Effective thermal conductivity

This experiment was carried out with an aim of evaluating viscosity of drilling mud by using Marsh Funnel Viscometer. Viscosity of drilling fluid is a very crucial parameter since it influences fluid's ability to carry cuttings, fluid circulation and drilling efficiency. Viscosity plays a major role in ensuring wellbore stability.

Drilling mud in the experiment was poured in a Marsh funnel and the time needed for a definite amount of mud to pass from the funnel was calculated. This value was used to estimate viscosity of drilling fluid. The results of the experiment were used to estimate suitability of drilling mud viscosity.

It can be seen that the Marsh Funnel Viscometer is a very effective instrument for measuring viscosity of drilling fluids. This method enables quick evaluation of the parameter and can be carried out both in the lab and in the field conditions.

This experiment aimed at determining the density of the mud in the drilling fluid using a mud balance. The density of the mud is among the most critical parameters of drilling fluid since it regulates formation pressure, keeps the wellbore stable and prevents blowout and lost circulation during drilling.

In this experiment, a mud balance was used to obtain an accurate determination of the density of the drilling mud sample. The mud was introduced to the balance cup and its weight was regulated until equilibrium was obtained. The respective value was then determined to be the mud density in the required units. This result would be analyzed to assess the suitability of the drilling fluid for drilling operation.

It has been demonstrated through this experiment that mud balance is a relatively straightforward instrument which is very useful in determining drilling fluid density.

The flow characteristics of purge gas helium in the pebble bed of the tritium breeding blanket are important in analyzing the tritium purging process and optimizing the design of the solid breeder blanket. Therefore, the flow characteristics of helium gas in randomly packed pebble beds are investigated experimentally with a focus on the analysis of the pressure loss distribution. The results show that gas velocity, bed dimension, and pebble diameters have an obvious influence on the helium flow characteristics in pebble beds. With the increase in the inlet helium gas velocity, the pressure drop gradient of helium in the pebble bed gradually increased. With increases in the pebble bed dimension, the pressure drop gradient of helium in the pebble bed gradually increased. With the increase in the pebble diameter, the pressure drop gradient gradually decreased. In addition, the effect of temperature on the pressure drop of helium in the pebble bed was also preliminarily investigated. The pressure drop gradient of the helium through the pebble bed obviously increased with the increase in the helium and the bed temperature. The experimentally obtained pressure loss characteristics can be used for the validation of the simulation of a blanket pebble bed and as input parameters in the thermo-hydraulic analysis of solid-tritium breeder blankets.

This book provides some of the most advanced research observations and in-depth knowledge behind lead-free soldering. Readers will find a description of different cutting-edge techniques used for improving the reliability of interconnects manufacturing. Some of the most unconventional topics covered in this book include solder joint formation for microelectronic devices at room temperature and the possibility of soldering ceramic materials, which is limited due to the poor wettability of ceramic substrates with commercial solders following classical soldering techniques. We also discuss the possibilities of nanoscale preparation of solder joints for bringing down the processing temperature so that it does not affect the packaging technologies. Readers will find that precise, systematic discussion of solder joint formation and its interfacial characterization has been depicted for each technique used in different chapters. This book is of interest to both fundamental researchers and ...

Analysis of potential of the guarded hot plate method and non-stationary temperature regime for experimental estimation of the thermal diffusivity and specific heat capacity of homogenous building materials is described in this paper. The advantages/disadvantages of different measurement schemes are analysed. Numerical estimation of accuracy influence of the process parameters is presented.

