Academic literature on the topic 'Contact-free temperature measurements'
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Journal articles on the topic "Contact-free temperature measurements"
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Bair, Scott. "The Variation of Viscosity With Temperature and Pressure for Various Real Lubricants." Journal of Tribology 123, no. 2 (June 27, 2000): 433–36. http://dx.doi.org/10.1115/1.1308024.
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To date, nearly all analyses of lubricant traction behavior in the Hertzian zone of concentrated contact have been performed with viscosity correlations which understate the effect of pressure and temperature at high pressures. We present viscometer measurements of lubricant viscosity for pressures to 1.4 GPa and temperatures to 165°C for various lubricants including automotive transmission fluids, aerospace lubricants, a turbine oil, and a metal working oil. Parameters of a free-volume correlation are provided for use in numerical modeling of traction, film thickness, and roughness interactions in concentrated contact.
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Kolmanovsky, Ilya, Michael P. Polis, and Irina F. Sivergina. "Identification of the Heat Flux in a Quasi-Static Thermoelastic System." Journal of Dynamic Systems, Measurement, and Control 128, no. 3 (November 28, 2005): 608–16. http://dx.doi.org/10.1115/1.2232685.
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This paper treats the problem of estimating the heat flux through the free end of a thermoelastic rod, which is allowed to come into contact with a rigid obstacle. This problem is motivated by the need to develop techniques for indirect measurement of heating in applications, such as, brake systems and machine tools. Under a quasi-static approximation, the problem becomes that of characterizing thermal processes in the rod. Assuming that direct and exact measurements at the contacting end of the rod cannot be taken, the problem is to determine if there is contact with the obstacle; and if there is contact, to characterize the conductivity processes at the contacting end. We study the case of weighted-average temperature measurements throughout the rod. Identifiability results and on-line recursive estimation procedures are developed.
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Bair, S. "Measurements of real non-Newtonian response for liquid lubricants under moderate pressures." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 215, no. 3 (March 1, 2001): 223–33. http://dx.doi.org/10.1243/1350650011543493.
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A thorough characterization of all viscous flow properties relevant to steady simple shear was carried out for five liquid lubricants of current interest to tribology. Shear stresses were generated to values significant to concentrated contact lubrication. Two types of non-Newtonian response were observed: shear-thinning as a power-law fluid and near rate-independence. Functions and parameters were obtained for the temperature and pressure dependence of the viscosity and of the time constant for the Carreau-Yasuda equation. Results are consistent with free volume and kinetic theory, but directly contradict many assumptions currently utilized for numerical simulation and for extracting rheological properties from contact measurements.
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Poongothai, N., R. Athira, and P. K. Neena. "A Green Approach to Preparing Bio-Inhibitor for Mild Steel Corrosion in Different Acid Mediums." International Journal of Engineering & Technology 7, no. 3.6 (July 4, 2018): 322. http://dx.doi.org/10.14419/ijet.v7i3.6.15124.
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Inhibition efficiency (I. E) of various concentrations of Carica Papaya (C. P)extracts on the corrosion of mild steel (MS) in 1M HCl and 0.5M H2SO4medium was investigated by weight loss and electrochemical methods at room temperature and elevated temperature. Acid extract of C. P was characterized by using FTIR and XRD spectral studies to identify the major constituents present in it. Zeta potential and EDAX analysis were carried out for the extract to identify electrochemical aspect of a particle’s surface, and information about a particle’s dispersibility, aggregability, and adhesion ability can be obtained from this measurement. Surface analysis studies such as FESEM and contact angle measurement were carried out for the C. P extracts to locate the surface coverage of the inhibitor and confirm the hydrophilic nature on the metal surface. Langmuir and Temkin adsorption isotherm confirm the mono layer adsorption and heterogeneity of the MS surface. Thermodynamic data’s such as activation energy, Gibbs free energy, enthalpy and entropy changes were calculated using weight loss measurements data at room as well as elevated temperatures and identified free energy of adsorption and exothermic reaction taking place during corrosion process. Phytochemical studies confirm the presence of chemical constituents with hetero atom that provide more I.E due to its adsorption of inhibitor on metal surface.
