Low grade heat (LGH) sources, here defined as below 80ºC, are one group of abundant energy sources that are under-utilised in the production of electricity. Industrial waste heat provides a convenient source of concentrated LGH, while solar ponds and geothermal resources are examples of sustainable sources of this energy. For a number of years RMIT has had two ongoing, parallel heat engine research projects aimed at the conversion of LGH into electricity. The Thermosyphon Rankine Engine (TSR) is a heat engine that uses water under considerable vacuum. The other research stream uses a hydrocarbon based working fluid in a heat engine employing the Trilateral Flash Cycle (TFC). The TSR Mk V was designed and built as a low cost heat engine for the conversion of LGH into electricity. Its main design advantages are its cost and the employment of only one moving part. Using the data gained from the experimental rig, deviations from the expected results (those derived theoretically) were explored to gain insight for further development. The results from the TSR rig were well below those expected from the design specifications. Although the experimental apparatus was able to process the required heat energy, the efficiency of conversion fell well below the expected 3% and was approximately 0.2%. The inefficiency was explained by a number of contributing factors, the major being form drag upon the rotor that contributed around 2/3 of the losses. Although this was the major cause of the power loss, other factors such as the interference with the rotor by the condensate on its return path contributed to the overall poor performance of the TSR Mk V. The RMIT TFC project came about from exploration of the available academic literature on the subject of LGH conversion. Early work by researchers into applying Carnot's theory to finite heat sources led them to explore the merits of sensible heat transfer combined with a cycle that passes a liquid (instead of a gas) though an expander. The results showed that it was theoretically possible to extract and convert more energy from a heat source of this type using this method than using any other alternative. This previous research was targeted at heat sources above 80ºC and so exploration of the theoretical and empirical results for sources below this temperature was needed. Computer models and an experimental rig using isopentane (with a 28ºC boiling point at atmospheric pressure) were produced to assess the outcomes of employing low temperature heat sources using a TFC. The experimental results from the TFC research proved promising with the efficiency of conversion ranging from 0.8% to 2.4%. Although s uch figures seem poor in isolation, it should be noted that the 2.4% efficiency represents an achievement of 47% of the theoretical ideal conversion efficiency in a rig that uses mainly off-the-shelf components. It also confirms that the TFC shows promise when applied to heat sources less than 80ºC.

In this thesis, an experimental research is conducted on scroll-based Organic Rankine Cycle (ORC) focusing on the expansion process. An important feature of the ORC is the ability to utilize low or moderate temperature heat sources derived from renewable energy such as concentrated solar radiation, biomass/biofuels combustion streams, geothermal heat and waste heat recovery. The ORC is more appropriate than steam Rankine cycle to generate power from low capacity heat sources (5-500 kW thermal). For example, expansion of superheated steam from 280oC/1000 kPa to a pressure corresponding to 35oC saturation requires a volume ratio as high as 86, whereas for the same operating conditions toluene shows an expansion ratio of 6 which can be achieved in a single stage turbine or expander. The objective of this work is to experimentally study the performance of a selected refrigeration scroll compressor operating in reverse as expander in an ORC. To this purpose, three experimental systems are designed, built and used for conducting a comprehensive experimental programme aimed at determining the features of the expansion process. In preliminary tests the working fluid utilized is dry air while the main experiments are done with the organic fluid R134a. Experimental data of the scroll expander are collected under different operating conditions. Power generation in various conditions is analyzed in order to determine the optimum performance parameters for the scroll expander. In addition, thermodynamic analysis of the system is conducted through energy and exergy efficiencies to study the system performance. Based on the experimental measurements, the optimum parameters for an ORC cycle operating with the Bitzer-based expander-generator unit are determined. The cycle energy and exergy efficiencies are found 5% and 30% respectively from a heat source of 120oC. / UOIT

The Marnoch heat engine (MHE) is a new type of power generation device that is under research and development at the University of Ontario Institute of Technology. In this thesis, the transient heat transfer behaviour of the source heat exchanger of the Marnoch heat engine is studied, and its operation for laminar and turbulent flows is modelled. The temperature variations of the working fluid, the heating fluid and the wall, are calculated. The temperature distribution of the fluids and the wall over the length of the heat exchanger is also calculated. It is found that the temperature of the working fluid rises sharply to a peak and then gradually decreases. The wall temperature decreases exponentially, and the temperature of the heating fluid falls sharply, and then gradually decreases. A base model for the step change in the mass flow of the working fluid is developed and compared against past works for the purpose of validation. / UOIT

