This study has focused on determining the heat flows in a production blast furnace hearth. This part of the blast furnace is exposed to high temperatures. In order to increase the campaign length of the lining an improved knowledge of heat flows are necessary. Thus, it has been studied both experimentally and numerically by heat transfer modeling. Measurements of outer surface temperatures in the lower part of a production blast furnace were carried out. In the experimental study, relations were established between lining temperatures and outer surface temperatures. These relations were used as boundary conditions in a mathematical model, in which the temperature profiles in the hearth lining are calculated. The predictions show that the corner between the wall and the bottom is the most sensitive part of the hearth. Furthermore, the predictions show that no studied part of the lining had an inner temperature higher than the critical temperature 1150°C, where the iron melt can be in contact with the lining. / QC 20101124

No description available.

Modern gas turbine blades and vanes are operated at temperatures above their material’s melting point. Active external and internal cooling are therefore necessary to reach acceptable lifetimes. One possible internal cooling method is called matrix cooling, where a matrix of intersecting cooling air channels is integrated into a blade or vane. To further increase the efficiency of gas turbines, the amount of cooling air must be reduced. Therefore it is necessary that heat transfer inside a cooling matrix is well understood. In the first part of the thesis, a methodology for estimating heat transfer in the flow of matrix cooling channels was established using Computational Fluid Dynamics. Two four-equation RANS turbulence models based on the k-ε turbulence model showed a good correlation with experimental results, while the k-ω SST model underpredicted the heat transfer significantly. For all turbulence models, the heat transfer showed high sensitivity towards changes in the numerical setup. For the k-ω SST turbulence model, the mesh requirements were deemed too computationally expensive and it was excluded from further investigations. As the second part of the thesis, a parameter study was conducted investigating the influence of several geometric parameters on the heat transfer in a cooling matrix. The matrix was simplified as a channel flow interacting with multiple crossing flows. The highest enhancement in heat transfer was seen with changes in taper ratio, aspect ratio and matrix angle. Compared to smooth pipe flow, an increase in heat transfer of up to 60% was observed. Rounded edges of the cooling channels showed a significant influence on the heat transfer as well. In contrast, no influence of the wall thickness on the heat transfer was observed. While no direct validation is possible, the base case and the parameter sweeps show a good correlation with similar cases found in the literature.

<p>Understanding of thermal transport in small scales gains more importance with increasing demand in microelectronics and advancing fabrication technologies. In addition, scarce in energy sources adds more pressure with increasing expectations on research in energy conversion devices and renewable energies. In parallel to these, new phenomena observable only in small scales are discovered with the research, bringing more opportunities for engineers to solve real-world problems by applying the discoveries and more questions to answer. Thermal radiation as a thermal transport phenomenon is the epicenter of this research. Recent developments such as near-field radiative heat transfer exceeding blackbody radiation or control of radiative cooling via biasing grows the attraction on thermal radiation because these examples challenge our long-lasting understanding of nature. Exploring nature further in the small scale may help us meet the expectations mentioned above.</p> <p> </p> <p>In this thesis work, first, we carry out analyses on radiative heat transfer of natural hyperbolic material, calcite, and compare to that of a polar material SiC. Our study reveals that the high- modes within the hyperbolic bands are responsible for the substantial enhancement in near field radiation. Comparison of calcite with SiC illustrates the significance of the high- modes in calcite vs. surface polariton modes in SiC in their contributions to near-field radiation enhancement, for temperature differences ranging from 1 K to 400 K. We also noticed that the contributions of high- modes in calcite to near-field radiation is comparable to that of surface polaritons in SiC. The results of these analyses will be helpful in the search of hyperbolic materials that can enhance near field radiative transfer.</p> <p> </p> <p>Second, we demonstrate an experimental technique to measure near-field radiative heat transfer between two parallel plates at gap distances ranging from a few nanometers to far-field. A differential measurement circuit based on resistive thermometry to measure the defined temperatures are explained. To predict the defined temperatures, a computational method is utilized. We also detail an alignment technique that consists of a coarse and fine alignment in the relevant gap regions. This technique presents a method with high precision for gap measurement, dynamic gap control, and reliable sensitivity for extreme near-field measurements. Finally, we report experimental results that shows 18,000 times enhancement in radiative heat transfer between two parallel plates.</p> <p> </p> <p>Third, we analyze near-field radiative transfer due to hyperbolic phonon polaritons, driven by temperature gradient inside the bulk materials. We develop a mesoscale many-body scattering approach to account for the role of hyperbolic phonon polaritons in radiative transfer in the bulk and across a vacuum gap. Our study points out the equivalency between the bulk-generated mode and the surface mode in the absence of a temperature gradient in the material, and hence provide a unified framework for near-field radiative transfer by hyperbolic phonon polaritons. The results also elucidate contributions of the bulk-generated mode and the bulk temperature profile in the enhanced near-field radiative transfer.</p> <p> </p> <p>Forth, we study radiative heat transfer in hyperbolic material, hyperbolic boron nitride (hBN), and show a major contribution to energy transport arising from phonon polaritons supported in Reststrahlen bands. This contribution increases spectral radiative transfer by six orders of magnitude inside Reststrahlen bands compared to that outside Reststrahlen bands. The equivalent radiative thermal conductivity increases with temperature increase, and the radiative thermal conductivity can be of the same order of the phonon thermal conductivity. Experimental measurements are discussed. We showed the radiative contribution can account for as much as 27 % of the total thermal transport at 600 K. Hence, in hBN the radiative thermal transport can be comparable to thermal conduction by phonons. We also demonstrate contribution of polaritons to thermal transport in MoO₃. To calculate radiative heat transfer in three principal coordinates separately, we modify and apply the derived many-body model. Our analysis shows that radiative thermal conductivity in both in- and out-of-plane directions increases with temperature and contribution to energy transport by polaritons exceeds that by phonons.</p> <p> </p> Fifth, we build an experimental setup to examine near-field properties of materials using an external thermal source. The nanospectroscopy setup combines near-field microscopy technique, near-field scanning optical microscopy (NSOM), and Fourier-transform infrared (FTIR) spectroscopy. We further explain challenges in building a nanospectroscopy setup using a weak thermal source and coupling two techniques. This method enables us to investigate spectral thermal radiation and local dielectric properties in nanoscale.