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Stephenson, D. A. "Assessment of Steady-State Metal Cutting Temperature Models Based on Simultaneous Infrared and Thermocouple Data." Journal of Engineering for Industry 113, no. 2 (May 1, 1991): 121–28. http://dx.doi.org/10.1115/1.2899668.
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Several models for metal cutting temperatures which could be applied in simulation programs have been reported in the literature. Since the temperature predicted by the models are difficult to measure, however, there is not sufficient experimental data to determine which available model is most accurate and whether further theoretical refinement is needed. In this paper calculations from four steady-state cutting temperature models are compared with simultaneous infrared and tool-chip thermocouple temperature measurements from end turning tests on 1018 steel, 2024 aluminum, free machining brass, and gray cast iron tubes. Deformation zone temperatures calculated using the models are compared to source temperatures determined from infrared measurements using a new inverse method. Calculated tool-chip contact temperatures are compared to rake face temperatures measured by the widely used tool-work thermocouple method. The data indicates most models, though quantitatively accurate, overestimate cutting temperatures. Models based on Jaeger’s friction slider solution which include workpiece thermal property variations, however, generally give results accurate to within the reliability of experimentai methods for the materials tested. Loewen and Shaw’s model, recently generalized to three-dimensional cutting by Venuvinod and Lau, seems most accurate over a broad range of workpiece and cutting conditions. No model accurately predicts tool-chip temperatures for cast iron or 2024 aluminum, indicating that further theoretical refinement for discontinuous chip formation is needed.
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Jiang, Guojun, and Sheng Xie. "Comparison of AFM Nanoindentation and Gold Nanoparticle Embedding Techniques for Measuring the Properties of Polymer Thin Films." Polymers 11, no. 4 (April 3, 2019): 617. http://dx.doi.org/10.3390/polym11040617.
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The surfaces of polymer and interfaces between polymer and inorganic particles are of particular importance for the properties of polymers and composites. However, the determination of the properties of surfaces and interfaces poses many challenges due to their extremely small dimensions. Herein, polystyrene and polymethyl methacrylate thin film on silicon wafer was used as a model system for the measurement of the properties of the polymer near free surface and at the polymer-solid interface. Two different methods, i.e., nanoindentation using atomic force microscopy (AFM) and the gold nanoparticle embedding technique, were used for these measurements. The results showed the elastic modulus of PS near the free surface determined by nanoindentation was lower than the bulk value. Based on contact mechanics analysis, nanoparticle embedding also revealed the existence of a lower-modulus, non-glassy layer near the free surface at temperatures below the bulk glass transition temperature (Tg). However, near the polymer-solid interface, the AFM nanoindentation method is not applicable due to the geometry confinement effect. On the other hand, the nanoparticle embedding technique can still correctly reflect the interactions between the polymer and the substrate when compared to the ellipsometry results.
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Kim, Jae Kwan, and Kahp Y. Suh. "Room Temperature Detachment Nanolithography Using a Rigiflex Polymeric Mold." Journal of Nanoscience and Nanotechnology 8, no. 7 (July 1, 2008): 3621–25. http://dx.doi.org/10.1166/jnn.2008.162.
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We report on detachment nanolithography of an organic thin film at room temperature mediated by ultraviolet (UV) exposure. A nanopatterned, UV curable polyurethane acrylate (PUA) mold was placed on a spin-coated organic film made of 4,4′-bis[N-1-napthyl-N-phenyl-amino]biphenyl (NPB) under a low pressure (1–2 bar). A higher work of adhesion at the organic/mold interface induced detachment of the contacting layer on silicon or gold substrate, resulting in well-defined nanopatterns without a residual layer. The detachment was highly improved by a short-term UV exposure, rendering the film surface free from contaminant hydrocarbons with a lower cohesive force, as confirmed by Fourier transform infrared (FTIR) spectroscopy and measurements of contact angle of water.
