A conceptual study to characterize properties of space debris from hypervelocity impacts through Thin Film Heat Flux Gauges

Process physics understanding, real time monitoring, and control of various manufacturing processes, such as battery manufacturing, are crucial for product quality assurance. While ultrasonic welding has been used for joining batteries in electric vehicles (EVs), the welding physics, and process attributes, such as the heat generation and heat flow during the joining process, is still not well understood leading to time-consuming trial-and-error based process optimization. This study is to investigate thermal phenomena (i.e., transient temperature and heat flux) by using micro thin-film thermocouples (TFTC) and thin-film thermopile (TFTP) arrays (referred to as microsensors in this paper) at the very vicinity of the ultrasonic welding spot during joining of three-layered battery tabs and Cu buss bars (i.e., battery interconnect) as in General Motors's (GM) Chevy Volt. Microsensors were first fabricated on the buss bars. A series of experiments were then conducted to investigate the dynamic heat generation during the welding process. Experimental results showed that TFTCs enabled the sensing of transient temperatures with much higher spatial and temporal resolutions than conventional thermocouples. It was further found that the TFTPs were more sensitive to the transient heat generation process during welding than TFTCs. More significantly, the heat flux change rate was found to be able to provide better insight for the process. It provided evidence indicating that the ultrasonic welding process involves three distinct stages, i.e., friction heating, plastic work, and diffusion bonding stages. The heat flux change rate thus has significant potential to identify the in-situ welding quality, in the context of welding process monitoring, and control of ultrasonic welding process. The weld samples were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to study the material interactions at the bonding interface as a function of weld time and have successfully validated the proposed three-stage welding theory.

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A Comparison of Radiation Versus Convection Calibration of Thin-Film Heat Flux Gauges

10.1115/imece1999-1106 ◽

1999 ◽

Author(s):

D. E. Smith ◽

J. V. Bubb ◽

O. Popp ◽

T. E. Diller ◽

Stephen J. Hevey

Keyword(s):

Thin Film ◽

Heat Flux ◽

Surface Temperature ◽

Temperature Response ◽

Turbine Rotor ◽

Separate Experiment ◽

Measured Temperature ◽

Conduction Model ◽

Time Resolved ◽

Turbine Rotor Blade

Abstract A transient, in-situ method was examined for calibrating thin-film heat flux gauges using experimental data generated from both convection and radiation tests. Also, a comparison is made between this transient method and the standard radiation substitution calibration technique. Six Vatell Corporation HFM-7 type heat flux gauges were mounted on the surface of a 2-D, first-stage turbine rotor blade. These gauges were subjected to radiation from a heat lamp and in a separate experiment to a convective heat flux generated by flow in a transonic cascade wind tunnel. A second set of convective tests were performed using jets of cooled air impinging on the surface of the gauges. Direct measurements were simultaneously taken of both the time-resolved heat flux and surface temperature on the blade. The heat flux input was used to predict a surface temperature response using a one-dimensional, semi-infinite conduction model into a substrate with known thermal properties. The sensitivities of the gauges were determined by correlating the semi-infinite predicted temperature response to the measured temperature response. A finite-difference code was used to model the penetration of the heat flux into the substrate in order to estimate the time for which the semi-infinite assumption was valid. The results from these tests showed that the gauges accurately record both the convection and radiation modes of heat transfer. The radiation and convection tests yielded gauge sensitivities which agreed to within ±11%.

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Submerged Jet Impingement Cooling of a Nanostructured Plate

Volume 7: Fluid Flow, Heat Transfer and Thermal Systems, Parts A and B ◽

10.1115/imece2010-39055 ◽

2010 ◽

Author(s):

Muhsincan Sesen ◽

Ali Kosar ◽

Ebru Demir ◽

Evrim Kurtoglu ◽

Nazli Kaplan ◽

...

