The heating curves for a number of different materials, including metals and non-metals, were observed while being irradiated with a beam from a C02 gas laser. The radiant energy spectrum emitted by the materials was measured and recorded, and from this data the heating and cooling rates of the materials were determined. Infrared measurements in the 3 to 5 micron and 8 to 14 micron regions were performed using two Barnes Spectral-Master Radiometers. Data was recorded with both stationary and moving target materials to determine the effect of airflow on the heating and cooling characteristics of the materials. The observed initial heating curve for the solid materials up to the melting point are compared with a theoretical model. The procedure for calibration of the equipment and for data collection is also contained in this thesis.These measurements are important because the experimental conditions closely approximate realistic environmental conditions for materials which are used in different types of aircraft during flight.

The thermal conductivity of gases has been the subject of experimental investigations over a period of several decades (54). The thermal conductivity (hereafter simply referred to as the "conductivity"), being, from a physical point of view, one of the basic properties of a gas, much of the classical kinetic theory was concerned with its interpretation. Its measurement was to examine the validity of the theory. The limits of this validity were similar to those imposed on the theory by other gaseous properities, which lead to the concept of the "ideal gas". As to the conductivity, the behaviour of the majority of naturally occuring gases approximated closely that of the "ideal gas" under normal conditions, i.e. at moderate or room temperatures and a pressure range up to atmospheric pressure. Serious deviations from experimental data occured, however, when it was attempted to apply the theory to gases at higher temperatures and pressures.[...]

Regenerators are key components in many thermal devices such as Stirling cryocoolers, magnetic refrigeration devices etc. They act as temporal thermal energy storage and therewith separate two thermal reservoirs. Regenerators are typically made up of porous structures referred to as the packing material that can lead to complex flow pathways of the heat transfer fluid through the regenerator. The nonisothermal and periodically reversing flow type allows for thermal energy exchange with the packing material of the regenerator. The performance of such devices depends greatly on the geometry of the porous structure, itsmaterial properties, length scales involved as well as operating conditions. This thesis is a study of thermohydraulic properties of thermal regenerators under oscillating flow conditions. In the first part of this thesis, thermodynamic models are developed for the extraction of the friction factor and Nusselt number from an experiment based on a harmonic approximation technique. These models are verified using a two dimensional pore scale model that allows to calculate friction factor and Nusselt number on a theoretical basis independent from an experiment. The second part of this thesis is devoted to the application of the models presented in part one to an experiment. A test apparatus that allows to measure temperature and pressure drop for various types of regenerators is presented. The measurements for a microchannel and packed bed of spheres regenerator are characterized using spectral analysis. Friction factor and Nusselt numbers are evaluated and parametrized using the models derived in the first part of this thesis. Themethodology presented in this thesis reveals insights in the dynamic effects of oscillating flow type heat transfer. The theoretical findings are applied to experimentally obtained data for a correct interpretation of friction factor and Nusselt number. / Graduate

In this work an attempt is made to correlate polymer miscibility with diffusion and with molecular interactions. A system with lower critical solubility temperature has been selected, namely polystyrene (PS) and polyvinyl methyl ether (PVME). Most of the published work has been done on polymers in solutions or on solvent cast specimens and therefore on ternary systems. The role of solvent has not yet been fully evaluated and it was of interest to compare the results on solvent cast samples with those prepared by mechanical blending and by diffusion. Molecular interaction is dependent on functional groups present and for this reason experiments have been performed on PVME blends with PS of different levels of sulfonation (SPS). Selective deuteration (d-PS) was used to identify and assign some absorption peaks in the infrared spectra. DSC measurements have shown that only one Tg is present for all blends prepared by solvent casting. It was necessary to use an extreme quenching rate down to liquid nitrogen in order to preserve the high temperature (above 150°C) phase separated structure, represented by two Tg of homopolymers. The mechanically blended system, on the other hand, did not show a single T g of the blend, unless annealed for one day at 110°C. This confirms the results obtained by diffusion studies using light microscopy and neutron reflectivity, that the diffusion rates are extremely slow and therefore do not control the phase formation and separation processes. These experiments also indicate that the microstructures of solvent cast samples and samples prepared by mechanical blending are different. The Tg of mechanical blended polymers indicate, that the composition of diffusion swollen PS does not correspond to the phase diagram measured in solutions, confirming thus the above result. The FTIR studies at different temperatures have shown that changes in spectra of polymer blends, as reported in the literature can be explained by temperature changes in pure homopolymers. This indicates that molecular interactions, which are responsible for miscibility, are not detectable by infrared absorptions and are therefore of unspecified strength and location. The FTIR of SPSIPVME blends show that sulfonate groups on PS affect polymer miscibility through changes in configuration of molecules, rather than through direct interaction with the PVME, as suggested in the literature. An attempt has been made to study diffusion of SPS and polycarbonate (PC) system by neutron reflectivity. Preliminary results indicate that surface relaxation effects make the data interpretation difficult.