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Kakar, Muhammad Rafiq, Meor Othman Hamzah, Mohammad Nishat Akhtar, and Junita Mohamad Saleh. "Evaluating the Surface Free Energy and Moisture Sensitivity of Warm Mix Asphalt Binders Using Dynamic Contact Angle." Advances in Civil Engineering 2019 (March 3, 2019): 1–15. http://dx.doi.org/10.1155/2019/9153603.
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From the environmental conservation perspective, warm mix asphalt is more preferable compared to hot mix asphalt. This is because warm mix asphalt can be produced and paved in the temperature range 20–40°C lower than its equivalent hot mix asphalt. In terms of cost-effectiveness, warm mix asphalt can significantly improve the mixture workability at a lower temperature and thus reduce greenhouse gas emissions, to be environment friendly. However, the concern, which is challenging to warm mix asphalt, is its susceptibility to moisture damage due to its reduced production temperature. This may cause adhesive failure, which could eventually result in stripping of the asphalt binder from the aggregates. This research highlights the significance of Cecabase warm mix additive to lower the production temperature of warm mix asphalt and improvise the asphalt binder adhesion properties with aggregate. The binders used in the preparation of the test specimen were PG-64 and PG-76. The contact angle values were measured by using the dynamic Wilhelmy plate device. The surface free energy of Cecabase-modified binders was then computed by developing a dedicated algorithm using the C++ program. The analytical measurements such as the spreadability coefficient, work of adhesion, and compatibility ratio were used to analyze the results. The results inferred that the Cecabase improved the spreadability of the asphalt binder over limestone compared to the granite aggregate substrate. Nevertheless, the Cecabase-modified binders improved the work of adhesion. In terms of moisture sensitivity, it is also evident from the compatibility ratio indicator that, unlike granite aggregates, the limestone aggregates were less susceptible to moisture damage.
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Diehl, K., M. Debertshäuser, O. Eppers, H. Schmithüsen, S. K. Mitra, and S. Borrmann. "Particle surface area dependence of mineral dust in immersion freezing mode: investigations with freely suspended drops in an acoustic levitator and a vertical wind tunnel." Atmospheric Chemistry and Physics 14, no. 22 (November 25, 2014): 12343–55. http://dx.doi.org/10.5194/acp-14-12343-2014.
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Abstract. The heterogeneous freezing temperatures of supercooled drops were measured using an acoustic levitator. This technique allows one to freely suspend single drops in the air without any wall contact. Heterogeneous nucleation by two types of illite (illite IMt1 and illite NX) and a montmorillonite sample was investigated in the immersion mode. Drops of 1 mm in radius were monitored by a video camera while cooled down to −28 °C to simulate freezing within the tropospheric temperature range. The surface temperature of the drops was contact-free, determined with an infrared thermometer; the onset of freezing was indicated by a sudden increase of the drop surface temperature. For comparison, measurements with one particle type (illite NX) were additionally performed in the Mainz vertical wind tunnel with drops of 340 μm radius freely suspended. Immersion freezing was observed in a temperature range between −13 and −26 °C as a function of particle type and particle surface area immersed in the drops. Isothermal experiments in the wind tunnel indicated that after the cooling stage freezing still proceeds, at least during the investigated time period of 30 s. The results were evaluated by applying two descriptions of heterogeneous freezing, the stochastic and the singular model. Although the wind tunnel results do not support the time-independence of the freezing process both models are applicable for comparing the results from the two experimental techniques.
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Lindemann, Joerg, Kerstin Wiesmiller, Tilman Keck, and Konrad Kastl. "Dynamic Nasal Infrared Thermography in Patients with Nasal Septal Perforations." American Journal of Rhinology & Allergy 23, no. 5 (September 2009): 471–74. http://dx.doi.org/10.2500/ajra.2009.23.3351.
