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Measurement of Thermal Diffusity and Flow Resistance for TCAP Materials

Description: SRS uses the Thermal Cycling Absorption Process (TCAP) to separate isotopes of hydrogen. The frequency of thermal cycles is a limit of the productivity of the process and that frequency is largely determined by the thermal diffusivity of the absorbent material. For a given tube diameter, a larger thermal diffusivity decreases the time required for each cycle. In 1998, the Engineering Development Laboratory measured thermal diffusivity and thermal conductivity for three TCAP materials in helium.
Date: November 11, 2004
Creator: Steimke, John
Partner: UNT Libraries Government Documents Department

Thermal, Electrical, and Structural Analysis of Graphite Foam

Description: A graphite foam was developed at Oak Ridge National Laboratory (ORNL) by Dr. James Klett and license was granted to POCO Graphite, Inc. to manufacture and market the product as PocoFoam™. Unlike many processes currently used to manufacture carbon foams, this process yields a highly graphitic structure and overcomes many limitations, such as oxidation stabilization, that are routinely encountered in the development of carbon foam materials. The structure, thermal properties, electrical resistivity, isotropy, and density uniformity of PocoFoam™ were evaluated. These properties and characteristics of PocoFoam™ are compared with natural and synthetic graphite in order to show that, albeit similar, it is unique. Thermal diffusivity and thermal conductivity were derived from Fourier's energy equation. It was determined that PocoFoam™ has the equivalent thermal conductivity of metals routinely used as heat sinks and that thermal diffusivity is as much as four times greater than pure copper and pure aluminum. SEM and XRD results indicate that PocoFoam™ has a high degree of crystalline alignment and near theoretical d spacing that is more typical of natural flake graphite than synthetic graphite. PocoFoam™ is anisotropic, indicating an isotropy factor of 0.5, and may yield higher thermal conductivity at cryogenic temperatures than is observed in polycrystalline graphite.
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Date: August 2001
Creator: Morgan, Dwayne Russell
Partner: UNT Libraries

Thermal Diffusivity and Conductivity in Ceramic Matrix Fiber Composite Materials - Literature Study

Description: A technical literature review was conducted to gain an understanding of the state of the art method, problems, results, and future of thermal diffusivity/conductivity of matrix-fiber composites for high temperature applications. This paper summarizes the results of test method development and theory. Results from testing on various sample types are discussed with concentration on the anisotropic characteristics of matrix-fiber composites, barriers to heat flow, and notable microstructure observations. The conclusion presents some observations from the technical literature, drawbacks of current information and discusses potential needs for future testing.
Date: May 2, 2000
Creator: Quinn, R.G.
Partner: UNT Libraries Government Documents Department

Thermal transport properties of grey cast irons

Description: Thermal diffusivity and thermal conductivity of grey cast iron have been measured as a function of graphite flake morphology, chemical composition, and position in a finished brake rotor. Cast iron samples used for this investigation were cut from ``step block`` castings designed to produce iron with different graphite flake morphologies resulting from different cooling rates. Samples were also machined from prototype alloys and from production brake rotors representing a variation in foundry practice. Thermal diffusivity was measured at room and elevated temperatures via the flash technique. Heat capacity of selected samples was measured with differential scanning calorimetry, and these results were used to calculate the thermal conductivity. Microstructure of the various cast iron samples was quantified by standard metallography and image analysis, and the chemical compositions were determined by optical emission spectroscopy.
Date: October 1, 1996
Creator: Hecht, R.L.; Dinwiddie, R.B.; Porter, W.D. & Wang, Hsin
Partner: UNT Libraries Government Documents Department

Thermal diffusivity mapping of 4D carbon-carbon composites

Description: High resolution, 2-D thermal diffusivity maps of carbon-carbon composites were obtained by a state-of-the-art infrared thermal imaging system. Unlike the traditional single-point IR detector used for thermal diffusivity measurements, the IR camera is capable of capturing images in its 256 x 256 pixel Focal Plane Array detector in a snap-shot mode. The camera takes up to 200 images at a rate of 120 frames/second. The temperature resolution of the Ir camera is 0.015 C and the spatial resolution is 20 {micro}m. Thermal diffusivity was calculated for each pixel. Four-direction carbon-carbon composites were used for the thermal diffusivity mapping study. The fiber bundles along the heat flow direction were found to have 25% higher diffusivity values than the surrounding matrix. The diffusivity map also showed detailed local variations in diffusivity which were impossible to measure using a single-point detector. Accurate diffusivity maps are very important to the design of composite materials.
Date: March 1997
Creator: Wang, H. & Dinwiddie, R. B.
Partner: UNT Libraries Government Documents Department

