Thermal energy storage(TES) air-conditioning system is a electrical load management technology with great potential to shift load from peak to off-peak utility periods. TES is now in widespread use for electric rate structures and energy policies and becomes a great contribution to energy conservation. However, TES is more complicated than conventional air-conditioning system in design and control strategies. According to practical field operation, the control of dynamic characters is especially difficult, and so are storage capacity design , discharging rate and charging capacity selection. This study set an example how to improve the energy performance of a retrofitted thermal energy storage air-conditioning system of a marine museum. Through full-scale experiment, historical air-conditioning operation data and computer simulation, the solution is provided on condition of unchanging major water pipe and equipment. This example can be a good demonstration for upping performance of TES. After testing and recording data for one year, this case indicates the investigation is effective and valuable to electric power management and green technology.

In this study, a pilot-scale Regenerative Thermal Oxidizer (RTO) was used to test its performance for volatile organic compound (VOC) destruction and degree of thermal energy conservation. The RTO is electrically heated and contains two 0.5 m ¡Ñ 0.5 m ¡Ñ 2.0 m (L ¡Ñ W ¡Ñ H) columns both packed with gravel particles of 1.0 cm in diameter to a height of 1.4 m. The bed has a void fraction of 0.415. The purpose of this study is to establish the influencing operating conditions and to improve the technique for further applications. Experiments include two phases: (1) energy conservation test with no VOC in the influent air stream , and (2) VOC destruction test with influent air streams containing one of the three VOCs: isopropyl alcohol, acetone, and xylene. Phase 1 experiments were conducted in the maximum gravel temperatures (Tmax) of 402-704 oC, superficial gas velocities (Ug, evaluated at ambient temperatures of 25-30 oC) of 0.15-0.50 m/s, and bed shift times (ts) of 0.5-2.0 min. Results indicate that the temperature raise (

<p>This thesis summarises the work performed within the project known as ICE-COOL at the Royal Institute of Technology (KTH) on low tem-perature applications of ice slurry. The ICE-COOL project is a Euro-pean Community funded project within the 5th Framework Program. The task given to KTH was to find and characterize the best possible aqueous solution with a freezing point of -25 °C applicable for ice slurry with an operating temperature of -35 °C. The circumstances differ for low temperature ice slurry from medium temperature as a result of for example the change in thermo-physical properties due to increased addi-tive concentration and the lower temperature.</p><p>Ice slurry is a mixture of fine ice crystals, water and freezing point de-pressant additives. The typical ice crystal size ranges between 0.1 to 1 mm in diameter. The main purpose of using ice slurries is to take advan-tage of the latent heat. More than a few requirements are to be fulfilled by an ideal ice slurry fluid. It should have good thermo-physical proper-ties, high heat transport and transfer abilities, as well as low pressure drop to facilitate small pumping power. The ice content of ice slurry af-fects all the mentioned abilities. Apart from the mentioned factors of the fluid, there are other aspects that have to be taken into consideration such as environmental pollution and toxicity, flammability, material compatibility, corrosion, handling security and cost.</p><p>This thesis reports on the experiences accomplished and the initial ex-periments performed on low temperature ice slurry. The thesis also gives the background and fundamentals necessary for a discussion and com-parison of different aqueous fluids suitable for ice slurry in general and for low temperature in particular. In addition to the low temperature ap-plication, the thesis also reports on an initial energy consumption com-parison between using ice slurry and single-phase fluid in supermarkets by means of the simulation program CyberMart developed by Jaime Arias at the Department of Energy Technology at KTH.</p>