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Background Nasal obstruction is a typical symptom in patients with nasal septal perforations. Rhinomanometry and acoustic rhinometry are not reliable in these cases because the perforations generate incorrect results. Infrared thermography camera (ITC) systems allow contact-free intranasal recordings of the nasal surface temperature and the semiquantification of nasal airflow. The aim of this study was to perform contact-free temperature measurements of the nasal vestibular surface by application of ITC systems in patients with septal perforations to investigate the disturbed intranasal heat exchange and nasal airflow. Methods The surface temperature profiles within the nasal vestibules of healthy volunteers (n = 10) and patients with septal perforations (n = 3) were recorded with an ITC during several breathing cycles. Thermal images were taken (60/s) displaying the surface temperature in degrees centigrade corresponding to a color scale. Results The temperature recordings showed a disturbed intranasal heat exchange during inspiration and expiration in patients with septal perforations in comparison with healthy subjects. A reduced and irregular inspiratory cooling of the entire surface within the nasal vestibules visualizes a reduced and disturbed airflow volume. Conclusion The study was able to prove the feasibility of intranasal temperature recordings of the surface with an ITC system in patients with septal perforations. Contrary to rhinomanometry and acoustic rhinometry, thermography cameras can be applied to examine airflow in patients with septal perforations. The detected reduced cooling of the surface during inspiration might be a possible explanation for the patients' feelings of nasal obstruction.
Dissertations / Theses on the topic "Contact-free temperature measurements"
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Mikula, Martin. "Termodiagnostika - dotykové a bezdotykové měření teploty." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231525.
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This thesis is concerned with thermodiagnostics in industrial practise, which is very important for the assessment of technical condition of object on the basis of temperature, in today's time. It includes summary of contact and contact-free methods and their principle, advantages and disadvantages for aplication in industrial practise. Because of thesis it was carried out measurement in company Daikin Device Czech republic with the use of contact thermometer and two available thermocameras for solving of topical tasks relating to production.
Conference papers on the topic "Contact-free temperature measurements"
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Perez-Diaz, J. L., M. A. Alvarez-Valenzuela, I. Valiente-Blanco, S. Jimenez-Lopez, M. Palacios-Cuesta, O. García, E. Diez-Jimenez, J. Sanchez-García-Casarrubios, and C. Cristache. "On the Influence of Relative Humidity on the Contact Angle of a Water Droplet on a Silicon Wafer." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63781.
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Contact angle analysis of liquids on surfaces has been extensively used to evaluating solid surface free energy, surface tension, and surface wetting characteristics. Despite the great interest in the contact angle, reported measurements has shown a high variety, which is often related to different contact angle measurement techniques or substrate preparation and oxidation among others. In addition, it is well know, that surface tension and contact angle are modified with temperature. However, no attention has been paid to the influence of the relative humidity (RH) in surface tension or contact angle measurements. In a previous work, we have demonstrated that (for a constant temperature) surface tension on a suspended droplet decreases linearly with RH in the air. In this paper, contact angle of a water droplet on a silicon wafer surface is studied and its relationship with the relative humidity in the air investigated.
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Pettes, Michael T., and Li Shi. "Thermal Conductance of Individual Single-Wall Carbon Nanotubes." In ASME 2008 3rd Energy Nanotechnology International Conference collocated with the Heat Transfer, Fluids Engineering, and Energy Sustainability Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/enic2008-53028.
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This work presents an experimental study of phonon transport in individual suspended single-wall carbon nanotubes (SWCNTs). Through the use of a micro fabricated device consisting of two adjacent suspended membranes, each with a platinum resistance heater and thermometer, the thermal conductance of several individual SWCNTs has been directly measured over the temperature range of 100 to 490 K. The effects of Umklapp phonon-phonon scattering remain weak and the thermal conductance remains roughly proportional to the calculated ballistic conductance throughout the temperature range. The macroscopic thermal conductance increases with temperature throughout the temperature range indicating static scattering processes or contact thermal resistance dominate transport in this regime. These results are an order of magnitude lower than the predicted ballistic thermal conductance calculated for a defect-free (18,0) nanotube. The results contrast with thermal conductance measurements reported using a high-bias DC self heating method. The discrepancy is discussed in terms of the differences in the contact thermal resistance, defects, and measurement methods.
