To determine the feasibility of using low thermal expansion ceramics and aluminum titanate in diesel engine applications, the mechanical and thermal properties and corrosion resistance were evaluated. NZP (Ba_1.25Zr₄P_5.5Si_.0.50₂₄ and Ca_0.5 Sr_O.5Zr₄P₆0₂₄) and aluminum titanate (AT) were exposed to a simulated diesel engine environment. The effects of thermal cycling from room temperature to 700°C, and a combination of alkali corrosion and thermal cycling on the mechanical and thermal properties of these ceramics were examined. It was found that NZP and AT materials demonstrated near zero bulk thermal expansion, good thermal up shock resistance and resistance to Na and V corrosion, because of their porous structure and low density. However, the AT materials exhibited lower flexural strength. This is a direct result of the inherent micro cracking across the AT grains upon cooling from the sintering temperature, which reduces the flexural strength and elastic modulus. / Master of Science

Reliable estimation of thermal properties is extremely important in the utilization of new advanced materials, such as composite materials. The accuracy of these estimates can be increased if the experiments are designed carefully. The objectives of this study are to design optimal experiments to be used in the prediction of these thermal properties and to then utilize these designs in the development of an estimation procedure to determine the effective thermal properties (thermal conductivity and volumetric heat capacity). The experiments were optimized by choosing experimental parameters that maximize the temperature derivatives with respect to all of the unknown thermal properties. This procedure has the effect of minimizing the confidence intervals of the resulting thermal property estimates. Both one-dimensional and two-dimensional experimental designs were optimized. A heat flux boundary condition is required in both analyses for the simultaneous estimation of the thermal properties. For the one-dimensional experiment, the parameters optimized were the heating time of the applied heat flux, the temperature sensor location, and the experimental time. In addition to these parameters, the optimal location of the heat flux was also determined for the two- dimensional experiments. Utilizing the optimal one-dimensional experiment, the effective thermal conductivity perpendicular to the fibers and the effective volumetric heat capacity were then estimated for an IM7-Bismaleimide composite material. The estimation procedure used is based on the minimization of a least squares function which incorporates both calculated and measured temperatures and allows for the parameters to be estimated simultaneously. / Master of Science

An experimental investigation has been completed which studied the breaking of window glass by fire. The experiments were carried out in a specially designed compartment to achieve two-layer flows characteristic of normal building fires. The experimental data was collected from two test groups: the first for windows with their edges insulated from the fire (edge-protected) and the second for windows uniformly heated by the fire (edge-unprotected). The results of the edge-protected window tests indicated that the glass breakage was caused by a critical temperature difference between the central heated portion of the pane and the glass edge. The experimental work showed the critical value to be approximately 90C. After the material properties of the glass were determined, the theoretical findings of Keski-Rahkonen were used to obtain a value of 70C; the difference attributed to radiative heating. The test results also demonstrated a distinctive loss of integrity by the windows. When breakage occurred, the cracks spread throughout the glass, joined together and caused at least partial collapse of the pane. The results from the edge-unprotected window tests were quite different. There were relatively few cracks developed and almost no propagation across the glass. Consequently, there was no window collapse in any of these cases. The breakage did initiate at a consistent glass temperature value, however, the mechanism for these tests is not known. / Master of Science

M. S.

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

The ultimate goal of this research was to determine the feasibility of measuring thermal conductivity of food materials using the bead thermistor with particular reference to high temperature. Feasibility was established by examining the effects of the input parameters and the measurement error associated with them on the ability to estimate the test medium thermal conductivity test medium. This study showed that estimation of effective radius and bead thermal conductivity, the probe parameters, had the most significant impact on the ability to estimate the thermal conductivity of food materials. The probe parameters were determined by standardizing the thermistor probe against materials of known thermal conductivity. The current lack of well defined thermal reference materials in the range of water and most food products is a primary source of error associated with the method. The accuracy and coefficient of variation of the Bead Thermistor Method were statistically documented in 10° increments over the temperature range of 25°C to 125°C. These results showed the method to have better than 10% accuracy across the entire temperature range. Distinct differences in accuracy between probes at a given temperature were also discovered. Standardization with water and castor oil resulted in a more accurate method than was achieved using water, castor oil, and glycerin. The minimum particle diameter necessary to maintain the infinite boundary condition assumption required by heat transfer theory was found to be >5 mm. The methodology was evaluated by examining the effects of temperature on the thermal conductivity of milk of different fat contents. A prediction equation for each product was attempted from the experimental data, but the data appear best fit by assuming a constant value across temperature. Heat altered the product physically which likely affected temperature dependence. Based on the results of this study, the bead thermistor method can be considered a practical method for determining thermal conductivity of food materials over the temperature range considered in this study. / Ph. D.