Thermoacoustic engines convert heat into acoustic pressure waves with no moving parts; this inherently results in high reliability, low maintenance and low manufacturing costs. Significant increases in the performance of these devices have enabled rivalry with more mature energy conversion methods in both efficiency and power output. This optimal production of acoustic power can be ultimately used to achieve cryogenic temperatures in thermoacoustic refrigerators, or can be interfaced with reciprocating electro-acoustic power transducers to generate electricity. This thesis describes the design, fabrication and testing of a Thermoacoustic Power Converter. The system interfaces a thermoacoustic-Stirling heat engine with a pair of linear alternators to produce 100 watts of electricity from a heat input. It operates with helium at 450 psig internal pressure and a hot side temperature of 1200F. Through thermoacoustic phenomena, these conditions sustain a powerful pressure wave at a system specific 100 Hz. This pressure wave is used to drive the two opposed linear alternators in equal and opposite directions to produce a single phase AC electrical output at that same system frequency. The opposing motion of the two alternators enables a vibration-balanced system. The engine has created 110 watts of acoustic power and the complete Thermoacoustic Power Converter system has produced 70 watts of AC electricity. Compensating for some heat leaks, the converter reaches 26.3% heat to acoustic power efficiency and 16.8% heat to electric efficiency when those maximum values are achieved. This conversion of heat to acoustic power is 40% of the Carnot thermodynamic efficiency limit.

Baigiamajame darbe išanalizuotas AB „Lietuvos geležinkeliai“ prekinių šilumvežių parkas. Išnagrinėti parko modernizacijos projektai. Atlikta prekinių šilumvežių dyzelinių degalų sąnaudų pasirinktame geležinkelio ruože lyginamoji analizė. Atlikta ekonominė analizė, nustatytas modernizuotų, remotorizuotų 2M62 serijos šilumvežių bei naujų SIEMENS ER20 CF prekinių šilumvežių ekonominis efektas pagal sutaupytą degalų kiekį, lyginant su 2M62 šilumvežiais, turinčiais 14D40 variklį. Nustatytas 2M62 serijos šilumvežių modernizacijos, remotorizacijos bei naujo SIEMENS ER20 CF atsipirkimo laikas pagal sutaupytą degalų kiekį ir kitas eksploatacines sąnaudas. Pateikta prekinių šilumvežių parko struktūrinė analizė, prekinių šilumvežių degalų sąnaudų priklausomybės nuo fizinių veiksnių tyrimas, prekinių šilumvežių ekonominis įvertinimas. Išnagrinėta informacija apibendrinta išvadomis ir pasiūlymais, pateiktas literatūros sąrašas. Darbo apimtis – 70 p. teksto be priedų, 36 iliustr., 24 lent., 15 bibliografinių šaltinių. Atskirai pridedami darbo priedai. / The paper analyzes Joint-Stock Company AB „Lietuvos Geležinkeliai“ depot of goods heat-engines. The paper investigates the projects of depot modernization. A comparative analysis of fuel expenditure by goods heat-engines has been conducted in the selected section of the railway. The economic analysis has been carried out, which determines the economic effect of the modernized and remotorized 2M62 series heat-engines and the new SIEMENS ER20 CF goods heat-engines with regard to the saved fuel amount as compared to 2M62 heat-engines with 14D40 engines. The time of covering the modernization and remotorization of 2M62 series heat-engines and the purchase of the new SIEMENS ER20 CF has been determined with regard to the saved fuel amount. The paper presents a structural analysis of the depot for goods heat-engines as well as the research of fuel expenditure by goods heat-engines dependence on physical factors, a comparative analysis of diesel fuel expenditure by goods heat-engines in the railway section as well as economic assessment of goods heat-engines have been conducted. The volume of the paper is 70 pages of text excluding appendices, 36 illustrations, 24 tables, 15 bibliography entries. The appendices are supplied separately.