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Freund, S., and S. Kabelac. "Measurement of Local Convective Heat Transfer Coefficients With Temperature Oscillation IR Thermography and Radiant Heating." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72855.
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A method using temperature oscillations to measure local convection coefficients from the outside of a heat-transferring wall has been developed. This method is contact-free, employing radiant heating with a laser and an IR camera for surface temperature measurements. The numerical model extends previous research to three dimensions and allows for rapid evaluation of the convection coefficients distribution of sizable heat exchanger areas. The technique relies first on experimental data of the phase-lag of the surface temperature response to periodic heating, and second on a numerical model of the heat-transferring wall that computes the local convection coefficients from the processed data. The temperature data processing includes an algorithm for temperature drift compensation and Single Frequency Discrete Fourier Transformations. The inverse heat conduction problem of deriving a surface map of convection coefficients from the phase-lag data is solved with a new numerical approach based on a complex 3-D finite-difference method. To validate the experimental approach, measurements of the temperature response of a semi-infinite specimen were analyzed. The results obtained were within 1.6% agreement with the analytical solution. The numerical model was verified by comparison with data generated by the FEM program ANSYS. The results of preliminary experiments investigating the local Nusselt number of water entering a tube are in agreement with established correlations. Future applications of this method will involve an aerodynamic vortex generator in a wind tunnel and plate heat exchangers. Another possible application of the experimental method is non-destructive testing of materials known as Lock-In Thermography.
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Ordonez, Richard C., Noah Acosta, Jordan Melcher, Nackieb Kamin, and David Garmire. "Investigation of Liquid Metal Ohmic Contacts for Graphene Photonic Devices." In ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ipack2015-48567.
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We demonstrate the first contact resistance measurements of graphene–galinstan (g-g) ohmic contacts in an effort to improve the performance of graphene photonic devices. The nobility of carbon materials provide an interesting graphene sensor application to explore an oxidation free liquid metal - semimetal interface that can be used to lower contact resistance at source/drain terminals of a standard graphene phototransistor. Our methods utilize photopolymerization of the reactive monomer Trimethlylolpropane Triacrylate (TMPTA) in order to fabricate micro structures necessary to overlay liquid metal contacts on graphene. With the use of an industry standard transfer length method (TLM), a contact resistance of −124±28Ω was measured at both standard temperature and pressure. The results from our study suggest that liquid metals such as galinstan are comparable alternatives to rigid semiconductor interfaces and demonstrates interesting boundary characteristics that may lead to heavy chemical doping and associated low resistance contacts that are required to increase sensitivity in graphene photonic devices.
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Wang, Xi, and Ali Shakouri. "Thermal Characterization of a Single MOSFET Transistor at Cryogenic Temperatures." In ASME 2009 InterPACK Conference collocated with the ASME 2009 Summer Heat Transfer Conference and the ASME 2009 3rd International Conference on Energy Sustainability. ASMEDC, 2009. http://dx.doi.org/10.1115/interpack2009-89084.