Volvo Cars is in a change of producing only electric and hybrid cars by 2025.Subcomponent testing is a crucial part to ensure the quality of the individual buildingblocks in an electric machine. Any way of making these tests more reliable and less timeconsuming is of great interest at Volvo. Force and temperature on bearings are especiallyhard to measure accurately, because of their placement and dynamic behavior. Accurateand reliable measurements is also a vital part in creating realistic Computer-AidedEngineering (CAE) models for simulation purposes. Simulations on bearings could lead tobetter bearing choices and accelerate the design process. This could increase bearing lifeand increase the Electrical Vehicle (EV) range due to minimized friction losses. FiberBragg Grating (FBG) sensors is a technology that has some key advantages overconventional sensors. They are immune to EMI, smaller in size, can have multiple sensorsin one fiber and can measure multiple physical quantities at the same time. Volvo Cars isinterested in investigating whether this sensor technology could be a candidate forreplacing some of the current measurement setup configurations.The project was divided into three parts, validating sensor equipment, find method forinstallation and measurement on a bearing and development of a CAE model for bearinglosses and heat transfer. To validate the sensor equipment a Measurement SystemAnalysis (MSA) was performed on two FBG fibers, one FBG isolated from strain fortemperature measurement and one FBG array with multiple sensing points. From theMSA it could be seen that the FBG temperature sensor had a total uncertainty of 3.4 °CThe FBG array had a strain uncertainty of 1.04 μ𝜀 and a temperature uncertainty of 0.4 °C.The uncertainty of both the FBG array and the FBG temperature sensor is highlydependent on the calibration of the sensitivity constant. The force measurement on thebearing was done with a concept based on the wavelength difference, produced by strain,between two FBG sensors. The concept was tested in a dynamic component rig where anaxial force could be applied, and the wavelength difference measured. The temperatureon the outer ring of the bearing was measured using an FBG isolated from strain. The testresults were promising, but since the FBG is sensitive to temperature and strain theincreased temperature difference between the two fibers affected the results. Thecalibration method needs to be compensated for the increased temperature differencebetween the fibers which is generated when the rotational speed is increased, and thiscould not be done with a single temperature measurement. The two developed CAEmodels was both constructed in MATLAB and showed similar behavior with experimentaltests done by others. To validate the models, physical test for heat transfer and bearinglosses should be performed.

Stationary spiral inserts can effectively enhance heat transfer and temperature blending in the heat convection systems. In this paper, the impact of the segment length on the performance of a stationary insert is studied for flow Re numbers from ~80 to ~7900 through numerical simulation of heat transfer in streams of cold and hot gases flowing across it. The segment length to width ratio is from 1.11 to 2.33. The temperature of the studied gas is from 300 K to 1300 K. It is shown that the insert with variable segment length is more effective in temperature blending for two compressible streams compared with an insert with constant segment length, especially for low-Re-number turbulent flows.

No description available.