Due to many unexpected difficulties which developed as the method was being worked out, all of the desired information on these coals was not obtained. Therefore, most of the allotted time has to be devoted to the standardizing of the apparatus. Many of the small but important points of technique, which gave trouble, have been overcome. / M.S.

Aluminum and magnesium wires were burned in 100% oxygen at pressures up to 550 psi. Two test series in moist atmospheres containing up to 25% water vapor were carried out with both metals at constant total pressure and at a constant temperature 0 of 280°F. In order to study these effects on the combustion reaction, the propagation rate of the burning zone along the wire was measured. It was believed that the participation of the condensed combustion products limited the reaction rate through their effect on the diffusion of oxygen. The products accumulation around the flame zone may also be responsible for the irregularities in the combustion velocity observed with both metals. The burning rate of aluminum and magnesium in moist atmospheres at higher pressures than atmospheric decreases with increasing moisture content. Aluminum wire combustion above 13-15% moisture did not occur. Fragmentation of the molten drop of metal ended the reaction. 120 Magnesium burned without fragmentation in atmospheres containing up to 25 per cent of water vapor. The reaction rate decreases continuously with increasing moisture concentration. / M. S.

This work details a computer-based modeling tool for predicting temperatures in three-dimensional multilayer microelectronic packages. It is capable of modeling surface connections (e.g., wire bonds and pins), edge connections (e.g., leads), and thermal vias. A three-dimensional control-volume finite difference method is used, permitting transient as well as steady solutions. Numerical behavior is examined with respect to the device geometry and external environment. The features of this tool are demonstrated on a sample multilayer package. The effects of the modeling scheme are discussed. An alternate version of the program removes a layer from the numerical model to simplify the solution of the problem. To compensate for the removal of the layer a contact resistance is added. This replaces the thermal resistance the removed layer provided in the z-direction. The x-y conductivity of the adjacent layers are modified based on the removed layer thickness and conductivity. This measure imitates the spreading resistance or conductance that the removed layer provided. The effect of removing a layer in the model is studied, documenting the relationship between layer thickness and conductivity and the error introduced by removing the layer. A simple relationship is sought which can indicate the instances in which the computer model can be simplified. The results are applicable to any method including finite element and series-analytical methods. / Master of Science

No / There is an increasing interest in the use of Ground Source Heat Pumps (GSHPs) as a source of renewable energy in temperate countries. GSHPs coupled with buried heat collectors can harness the thermal energy from near-surface soils to provide the heating required for domestic properties. The performance of a GSHP system depends greatly on the thermal conductivity of the surrounding soils. Near-surface soils undergo cycles of drying and wetting due to, for example, the infiltration of rain water and/or fluctuations of the ground water table. Several parameters - including the properties of soil, suction head and saturation history - affect the thermal properties as well as the retention and flow of water. This paper presents results from a comprehensive laboratory investigation on sand samples with markedly different grain size distribution. Simultaneous measurements of thermal and hydraulic properties of the sands were taken under incremental increase/decrease in the suction head values to simulate cycles of drying and wetting. The results clearly suggest that the thermal conductivity is better expressed as a function of the matric suction head so as to reflect the saturation history. There has been almost five-fold increase in the measured value of thermal conductivity when the soil was wetted to a residual degree of saturation from being dry.