Thermal imaging measurement of lateral thermal diffusivity in continuous fiber ceramic composites

Description: Infrared thermal imaging has become a common technique for nondestructive evaluation and measurement of thermal properties in ceramic specimens. Flash thermal imaging can be used to determine two-dimensional through-thickness thermal diffusivity in a planar specimen. In this study, the authors extended the method to determine lateral, or transverse, thermal diffusivity in the specimen. During the flash thermal imaging test, pulsed heat energy is applied to a specimen's back surface, which is partially shielded, and the change of temperature distribution on the front surface is monitored by an infrared thermal imaging system. The temperature distribution represents the effect of both the normal heat transfer through the specimen's thickness and the lateral heat transfer through the interface between the shielded and unshielded back-surface regions. Those temperature distributions are then fitted with a theoretical solution of the heat transfer process to determine the lateral thermal diffusivity at the interface. This technique has been applied to measure lateral thermal diffusivity in a steel plate and a continuous fiber ceramic composite specimen.
Date: February 18, 2000
Creator: Sun, J. G.; Deemer, C. & Ellingson, W. A.
Partner: UNT Libraries Government Documents Department

A correlation of air-coupled ultrasonic and thermal diffusivity data for CFCC materials

Description: An air-coupled (non contact) through-transmission ultrasonic investigation has been conducted on 2D multiple ply Nicalon{trademark} SiC fiber/SiNC CFCC panels as a function of number of processing cycles. Corresponding thermal diffusivity imaging was also conducted. The results of the air-coupled ultrasonic investigation correlated with thermal property variations determined via infrared methods. Areas of delaminations were detected and effects of processing cycles were also detected.
Date: January 1, 1997
Creator: Pillai, T.A.K.; Easler, T.E. & Szweda, A.
Partner: UNT Libraries Government Documents Department

JET Radiative Mantle Experiments in ELMy H-Mode

Description: Radiative mantle experiments were performed on JET ELMy H-mode plasmas. The Septum configuration was used where the X-point is embedded into the top of the Septum. Argon radiated 50% of the input power from the bulk plasma while Z{sub eff} rose from an intrinsic level of 1.5 to about 1.7 due to the injected Argon. The total energy content and global energy confinement time decreased 15% when the impurities were introduced. In contrast, the effective thermal diffusivity in the core confinement region (r/a = .4--.8) decreased by 30%. Usually, JET ELMy H-mode plasmas have confinement that is correlated to the edge pedestal pressure. The radiation lowered the edge pedestal and consequently lowered the global confinement. Thus the confinement was changed by a competition between the edge pedestal reduction lowering the confinement and the weaker RI effect upon the core transport coefficients raising the confinement. The ELM frequency increased from 10 Hz Type I ELMs, to 200 Hz type III ELMs. The energy lost by each ELM reduced to 0.5% of the plasma energy content.
Date: September 28, 1999
Creator: Budny, R.; Coffey, I.; Dumortier, P.; Grisolia, C.; Strachan, J.D. & al, et
Partner: UNT Libraries Government Documents Department

An Analytical Model for Simulating Heavy-Oil Recovery by Cyclic Steam Injection Using Horizontal Wells, SUPRI TR-118

Description: In this investigation, existing analytical models for cyclic steam injection and oil recovery are reviewed and a new model is proposed that is applicable to horizontal wells. A new flow equation is developed for oil production during cyclic steaming of horizontal wells. The model accounts for the gravity-drainage of oil along the steam-oil interface and through the steam zone. Oil viscosity, effective permeability, geometry of the heated zone, porosity, mobile oil saturation, and thermal diffusivity of the reservoir influence the flow rate of oil in the model. The change in reservoir temperature with time is also modeled, and it results in the expected decline in oil production rate during the production cycle as the reservoir cools. Wherever appropriate, correlations and incorporated to minimize data requirements. A limited comparison to numerical simulation results agrees well, indicating that essential physics are successfully captured. Cyclic steaming appears to be a systematic met hod for heating a cold reservoir provided that a relatively uniform distribution of steam is obtained along the horizontal well during injection. A sensitivity analysis shows that the process is robust over the range of expected physical parameters.
Date: August 9, 1999
Creator: Diwan, Utpal & Kovscek, Anthony R.
Partner: UNT Libraries Government Documents Department