Endwall contouring has been widely studied as an effective measure to improve aerodynamic performance by reducing secondary flow strength. The effects of endwall contouring with discrete holes and an upstream purge slot for a high turning (127") airfoil passage under transonic conditions are investigated. The total pressure loss and secondary flow field were measured for two endwall geometries. The non-axisymmetric endwall was developed through an optimization study [1] to minimize secondary losses and is compared to a baseline planar endwall. The blade inlet span increased by 13 degrees with respect to the inlet in order to match engine representative inlet/exit Mach number loading in a HP turbine.  The experiments were performed in a quasi-2D linear cascade with measurements at design exit Mach number 0.88 and incidence angle. Four cases were analyzed for each endwall -- the effect of slot presence (with/without coolant) and the effect of discrete holes (with/without coolant) without slot injection. The coolant to mainstream mass flow ratio was set at 1.0% and 0.25% for upstream purge slot and discrete holes, respectively.  Aerodynamic loss coefficient is calculated with the measured exit total pressure at 0.1 Cax downstream of the blade trailing edge. CFD studies were conducted in compliment. The aero-optimized endwall yielded lower losses than baseline without the presence of the slot. However, in presence of the slot, losses increased due to formation of additional vortices. For both endwall geometries, results reveal that the slot has increased losses, while the addition of coolant further influences secondary flow development. / Master of Science

The ignition of a solid is an inherently complex phenomenon influenced by heat and mass transport mechanisms that are, even to this day, not understood in entirety. In order to use ignition data in meaningful engineering application, significant simplifications have been made to the theory of ignition. The most common way to classify ignition is the use of material specific parameters such as such as ignition temperature (Tig) and the critical heat flux for ignition (CHF). These parameters are determined through standardized testing of solid materials – however, the results of these tests are generally used in applications different from the environments in which these parameters were actually determined. Generally, ignition temperature and critical heat flux are used as material properties and are presented readily in sources such as the SFPE Handbook. However, these parameters are not truly material properties; each are inherently affected by the environment and orientation in which they are tests. Ignition parameters are therefore system dependent, tied to the conditions in which the parameters are determined. Previous work has demonstrated that ignition parameters (such as Tig or CHF) for the same material can vary depending on whether the sample is tested in a vertical or horizontal orientation. While the results are clear, the implications this may have on the use of ignition data remains uncertain. This work outlines the fundamental theory of ignition as well as a review of studies related to orientation. The aim of this study it to analyze the influence of sample orientation on ignition parameters. All experimental work in this study was conducted using cast black polymethyl methacrylate (PMMA or commonly referred to as acrylic). This study explores ignition parameters for PMMA in various orientations and develops a methodology through which orientation can be incorporated into existing ignition theory. An additional study was also conducted to explore the statistical significance of current flammability test methodologies. Ultimately, this study outlines the problem of the system dependency of ignition and provides commentary on the use of ignition data in engineering applications

Multiphase flows are ubiquitous across engineering disciplines: water-sediment river flows in civil engineering, oil-water-sand transportation flows in petroleum engineering; and sorbent-flue gas reactor flows in chemical engineering. These multiphase flows can include a combination of momentum, heat, and mass transfer. Studying and understanding the behavior of multiphase, multiphysics flow configurations can be crucial for safe and efficient engineering design. In this work, a framework for the development and validation, verification and uncertainty quantification (VVUQ) of subgrid models for heat transfer in multiphase flows is presented. The framework is developed for a carbon capture reactor; however, the concepts and methods described in this dissertation can be generalized and applied broadly to multiphase/multiphysics problems. When combined with VVUQ methods, these tools can provide accurate results at many length scales, enabling large upscaling problems to be simulated accurately and with calculable errors. The system of interest is a post-combustion solid-sorbent carbon capture reactor featuring a solid-sorbent bed that is fluidized with post-combustion flue gas. As the flue gas passes through the bed, the carbon dioxide is exothermically adsorbed onto the sorbent particle’s surface, and the clean gas is passed onto further processes. To prevent overheating and degradation of the sorbent material, cooling cylinders are immersed in the flow to regulate temperatures. Simulating a full-scale, gas-particle reactor using traditional methods is computationally intractable due to the long time scale and variations in length scales: reactor, O(10 m); cylinders, O(1 cm); and sorbent particles, O(100 um). This research developed an efficient subgrid method for simulating such a system. A constitutive model was derived to predict the effective suspension-cylinder Nusselt number based on the local flow and material properties and the cylinder geometry, analogous to single-phase Nusselt number correlations. This model was implemented in an open source computational fluid dynamics code, MFIX, and has undergone VVUQ. Verification and validation showed great agreement with comparable highly-resolved simulations, achieving speedups of up to 10,000 times faster. Our model is currently being used to simulate a 1 MW, solid-sorbent carbon capture unit and is outperforming previous methods in both speed and physically accuracy. / 2017-06-21T00:00:00Z