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The single family housing sector currently accounts for approximately 15% (US DOE 2002) of the total national energy consumption with the majority of the energy use associated with the HVAC system to provide comfort for the residents. In response to recent concern over the unpredictability of the energy supply and the pollution associated with its consumption, new methods are constantly being developed to improve the energy efficiency of homes. A variety of concrete wall systems including Multi-functional Precast Panel (MPP) systems and Insulating Concrete Form (ICF) systems have been proposed to not only improve the building envelope thermal performance but other important residential characteristics such as durability and disaster and fire resistance. MPPs consist of Precast Concrete Panels (PCPs) that incorporate structural elements, interior and exterior finishes, insulation, and even heating/cooling systems into a single manufactured building panel. The ICF system is a cast-in-place concrete panel system that does not offer the level of integration found in the MPP system but has become increasingly accepted in the building construction industry. This research evaluates the thermal performance benefits of concrete wall systems in detached, single family home applications. The thermal performance benefits of two MPP systems and an ICF system are analyzed within the context of a representative or prototypical home in the U.S. and are compared to two wood frame systems; one representing a typical configuration and the other an energy efficient configuration. A whole wall approach is used to incorporate the two and three dimensional conduction and transient characteristics of the entire wall assembly, including the clear wall and wall detail regions, into a whole building simulation of the prototypical house. The prototypical house heating and cooling energy consumption associated with each wall system is determined for six representative climates throughout the U.S. to evaluate the effect of various ambient conditions on the relative energy savings. For each wall system, the effect of thermal bridging on overall R value, the effect of thermal capacitance, and the role of infiltration on energy use are investigated. The results of the research include a comparison of the prototypical house energy savings associated with each of the wall systems; an assessment of the relative importance of the increased insulation, thermal mass, and improved air tightness on the overall energy load; and a comparison of the cost of ownership for the various wall systems. The results indicate that properly designed concrete wall systems can reduce annual heating and cooling costs. In addition, the results show that the most significant impacts of improved wall systems are, from greatest to least: infiltration reduction, improved insulation configuration, and thermal capacitance. Finally, the results show that while there are energy savings associated with concrete wall systems, economic justification of these systems must also rely on the other attractive features of concrete systems such as greater durability and disaster resistance. / Master of Science

A transient technique was validated for making thermal conductivity measurements. The technique incorporated a small, effectively spherical, heat source and temperature sensing probe. The actual thermal conductivity measurements lasted 30 seconds. After approximately 15 minutes of data reduction, a value for thermal conductivity was obtained. The probe yielded local thermal conductivity measurements. Spherical sample volumes less than 8 cm² were required for the materials tested. Thermal conductivity (and moisture) distributions can be measured for relatively dry or wetted samples. The technique employs an encapsulated bead thermistor. A thermistor, more commonly used as a temperature transducer, has the inherent feature of being readily self-heated. A computer-based data acquisition and control system regulates the power supplied to the thermistor such that its self-heated temperature response approximates a step change. Thermal conductivity is deduced from the transient measurement of the power dissipated by the probe as a function of time. The technique was used to measure the thermal conductivity of fifteen liquids and five insulation materials. Two different thermistor types, glass-encapsulated and Teflon-encapsulated, were evaluated. Capabilities and limitations of each probe type and the measurement technique, in general, were observed. / M.S.

The master's thesis focuses on creating a numerical model of a polymeric heat sink with emphasis on its significant thermal conductivity anisotropy. This anisotropy is caused by highly thermally conductive graphite filler. Its final orientation is given by the melt flow inside the mould cavity during injection molding. The numerical model is created on the basis of a heat sink prototype subjected to experimental measurements, whose physical conditions are reliably replicated by the model. The determination of anisotropy is divided into two parts. The qualitative part is based on the fracture analysis of the heat sink prototype and determines the principal directions of the conductivity tensor in individual sections of the geometry. The computation of principal conductivities falls into the quantitative part, in which this task is formulated as an inverse heat conduction problem. The input data for the proposed task are experimentally obtained temperatures at different places of the geometry. The values of principal conductivities are optimized to minimize the difference between the measured and simulated temperatures.

