No description available.

Cooling and ventilation of office spaces by displacement ventilation and chilled ceiling panel systems is potentially more energy efficient than conventional air conditioning systems. Heat transfer in this type of system is characterised by the presence of vertical temperature gradients and significant radiant asymmetry. The room heat transfer models used in current building simulation methods do not allow adequate representation of this type of system due to their reliance on a single node to define the internal air temperature. The overall aim of the work described in the thesis has been to develop a model of this type of system that is suitable for use in annual building energy simulation. The model presented, is intermediate in complexity between a CFD numerical model and the current single air node models, having ten air nodes. The operating characteristics of displacement ventilation systems, used both with and without chilled ceiling panels, have been studied by making experimental measurements in a test chamber and by reference to published experimental data. Numerical calculations of the flow and temperature fields have been made with a coupled flow and radiant exchange CFD code. Steady state calculations have been made of displacement ventilation using a conjugate heat transfer method. Interesting oscillations in the flow and temperature field of displacement ventilation operating with a chilled ceiling have been found through adopting a fully transient calculation procedure. The thesis describes how the experimental and numerical data has been used to develop the structure and define the parameters of a simplified nodal model. The logical development of the model structure, from the most elementary model to one which is able to capture the effects of the temperature gradients and incomp1ete mixing of the air in the room is described. A method is also presented whereby the parameters of the model are found directly from the experimental data by solving the heat and mass balance equations of the nodal model. The parameters of the model have been generalised by analysing these calculations and by making use of established convection coefficient correlations. The performance of the model is demonstrated by firstly making comparisons of the experimental and numerical data under steady state conditions, and also by demonstrating that the model is able to reproduce the characteristics of displacement ventilation and chilled ceiling systems under different operating conditions.

Thesis (M.S.)--University of Michigan, 1961.

Thesis--Wisconsin. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 182-186). Also available on the Internet.

No description available.

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No description available.

The objective of this thesis is to explore the properties of supercritical carbon dioxide (CO2). In addition, the feasibility of building a small-scale low cost system will be explained. A supercritical fluid is a fluid which exhibits properties between liquid and gas with liquid like densities and viscosities similar to a gas. Since the discovery of supercritical fluids in 1822, the use of supercritical fluids, specifically supercritical CO2, has grown in popularity. The application of supercritical CO2 has continued to grow in industrial applications since the 1970’s. Supercritical CO2’s has many beneficial properties as a “green” solvent. Supercritical CO2 as a solvent is able to be implemented in a wide range of applications from aerospace, microchip manufacturing, food production, biomedical, pharmaceutical, dry-cleaning, and many more. This thesis project included designing, building and testing a supercritical CO2 extraction apparatus that examines the use of supercritical CO2 as a solvent in the extraction process of decaffeinating coffee. Due to the fact that supercritical CO2 requires high pressure operating conditions, the apparatus design is important not only for function but also for safety. In the description portion of this paper, design considerations related to each component’s function and their specific roles in the overall system are clearly stated. Furthermore, the build process is outlined along with the overall step-by-step operation of the apparatus. Different methods of data measurements are taken while the system is running, in order to interpret the apparatus’ overall functionality. Through the exploration of this experimental data, the results were compared between different operating parameters. In order to determine the feasibility of the supercritical apparatus, the devise was tested by applying the supercritical CO2 as a solvent for the extraction of caffeine from coffee beans. Analysis of the analytical data recorded from experimental testing confirms that the apparatus produced supercritical CO2. After testing specific operating conditions, it is proven that the supercritical CO2 is able to function as a “green” solvent in this small-scale system. The experimental results from these analytical runs are compared with theoretical maximums in order to determine the efficiency of the devise. Lastly, the paper presents an overview including lessons learned from the design process and from the information gathered. Data from experimental testing is interpreted and the system design is reevaluated with suggestions for future improvements.