After giving the theoretical summary of the structure function method for the evaluation the thermal transient measurement results, the broad applicability of the method is demonstrated by practical examples. The first example shows how to control the quality of the die attachment or soldering of packages with fast transient measurements and subsequent evaluation. The second example presents how can transient testing be used to determine thermal material parameters; e.g. the effective thermal conductivity of printed circuit boards. Thermal Challenges in Next Generation Electronic Systems, Joshi & Garimella (eds)

The thermal conductivity of a solid thin film was investigated by using two nonequilibrium molecular dynamics (NEMD) methods and changing the calculation conditions. Solid argon was selected as a target material because it has a typical Lennard-Jones (L-J) potential; hence, there was no need to consider the contribution by free electrons to a thermal conductivity. The results were not influenced by the adopted NEMD method, and there were no appreciable effects due to changes in the calculation conditions. The thermal conductivities calculated by using the MD simulations were compared with the available experimental data obtained from the bulk state, and the system's temperature and internal stress were confirmed to affect the thermal conductivity. From our investigation, the internal stress is explicitly an important factor that influences the thermal conductivity of solids; a micro-scale system has a lower thermal conductivity than the bulk material does. The temperature dependence was also carefully investigated, and good qualitative agreement with existing experimental data was obtained.

This paper presents detailed numerical simulations predicting the effective thermal conductivity of spherical monodisperse and polydisperse core-shell particles ordered or randomly distributed in a continuous matrix. First, the effective thermal conductivity of this three-component composite material was found to be independent of the capsule spatial distribution and size distribution. In fact, the study established that the effective thermal conductivity depended only on the core and shell volume fractions and on the core, shell, and matrix thermal conductivities. Second, the effective medium approximation reported by Felske (2004) [21] was in very good agreement with numerical predictions for any arbitrary combination of the above-mentioned parameters. These results can be used to design energy efficient composites, such as microencapsulated phase change materials in concrete and/or insulation materials for energy efficient buildings.

The metal hydride reactors are widely used in many industrial applications, for example, hydrogen storage, heat pump, thermal compression, gas separation, etc. The performance of the reactor is greatly affected by its design, which deserves careful study. Given the complicated nature of the hydride formation/decomposition processes, a series of technical issues are involved in the design of metal hydride reactors, such as primary configuration, thermal management, hydrogen transfer and mechanistic strength. These issues should be well addressed to fulfil the requirement of specific application. In this paper, the representative achievements with regards to the design issues so far were reviewed in detail, and some comments were made accordingly. It was concluded that an optimized reactor design comes from integrated considerations of numerous factors, particularly requirements for the applications and characteristics of the metal hydride system. The analytic hierarchy process was recommended for use in the selection of the optimum reactor scheme.

Solar cooling is a promising solution to overcome the high energy demand of buildings. Nevertheless, the time dependent nature of the solar source leads to the need of storage systems in order to better match the energy demand and supply. For this purpose, thermal energy storage was considered during last decades as the optimal solution at commercial scale. Latent thermal energy storage offers higher energy densities together with more constant outlet temperature than sensible heat storage, but the low thermal conductivities of PCMs represents the main drawback which limits its applicability. Several studies based on heat transfer enhancement techniques applied in latent thermal energy storage have already been performed. Specifically, the technique of adding fins in storage tanks, which is the most known and studied. However, there are few experimental studies at pilot plant scale focused on this technique and less on the analysis of the heat transfer enhancement through the parameter effective thermal conductivity. This paper presents an experimental study where this parameter is determined and compared using of two identical latent storage tanks, one with 196 transversal squared fins and another one without fins. In this case, hydroquinone was selected as PCM. A set of six experiments was performed at pilot plant of the University of Lleida (Spain), combining three different HTF flow rates and two temperature gradients between HTF inlet temperature and initial PCM temperature. Experimental results showed that the addition of fins can increase the effective thermal conductivity between 4.11% and 25.83% comparing the experiment with highest and lowest thermal power supplied to the PCM, respectively.