Theories of the metal-electrolyte interface are reviewed with particular attention to the prediction of thermodynamic quantities. A comparison of the different theories is made using a range of experimental results on Hg-aqueous electrolyte systems. Certain widespread failings of the models are revealed. These are identi- fied as being the results of a neglect of solvent structure and of chemical interactions. Next a solvent-free metal-molten salt system is investigated using a model based on the MSA. Thermodynamic properties, parti- cularly the capacitance and the potential at the point of zero charge and their variation with temperature, are calculated. The magnitudes for a range of ionic species are in agreement with experiments for Pb-alkali halide systems, but the (relatively weak) temperature dependence is not predicted correctly. The success of this application of the MSA compared to applications to aqueous systems shows the great importance of the solvent in determining the properties of these systems. To attempt to improve on the MSA model a new model based on the EXP approximation is developed. The predicted trend of the temperature dependence of capacitance is now given correctly but in other respects the predictions are worse than those of the MSA. In our first MSA model the metal is treated as a hard wall. A more realistic representation is now introduced which incorporates electron spill-out. By a phenomenological analysis the extent of spill-out into the electrolyte is estimated. No direct measurement of this quantity has been made. It is consistent with theoretical estimates made for aqueous systems when allowance ,is made for the effect of the solvent.

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Given the importance of heat balance being maintained between a person and their environment an appropriate clothing choice is essential. Since military personnel are required to work effectively when deployed in any of the world's climates it is important that the thermal protection afforded by their clothing is considered as well as its more obvious protective properties such as those relating to the chemical and abrasive environments. Clothing descriptions restricted to details of heat and water vapour transfer characteristics alone, as is commonly the case, are recognised as being insufficient. Of particular note, where these data are obtained under 'artificial' conditions, ie intrinsic values, they are unlikely to represent the 'resultant' values as observed when worn by human subjects engaged in actual work tasks. Where intrinsic data are used in predictive standards calculations, to estimate safe work times etc, the workforce under consideration may not always be protected. One source of change in the thermal properties of clothing, when in the workplace, occurs due to increased convective and evaporative heat transfer at the wearer's skin surface caused by air movement through the clothing. This may occur as a result of wearer body movements or increased environmental air speed. The Ventilation Index has previously been suggested as an accurate and repeatable method for quantifying clothing ventilation characteristics. Although several other measurement techniques have also been suggested, the Ventilation Index is simple (albeit laborious) to conduct, and does not require the use of expensive equipment. Work conducted towards this thesis has shown that the Ventilation Index may be suitable for use in either manikin testing or human studies assessmentso f clothing. The aim of this thesis was to investigate the suitability of the Ventilation Index as a measurementt echnique for the assessmenot f clothing ventilation characteristics, particularly to consider the relationship between clothing ventilation and wearer physiological responses and to identify the factors which can affect this. The Ventilation Index measurement systems constructed as part of this research have improved on those used previously in similar research. New materials technology has provided an improved air-tight oversuit for use during measurement of the clothing micro-environment (a constant source of fiustration, it appears, for previous authors), while extensive calibration of the whole system has proved its accuracy. Using the Ventilation Index has shown that the ingress and egress of air into and from the clothing micro-environment may induce a physiological response from the wearer of the clothing (chapter 6) such increases in air movement being reflected by a drop in insulation afforded by the clothing (chapter 7). Of particular interest to persons involved in the thermal assessment of clothing, will be the suggestion that clothing may exhibit different ventilation characteristics when tested on a thermal manikin to when worn by human subjects. This difference appearing to be related to clothing fit (investigated in chapter 9). Of interest to wearer's of protective, is the observation that air-impermeable clothing does not necessarily withstand changes in environmental air movement (chapter 10). The technique is not without criticism. The standard tracer gas technique, used to calculate clothing air exchange rate, considers only air movement occurring next to the wearer's skin. In multi-layer clothing ensembles, the movement of air in clothing layers more distant will change the clothing micro-environment and thus have consequences for the wearer. Preliminary investigation suggests that distribution of nitrogen to each clothing layer should enable assessmenot fair movement in each of these layers.