Parameter Identification of a Numerical Transport Code

Description: A parameter identification process is presented to obtain effective, resultant properties of a numerical transport code. The method is demonstrated using NUFT (Nonisothermal Unsaturated-Saturated Flow and Transportation model) [1], as a transport code, and the effective heat conductivity and thermal diffusivity as effective parameters. A numerical application example shows that effective transport code in a variety of boundary conditions.
Date: February 26, 2002
Creator: Danko, G. & Jain, A.
Partner: UNT Libraries Government Documents Department

Final MTI Data Report: Ivanpah Playa

Description: The Savannah River Technology Center (SRTC) conducted four reflectance and thermal vicarious calibrations for the MTI satellite at Ivanpah Playa, California since July 2000. The vicarious reflectance campaigns held on July and September 2000 were a joint effort between SRTC and the Remote Sensing Group (RSG) of the University of Arizona. The campaign conducted on May 2001 at Ivanpah Playa and Roach Lake was a joint effort between SRTC and Los Alamos National Laboratory (LANL). An additional campaign was conducted on March 2002. The results presented here are a summary of our reflectance and thermal campaigns and interpretation of the satellite imagery.
Date: October 24, 2002
Creator: Villa-Aleman, E.
Partner: UNT Libraries Government Documents Department

International Round-Robin Testing of Bulk Thermoelectrics

Description: Two international round-robin studies were conducted on transport properties measurements of bulk thermoelectric materials. The study discovered current measurement problems. In order to get ZT of a material four separate transport measurements must be taken. The round-robin study showed that among the four properties Seebeck coefficient is the one can be measured consistently. Electrical resistivity has +4-9% scatter. Thermal diffusivity has similar +5-10% scatter. The reliability of the above three properties can be improved by standardizing test procedures and enforcing system calibrations. The worst problem was found in specific heat measurements using DSC. The probability of making measurement error is great due to the fact three separate runs must be taken to determine Cp and the baseline shift is always an issue for commercial DSC. It is suggest the Dulong Petit limit be always used as a guide line for Cp. Procedures have been developed to eliminate operator and system errors. The IEA-AMT annex is developing standard procedures for transport properties testing.
Date: November 1, 2011
Creator: Wang, Hsin; Porter, Wallace D; Bottner, Harold; Konig, Jan; Chen, Lidong; Bai, Shengqiang et al.
Partner: UNT Libraries Government Documents Department

Heat Loss by Helicity Injection II

Description: Arguments are reviewed showing that helicity transport always flattens the temperature profile, yielding unit current amplification in SSPX and flat temperature profiles in RFP's whenever the dynamo is active. The argument is based on transport theory yielding a hyper-resistivity {Lambda} {approx} (c{sup 2}/{omega}{sub pc}{sup 2}){chi}{sub c} with electron thermal diffusivity {chi}{sub c}, valid for any process producing a random-walk in electron constants of motion in the unperturbed field. The theory could be tested by deriving {Lambda} from helicity transport in SSPX, by analogy with recent analysis yielding {chi}{sub c} from heat transport. If the predicted ratio {Lambda}/{chi}{sub c} is confirmed, efforts to increase current amplification in SSPX must be based on scenario scenarios consistent with slow helicity transport compared to heat s transport (pulsed reactor, multipulse, neutral beam injection).
Date: April 25, 2006
Creator: Fowler, T K
Partner: UNT Libraries Government Documents Department

Thermal Diffusivity and Conductivity Measurements in Diamond Anvil Cells

Description: We have undertaken a study of the feasibility of an innovative method for the determination of thermal properties of materials at extreme conditions. Our approach is essentiality an extension of the flash method to the geometry of the diamond-anvil cell and our ultimate goal is to greatly enlarge the pressure and temperature range over which thermal properties can be investigated. More specifically, we have performed test experiments to establish a technique for probing thermal diffusivity on samples of dimensions compatible with the physical constraints of the diamond anvil cell.
Date: February 22, 2007
Creator: Antonangeli, D & Farber, D L
Partner: UNT Libraries Government Documents Department

An analytical solution for estimating percolation rate by fitting temperature profiles in the Vadose Zone