Ocean Thermal Energy Conversion (OTEC) is the process of harnessing the temperature differential that exists in the equatorial oceans between the warm surface water and the cool water thousands of feet below to produce electricity. Due to the massive scale of the ocean thermal resources, OTEC power generation is appealing. The purpose of this thesis was to investigate OTEC and assess its potential viability as an energy source from both engineering and economic perspectives. This thesis provides an introduction to the research, and outlines the scope of the project in Chapter 1. Chapter 2 proves an overview of OTEC, from the basic operation and viable locations, to information on some of the major components that make up the plant. Chapter 3 describes the thermodynamics, heat transfer, and fluid mechanics that govern the physical operation of the OTEC plant. Chapter 4 provides an analysis of different plant design parameters to examine effects different parameters have on plant operations and equipment sizing. Chapter 5 describes the cost estimation for an OTEC plant, and provides subsequent analysis by comparing the estimated cost with other technologies and electricity prices from four island communities. The primary research of this thesis was the development of an integrated thermal fluids systems model of a closed-cycle OTEC power plant for the purpose of analyzing the effects of key design parameters on the plant performance. A simple Levelized Cost of Electricity (LCOE) economic model was also developed and integrated with the Thermal Fluid Systems model in order to assess the potential economic viability of a 20 MW OTEC power plant. The analyses from these models suggest that OTEC is definitely viable from an engineering standpoint, but economic viability for a 20 MW plant would likely be limited to small or remote island communities. / text

Drying laundry has become a huge consuming factor of energy in residential areas through drying machines as tumble dryers and cabinet dryers. In USA the increasing use of drying machines in households increased from 40% during the 1970 to 80% in the 1990, which correspond to a usage of approximately 76 million drying machines. The European market for drying cabinets is not huge. It is mainly Scandinavia that is using cabinet dryers for drying laundry these days. Nowadays cabinet dryers that use hoses to evacuate humid air out the building are developed in the market. Asko Cylinda AB has developed a new condenser cabinet dryer out of a regular cabinet dryer. With the new condenser cabinet dryer no hoses are required because the drying process take place in a closed recirculation system. Several openings at the back of the condenser cabinet dryer make it possible to dry laundry horizontal in different sections. In this thesis the condenser cabinet dryer has been studied in a simulation program that is called Comsol MultiPhysics. A 2-dimensonal model was created where the airflow patterns and temperature distribution in the dryer was simulated. On the basis from the basic model of the dryer several modifications was created to attain knowledge of which modifications contributes to an improved airflow pattern. The temperature distribution in the condenser cabinet dryer is uneven in the sections according to the simulations the air distribution is good in section 2 and 3 in the basic model. The factor that has the largest impact on the air distribution is the air stream that flows up at the back inside the cabinet, the air stream restrains a part of the hot air jet from the openings at the back. Case 1.1 is the modification that created the best airflow profile, which contributed to an even temperature distribution. In the modification the textiles were used to cover up the space at the back of the cabinet to eliminate the air stream to flow up between the textile and the openings. The effect transport between the textile and the air increased with 50 % at several sections when the modification was carried out according to case 1.1. This study is a good basis for further studies in simulation of airflow and temperature distribution in the condenser cabinet dryer. The next step in the study is to create a 3-dimensional model of the cabinet. With this study the 3-D model could be accomplished easier by using parameters from the 2-D model as data on the boundaries. By doing so the system could be delimited, this would reduce the use of computer capacity. / Torkning av kläder har med tiden utvecklats till att bli en stor faktor av energiförbrukning i bostadsområden genom maskiner som bl. a. torktumlare och torkskåp. I USA ökade användningen av torkmaskiner i hushåll från 40% under 1970 till 80% i 1990, vilket motsvarar en användning av ca 76 miljoner torkmaskiner. Marknaden för torkskåp är inte stor i Europa. Det är främst Norden som använder torkskåp för torkning av kläder. I dagsläget tillverkas s.k. avluftarskåp, d.v.s. det krävs en slang ut ur huset för att evakuera den fuktiga luften. Asko Cylinda AB har på senare tid utvecklat ett nytt kondensorskåp av ett sådant avluftarskåp. Med det nya kondensorskåpet behövs det inte någon evakueringsslang ut ur huset eftersom torkningen sker i ett recirkulerande system. Gälarna i bakkanten av torkskåpet möjliggör plantorkning eftersom luften skickas in i flera sektioner. I uppsatsen har kondensorskåpet studerats i ett simuleringsprogram som kallas Comsol MultiPhysics. En 2-dimensionell modell skapades där bl.a. luftströmningsbilden och temperaturfördelningen i skåpet simulerades. Utifrån grundmodellen skapades ett antal modifieringar på kondensorskåpet för att erhålla kunskap om vilka modifieringar som ger bättre luftflödesbilder. Temperaturfördelningen i kondensorskåpet är ojämn enligt simuleringarna då luftdistributionen är bäst i sektion 2 och 3 i grundmodellen. Faktorn som har störst påverkan på luftströmningsprofilen är den uppströmmande luften vid baksidan av skåpet, luften bromsar upp den varma luftstrålen ut från gälarna. Fall 1.1 är modifieringen som skapa den bästa luftströmningsprofilen vilket bidrog med en jämnare temperatur-fördelning. I modifieringen användes textilerna för att täppa igen ytorna vid baksidan av kondensorskåpet för att eliminera uppströmmande luft framför gälarna. Effekttransporten mellan textilen och luften ökade med upp till 50 % på flera sektioner då grunduppställningen modifierades enligt fall 1.1. Studien i denna rapport är ett bra underlag för fortsatta studier inom simulering av luftströmningen och temperaturfördelningen i kondensorskåpet. Nästa steg i studien är att konstruera en 3-dimensionell modell av skåpet. Med hjälp av den här studien kan en 3-D modell underlättas genom att använda parametrar från 2-D modellen som indata på randvillkor. Genom det kan systemet avgränsas för att minimera 3-D modellens konsumtion av dataminne.