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The aggressive miniaturization trend in microelectronic design has pushed the transistor gate length to a range of hundreds of nanometers. The study of heat transport and dissipation at the device level is becoming an important part of the overall thermal design. In general, temperature non-uniformity peaks in the transistor drain region due to the higher electric potential field and electron thermalization close to the drain. Drastic changes in both electrical current flow and the thermal heat flow to the heat sink can be caused by this localized temperature non-uniformity. Ballistic transport that happens when gate length approaches the phonon mean free path re-shapes the temperature distribution. Extensive theoretical studies have been done in this area during the past several years [1–3], but no direct experimental observation has yet been reported. The main challenge is the possibility to detect electron and/or lattice temperatures in sub micron ranges. In this paper, we measure the surface temperature distribution of a 180nm gate length silicon MOSFET (Metal Oxide Semiconductor Field Effect Transistor) at both ambient and cryogenic temperatures (10K). The purpose of cryogenic measurement is that the temperature distribution is significantly modified due to much longer phonon ballistic transport as well as possible thermal resistance change. We used thermoreflectance imaging to measure the surface temperature with 100’s nm spatial resolution and 0.1C° temperature resolution [4]. Thermoreflectance is a non-contact, nondestructive thermal characterization technique which is suitable for small scale, high precision measurements. A cryostat is used to keep the sample cold during experiment. The sample chamber is also kept at high vacuum condition (< 1e−5 torr) to prevent condensation and heat loss through air convection. Preliminary results show qualitative changes in the temperature distribution.
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Borca-Tasciuc, Theodorian. "Heat Conduction Across Nanoscale Interfaces and Nanomaterials for Thermal Management and Thermoelectric Energy Conversion." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-31312.
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Nanoscale heat conduction plays a critical role in applications ranging from thermal management of nanodevices to nanostructured thermoelectric materials for solid state refrigeration and power generation. This lecture presents recent investigations in our group. The first part of the lecture demonstrates heat conduction across nanoscale interfaces formed between individual nanoscale heaters and the silicon substrate [1]. A systematic experimental study was performed of thermal transport from individual nanoscale heaters with widths ranging between 77nm-250nm to bulk silicon substrates in the temperature range of 80–300K. The effective substrate thermal conductivity was measured by joule heating thermometry. We report up to two orders of magnitude reductions in the measured effective thermal conductivity of the silicon substrate when the heater widths are smaller than the mean free path of the heat carriers in the substrate, as summarized in Fig. 1. The effective mean free path of the silicon substrate was extracted from the measurements and was found to be comparable with recent molecular dynamics simulations. A proof of concept demonstration of a novel Thermal Interface Material (TIM) is presented next. The high thermal conductivity TIM is based on a highly connected high thermal conductivity nanostructured filler network embedded in a polymer matrix where the contribution of filler-matrix interfaces to thermal resistance is minimized. It was found [2] that the thermal conductivity could be varied from ∼0.2 to 20 W/mK when the volume fraction of metallic nanoparticles was varied from 0–20%. For similar volume fractions and filler composition, microparticle based composites have two orders of magnitude lower thermal conductivities. SEM characterization and thermal transport modeling are employed to support the conclusion that morphological changes in the nano-TIM are responsible for the thermal conductivity reduction. Thermoelectric transport investigations are discussed for a novel class of highly scalable nanostructured bulk chalcogenides developed at Rensselaer Polytechnic Institute [3]. Un-optimized, single-component bulk assemblies of Bi2Te3 and Sb2Te3 single crystal nanoplates show large enhancements (25–60%) in the room temperature thermoelectric figure of merit compared with individual bulk counterparts (Table 1). Nanostructuring was found to lead to strong thermal conductivity reduction without significantly affecting the mobility of the charge carriers, as shown in Table 2. A scanning thermal microprobe technique developed for simultaneous thermal conductivity (κ) and Seebeck coefficient (α) measurements in thermoelectric films is also presented [4]. In this technique, an AC alternative current joule-heated V-shaped microwire that serves as heater, thermometer and voltage electrode, locally heats the thin film when contacted with the surface (Fig. 2). The κ is extracted from the average DC temperature rise thermal resistance of the microprobe and α from the DC Seebeck voltage measured between the probe and unheated regions of the film by modeling the heat transfer in the probe, sample and their contact area, and by calibrations with standard reference samples. Application of the technique on sulfur-doped porous Bi2Te3 and Bi2Se3 films reveals α = −105.4 and 1.96 μV/K, respectively, which are within 2% of the values obtained by independent measurements carried out using microfabricated test structures. The respective κ values are 0.36 and 0.52 W/mK, which are significantly lower than the bulk values due to film porosity, and are consistent with effective media theory. The dominance of air conduction at the probe-sample contact area determines the microscale spatial resolution of the technique and allows probing samples with rough surfaces. Non-contact mode measurement of thermal conductivity was also demonstrated and confirmed by independent characterization [5]. In non-contact mode the technique utilizes ballistic air conduction as the dominant heat transfer mechanism between the thermal probe and the sample and thus eliminates uncertainties due to solid contact and liquid meniscus conduction.
