abstract: The presence of huge amounts of waste heat and the constant demand for electric energy makes this an appreciable research topic, yet at present there is no commercially viable technology to harness the inherent energy resource provided by the temperature differential between the inside and outside of buildings. In a newly developed technology, electricity is generated from the temperature gradient between building walls through a Seebeck effect. A 3D-printed triply periodic minimal surface (TPMS) structure is sandwiched in copper electrodes with copper (I) sulphate (Cu2SO4) electrolyte to mimic a thermogalvanic cell. Previous studies mainly concentrated on mechanical properties and the electric power generation ability of these structures; however, the goal of this study is to estimate the thermal resistance of the 3D-printed TPMS experimentally. This investigation elucidates their thermal resistances which in turn helps to appreciate the power output associated in the thermogalvanic structure. Schwarz P, Gyroid, IWP, and Split P geometries were considered for the experiment with electrolyte in the thermogalvanic brick. Among these TPMS structures, Split P was found more thermally resistive than the others with a thermal resistance of 0.012 m2 K W-1. The thermal resistances of Schwarz D and Gyroid structures were also assessed experimentally without electrolyte and the results are compared to numerical predictions in a previous Mater's thesis. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2020

There is interest concerning the energy performance of buildings in the United States. Buildings, whether residential, commercial or institutional, generally underperform in terms of energy efficiency when compared to buildings that are constructed following sustainably and energy efficiency standards. A substantial percentage of energy loss in these buildings is associated with the thermal efficiency of its envelope (exterior walls, windows roof, floors and doors). The objective of this study will evaluate the results of three energy modeling techniques developed to investigate the energy transfer through the envelope of existing campus buildings. The techniques employed are solving the heat transfer calculations using spreadsheets, using a stand-alone modeling software (OpenStudio) and using an integrated building energy modeling software (eQuest) employed in Autodesk Revit. The first technique is somewhat different from the other two because it does not require a 3D representation of the building to be generated as the first step in the modeling process. It is the application of a mathematical methodology employing heat transfer algorithms entered into the spreadsheet’s cells to estimate the heat transfer through the building envelope. Data needed for this technique are weather data of the buildings location, surface area of the building envelope, and the overall heat transfer coefficient (U-value) of each component of the building envelope. The OpenStudio technique involves a 3D representation of the building. The building is drawn on a 3D modeling computer program called SketchupPro, which communicates directly to the OpenStudio energy modelling interface. The building operations as well as the building characteristics, such as the composition and type of the elements that made up the building envelop, the thermal zone, occupancy schedule and the space type was inputted in the OpenStudio engine. The OpenStudio engine runs the simulation and generates a detail result about the energy usage and energy transfer in the building. The third method that employs AutoCAD Revit software is a standalone technique that does not require an external software for sketching the building model. Revit the ability to draw the model as well as perform the energy analysis at the same time with the aid of inbuilt eQuest modeling engine. The model in Revit is generated with the right building envelope characteristics as the existing building and the weather file. The process is somewhat similar to the OpenStudio technique; the main difference is the level of detail and limitation provided by both the energy modeling engine (eQuest and EnergyPlus). At the end of the simulation, the building energy modeling using Autodesk Revit presents a detailed result of the energy usage and energy flow in the building. The underlying reason of the comparison of three techniques is to understand the simplest, most efficient, accurate method to quantify heat transfer through the building envelope. By the end of this study, the most efficient technique for investigating the building envelope will be expected to be the EnergyPlus technique because of the usage simplicity, ability to take in a lot of details required for simulation and the periodical software updates.

This diploma thesis is focused on the assessment of the influence of moisture on the thermal properties of the gloves. The first part of the thesis deals with the research of topics related to the given issue as well as with the derivation of the computational relations needed for evaluation of experimental measurements. The main focus of the work lies on defining the hypotheses and experiments that are used to verify the influence of moisture on the thermal resistance of gloves. As for the experimental part, it describes the individual methods of moistening the gloves from which the moistening through the air humidity and the moistening by the immersion were analysed. To verify the suitability of selected moistening methods, the tested glove samples were measured on the thermal manikin both in a dry and a moistened state under the conditions defined by ČSN EN 511 and ČSN EN ISO 15831 standards. Individual states were repeatedly measured and afterwards the progresses of thermal resistance depending on time were graphically displayed. The thesis also includes analysis of measurement uncertainties as well as evaluation of measurement repeatability. From the obtained results, both the defined hypotheses and theoretical assumptions about the decrease of the thermal resistance of a textile material due to the influence of moisture were confirmed in the conclusion of the diploma thesis.