The development of portable equipments, wireless sensors networks and self-powered devices in a general manner generates a strong demand for micro-energy harvesting devices. One of the most challenging ways to self power devices is the development of systems that recycle ambient energy and continually replenish the energy consumed by the system. Apart from electromechanical energy harvesting, it is also interesting to convert thermal energy, which is "available" everywhere, into suitable electrical energy. In this thesis, the thermal to electrical energy conversion from temperature fluctuations was developed and improved, and the feasibility of this technique was also confirmed by implementing the experimental experiment. Among different ferroelectric materials, PZN-4.5PT single crystal and P(VDF-TrFE-CFE) 61.3/29.7/9 mol% were chosen as active materials due to their outstanding properties under electric field. By means of some intelligent thermodynamic cycles, e.g., Ericsson or Stirling cycle, which has been presented in previous research, the efficiency of energy conversion could be improved greatly. In the first part, pyroelectric energy harvesting on PZN-4.5PT single crystals with an Ericsson cycle was mainly investigated from two aspects: frequency effect and phase transitions. It was shown that the harvested energy demonstrated a nonlinear decrease with an increase of frequency, and the optimal use of the phase transitions during the Ericsson cycle could greatly improve the harvested energy by choosing the appropriate working temperature range. Based on it, two asymmetric Ericsson models (L-H and H-L cycles) were attempted successfully, and it was confirmed that the H-L cycle is the most effective thermal energy harvesting cycle for this material. The second part concentrated on electrostatic energy harvesting by nonlinear capacitance variation on P(VDF-TrFE-CFE) 61.3/29.7/9 mol% terpolymer. Ericsson cycle was tested experimentally between 25 and 0°C and compared with the simulation from dielectric constant values obtained under DC electric field. The identical result between simulation and experiment proved the reliability of our theoretical evaluation. It was found, from simulation, that the harvested energy increased up to 240 mJ/cm3 when raising the electric field at 80 kV/mm. The further study on Ericsson and Stirling cycle was also made under different temperature and electric field conditions for evaluation. The harvested energy increases with the rising of temperature variation and electric field in both cycles, but in contrast to Ericsson cycle, Stirling cycle can harvest more energy for the same injected energy.