The present study aims at investigating an opportunity of enhancing heat conduction ability of a typical particulate filled polymer composite. A mathematical correlation for evaluating the effective thermal conductivity (keff) of polymer composites filled with elliptical shape particles is developed. To validate this model, high thermal conductivity aluminium powders were incorporated in the epoxy matrix for the first set of polymer composites whereas, for the second set, an industrial waste, i.e., red mud is taken as a filler material. Simple hand lay-up technique is used for fabrication purpose. Thermal conductivities of these fabricated composite samples are determined experimentally using the Unitherm™ Model 2022 tester which works on the principle of double guarded heat flow meter method according to ASTM E1530 standard. Measured values are then compared with the values obtained from the proposed mathematical model and also with some already existing correlation. It has been observed that the results obtained from the proposed model fits well with the experimental data. An improvement of about 260% in the value of keff is recorded with addition of 25 vol% of aluminium filler in epoxy resin whereas with similar loading of red mud, it is noticed that keff increases by about 200%. Apart from this thermal investigation, physical properties like density and void content along with morphological behaviour of the fabricated composites are also reported.

Three aspects of the finite radius of spherical particles in disperse two-phase flows are described. The first one is the relation between the exact volume fractio~n and the widely used approximation nv (n is the particle number density and v is the particle volume). The approximation affects the behavior of the effective equations at short wavelengths with possible consequences on stability and hyperbolicity. Secondly, the dilute theory ofinviscid suspensions is corrected retaining the next leading order in the particle size and an application of this result to the linear problem is described. Thirdly, it is shown how several important properties of suspensions such as effective thermal conductivity and viscosity depend on the subtle effect of translation of the average fields over distances of the order of the particle size.

A new type consolidated composite activated carbon (AC) was developed with the host matrix of the expanded natural graphite treated with sulphuric acid (ENG-TSA). The samples with different density, different grain size of AC, and different proportion of AC were produced, and the thermal conductivity, permeability, specific heat capacity and adsorption performance were tested. Results show that the highest thermal conductivity, effective thermal conductivity, and thermal diffusivity of consolidated composite AC were 34.15 W m -1 K -1 , 20.3 W m -1 K -1 , and 2.44×10 -5 m 2 s -1 , which were improved by 150 times, 88 times and 45 times, respectively, if compared with the data of granular AC. The permeability of adsorbents ranged between 1.24×10 -14 m 2 to 7.81×10 -10 m 2 while the density ranged between 215 to 448 kg m -3 . Under some conditions the permeability increased with the increasing bulk density of AC mainly because that the AC grain disconnected the connections among ENG-TSA micro layers. The adsorption performance for composite AC and granular AC was tested and compared, and the equilibrium D-A equations were fitted by the experimental data. Results show that the additive of

In this paper, a Lattice Monte Carlo method is used to determine the effective thermal conductivity in two dimensional models of adhesively bonded metallic hollow sphere structures (MHSS). In contrast to earlier approaches, more realistic distributions of spheres without the simplification of cubic symmetric arrangements are considered in this study. For the Monte Carlo analyses, two-dimensional periodic lattices representing different cutting planes through MHSS are generated. Therefore, an algorithm is used which sequentially fills the lattice by adding cut spherical shells and inclusions in the matrix. Another focus of this work is the analysis of the influence of different geometric circle distributions on the effective thermal conductivity. The findings of the random arrangements are also compared to a regular primitive cubic arrangement and with a Maxwell-type approach.

This paper presents Lattice Monte Carlo (LMC) and Finite Element (FE) analyses on the effective thermal conductivity of sintered Metallic Hollow Spheres Structures (MHSS). A novel analysis technique applying LMC permits the utilisation of large high resolution models and can be based on computed tomography (CT) images. As a consequence, simulations are performed using the real geometry and no simplifications, such as the use of model structures, need to be introduced. In the first part, the influence of the micro-porosity on the effective thermal conductivity of the cell wall material is determined. Using these results, the second part of the analyses directly addresses the thermal properties of sintered MHSS. The findings of the LMC analyses are compared with FE results.