Keyword(s):

Thin Film ◽

Heat Transfer ◽

Heat Flux ◽

Silicon Wafer ◽

Heat Removal ◽

Jet Impingement ◽

Wafer Surface ◽

Small Scale ◽

Copper Thin Film ◽

Thin Film Layer

In this paper, the results of a series of heat transfer experiments conducted on a compact electronics cooling device based on single phase jet impingement techniques are reported. Deionized-water is propelled into four microchannels of inner diameter 685 μm which are used as nozzles and located at a nozzle to surface distance of 2.5mm. The generated jet impingement is targeted through these channels towards the surface of a nanostructured plate. This plate of size 20mmx20mm consisted of ∼600 nm long copper nanorod arrays with an average nanorod diameter of ∼150 nm, which were integrated on top of a silicon wafer substrate coated with a copper thin film layer (i.e. Cu-nanorod/Cu-film/Silicon-wafer). Heat removal characteristics induced through jet impingement are investigated using the nanostructured plate and compared to results obtained from a flat plate of copper thin film coated on silicon wafer surface. Enhancement in heat transfer up to 15% using the nanostructured plate has been reported in this paper. Heat generated by small scale electronic devices is simulated using a thin film heater placed on an aluminum base. Surface temperatures are recorded by a data acquisition system with the thermocouples integrated on the surface at various locations. Constant heat flux provided by the film heater is delivered to the nanostructured plate placed on top of the base. Volumetric flow rate and heat flux values were varied in order to better characterize the potential enhancement in heat transfer by nanostructured surfaces.

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Capillary-Limited Evaporation From Well-Defined Microstructured Surfaces

ASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2013-22120 ◽

2013 ◽

Cited By ~ 1

Author(s):

Solomon Adera ◽

Rishi Raj ◽

Evelyn N. Wang

Keyword(s):

Thin Film ◽

Heat Transfer ◽

Heat Flux ◽

Phase Change ◽

Thermal Management ◽

Latent Heat ◽

Thin Film Evaporation ◽

Film Evaporation ◽

Microstructured Surfaces ◽

Latent Heat Of Vaporization

Thermal management is increasingly becoming a bottleneck for a variety of high power density applications such as integrated circuits, solar cells, microprocessors, and energy conversion devices. The performance and reliability of these devices are usually limited by the rate at which heat can be removed from the device footprint, which averages well above 100 W/cm2 (locally this heat flux can exceed 1000 W/cm2). State-of-the-art air cooling strategies which utilize the sensible heat are insufficient at these large heat fluxes. As a result, novel thermal management solutions such as via thin-film evaporation that utilize the latent heat of vaporization of a fluid are needed. The high latent heat of vaporization associated with typical liquid-vapor phase change phenomena allows significant heat transfer with small temperature rise. In this work, we demonstrate a promising thermal management approach where square arrays of cylindrical micropillar arrays are used for thin-film evaporation. The microstructures control the liquid film thickness and the associated thermal resistance in addition to maintaining a continuous liquid supply via the capillary pumping mechanism. When the capillary-induced liquid supply mechanism cannot deliver sufficient liquid for phase change heat transfer, the critical heat flux is reached and dryout occurs. This capillary limitation on thin-film evaporation was experimentally investigated by fabricating well-defined silicon micropillar arrays using standard contact photolithography and deep reactive ion etching. A thin film resistive heater and thermal sensors were integrated on the back side of the test sample using e-beam evaporation and acetone lift-off. The experiments were carried out in a controlled environmental chamber maintained at the water saturation pressure of ≈3.5 kPa and ≈25 °C. We demonstrated significantly higher heat dissipation capability in excess of 100 W/cm2. These preliminary results suggest the potential of thin-film evaporation from microstructured surfaces for advanced thermal management applications.