In order to reduce the discharge of the greenhouse gas CO2, the use of biomass is nowadays promoted as fuel in boilers. Compared to boilers fired with coal and oil the biomass-fired boilers have more complications related to both fouling and corrosion on the heat transfer surfaces. After the combustion, unburned inorganic matter in state of vapour, melts and solid particles are transported in the flue gas and may form deposits on heat transfer surfaces. Deposits on the heat transfer surfaces may result in both increasing corrosion and decreasing boiler efficiency as the heat transfer rate to the superheaters and reheaters decrease by deposits. In order to understand the process of deposit build-up, the whole combustion and transport process had to be analysed including aspects such as, boiler design, fuel properties and combustion environment, followed by particle transport phenomena and the probability for particles to get stuck on the heat transfer tubes. In this thesis numerical simulation of particle trajectories has been conducted as well as measurements of deposits on a special designed deposit probe followed by investigation of on-site measurements of deposit depth on the super-heater tubes in a circulating fluidised bed in Västerås, Sweden. Numerical simulations of particle trajectories in the vicinity of two super-heater tubes were conducted in an Eulerian-Lagrangian mode considering the flue gas and ash particles phase. Particle impingements on the tubes were investigated for different particle sizes. The results from the particle trajectory simulations show that particle larger than 10 µm will mainly impinge on the windward side of the first tube but, however also on the sides of the second tube in the flue gas flow direction. In theory as well as from observations and measurements two tubes can merge together by the deposit build-up. Smaller particles are usually more dispersed due to turbulence and thermophorectic forces, resulting in a more even impingement distribution on the whole surface of the tubes. Probe measurements reveal that the deposit layer growth rate have a significant temperature and time dependence. After the initial deposit build-up a sintering process occurs and sintering is also proven to be dependent on temperature and exposure time. Soot-blowing is the most common method to reduce the effect of deposits on the heat transfer tubes. In the present thesis the soot boiling efficiency is therefore also investigated. The soot-blowing show a strong positive effect on the heat transfer rate in a short time (hours) perspective after a soot-blowing cycle is completed. This positive effect is much weaker when considering a time period of three years. This is an effect of fact that soot-blowing mostly remove the loose part of the deposit material leaving the hard sintered part unaffected. The subject of deposit build up on superheater tubes in large scale boilers involves multi-discipline knowledge and historically, the related research is mostly conducted as measurements and experiments on operating plants. Possibly in the future, theoretical simulations will have a bigger part of research on deposit build-up where the calculations are to be calibrated through measurements on real sites plants.

In this thesis proposals for different designs of a borehole thermal energy storage (BTES) have been developed for the building DN-huset in Stockholm, Sweden. To build a BTES results in savings in energy costs by approximately 44 %, i.e. 2 million Swedish crowns annually. Furthermore, a BTES would reduce the annual environmental impact with roughly 75-157 tonnes of CO2 equivalents per year, depending on how the electricity consumption’s environmental impact is estimated. The payback period is about 11 years, including the warm-up period that is necessary before commissioning the BTES. The savings in environmental impact and operating costs are a result of energy being reused. During the summer heat is stored in the bedrock beneath the building for retrieval about half a year later in the winter, when there is a heating demand. In addition to developing proposals for different BTES designs the thesis also examines the influence of certain design parameters, conservative choices and operating conditions.

Phase change phenomena of a fluid flowing in a micro channel may be exploited to make the heat exchangers more compact and energy efficient. Compact heat exchangers offer several advantages such as light weight, low cost, energy efficiency, capability of removing high heat fluxes and charge reduction are a few to mention. Phase change phenomena in macro or conventional channels have been investigated since long but in case of micro channels, fewer studies of phase change have been conducted and underlying phenomena during two-phase flow in micro channels are not yet fully understood. It is clear from the literature that the two-phase flow models developed for conventional channels do not perform well when extrapolated to micro scale. In the current thesis, the experimental flow boiling results for micro channels are reported. Experiments were conducted in circular, stainless steel and quartz tubes in both horizontal and vertical orientations. The internal diameters of steel tubes tested were 1.70 mm, 1.224 mm and the diameter of quartz tube tested was 0.781 mm. The quartz tube was coated with a thin, electrically conductive, transparent layer of Indium-Tin-Oxide (ITO) making simultaneous heating and visualization possible. Test tubes were heated electrically using DC power supply. Two refrigerants R134a and R245fa were used as working fluids during the tests. Experiments were conducted at a wide variety of operating conditions. Flow visualization results obtained with quartz tube clearly showed the presence of confinement effects and consequently an early transition to annular flow for micro channels. Several flow pattern images were captured during flow boiling of R134a in quartz tube. Flow patterns recorded during the experiments were presented in the form of Reynolds number versus vapour quality and superficial liquid velocity versus superficial gas velocity plots. Experimental flow pattern maps so obtained were also compared with the other flow pattern maps available in the literature showing a poor agreement. Flow boiling heat transfer results for quartz and steel tubes indicate that the heat transfer coefficient increases with heat flux and system pressure but is independent on mass flux and vapour quality. Experimental flow boiling heat transfer coefficient results were compared with those obtained using different correlations from the literature. Heat transfer experiments with steel tubes were continued up to dryout condition and it was observed that dryout conditions always started close to the exit of the tube. The dryout heat flux increased with mass flux and decreased with exit vapour quality. The dryout data were compared with some well known CHF correlations available in the literature. Two-phase frictional pressure drop for the quartz tube was also obtained under different operating conditions. As expected, two-phase frictional pressure drop increased with mass flux and exit vapour quality. / QC 20101206

