Recent global efforts have focused on developing new lightweight alloys specifically designed for high-pressure die casting (HPDC) processes, aiming to achieve the lightweight of electrified vehicles. HPDC offers a distinct advantage by allowing the production of neat-net-shape automotive components, minimizing the need for further processing. An inherent characteristic of HPDC is its rapid cooling rates, making the understanding and characterization of the thermophysical properties of these newly developed lightweight alloys under high cooling rates a must. These properties have a significant effect on controlling the HPDC process and developing suitable filling and solidification models to simulate the HPDC process intricacies for commercial production adaptation. The thermophysical properties of these alloys are shown to exhibit considerable variability with temperature, particularly under rapid solidification conditions, like in HPDC. Hence, an essential step in developing such alloys is to thoroughly investigate the variation of their thermophysical properties with temperature under high cooling rates. To fulfill such a need, an experimental setup has been developed to allow the solidification of molten metal samples under varying cooling rates using a set of impinging water jets. An inverse heat transfer algorithm has been developed to estimate the thermal conductivity and thermal diffusivity as a function of the temperature of the solidifying samples under high cooling rates. To validate the accuracy of the inverse heat transfer algorithm and the experimental methodology, a set of experiments has been carried out using pure Tin, which is a well-characterized material. Its thermal diffusivity and thermal conductivity are readily available in the literature. The estimated thermal diffusivity and thermal conductivity of Tin have been compared with the published data. The estimated thermal diffusivity and conductivity of the solid phase were in good agreement with the published values. A maximum deviation ranging from +10.1% to -3.47% was observed in the estimated thermal diffusivity. The maximum deviation in the estimated thermal conductivity was between +7.8% and -13.6%. Higher deviations have been observed in the estimated thermal diffusivity and conductivity of the liquid phase with deviations in the range of +33.71% to -4.86% and +0.76% to 26.53%, respectively. The higher deviations observed for the liquid phase might be attributed due to the natural convection that developed in the tested liquid sample. The effect of natural convection was examined using a set of numerical simulations that confirmed the existence of a convection-induced movement within the liquid phase. A sensitivity analysis was carried out to examine the impact of the accuracy of thermocouple positions and the effect of temperature sensing accuracy on the estimated thermal properties. / Thesis / Master of Applied Science (MASc) / An inverse heat transfer algorithm along with an experimental setup has been developed to estimate the temperature-dependant thermophysical properties during solidification of metallic alloys under high cooling rates. To verify the accuracy of the developed algorithm and the experimental setup the estimated thermal conductivity and diffusivity of pure Tin have been compared with data available in the literature. The results showed reasonable agreement.

The purpose of this investigation was to develop an apparatus to measure the thermal conductivity of polymer melts, and to use the apparatus to measure the thermal conductivity of selected melts as a function of melt temperature. The steady-state, coaxial cylinder method with guard heaters was used and the annular gap was 0.075 inch. The polymer was melted in a cylindrical melt chamber, then metered to the thermal conductivity measuring apparatus. Cartridge heaters provided heat input and temperature measurements were made with calibrated, differential, iron-constantan thermocouples. The thermal conductivity of polyethylene, polystyrene and nylon melts tested increased with increased temperature. The thermal conductivity of the polypropylene sample was temperature independent. Complexity of molecular structure lowered melt thermal conductivity. Radiation losses were accounted for and convection was determined to be absent. The results were shown to be within a 3 percent experimental measurement error. Meaningful confidence limits cannot be calculated because of the limited number of data points. / Master of Science

Yes / Polyamide 6 (PA6) is an important engineering thermoplastic, very widely used but prone to thermal degradation during extrusion at temperature not far from its melt temperature (220 oC). Typically, and as measured in this study, PA6 extruded at temperature of 300 oC shows a 40% decrease in tensile modulus compared to non-extruded PA6. To rebuild PA6 molecular weight, the easiest and cheapest method is to use an appropriate chain extender. Many chain extenders have been used in the past but they are essentially suited to nucleophile induced degradation, targeting split PA6 chains carboxyl COOH and amine NH2 end groups. What has been lacking are effective chain extenders for thermally only induced degradation, i.e. for the practical cases where the PA6 is thoroughly dried before extrusion. For such a case, the degradation reaction mechanism dictates that the solution is to develop chain extenders that target the split PA6 chains amide CONH2 groups not the carboxyl COOH and amine NH2 end groups. As amide groups strongly react with anhydride functionalities, we test the effectiveness of a novel chain extender, Joncryl® ADR 3400, a styrene maleic anhydride copolymer with multiple, repeating anhydride functionality. Assessment of chain extension in this study is done as with previous work, using rheology, mechanical and thermal properties of PA6 extruded on its own and with the chain extender. The viscoelastic data conclusively show the efficacy of such chain extender with more than 10 fold changes in the comparative values of the extruded sample storage modulus G' and as much as an 85% increase in the tensile modulus. / Republic of Turkey, Ministry of National Education. University of Bradford