We describe the development of a new technology for cooling microelectronics. This report documents the design, fabrication, and prototype testing of micro scale heat pipes embedded in a flat plate substrate or heat spreader. A thermal model tuned to the test results enables us to describe heat transfer in the prototype, as well as evaluate the use of this technology in other applications. The substrate walls are Kovar alloy, which has a coefficient of thermal expansion close to that of microelectronic die. The prototype designs integrating micro heat pipes with Kovar enhance thermal conductivity by more than a factor of two over that of Kovar alone, thus improving the cooling of microelectronic die.

The study of drilling fluid behaviour across various temperature conditions is of paramount importance for industries such as oil and gas extraction, mineral exploration, and large-scale construction projects. To address this need, a custom-designed viscometer known as the Australian University of Kuwait Taylor-Couette System (AUTCS) was developed. The AUTCS apparatus incorporates a Taylor-Couette system, consisting of two co-axial cylinders with a testing liquid capacity of 100 ml. The inner cylinder can be rotated at speeds ranging from 0 to 3000 rpm. This configuration provides an economical testing system that is particularly suitable for studying expensive drilling fluids. To investigate high-temperature (HT) conditions, the apparatus is equipped with a controllable heating film jacket capable of warming fluids up to 350 F. One specific area of interest in the drilling industry is the exploration of less commonly used polymers, such as Flowzan and Xanthan, in water-based mud (WBM). Flowzan has gained increasing attention due to its potential applications in drilling fields. To facilitate the study of Flowzan and Xanthan, the AUTCS viscometer was fine-tuned using the standard conventional lab viscometer, FANN, that has limitations in terms of rotational speed range (0-600 RPM) and temperature range. The rheology characteristics of Flowzan and Xanthan including consistency charts, viscosity, and darcy friction factor are obtained and presented at temperatures of 79 F, 104 F, and 150 F, across a range of speeds from 0 to 3000 RPM. The findings were examined across several correlation functions. It is found that the Herschel-Bulkley model best represent Flow Zan and Xanthan polymers. These correlations contribute to a comprehensive understanding of the new polymers' performance under different temperature and speed conditions in drilling applications.

The study of drilling fluid behaviour across various temperature conditions is of paramount importance for industries such as oil and gas extraction, mineral exploration, and large-scale construction projects. To address this need, a custom-designed viscometer known as the Australian University of Kuwait Taylor-Couette System (AUTCS) was developed. The AUTCS apparatus incorporates a Taylor-Couette system, consisting of two co-axial cylinders with a testing liquid capacity of 100 ml. The inner cylinder can be rotated at speeds ranging from 0 to 3000 rpm. This configuration provides an economical testing system that is particularly suitable for studying expensive drilling fluids. To investigate high-temperature (HT) conditions, the apparatus is equipped with a controllable heating film jacket capable of warming fluids up to 350 F. One specific area of interest in the drilling industry is the exploration of less commonly used polymers, such as Flowzan and Xanthan, in water-based mud (WBM). Flowzan has gained increasing attention due to its potential applications in drilling fields. To facilitate the study of Flowzan and Xanthan, the AUTCS viscometer was fine-tuned using the standard conventional lab viscometer, FANN, that has limitations in terms of rotational speed range (0-600 RPM) and temperature range. The rheology characteristics of Flowzan and Xanthan including consistency charts, viscosity, and darcy friction factor are obtained and presented at temperatures of 79 F, 104 F, and 150 F, across a range of speeds from 0 to 3000 RPM. The findings were examined across several correlation functions. It is found that the Herschel-Bulkley model best represent Flow Zan and Xanthan polymers. These correlations contribute to a comprehensive understanding of the new polymers' performance under different temperature and speed conditions in drilling applications.