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Thermal analysis in thin-film fluid regions of rectangular microgroove

Thermal Science ◽

10.2298/tsci160114288g ◽

2018 ◽

Vol 22 (2) ◽

pp. 899-897

Author(s):

Xiaohong Gui ◽

Xiange Song ◽

Baisheng Nie

Keyword(s):

Thin Film ◽

Heat Transfer ◽

Heat Flux ◽

Contact Angle ◽

Film Thickness ◽

Flux Distribution ◽

Total Heat ◽

Heat Flux Distribution ◽

Total Heat Transfer ◽

Thin Film Thickness

The effects of contact angle and superheat on thin-film thickness and heat flux distribution occurring in a rectangle microgroove are numerically simulated. Accordingly, physical, and mathematical models are built in detail. Numerical results indicate that meniscus radius and thin-film thickness increase with the improvement of contact angle. The heat flux distribution in the thin-film region increases non-linearly as the contact angle decreases. The total heat transfer through the thin-film region increases with the improvement of superheat, and decreases as the contact angle increases. When the contact angle is equal to zero, the heat transfer in the thin-film region accounts for more than 80% of the total heat transfer. Intensive evaporation in the thin-film region plays a key role in heat transfer for the rectangle capillary microgroove. The liquid with higher wetting performance is more capable of playing the advantages of higher intensity heat transfer in thin- film region. The current investigation will result in a better understanding of thin- -film evaporation and its effect on the effective thermal conductivity in the rectangle microgroove.

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Flexible Non-Intrusive Heat Flux Instrumentation for the AFRL Research Turbine

Volume 5: Heat Transfer, Parts A and B ◽

10.1115/gt2011-46853 ◽

2011 ◽

Cited By ~ 7

Author(s):

Richard J. Anthony ◽

John P. Clark ◽

Stephen W. Kennedy ◽

John M. Finnegan ◽

Dean Johnson ◽

...

Keyword(s):

Thin Film ◽

Heat Flux ◽

Large Scale ◽

Thermal Loading ◽

Pressure Sensors ◽

Large Data ◽

Fast Response ◽

Data Sets ◽

Unsteady Aerodynamic ◽

Analysis System

This paper describes a large scale heat flux instrumentation effort for the AFRL HIT Research Turbine. The work provides a unique amount of high frequency instrumentation to acquire fast response unsteady heat flux in a fully rotational, cooled turbine rig along with unsteady pressure data to investigate thermal loading and unsteady aerodynamic airfoil interactions. Over 1200 dynamic sensors are installed on the 1 & 1/2 stage turbine rig. Airfoils include 658 double-sided thin film gauges for heat flux, 289 fast-response Kulite pressure sensors for unsteady aerodynamic measurements, and over 40 thermocouples. An overview of the instrumentation is given with in-depth focus on the non-commercial thin film heat transfer sensors designed and produced in the Heat Flux Instrumentation Laboratory at WPAFB. The paper further describes the necessary upgrade of data acquisition systems and signal conditioning electronics to handle the increased channel requirements of the HIT Research Turbine. More modern, reliable, and efficient data processing and analysis code provides better handling of large data sets and allows easy integration with the turbine design and analysis system under development at AFRL. Example data from cooled transient blowdown tests in the TRF are included along with measurement uncertainty.

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Use of Scanning Microphotometer to Determine the Evaporative Heat Transfer Characteristics of the Contact Line Region

Journal of Heat Transfer ◽

10.1115/1.3244461 ◽

1981 ◽

Vol 103 (2) ◽

pp. 325-330 ◽

Cited By ~ 26

Author(s):

R. Cook ◽

C. Y. Tung ◽

P. C. Wayner

Keyword(s):

Thin Film ◽

Heat Transfer ◽

Heat Flux ◽

Contact Line ◽

Heat Transfer Characteristics ◽

Thin Film Thickness ◽

Thickness Profile ◽

Line Region ◽

Evaporative Heat Transfer

A scanning microphotometer was used to measure in situ the profile of an evaporating decane meniscus in the contact line region on a smooth inclined silicon substrate as a function of the evaporative heat flux. The use of this new experimental design to determine the effect of heat flux on the profile in the contact line region is discussed. The results support the hypothesis that fluid flow in the contact line region of an evaporating thin film results from a change in the thin film thickness profile.

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