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Sim, Kyuho, Jin Woo Song, Yong-Bok Lee, and Tae Ho Kim. "Thermal Performance of a Bump Type Gas Foil Bearing Floating on a Hollow Shaft for Increasing Rotating Speed and Static Load." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46499.
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Identifying thermal characteristics of gas foil bearings (GFBs) provides an insight for successful implementation into high speed oil-free turbomachinery. The paper presents temperature measurements of a bump type GFB floating on a hollow shaft for various operating conditions. Two angular ball bearings support the hollow shaft at one end (right), and the other end (left) is free. Test GFB has the outer diameter of 100 mm and the axial length of 45 mm, and the hollow shaft has the outer and inner diameters of 60 mm and 40 mm, respectively. An electric motor drives the hollow shaft using a spline coupling connection. A mechanical loading device provides static loads on test GFB upward via a metal wire, and a strain gauge type load cell placed in the middle of the wire indicates the applied loads. During experiments for shaft speeds of 5 krpm, 10 krpm, and 15 krpm and with static loads of 58.86 N (6 kgf), 78.48 N (8 kgf), and 98.1 N (10 kgf), twelve thermocouples measure the outer surface temperatures of test GFB at four angular locations of 45 deg, 135 deg, 215 deg, and 315 deg, with an origin at the top foil free end, and three axial locations of bearing centerline and both side edges at each angle. Two infrared thermometers measure the outer surface temperature of the hollow shaft at free and supported ends close to test GFB. Test results show that GFB temperatures increase as the shaft speed increases and as the static load increases, with higher temperatures in the loading zone (135 deg and 215 deg) than those in the unloading zone (45 deg and 315 deg). In general, the recorded temperatures are highest at 225 deg where a highest hydrodynamic pressure is expected to build up. Measured temperatures at the bearing centerline are higher than those at the side edges, as expected. In addition, large thermal gradients are recorded in the hollow shaft along the axial direction with higher temperatures at the supported end. Angular ball bearings and lip seal supporting the hollow shaft might produce significant heat generation due to mechanical contact as the shaft speed increases. The axial thermal gradient of the shaft is thought to cause higher temperatures at the bearing right edge facing the ball bearing support than those at the left edge. The present test data along with detailed test GFB/shaft geometries and material properties benchmark thermohydrodynamic (THD) model predictions of test GFB with a rotating hollow shaft.
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Pavlidis, Georges, James Dallas, Sukwon Choi, Shyh-Chiang Shen, and Samuel Graham. "Steady State and Transient Thermal Characterization of Vertical GaN PIN Diodes." In ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2017 Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ipack2017-74149.
