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A novel experimental method to determine the activity of alloy components in very dilute liquid metal solutions has been developed. The method is applied to the measurement of magnesium vapour pressure over nickel alloys to find the thermodynamic properties of magnesium in dilute liquid solutions at 1470°C. The experimental method employs a commercial Atomic Absorption Spectrophotometer to determine directly the vapour pressure of magnesium over the alloys. A radiatively heated Knudsen cell inside a vacuum system contains the metal. Equilibrium constants are given for the reactions, [Formula Omitted] where Al, 0 and Mg are dissolved in liquid nickel. Further, values for the metal-oxygen interaction coefficients [Formula Omitted] and [Formula Omitted] are determined. Finally, a value for the Raoultian activity coefficient at infinite dilution is suggested. A significant change in the activity of magnesium upon the addition of 20% chromium or iron to the dilute liquid nickel alloys was not detected. This is believed due to overpowering magnesium-oxygen interaction at these levels of chromium and iron. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The capabilities of remote sensing can be utilized to map the thermal inertia of a surface. Thermal inertia is a property governing the temperature response of a medium to a heat flux at its surface and is beneficial to geologic mapping and soils stud ies. It is hypothesized that a method using only nighttime cooling will give a simple thermal inertia model requiring a minimum of input. Albedo and topographic slope and aspect data are not required. Since latent heat flux is commonly small at night the model should be applicable over surfaces of varying moisture content. The objective of this thesis is to develop a nighttime cooling model for remote sensing thermal inertia mapping. Three models (I, II, and III) are presented. They are based on solutions to the one-dimensional heat conduction equation for a semi-infinite homogeneous solid with isothermal initial temperature and time dependent boundary conditions of heat flux at the surface. Tests of the models on several soil types using ground based data indicate that all three models give meaningful relative relationships between thermal inertias and that model III often yields accurate quantitative results. For the remote sensing implementation of the model ground heat flux is determined as the residual of the energy balance of the surface. Thus, a procedure for determining net radiation using remotely sensed temperature is discussed. Also, aerodynamic heat transfer theory is used to develop a remote sensing method of estimating sensible heat flux. Corrections for the surface sublayer are necessary. Results for vegetated surfaces are expected to be unreliable. Latent heat flux is assumed to be zero or the average of several sites. Tests of these methods using ground based data give good results. An error analysis approach is used to estimate the errors resulting from a remote sensing implementation of Model III. Airborne thermal line-scan data and ground based micrometeorological observations are used to determine typical errors in the input parameters of the model. Errors in determining the energy balance components are also analyzed in detail. With good input, model III gives reasonable results (generally less than 50 percent probable error) at low thermal inertias (< 2000 J m⁻² C⁻¹ s⁻[sub ½] ). For surfaces of high thermal inertia, errors are large. The limitation of the model is not in the model itself, but in the accuracy of remotely sensed surface temperature as determined from thermal infrared line-scan surveys. For surfaces of low thermal inertia model III provides a simple thermal inertia mapping method which requires a minimum of input and is applicable over a wide variety of terrain and ground moisture conditions. The model is most suitable for the investigation of soils and may provide a useful model for planetary studies. / Land and Food Systems, Faculty of / Graduate

A method to distinguish human level of comfort has been developed by using a thermal camera, physiological sensors, and a surroundings sensor. The method has successfully collected data from hominal facial features, breathing rate, skin temperature, room temperature, blood volume pressure, relative humidity, and air velocity. Participants from all genders and races were involved in two sessions of a human comfort experiment including a psychology survey session. The variables, such as room temperature and clothing are controlled to maintain steady test conditions. The region of interest was determined by body temperature and facial temperature as registered by the thermal imaging camera. To experience different levels of discomfort, participants were required to perform two different activities. The first session included an activity on the air resistance elliptical and the second session required the subjects to remain steady in front of a fan. The data was subsequently compared on all subjects to determine whether human discomfort and comfort can be predicted by using various approaches. The parameters of discomfort and comfort were simulated to characterize human levels of comfort. According to arrangement of correlation among thermal comfort responses, blood volume pressure, skin temperature, respiration, and skin conduction, we are be able to predict discomfort and comfort affective states.