A new mathematical model has been developed along with a new parameter estimation routine using surface temperature and heat flux measurements to estimate blood perfusion and thermal resistance in living tissue. Dynamic thermal measurements collected at the surface of the sensor before and after imposing a dynamic thermal cooling event are used with the model to estimate the blood perfusion, thermal resistance and core temperature. The Green\'s function based analytical solution does not require calculation of the whole tissue temperature distribution, which was not the case for the previous models. The result from the new model was proved to have better and more consistent results than previous models. The new model was validated to solve one of the unsolved biomedical problems which is the ability of detecting burn severity. The method was tested with a phantom perfusion system. The results matched known blood perfusion and thermal resistance values. The method was also tested with burns on animal models. Inflammation effects associated with the burns were studied using a newly developed term called the Burn Factor. This correlated with the severity of imposed burns. This work consists of three journal papers. The first paper introduces the mathematical model and its validation with finite-difference solutions. The second paper validates the physical aspects of the usage of the model with thermal measurement in detecting simulated burned layers and the associated perfusion. The third paper demonstrates the ability of the model to use thermal measurements to detect different burn severity of an animal model and to study the healing process. / Ph. D.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21369号 / 工博第4528号 / 新制||工||1705(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 田中 功, 教授 中村 裕之, 教授 安田 秀幸 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

Black-fly larvae, and mosquito larvae and pupae, are shown to select certain temperature ranges when given a choice in a linear gradient. Larval age has little effect on the temperature selected, but pupae are tolerant of higher temperatures than larvae. The significance of this observation is discussed. The temperature selected is affected by the previous thermal history of the insect, although acclimation to the ambient temperature may be rapid. The final selected temperature of fourth-instar Aedes aegypti larvae was determined. Rearing temperature has a profound effect on the thermal resistance of Aedes aegypti exposed to high temperatures. / Thesis / Master of Science (MS)

This research is focused on the processing of an innovative three-dimensional packaging architecture for power electronics building blocks with soldered device interconnections and subsequent characterization of the module's critical interfaces. A low-cost approach termed metal posts interconnected parallel plate structure (MPIPPS) was developed for packaging high-performance modules of power electronics building blocks (PEBB). The new concept implemented direct bonding of copper posts, not wire bonding of fine aluminum wires, to interconnect power devices as well as joining the different circuit planes together. We have demonstrated the feasibility of this packaging approach by constructing PEBB modules (consisting of Insulated Gate Bipolar Transistors (IGBTs), diodes, and a few gate driver elements and passive components). In the 1st phase of module fabrication with IGBTs with Si₃N₄ passivation, we had successfully fabricated packaged devices and modules using the MPIPPS technique. These modules were tested electrically and thermally, and they operated at pulse-switch and high power stages up to 6kW. However, in the 2nd phase of module fabrication with polyimide passivated devices, we experienced significant yield problems due to metallization difficulties of these devices. The under-bump metallurgy scheme for the development of a solderable interface involved sputtering of Ti-Ni-Cu and Cr-Cu, and an electroless deposition of Zn-Ni-Au metallization. The metallization process produced excellent yield in the case of Si₃N₄ passivated devices. However, under the same metallization schemes, devices with a polyimide passivation exhibited inconsistent electrical contact resistance. We found that organic contaminants such as hydrocarbons remain in the form of thin monolayers on the surface, even in the case of as-received devices from the manufacturer. Moreover, in the case of polyimide passivated devices, plasma cleaning introduced a few carbon constituents on the surface, which was not observed in the case of Si₃N₄ passivated devices. X-Ray Photoelectron Spectroscopy (XPS) Spectra showed evidence of possible carbon contaminants, such as carbide (~282.9eV) and graphite (~284.3eV) on the surface at binding energies below the binding energy of the hydrocarbon peak (C 1s at 285eV). Whereas above the hydrocarbon peak energy level, carbon-nitrogen compounds, single bond carbon compounds (~285.9eV) and double bond carbon compounds (~288.5eV) were evident. The majority of the carbon composition on the pad surface was associated with hydrocarbons, which were hydrophobic in nature, thus making the device contact pad less wettable. XPS data showed that, after the plasma cleaning process, absorbed monolayers on the Si₃N₄ passivated and polyimide passivated surfaces consisted of different chemical compositions and accordingly, the attraction forces of these absorbed layers are also different, which affects the bonding properties of the subsequent metallization, resulting in different contact resistances. On the other hand, with an electroless Zn-Ni-Au deposition, it was found that the polyimide passivation on the devices degraded due to due alkaline exposure in the plating baths, thus lowering the device breakdown voltage significantly. Furthermore, interfacial thermal resistances of solder preform, solder paste and silver epoxy (between the power module and the heat spreader) were characterized for process optimization. Void content at the resulting interface was found to be dependent on the flux content and flux activity. Solder preform with no-clean flux, reflowed in nitrogen results in the least resistant and minimized void-content interface. It is most likely that the flux added to the preform had a higher fluxing action than the flux contained in the solder paste. On the other hand, the outgassing of the entrapped flux profoundly affects the void formation and a lower void content indicates a lesser amount of trapped flux. In the case of a solder paste, the flux is in direct contact with the surface oxide of the powders and the surface to be soldered. Consequently, during reflow, any residual oxide can be expected to have some flux adhered to it. In the case of solder preform with added flux, the higher activity flux eliminated the oxide more rapidly and more thoroughly, thus leaving fewer spots for the flux to adhere to. Void contents in all cases of nitrogen reflow are consistently lower than the air-reflowed samples. Silver epoxy with a higher thermal conductivity (60W/mK) than Pb-Sn eutectic solder did not produce low-resistance interfaces. We found that thermal conductivity of the interface material is not the most crucial factor in reducing thermal resistance, rather it is the contact thermal resistance of the interfaces, which constitutes the largest part of the total interfacial thermal resistance. Process optimization with applied pressure and nitrogen reflow resulted in a significant lowering of contact resistance (from 0.55°C/W to 0.25°C/W) for the solder preform interfaces. We concluded that contact resistance needs to be duly accounted for in thermal modeling for an accurate representation of an interface; at the same time, the module attachment process must be tailored to reduce contact resistance for improved thermal management. / Ph. D.