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In this work, we investigate the thermal response of GaN PIN diodes grown on a sapphire substrate and compare the results to GaN PIN diodes grown on a free standing GaN substrate (FS-GaN). Until now, thermal characterization techniques have been developed to assess the temperature distribution across lateral devices. Raman thermometry has shown to accurately measure the temperature rise across the depth of the GaN layer. Implementing this technique to assess the temperature distribution across the depth of a vertical GaN device is more challenging since a volumetric depth average is measured. The use of TiO2 nanoparticles is shown to overcome this issue and reduce the uncertainty in the peak temperature by probing a surface temperature on top of the device. For the sapphire substrate, an additional temperature rise of about 15 K was seen on the surface of the PIN diode as compared to the average in the bulk. While the steady state thermal measurements show an accurate estimation of the device’s peak temperature, the PIN diodes are normally operated under pulsed conditions and the thermal response of these devices under periodic joule heating must be assessed. A recently developed transient thermoreflectance imaging technique (TTI) is used in this study to monitor transient temperature rise and decay of top metal contact. Under the same biasing conditions, the FS-GaN PIN diode is found to result in less than half the temperature rise obtained by the sapphire substrate diode. Extracting time constants, a longer rise and decay is also observed in the sapphire substrate diode.
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Saab, Joseph, Ramy Abou Naccoul, Juliette Stephan, Rosette Ouaini, Jacques Jose, and Naim Ouaini. "Dynamic Fluid Saturation Method for Hydrocarbons Thermodynamics’ Properties Determination." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37114.
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Low solubility compounds suffer from lack of data, leading to an impoverishment in thermodynamic parameters such as Gibbs free energy (ΔG), enthalpy of dissolution (ΔH), entropy (ΔS), infinite dilution coefficient (γ∞) and isobaric heat capacity (Cp) of utmost practical importance for industrial optimization processes. Dynamic fluid method is a novel technique for low solubility (expressed as molar fraction χ) determination based on the saturation of a specific heated fluid passing through a saturation cell. The heated components are kept inside a chromatographic oven maintained at a constant temperature to within ± 0.05°C by means of a PID temperature controller. A regular stream of fluid, using a constant flow pump, passes through the saturation cell packed with an inert stationary phase (Gaz chrom R 60/80) pre-coated with the organic compound. The solute transported by the fluid is subsequently trapped in a specific extraction column (inverse phase). The organic compound is removed by back flushing using the appropriate solvent in order to dissolve and carry out the totality. A low flow of fluid through the generator column is to be set to avoid safely the formation of colloidal dispersion, to increase the contact time and to keep small pressure drops across the generator/extractor column. The gas chromatography coupled to mass spectrometer detector is used in order to quantify the solute. The validation of this apparatus was achieved by comparison of our values with the ones extracted from previous papers using the static method to determine aqueous solubility of the ethylbenzene, and a precision of our solubility measurements was established to be better than 0.2%. In continuous, aqueous solubility and thermodynamics properties of perfluorocarbons compounds were determined in the range of temperature from 273 K to 333 K. Considering the contribution of chromatographic, calibration and other operational errors, the combined measurement uncertainty (standard deviation) was established to be less than 3%.
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Coste, Pierre, Je´roˆme Pouvreau, Je´roˆme Lavie´ville, and Marc Boucker. "A Two-Phase CFD Approach to the PTS Problem Evaluated on COSI Experiment." In 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48882.
Full textAbstract:
The study is done in the context of Pressurized Thermal Shock (PTS) CFD investigations related to PWR life duration safety studies. In the simulations of such situations direct contact condensation on free surfaces much larger than cells size is a key phenomenon. Those large interfaces require a special full set of models which has been recently implemented in the NEPTUNE_CFD code. Out of large interfaces regions, some dispersed or churn flows can take place. Both situations can be taken into account in the computational domain. The approach includes an interface recognition but not an interface reconstruction. It is evaluated on COSI experiment. COSI facility is scaled 1/100 for volume and power from a 900 MW PWR under LOCA thermal hydraulic conditions. Measurements include temperature profiles at various axial positions in the pipe. The paper focuses on one test corresponding to a situation with a low water level in the leg. It is a demanding case for two-phase CFD because -a- the liquid layer which is of prime importance in PTS studies can be quite thin in comparison with the whole computational domain -b- the emergency core cooling jet plays an important role. Results are within a reasonable range even with a coarse mesh. Calculations with finer meshes quantify the effect of a better simulation of the jet fall and impact on the wall.