A full electro-thermal simulation of a three-phase space-vector-modulated (SVM) inverter is performed and validated with measurements. Electrical parameters are extracted over temperature for the insulated gate bipolar transistor (IGBT) and diode electro-thermal models. A thermal network methodology that includes thermal coupling between devices is applied to a six-pack module package containing multiple IGBT and diode chips. The electro-thermal device models and six-pack module thermal model are used to simulate SVM inverter operation at several power levels. Good agreement between model and measurement is obtained for steady state operation of the three-phase inverter. In addition, transient heating of a single IGBT in the six-pack module is modeled and validated, yielding good agreement. / Master of Science

In the near future, Gen II, III, and IV nuclear reactors will be in operation. UO2 is a common fuel for reactors in each of these generations and molten salts are used as coolant/fuel in Gen IV molten salt reactors. This thesis investigates potential ways to measure thermal conductivity for these materials: Raman thermometry for UO2 and a needle probe for molten salts. Four Raman thermometry techniques are investigated in this thesis: The Two Laser Raman (TLR), Time Differential Domain Raman (TDDR), Frequency Resolved Raman (FRR), and Frequency Domain Raman (FDR). The TLR is a steady state method used with a thin film. The TDDR and FRR are both time domain methods used with thin cantilever samples. The FDR is a frequency domain method used with a thermally thick sample. Monte Carlo like simulations are performed for each technique. In the simulations, the affect introduced uncertainty has on the measurement of thermal conductivity and thermal diffusivity is measured. From the results, it is recommended that the TLR should be used for measuring thermal conductivity and the FRR used for measuring thermal diffusivity. The TDDR and FDR were heavily affected by the uncertainty which resulted in inconsistent measured thermal properties. For measuring the thermal conductivity of molten salt, a needle probe was designed and manufactured to withstand the corrosive environment found in using molten salts. The probe uses modulated joule heating and measures the temperature rise in a thermocouple. The phase delay and temperature amplitude of the thermocouple are used in determining the thermal conductivity. A new thermal quadrupole based analytical solution, which takes into consideration convection and radiation, to the temperature rise of the probe is presented. The analytical solution is verified using a numerical solution found using COMSOL. Preliminary data was obtained with the probe in water.

Thermal diffusivity (D), measuring how fast heat propagates in a medium, is an important quantity in heat conduction. For a medium with great thermal diffusivity, it will reach thermal equilibrium in shorter time. In the field of solid state materials, thermal diffusivity can give information about the quality and morphology of solid, since D is very sensitive to microstructures. However, studies on the thermal diffusion of organic semiconductors are very scarce. In this thesis, the thermal diffusion of different classes of photovoltaic polymers and their blends with molecular electron acceptors were studied by scanning photothermal deflection (SPD) technique. The reliability of the technique was confirmed by the good matching between the SPD derived experimental D values and the nominal D values of different reference materials obtained from literatures. To illustrate that determination of thermal diffusivity is a possible method for studying microscopic properties of organic photovoltaic materials, SPD technique was applied to various films of photovoltaic polymers with different crystallinities. It is observed that photovoltaic polymers always possess small D values in the range of 0.3mm2/s to 2.3mm2/s. It is also discovered that photovoltaic polymers with more planar molecular structure, stronger π-π stacking and higher crystallinity would possess larger D values. When photovoltaic polymers are blended with small molecular acceptors bulk heterojunctions (BHJs), the thermal diffusivity is always reduced due to disrupted polycrystalline structure and increase probability of intermolecular phonon transport. However, for all-polymer BHJs with polymeric acceptor, the reduction in thermal diffusivity can be moderate as the proportion of ultrafast intramolecular phonon transport is SPD technique was also applied to PBDB-T:(ITIC-M+N2200) ternary BHJs with different ITIC-M to N2200 weight ratio. The thermal diffusivity of the ternary blend increases with the weight percentage of N2200 polymeric acceptor. It is observed that PBDB:(ITIC-M+N2200) ternary photovoltaic devices with enhanced thermal diffusion can possess enhanced photostability. Such enhancement in photostability is attributed to the reduced heat trapping at the area being illuminated due to the improved thermal diffusion.

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