Description: We present a simple analytical solution for one dimensional steady heat transfer with convection and conduction through a multi-layer system such as a vadose zone. We assume that each layer is homogeneous and has a constant thermal diffusivity. The mass/heat flow direction is perpendicular to the layers, and the mass flow rate is a constant. The analytical solution presented in this study also assumes constant known temperatures at the two boundaries of the system. Although the analytical solution gives the temperature as a function of a few parameters, we focus on the inverse application to estimate the percolation rate to high degree of accuracy (e.g., to mm/y). In some other cases the solution may also be helpful in characterizing potential lateral flow along layer divides.
Date: March 11, 2003
Creator: Shan, Chao & Bodvarsson, Gudmundur
Partner: UNT Libraries Government Documents Department


Description: In plasmas where the transport processes are dominated by turbulence, it is not always straightforward to identify the magnitude of the experimental transport diffusion coefficients. This is primarily due to the fact that with turbulent transport, the separation of the convective and conductive terms depends upon the type of turbulence and/or the model which is used to describe it. For the energy transport it is not just a matter of deciding whether the convection term is 5/2 or 3/2 times the product of the particle flux and the temperature. It is also important to identify turbulence generated convection terms such as heat pinches which can obscure the correct evaluation of the thermal diffusivity. Here we show that inclusion of the turbulence induced stresses into the transport model identifies a heat pinch term and changes the expression for the thermal diffusivity. Comparison with experimental results shows that the new calculated ion thermal diffusivity is no longer less than the neoclassical value even for plasmas with very good ion thermal confinement.
Date: July 1, 2002
Creator: BAKER, DR
Partner: UNT Libraries Government Documents Department

Thermal imaging and air-coupled ultrasound characterization of a continuous-fiber ceramic composite panels.

Description: SYLRAMIC{trademark} continuous fiber ceramic-matrix composites (Nicalon{trademark} fiber/SiNC matrix) were fabricated by Dow Corning Corporation with the polymer-impregnation and pyrolysis (PIP) process. The composite microstructure and its uniformity, and the completeness of infiltration during processing were studied as a function of number of PIP cycles. Two nondestructive evaluation (NDE) methods, i.e., infrared thermal imaging and air-coupled ultrasound (UT), were used to investigate flat composite panels of two thicknesses and various sizes. The thermal imaging method provided two-dimensional (2D) images of through-thickness thermal diffusivity distributions, and the air-coupled UT method provided 2D images of through-thickness ultrasonic transmission of the panel components. Results from both types of NDEs were compared at various PIP cycles during fabrication of the composites. A delaminated region was clearly detected and its progressive repair was monitored during processing. The NDE data were also correlated to results obtained from destructive characterization.
Date: April 1, 1998
Creator: Sun, J. G.; Easler, T. E.; Szweda, A.; Pillai, T. A. K.; Deemer, C. & Ellingson, W. A.
Partner: UNT Libraries Government Documents Department

Advanced thermal imaging of composites

Description: Composite materials were studied by Scanning Thermal Conductivity Microscope (STCM) and high speed thermography. The STCM is a qualitative technique which is used to study thermal conductivity variations on a sub-micrometer scale. High speed thermography is a quantitative technique for measuring thermal diffusivity with a variable spatial resolution from centimeters down to less than 25 gm. A relative thermal conductivity contrast map was obtained from a SiC/Si3N4 continuous fiber ceramic composite using the STCM. Temperature changes of a carbon/carbon composite after a heat pulse were captured by an IR camera to generate a thermal diffusivity map of the specimen. Line profiles of the temperature distribution showed significant variations as a result of fiber orientation.
Date: June 1, 1996
Creator: Wang, H. & Dinwiddie, R.B.
Partner: UNT Libraries Government Documents Department

Scaling of confinement with isotopic content in deuterium and tritium plasmas

Description: The scaling of the electron thermal diffusivity, {chi}{sub e}, with relative gyro radius, {rho}*, has been measured on TFTR by comparing nearly identical ICRF-heated discharges which differ only in hydrogenic isotopic content. Contrary to the gyro-Bohm scaling ({chi}{sub e} {approximately} {chi}{sub B}{rho}*, where {chi}{sub B} is the Bohm diffusivity) observed on DIII-D when {rho}* was varied through a scan of magnetic field strength, {chi}{sub e} is found to scale inversely with {rho}*. Hence, global energy confinement is 8--11% higher in deuterium-tritium plasmas than in deuterium only plasmas, with the higher stored energy attributed almost entirely to the electrons.
Date: January 1, 1997
Creator: Phillips, C.K.; Scott, S.D. & Bell, M.
Partner: UNT Libraries Government Documents Department