Made available in DSpace on 2014-06-11T19:25:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-06-27Bitstream added on 2014-06-13T19:32:34Z : No. of bitstreams: 1 souza_lmp_me_bauru.pdf: 1572366 bytes, checksum: b4f3b5bc0ddb17fad3e39f5f59ec6a72 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / No estudo de reaproveitamento de energia térmica, os refrigeradores domésticos dissipam calor para o meio ambiente, através do seu condensador, e esse calor pode ser reciclado, ou seja, recuperado através de escoamento de água, como fluido refrigerante escoando pelo condensador e armazenada em um reservatório. Para isto, construi-se um aparato experimental contendo um refrigerador doméstico, duplex com capacidade de 263 litros para o gabinete de refrigeração e 74 litros para o gabinete de congelamento. O refrigerador tem seu condensador acrescido por um trocador de calor tipo tubos concêntricos em contra corrente, cuja fruição é condensar o fluido refrigente utilizando água em circulação. Dessa forma, caso ocorra o carregamento térmico total do tanque de armazenagem, o calor será originalmente dissipado para o meio ambiente, através do condensador aletado. A água aquecida é então armazenada em um reservatório térmico via estratificação térmica. Assim calculou-se as vazões de água aquecida e fluido refrigerante, como também o coeficiente de desempenho do sistema acumulado. Os resultados mostraram que a vazão de água bem como o coeficiente de desempenho do sistema aumenta de acordo com o aumento da pressão hidrostática. Desta maneira, dos resultados obtidos pode-se concluir que a otimização do experimento se dá de forma eficaz e que, o reaproveitamento da água quente proveniente do condensador é perfeitamente possível, reduzindoo consumo de energia elétrica com aquecedores de água e ainda, minimizando a dissipação de calor para o meio ambiente, sem alterar o funcionamento do refrigerador / In the study of recycling thermal energy it is know that domestic refrigerators dissipate heat to environment through the condenser. This heat can be recycled by a water flow, as a coolant in a modified condenser, and stored in a Domestic Hot Water Storage Tanks (DHWST). Thereby, an experimental apparatus was built containing one domestic refrigerator, each one with capacity of 263 liters in the cooling cabinet and 74 liters in the freezing cabinet. The refrigerators had the condenser increase by a type heat exchanger concentric tubes with a counter-current flow, which has the function of replace the original finned exchanger, condensing the coolant with water flow. Thus, in case the total thermal loading of the storage tank, the heat is dissipated to the original environment through the condenser finned. The heated water is then stored in a thermal reservoir via thermal stratification. In these conditions, the flow of heated water and refrigerant was calculated, as well as the coefficient of performance of the system. The results show that the water flow rate and the coefficient of performance of the system increases with the increase in hydrostatic pressure. According to these results, the experiment optimization is effective and it is totally possible to reuse the warm from modified condenser system, what could reduce the electric energy consumption in water beater and minimize the heat dissipation to environment, without modifying the refrigerator operation