Vita. / Digitized by Kansas Correctional Industries

The thermal contact conductance (TCC) between two machined pieces of stainless steel was studied. A guarded hot plate thermal conductivity test fixture was designed and built for the experiment. Factors investigated included the contact pressure, surface roughness, interface material and average test temperature. The contact pressure at the interface ranged from 80 to 800 psi. The mean surface roughness of the opposing surfaces was 2.8 ��in (.0708 ��m) parallel to the sanding direction and 1.9 ��in (.0482 ��m) perpendicular to the sanding direction. Interface materials included air, indium foil, copper foil, Teflon tape, silver filled paint and thermal grease. Average test temperatures ranged from 0��C to 100��C, in 20��C increments. With air alone in the interface gap the TCC was nearly insensitive to contact pressure. The thermal grease and silver filled paint most increased the TCC over air alone while being nearly insensitive to pressure. With indium foil the TCC was similar to air, but improved somewhat with increasing pressure. With copper foil the TCC was lower than air alone, but increased with increasing pressure. The Teflon tape had a lower TCC than air at low contact pressure, but a higher TCC than air at higher pressures. In general the TCC improved somewhat at higher temperatures. The ability of an interface material to improve the TCC is more a function of its flow stress and wetting ability than its thermal conductivity. An existing mathematical model was used to predict the TCC with air as the interface material, and was found to over-estimate the TCC by an order of magnitude. It was found that the model did not accurately predict the effective surface spacing for very smooth surfaces as used in this work. When a modification for smooth contact surfaces was incorporated into the model it yielded results that were consistent with experimental results. / Graduation date: 1999

Thermally enhanced greases made of dispersions of small conductive particles suspended in fluidic polymers can offer significant advantages when used as a thermal interface material (TIM) in microelectronics cooling applications. A fundamental problem which remains to be addressed is how to predict the effective thermal conductivity of these materials, an important parameter in establishing the bulk resistance to heat flow through the TIM. <br /><br /> The following study presents the application of two simple theorems for establishing bounds on the effective thermal conductivity of such inhomogeneous media. These theorems are applied to the development of models which are the geometric means of the upper and lower bounds for effective thermal conductivity of base fluids into which are suspended particles of various geometries. <br /><br /> Numerical work indicates that the models show generally good agreement for the various geometric dispersions, in particular for particles with low to moderate aspect ratios. The numerical results approach the lower bound as the conductivity ratio is increased. An important observation is that orienting the particles in the direction of heat flow leads to substantial enhancment in the thermal conductivity of the base fluid. Clustering leads to a small enhancement in effective thermal conductivity beyond that which is predicted for systems composed of regular arrays of particles. Although significant enhancement is possible if the clusters are large, in reality, clustering to the extent that solid agglomerates span large distances is unlikely since such clusters would settle out of the fluid. <br /><br /> In addition, experimental work available in the literature indicates that the agreement between the selected experimental data and the geometric mean of the upper and lower bounds for a sphere in a unit cell are in excellent agreement, even for particles which are irregular in shape.

Thermally enhanced greases made of dispersions of small conductive particles suspended in fluidic polymers can offer significant advantages when used as a thermal interface material (TIM) in microelectronics cooling applications. A fundamental problem which remains to be addressed is how to predict the effective thermal conductivity of these materials, an important parameter in establishing the bulk resistance to heat flow through the TIM. <br /><br /> The following study presents the application of two simple theorems for establishing bounds on the effective thermal conductivity of such inhomogeneous media. These theorems are applied to the development of models which are the geometric means of the upper and lower bounds for effective thermal conductivity of base fluids into which are suspended particles of various geometries. <br /><br /> Numerical work indicates that the models show generally good agreement for the various geometric dispersions, in particular for particles with low to moderate aspect ratios. The numerical results approach the lower bound as the conductivity ratio is increased. An important observation is that orienting the particles in the direction of heat flow leads to substantial enhancment in the thermal conductivity of the base fluid. Clustering leads to a small enhancement in effective thermal conductivity beyond that which is predicted for systems composed of regular arrays of particles. Although significant enhancement is possible if the clusters are large, in reality, clustering to the extent that solid agglomerates span large distances is unlikely since such clusters would settle out of the fluid. <br /><br /> In addition, experimental work available in the literature indicates that the agreement between the selected experimental data and the geometric mean of the upper and lower bounds for a sphere in a unit cell are in excellent agreement, even for particles which are irregular in shape.

No description available.

No description available.