Experimental investigations are made into the electrical conductivity of suspensions of non-conducting particles of various shapes. Theoretical relations so far available for spheroidal particle systems are tested and the Fricke equation is used for determining particle shape as the aspect ratio of an equivalent spheroid. The electrical conductivities of suspensions of disks and cylindrical particles are obtained experimentally. The effect of the shape distribution on the conductivity of suspensions is also discussed. The TV image processing system2'5) accurately measures particle profiles, but it is two-dimensional and usually restricted to a stable orientation, and shape characterization is time-consuming. Moreover,

Theoretical calculations predict that by coupling an exothermic chemical reaction with a nanotube or nanowire possessing a high axial thermal conductivity, a self-propagating reactive wave can be driven along its length. Herein, such waves are realized using a 7-nm cyclotrimethylene-trinitramine annular shell around a multi-walled carbon nanotube and are amplified by more than 10 4 times the bulk value, propagating more than 2 m/s, with an effective thermal conductivity of 1.28 ± 0.2 kW/m/K at 2860 K. This wave produces a concomitant electrical pulse of disproportionately high specific power, as large as 7 kW/kg, that we identify as a thermopower wave. Thermally excited carriers flow in the direction of the propagating reaction with specific power that scales inversely with system size. The reaction also evolves an anisotropic pressure wave of high total impulse per mass (300 N-s/kg). Such waves of high power density may find uses as unique energy sources.

• A new set-up to measure the effective thermal conductivity of a pebble bed was built. • Bare thermocouples were used to improve the measuring accuracy of the temperature. • Pebble bed container made of quartz glass improved the reality of the testing values. • Low temperature difference in the direction of heat flow was applied in the work. • The effective thermal conductivity increased with the increase of temperature.

We comparatively investigated the transport properties for S-and Te-substituted FeSe thin films under magnetic fields to clarify the origin of the contrasting behavior of the superconducting transition temperature in S and Te substitution. A classical two-carrier analysis revealed that the carrier densities of the films increased with increasing Te content, while no significant change was observed for the S substitution, which suggests a correlation between T c and the carrier densities. These observations suggest that the structural transition affects the electronic structure in a different manner between Fe(Se,S) and Fe(Se,Te) and that this fact is the direct cause of the difference in the T c behaviors at the end point of the structural transition.

Metal hydrides can be used for a variety of applications. The thermal conductivity of metal hydride powders and the heat transfer coe cient between metal hydride powder beds and the walls of reaction beds are usually low. Heat transfer enhancement techniques have to be applied, when metal hydride powders are used. Here, expanded natural graphite/metal hydride compacts are described, possessing a high e ective thermal conductivity ( e ≈ 19 W m -1 K -1 ). Reaction kinetics of these compacts have been measured and compared to those of metal hydride beds employing Al-foams as heat transfer matrices. It was found that hydrogen absorption rates were only slightly decreased by the expanded natural graphite/metal hydride compacts, thus providing an e cient, cost-e ective and simple solution.

The thermal conductivity of metal hydride powders and the heat transfer coe cients between metal hydride powder beds and the walls of reaction beds are usually low. When metal hydride powders are used in practical applications, heat transfer enhancement techniques have to be generally applied. Here, expanded natural graphite/metal hydride compacts are described, possessing a high-e ective thermal conductivity. Furthermore, the heat transfer coe cient between expanded natural graphite pellets and the inner surface of the surrounding steel tube has been investigated.

In this paper a breakup model for analysing the evolution of transient fuel sprays characterised by a coherent liquid core emerging from the injection nozzle, throughout the injection process, is proposed. The coherent liquid core is modelled as a liquid jet and a breakup model is formulated. The spray breakup

Anisotropic conductive paste (ACP) or anisotropic conductive film (ACF) consisting of a polymer matrix and a a a a a metal-coated polymer bead are introduced as interconnection materials in mini-LED display panel packaging through a thermal compression bonding process. However, this packaging solution has been leading to important problems such as alignment difficulties due to high bonding temperature and pressure, and its repair issues for bad LED devices after the bonding process. Recently, laser-assisted bonding (LAB) process for mini-LED display packaging has been introduced to solve these problems[Ref. 1-2]. This study introduces, an anisotropic solder paste (ASP) using conductive solder particles and applies it to the mini-LED packaging through the LAB process.