smaller touchdown power than the simulation without adhesion force.

scholarly journals Experimental Investigation of Flow Condensation in Microgravity

2013 ◽  
Author(s):  
Hyoungsoon Lee ◽  
Ilchung Park ◽  
Christopher Konishi ◽  
Issam Mudawar ◽  
Rochelle I. May ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Condensation Heat Transfer ◽  
Interfacial Structure ◽  
Sensible Heat ◽  
Two Phase ◽  
The Heat Transfer Coefficient

Future manned missions to Mars are expected to greatly increase the space vehicle’s size, weight, and heat dissipation requirements. An effective means to reducing both size and weight is to replace single-phase thermal management systems with two-phase counterparts that capitalize upon both latent and sensible heat of the coolant rather than sensible heat alone. This shift is expected to yield orders of magnitude enhancements in flow boiling and condensation heat transfer coefficients. A major challenge to this shift is a lack of reliable tools for accurate prediction of two-phase pressure drop and heat transfer coefficient in reduced gravity. Developing such tools will require a sophisticated experimental facility to enable investigators to perform both flow boiling and condensation experiments in microgravity in pursuit of reliable databases. This study will discuss the development of the Flow Boiling and Condensation Experiment (FBCE) for the International Space Station (ISS), which was initiated in 2012 in collaboration between Purdue University and NASA Glenn Research Center. This facility was recently tested in parabolic flight to acquire condensation data for FC-72 in microgravity, aided by high-speed video analysis of interfacial structure of the condensation film. The condensation is achieved by rejecting heat to a counter flow of water, and experiments were performed at different mass velocities of FC-72 and water and different FC-72 inlet qualities. It is shown that the film flow varies from smooth-laminar to wavy-laminar and ultimately turbulent with increasing FC-72 mass velocity. The heat transfer coefficient is highest near the inlet of the condensation tube, where the film is thinnest, and decreases monotonically along the tube, except for high FC-72 mass velocities, where the heat transfer coefficient is enhanced downstream. This enhancement is attributed to both turbulence and increased interfacial waviness. One-ge correlations are shown to predict the average condensation heat transfer coefficient with varying degrees of success, and a recent correlation is identified for its superior predictive capability, evidenced by a mean absolute error of 21.7%.

scholarly journals A TECHNIQUE TO ESTIMATE THE TRANSIENT COEFFICIENT OF HEAT TRANSFER BY CONVECTION

2020 ◽  
Vol 50 (3) ◽  
pp. 229-234
Author(s):  
Guillermo Federico Umbricht ◽  
Diana Rubio ◽  
Rodolfo Echarri ◽  
Claudio El Hasi
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Initial Temperature ◽  
Transient State ◽  
Elasticity Analysis ◽  
Circular Section ◽  
One Dimensional ◽  
Novel Approach ◽  
The Right ◽  
The Heat Transfer Coefficient

In this work we study the characteristics of the dissipation by convection of a solid circular section of a diameter d in a fluid. We assume that this section increases its temperature homogeneously over its whole surface from an initial temperature 𝒕𝒂 to the (asymptotic) temperature value 𝒕𝒎𝒂𝒙. To simulate its temperature behavior, we model the transfer of heat by conduction in an isolated one-dimensional bar of length L, where a constant temperature source F is considered at the left end, while keeping free the right end causing heat dissipation by convection. We propose a novel approach to estimate the heat transfer coefficient in the transient state. Numerical experiments are carry out for different materials. In order to measure the performance in the estimation, we conduct elasticity analysis. Also a comparison with data used in the literature is included.

Effect of a Shield on Mixed Convection in a Rectangular Enclosure with Moving Cold Sidewalls and a Heat Source on the Bottom Wall

2010 ◽  
Vol 297-301 ◽  
pp. 584-589
Author(s):  
Ghanbar Ali Sheikhzadeh ◽  
S.H. Musavi ◽  
N. Sadoughi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Source ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Bottom Wall ◽  
Governing Equations ◽  
Thermal Shield ◽  
The Heat Transfer Coefficient ◽  
Specific Distance

In this work, the mixed convention of air inside a rectangular cavity with moving cold sidewalls is studied numerically. A constant flux heat source is attached to the bottom wall of the cavity. A thin thermal shield is located at a specific distance above the heat source. The governing equations are solved using appropriate numerical methods. A parametric study has been conducted and the effects of heat source length, its location and the shield distance from the source on the heat transfer have been investigated. The results show that the heat dissipation increases as the heat source and the shield are moved up to a certain distance towards either sidewall. However, moving them beyond this limiting distance results in the reduction of heat dissipation. It is shown that the presence of shield results in the reduction of the heat transfer coefficient. However, for the normalized distance of the shield from the heat source greater than , the shield’s effect on the reduction of the heat transfer coefficient is less than.

