Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 72-74).

Thesis (Ph. D.)--University of Florida, 1982. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 140-143).

Thermal energy storage via the latent heat of suitable phase change materials has the advantages of higher energy storage density and relatively isothermal behaviour compared to sensible heat storage systems. Glauber's salt (Na₂S0₄∙10H₂0) is one of the most extensively studied phase change materials for solar energy systems because of its low price, suitable phase change temperature and high latent heat. However, segregation due to incongruent melting behaviour leading to loss in the heat storage efficiency upon repeated melting-freezing cycling is a serious problem which has severely limited application of Glauber's salt. In this study Glauber's salt was encapsulated in 25 mm diameter hollow spheres and agitated in different systems including a liquid fluidized bed, rotating drum and rotating tube to reduce or eliminate the Toss in its heat storage efficiency. The encapsulated mixture consisted of 96% Glauber's salt and 4% borax by weight with 5% by volume air space in the capsules. Some capsules containing 25%, 15% and 5% by weight excess sodium sulfate and 10% by weight excess water were also prepared, to test the effect of sodium sulfate concentration under different agitation conditions. The heat storage capacity of 5756 capsules, agitated by fluidizing with water in a pilot plant size (0.34 m diameter) column, showed a decrease over the first three cycles to about 60% of that theoretically possible, but there was no further decrease over the next 93 cycles under fluidization conditions. The heat storage efficiency was found to be improved by increasing the superficial water velocity and by decreasing the cooling rate. Heating rate had little or no effect. The fluidized capsules provide enhanced heat transfer rates to or from the heat storage medium, enabling the energy to be charged or discharged in about one hour with realistic inlet and outlet temperatures. The high heat transfer rates are an important advantage for the system and may open new areas of applications for thermal energy storage by encapsulated phase change material. Economic analysis of the liquid fluidized bed heat storage system shows that operating costs are almost negligible compared to fixed capital costs. The heat storage efficiency of capsules decreased to 38.4% of the theoretical capacity or 67% of the corresponding agitated (fluidized) system in only 7 cycles under fixed bed conditions, and the efficiency decreased with further cycling. 97.5% of the original heat storage-capacity was recovered within three cycles when these capsules were refluidized. Performances of the regular and different composition capsules were tested in the rotating tube, with rotation around a fixed horizontal axis passing through the capsules' centers, and in the rotating drum, with impact due to collisions in addition to rotation. The results showed that full rotation of a capsule around a horizontal axis improves the heat storage efficiency. However, full recovery of the theoretical capacity was not possible, even under vigorous mixing conditions. The efficiencies in the rotating tube were similar to those in the rotating drum for capsules subject to the same number of rotations around a horizontal axis. At high rotation speeds centrifugal force had a negative influence, especially in the rotating tube. On the basis of heat storage capacity per unit volume or weight of phase change material, 47% by weight sodium sulfate concentration was found to be optimal for the rotating drum and the rotating tube cases. Some small scale experiments were performed to determine the relative importance of different factors in the loss of heat storage capacity. Sodium sulfate concentration gradients in the capsules with different thermal cycling histories were found by thermogravimetric analysis. The results showed that bulk segregation of anhydrous sodium sulfate is not the only reason for the loss of heat storage capacity in systems using Glauber's salt. Microencapsulation of anhydrous sodium sulfate beneath a layer of Glauber's salt crystals is at least as important. Experiments to determine the degree of subcooling, believed to be another factor in the loss of heat storage capacity, showed that a mixture of 96% Glauber's salt and 4% borax by weight undergoes subcooling of about 5 K in gently agitated capsules. Nucleation and crystallization temperatures both increase with increased agitation. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

No description available.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references. Also available on the Internet.

No description available.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 3, 2007) Includes bibliographical references.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "December, 2005." Includes bibliographical references (leaves 121-124). Online version available on the World Wide Web.

Space heating is one of the simplest and most appealing applications of solar energy. The Roof Integrated Solar Heating System (RISHS) initiated by the Sustainable Energy Centre (SEC) of the University of South Australia offers a practical solution for this application. The main objective of this project is to study the technical viability of this system for domestic applications in Australia. / The research work carried out and reported in this thesis brings together the pioneering work on RISHS, namely: modelling and analysis of both the roof integrated heating system and the phase change material (PCM) thermal storage. The work accomplished includes: developing an improved model for the PCM thermal storage unit (TSU), the development of a comprehensive collector model, the development of control strategy of the total system, the development of TRNSYS-based simulation tool for analysing individual component as well the total system, and analysis of the thermal performance of the system. / The new phase change thermal storage model allows for the inclusion of sensible heat both prior to and after the phase change is complete. It relies on the newly developed phase change processor (PCP) algorithm for accurately predicting the outlet temperature and heat transfer rate. The PCP algorithm facilitates the iterative process required to simulate the phase change process, a phenomenon which cannot be dealt with using the general conduction heat transfer equations. The work has also identified that a melting or freezing process of PCM can be divided into three stages; (a) the sensible heat exchange stage characterised by very high heat transfer rates, (b) predominant latent heat transfer stage with much reduced but relatively constant heat transfer rate, and (c) the stage of combined sensible and latent heat exchange with much a further reduced rate. Two temperature differences governing the melting and freezing processes have been introduced. It has been found that these two quantities affect melting and freezing significantly. Given the clear significance of these two newly introduced quantities, the research work questions some previous claims about the effects of natural convection in certain PCM TSU geometries. / The work on the roof integrated solar collector includes the development of a comprehensive solar collector model where the collector dimensions, construction and material properties become inputs or parameters. Using this model, thermal performance of the collector can be evaluated and the collector standard thermal parameters such as collector heat removal factor and collector heat loss coefficient can be evaluated. / The development of a control strategy of the total system which includes the house being heated, the collector, the PCM, the fan and the auxiliary heater, has been carried out. In the control strategy, the characteristics of each component are taken into account and the schedule of energy flow from the heat source and / or thermal storage are designed to maximise the solar contribution and minimise the auxiliary heating required throughout the heating period. To achieve this, an integrated control strategy of auxiliary and solar heating / thermal storage unit has been proposed. Using this approach, the optimum solar contribution for a specified RISIS can be established. The air mass flow rate and the room space temperature difference are the key parameters which influence the system thermal performance. / The subroutines for modelling the PCM thermal storage and the roof integrated solar collector and the system control strategy have been incorporated into the TRSNSYS simulation package to analyse the total system. The analysis carried out indicates that the RISHS is a technically viable system which can provide significant heating contribution for house heating in Adelaide and Melbourne. The introduction of the PCM thermal storage in the system is a technically viable option; it is in fact the main factor which improves RISHS overall performance. The analyses on three PCMs have revealed that the main factors which dictate their thermal performance are the charge temperature and the melting point (which affect the chargeability), mass flow rate and charge and discharge temperature differences. / The TRNSYS-based simulation tool developed during the research project is expected to become a reliable tool for designing any real system for any location and applications. / Thesis (PhDMechanicalEng)--University of South Australia, 2005.