Nanofluids as an innovative class of heat transfer fluids created by dispersing nanometre-sizedmetallic or non-metallic particles in conventional heat transfer fluids displayed the potential toimprove the thermophysical properties of the heat transfer fluids. The main purpose of this study is toinvestigate the influence of the use of nanofluids on two-phase heat transfer, particularly on thethermal performance of the heat pipes. In the first stage, the properties of the nanofluids were studied,then, these nanofluids were used as the working fluids of the heat pipes. The thermal performance ofthe heat pipes when using different nanofluids was investigated under different operating conditionsexperimentally and analytically. The influences of the concentration of the nanofluids, inclinationangles and heat loads on the thermal performance and maximum heat flux of the heat pipes wereinvestigated.This study shows that the thermal performance of the heat pipes depends not only on thermophysicalproperties of the nanofluids but also on the characteristics of the wick structure through forming aporous coated layer on the heated surface. Forming the porous layer on the surface of the wick at theevaporator section increases the wettability and capillarity and also the heat transfer area at theevaporator of the heat pipes.The thermal performance of the heat pipes increases with increasing particle concentration in all cases,except for the heat pipe using 10 wt.% water/Al2O3 nanofluid. For the inclined heat pipe, irrespectiveof the type of the fluid used as the working fluid, the thermal resistance of the inclined heat pipes waslower than that of the heat pipes in a horizontal state, and the best performance was observed at theinclination angle of 60o, which is in agreement with the results reported in the literature. Otheradvantages of the use of nanofluids as the working fluids of the heat pipes which were investigated inthis study were the increase of the maximum heat flux and also the reduction of the entropy generationof the heat pipes when using a nanofluid.These findings revealed the potential for nanofluids to be used instead of conventional fluids as theworking fluid of the heat pipes, but the commercialization of the heat pipes using nanofluids for largescale industrial applications is still a challenging question, as there are many parameters related to thenanofluids which are not well understood. / <p>QC 20170228</p>

L'objectif de cette thèse est de caractériser la résistance thermique de contact au niveau de deux interfaces bien distinctes. La première est une interface physique entre le Silicium(111) et l'Hélium-4 superfluide. La résistance thermique de contact est alors mesurée expérimentalement pour des températures allant 0.3K à 2.0K et en variant la pression depuis la pression de vapeur saturante jusqu'à la pression de solidification de l'Hélium-4 (i.e. 25bars). L'analyse des résultats expérimentaux par le modèle d'Adamenko et Fuks montre la prédominance de la nano-rugosité de surface dans la transmission de la chaleur à l'interface entre ces deux matériaux. Lors de la solidification de l'Hélium-4, une transition du premier ordre dans la résistance thermique est mise en évidence. La deuxième interface étudiée est une forte constriction créée par une jonction de taille micrométrique entre deux membranes suspendues. Sans discontinuité de matériaux, les simulations numériques Monte-Carlo montrent la présence d'une résistance thermique de contact entre la membrane et l'entrée de la jonction dans le régime de diffusion des phonons les parois du système. Les simulations permettent alors d'explorer les effets des dimensions de la jonction ainsi que de la rugosité de surface des micro-structures bidimensionnelles et tridimensionnelles. / This thesis aims at characterizing the thermal contact resistance at two interfaces of different nature. The first is a physical interface between Silicon(111) and superfluid Helium-4. The thermal contact resistance is evaluated experimentally for temperatures between 0.3K and 2.0K while varying pressure from the saturated vapor pressure to the Helium-4 solidification pressure (i.e. 25bars). Experimental results, analysed with Adamenko and Fuks model, show that nanoscale surface roughness governs heat transmission at this interface. Furthermore, a first order transition in the thermal contact resistance is revealed due to Helium-4 solidification. The second studied interface is an abrupt constriction created by a micro-junction between two suspended membranes. Even though there is no material discontinuity, Monte-Carlo numerical simulations show the existence of a thermal contact resistance between the membrane and the entrance of the junction. Using simulations we explore the effects of geometry and nanoscale surface roughness in bidimensional and tridimensional micro-structure.