Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 141-143).

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published_or_final_version / Mechanical Engineering / Master / Master of Science in Engineering

The performance of two innovative collector-loop heat exchangers used in pumped circulation solar water heaters was investigated experimentally and numerically, and TRNSYS simulation models were developed for evaluating long-term performance. The heat exchangers evaluated are a narrow gap mantle on a vertical tank and a falling film system in a standard gas hot water tank. The falling film system is based on minor changes to a mass produced tank and does not require the addition of a special purpose heat exchanger. The heat exchangers were assessed for a range of operating conditions to quantify the overall heat exchanger UAhx value and the effect of thermal stratification in the tank. Flow visualisation experiments and CFD modelling were also performed to provide detailed understanding of the operation characteristics of the heat exchangers. For each heat exchanger, the measured and computed collector loop side heat transfer coefficients were correlated by developing new Nusselt number versus Reynolds and Prandtl number functions. New heat transfer correlations were developed for both types of heat exchanger and have been implemented into full solar water heater simulation models in TRNSYS. Predictions of tank stratification conditions in each heat exchanger were in good agreement with experimental data. Compared to a standard direct circulation system, the annual performance of the mantle system and falling film system are 8% and 18% less respectively. The decrease in system performance is due to the heat exchanger penalty and reduced thermal stratification in the storage tank, however they have the added features of freeze protection and suitability for hard water areas. They are also cheaper to manufacture than convectional heat exchange systems. The annual performance of a falling film solar water heater was shown to be affected by de-stratification if an in-tank electric booster was used. However, improved performance can be achieved if an advanced switching controller is used to modulate the flow rate such that the collector return temperature is always higher than the temperature in the top of the tank.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1983. / Vita. Abstract. Includes bibliographical references (leaves 80-82). Also available via the Internet.

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The performance of two innovative collector-loop heat exchangers used in pumped circulation solar water heaters was investigated experimentally and numerically, and TRNSYS simulation models were developed for evaluating long-term performance. The heat exchangers evaluated are a narrow gap mantle on a vertical tank and a falling film system in a standard gas hot water tank. The falling film system is based on minor changes to a mass produced tank and does not require the addition of a special purpose heat exchanger. The heat exchangers were assessed for a range of operating conditions to quantify the overall heat exchanger UAhx value and the effect of thermal stratification in the tank. Flow visualisation experiments and CFD modelling were also performed to provide detailed understanding of the operation characteristics of the heat exchangers. For each heat exchanger, the measured and computed collector loop side heat transfer coefficients were correlated by developing new Nusselt number versus Reynolds and Prandtl number functions. New heat transfer correlations were developed for both types of heat exchanger and have been implemented into full solar water heater simulation models in TRNSYS. Predictions of tank stratification conditions in each heat exchanger were in good agreement with experimental data. Compared to a standard direct circulation system, the annual performance of the mantle system and falling film system are 8% and 18% less respectively. The decrease in system performance is due to the heat exchanger penalty and reduced thermal stratification in the storage tank, however they have the added features of freeze protection and suitability for hard water areas. They are also cheaper to manufacture than convectional heat exchange systems. The annual performance of a falling film solar water heater was shown to be affected by de-stratification if an in-tank electric booster was used. However, improved performance can be achieved if an advanced switching controller is used to modulate the flow rate such that the collector return temperature is always higher than the temperature in the top of the tank.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Srinivas Garimella; Committee Member: David Sanborn; Committee Member: Sheldon Jeter.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009 / This study presents an intelligent Hot Water Cylinder (HWC) usage profiling system to provide peak demand side management and improve HWC efficiency in a typical household. In this research HWCs will be referred to as geysers. Research was done into various techniques available to improve energy efficiency in South Africa, as well as the different sectors South Africa's electricity supplier, Eskom, has highlighted where improvements in energy efficiency can be made. From this it was decided to refine the scope of the project to the residential sector, and more importantly geyser. A typical geysers operation and power consumption was researched and analysed to determine where efficiency improvements could be made. A system was required that would reduce the amount of energy consumed by the geyser, and provide the consumer with hot water at the same time. Based on the research it was decided to design a profile based geyser controller. The profiling system comprised of a PIC microcontroller, four digital temperature sensors and a time keeper used to determine individually based hot water usage profiles for the home. The profile was based on three parameters, namely the frequency (repetitiveness) of hot water being drawn, the length of the draw period, and the time of day when the water was drawn. Once the profile had reached a 90% accuracy, the profile implemented itself. Based on the profile, the controller then regulated the temperature of the geyser according to the demand of the household, without manual intervention. If the household's routine were changed, the profile would adapt itself accordingly. The controller is therefore fully intelligent and continues to refine the profile on a day to day basis. By introducing the profile based controller, the monthly average geyser temperature was reduced, reducing the amount of standing losses, which in torn reduced the total amount of energy consumed by the geyser. The profile controller was designed to aid in the reduction of the energy demand of geysers on the power grid. This will benefit both the consumer as well as Eskom, as Eskom will have a reduced power load, and the consumer will have a reduced electricity bill. The results of the experiments are shown, as well as a comparison between calculated versus measured results, to justify the accuracy of the calculations.