Electric motors for vehicle applications are required to have high efficiency and small size and weight. Accurately modeling the thermal properties of an electric motor is critical to properly sizing the motor. Improving the cooling of the motor windings allows for a more efficient and power-dense motor. There are a variety of methods for predicting motor temperatures, however this paper discusses the advantages and accuracy of using a nodal lumped thermal model. Both commercially available and proprietary motor thermal modeling software are evaluated and compared. Thermal improvements based on the model in both contact interfaces and winding encapsulant are evaluated, showing motor improvements in the ability to handle heat losses of approximately forty percent greater than the baseline, resulting in either higher power or lower motor temperatures for the same package size. / Master of Science

The main objective of the thesis is to study the thermal properties of Si-based polymer derived ceramics (PDCs) at elevated temperatures and to classify the main factors affecting the thermal transport through these ceramics. The polymer derived ceramics with the chemistry Si- O-C-N were prepared starting from commercial polycarbosilane, polysiloxane, and polysilazane precursors. These precursors are cross-linked at room temperature to obtain the preceramic, followed by controlled pyrolysis (at different temperatures ranging from 1200 oC to 1800 oC in argon, nitrogen or carbon-di-oxide atmospheres), to get the final ceramic. The first part of the thesis discusses on development and studies of dense polymer derived thin disks having a basic chemistry, Si-C, Si-O- C, and, Si-C-N-O, developed via a casting technique followed by specific pyrolysis cycles. Having a thickness in the range of 100 μm- 300 μm, these ceramic disks were studied to be nanocrystalline/amorphous at least up to a temperature of 1400 oC and were found to have a significant amount of Cfree phase existing in them along with the intended chemistry. The high-temperature thermal properties were primarily investigated on ceramics prepared at a pyrolysis temperature of 1200 oC (ceramic still in nanocrystalline/amorphous glassy phase). The disks were found to have very low expansion coefficients (CTE) measured up to ~900 oC and the thermal diffusivity (k) and thermal conductivity (l) of these disks were also measured. An attempt to understand the influence of the different phases in a SiOC ceramic (mainly the Cfree phase, studied by enriching the carbon percentages using DVB) in determining the final thermal properties was also conducted. The influence of carbon enrichment on the mechanical properties of these disks is also studied as a sub-part of this work. The second part of the work deals with testing the possibility to use these ceramics for high-temperature insulation applications. ‘Reticulated’ ceramic foams of relatively same chemistries as that of the disks were prepared by a template replica approach, using polyurethane (PU) foams (more open-celled to more closed-celled types of PU foams were used in the study) as the template. Porous structures having densities ranging from as low as 0.02 g.cm-3 to 0.56 g.cm-3 and with a porosity ~ 80 % to ~99% were prepared and tested. The developed foams showed excellent thermal stability up to a temperature of 1400 oC and possessed very low thermal expansion. The thermal conductivity measured on them at RT gave values in the range 0.03 W.m-1.K-1- 0.25 W.m-1.K-1. A Gibson-Ashby modeling approach to explain the thermal conductivity of the porous ceramics was also attempted. The developed foams were also found to be mechanically rigid. In a nutshell, the thesis work studies the thermal properties of Si-O-C- N ceramics in detail and probes into the possibility to develop these class of Si-O-C-N ceramics into promising high-temperature insulation material.

No description available.

Call number: LD2668 .T4 1979 N89 / Master of Science

Poster exhibited at GPSC Student Showcase, February 24th, 2016, University of Arizona.

This thesis presents a body of work conducted in the field of domestic thermal comfort. The aim of this research was to determine the suitability of the Predicted Mean Vote (PMV) index in homes within the UK. Two field studies were conducted with a sample of participants living in owner occupied properties in a UK city (London) and a UK provincial town (Loughborough). Research findings indicate that the PMV is indeed a good predictor of thermal sensation in homes when conditions are steady state and people are engaged in near-sedentary activities. When conditions are not steady state and people are engaged in a variety of household activities, the accuracy of the PMV index can be improved by using a metabolic rate coefficient of 1.7. Further research work is required to ascertain this and likewise the range of applicability of the Adaptive Model.

Measurements performed from stereo reconstruction can be obtained with a high accuracy with correct calibrated cameras. A stereo camera rig mounted in an outdoor environment is exposed to temperature changes, which has an impact of the calibration of the cameras. The aim of the master thesis was to investigate the thermal impact of a calibrated stereo camera rig. This was performed by placing a stereo rig in a temperature chamber and collect data of a calibration board at different temperatures. Data was collected with two different cameras and lensesand used for calibration of the stereo camera rig for different scenarios. The obtained parameters were plotted and analyzed. The result from the master thesis gives that the thermal variation has an impact of the accuracy of the calibrated stereo camera rig. A calibration obtained in one temperature can not be used for a different temperature without a degradation of the accuracy. The plotted parameters from the calibration had a high noise level due to problems with the calibration methods, and no visible trend from temperature changes could be seen.