Thermal Properties of Porous Copper Manufactured by Lost Carbonate Sintering

2014 ◽  
Vol 783-786 ◽  
pp. 1603-1608 ◽  
Author(s):  
Z. Xiao ◽  
Y.Y. Zhao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Pore Size ◽  
Heat Dissipation ◽  
Fluid Transport ◽  
Porous Metals ◽  
Porous Copper ◽  
Layer Structures ◽  
The Heat Transfer Coefficient

Active cooling techniques are often required to achieve high rates of heat dissipation in thermal management applications. Open-cell porous metals are good candidates for use as heat exchangers. This paper studies the fluid transport and thermal properties of porous copper samples with different pore structures manufactured using the LCS method. The results showed that the permeability increases with porosity but decreases with pore size. The thermal conductivity increases with relative density according to the power law. The effects of porosity and pore size on the heat transfer performance of the porous copper samples are significant, due to their effects on the permeability and thermal conductivity. For the porous copper samples with double-layer structures, the permeability follows the rule of mixture and the heat transfer coefficient can be predicted by a recently developed segment model.

Stress Induced Permanent Magnetic Signal Degradation of Perpendicular Magnetic Recording System

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Sung-Chang Lee ◽  
Soo-Youl Hong ◽  
Na-Young Kim ◽  
Joerg Ferber ◽  
Xiadong Che ◽  
...  
Keyword(s):  
Magnetic Recording ◽  
Hard Disk Drives ◽  
Magnetic Layer ◽  
Mechanical Damage ◽  
Hard Disk ◽  
Disk Drive ◽  
Magnetic Signal ◽  
Perpendicular Magnetic Recording ◽  
Signal Degradation ◽  
The Media

Model scratches of the size found in hard disk drives are produced under controlled conditions at a series of applied loads on both longitudinal magnetic recording (LMR) media and perpendicular magnetic recording (PMR) media using a diamond tip. The scratches are created at low speed, eliminating thermal considerations from the interpretation of the media response. Nanoindentations are produced as well. The scratches and indentations are characterized by atomic force microscope (AFM), magnetic force microscope (MFM), and also by the same magnetic reader and writer used in an integrated hard disk drive (HDD). A comparison of the response of PMR and LMR media shows the PMR media to have larger scratches and greater magnetic signal degradation than LMR media for a given scratch load. The extent of magnetic damage, as measured by MFM, is greater than the extent of surface mechanical damage, as measured by AFM. Analysis of scratches using the HDD reveals that the magnetic damage is irreversible and permanent damage in magnetic layer, which is confirmed by cross section transmission electron microscope image. The experiments reveal the mechanism for magnetic scratch erasure in the absence of thermal effects. This understanding is expected to lead to improved designs for mechanical scratch robustness of next-generation PMR media.

Thermal and Hydrodynamic Phenomena Associated with Melting of a Horizontal Substrate Placed beneath a Heavier Immiscible Liquid

1979 ◽  
Vol 101 (2) ◽  
pp. 318-325 ◽  
Author(s):  
K. Taghavi-Tafreshi ◽  
V. K. Dhir ◽  
I. Catton
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Immiscible Liquid ◽  
Rate Of Change ◽  
Static Mode ◽  
Proposed Model ◽  
Interfacial Heat Flux ◽  
Horizontal Substrate ◽  
The Heat Transfer Coefficient

The melting of a horizontal slab of frozen olive oil placed beneath a pool of warm water has been studied experimentally. The interfacial heat flux data are taken in quasi-static mode by noting the time rate of change of enthalpy of the pool of water. Because of little agitation of the pool due to low melt volume flux (ρwater/ρolive oil ≃ 1.09; ΔT ≃ 5–45 K), the pool was found to stratify with time. Hence, heat transfer coefficient data have been based on the interfacial temperature rather than on the mean pool temperature. Visual observations show that melt removal is governed by Taylor instability and that melt releasing nodes lie about a Taylor wavelength apart. Predictions of the growth of the interface based on equilibrium between surface tension and buoyant forces have been made and found to compare well with the data obtained from the movies. The heat transfer coefficient data obtained at higher pool temperatures are found to correlate well with the predictions based on the proposed model.

A Numerical Study of the Nanoscale Heat Transfer in the Head-Disk Interface for Heat Assisted Magnetic Recording

2016 ◽  
Author(s):  
Haoyu Wu ◽  
David Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Transfer Problem ◽  
Numerical Study ◽  
Near Field ◽  
Experimental Result ◽  
Head Disk Interface ◽  
Heat Assisted Magnetic Recording ◽  
Disk Interface ◽  
Nanoscale Heat Transfer

The near field transducer (NFT) overheating problem is an issue the hard disk drive (HDD) industry has faced since heat-assisted magnetic recording (HAMR) technology was first introduced. In this paper, a numerical study of the head disk interface (HDI) is performed to predict the significance of the nanoscale heat transfer due to the back heating from the disk. A steady-state heat transfer problem is first solved to get the disk temperature profile. Then an iterative simulation of the entire HDI system is performed. It shows that the heat transfer coefficient in the HDI increases to about 6:49 × 106 W/(m2K) when the clearance is 0:83 nm. It also shows that in the free space laser scenario, the simulation result is close to the experimental result.

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