There are many sources of free energy available in the form of heat that is often simply wasted for want of an effective way to convert it into useful energy such as electricity. The aim of this research project is to design and build a low temperature differential Stirling engine capable of generating electric power from heat sources such as waste hot water or geothermal springs. The engine that has been developed is a research prototype model of a new type of design featuring a rotating displacer which is actuated by a pair of stepper motors. The rotating displacer design enables the use of readily available and comparatively cheap and robust steam pipe as the housing for the engine, and it also avoids problems associated with sealing and heat exchange that would be present in a large engine of a more traditional configuration. Owing to the fact that this engine is a research prototype, it has the ability to have some of its critical operating parameters such as phase angle and stroke length adjusted to investigate the effects on performance. When the next phase of development takes place most of these parameters will be fixed at the optimum values which will make manufacture cheaper and easier. Unfortunately, construction of the prototype engine has not been completed at the time of writing so no power producing results have been achieved; however thorough results are presented on the operation of the control system for the stepper motors which actuate the displacer. Additionally, after a thorough history and background of Stirling engines was researched, the understanding gained of how these engines work has enabled a design process to take place which has hopefully led to a successful design. Analysis of various aspects of the engine have been carried out and results look promising for the engine to produce around 500 Watts of electrical power output whilst running on hot water up to around 90°C.

The phenomenal growth rate for the use of engineering ceramics is attributed to successful scientific responses to industrial demand. These materials are replacing metal and its alloys in diverse applications from cutting tools and heat engine components to integrated circuits. Joining technology plays a vital role in this changing and evolving technology as success and failure comes with breaking new barriers. It is important to improve existing techniques and to develop new techniques that reliably join simple shape components to form complex assemblies or join dissimilar materials such as metal to ceramic. Joining of ceramics is not simple due to their high chemical stability and low coefficient of thermal expansion (CTE). Joining between metal and ceramic is usually carried out at elevated temperatures and upon cooling thermal residual stresses are induced that lead to joint failure or poor strength. Most metal-ceramic joints cannot be used over 500°C primarily due to the low melting temperature of the interlayer. This investigation was concerned with the successful joining for higher temperature applications (above 500°C) of two dissimilar high temperature oxidation and corrosion resistant materials, Fecralloy and silicon nitride. The primary focus was on the effects of process conditions upon the microstructure and mechanical properties of the joint and to also study/identify the joining mechanism. Two novel techniques were employed to join successfully the metal to ceramic. The first was by use of a thin Cu foil that did not remain after joining. Joining occurs by a process that results in partial melting of the Fecralloy interface, where Fe, Cr, Al and Cu reactively infiltrate into the silicon nitride. This liquid mixture causes partial dissolution of the silicon nitride interface, where Si and N diffuse into the Fecralloy. A thin reaction product layer was formed at the silicon nitride interface and our results suggested that this was AIN. The free surface Si and porosity of the silicon nitride along with the eutectic temperatures above 1100°C are all vital for this joining process. The highest average shear strength of a Fecralloy-silicon nitride joint produced by the method was 67.5 MPa. The second route was that of a powder metallurgy one, where cold pressed Ni-Al (1:1 molar) compacts were used to join successfully the Fecralloy to silicon nitride. The formation of NiAl from its constituents is highly exothermic and this is initiated between 500-650°C. The high temperature reached causes partial melting of the Fecralloy interface and dissolution/reactive wetting at the silicon nitride interface. Mostly Fe infiltrates the NiAl improving room temperature ductility, fracture toughness and yield strength. Molten Al from the interlayer reacts and wets the silicon nitride interface with small amount of infiltration and no reaction product forming. The reaction synthesis of NiAl was studied using DTA and TGA, where the effects of Ni particle size and heating rate were investigated. This joining process is highly dependant upon process conditions, the most important of which are applied pressure, heating rate and Ni/A1 particle size. The highest average shear strength attained was 94.30 MPa and this is attributed to good interfacial bonding, high pressure, moderate process temperature and dwell time. The exothermic formation of the NiAl interlayer that is densified and monophase was paramount for this joining process. The Bansal-Doremus kinetic model for evaluating the kinetic parameters from non-isothermal DTA data was shown to be valid. The results obtained were identical to those by other authors who used a different model and approach.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-10-19T12:54:26Z No. of bitstreams: 1 PDF - Alexandre dos Santos Pascoal.pdf: 2352988 bytes, checksum: c311ea77167cf72630e47d718c89ef19 (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2016-10-19T17:11:33Z (GMT) No. of bitstreams: 1 PDF - Alexandre dos Santos Pascoal.pdf: 2352988 bytes, checksum: c311ea77167cf72630e47d718c89ef19 (MD5) / Made available in DSpace on 2016-10-19T17:11:34Z (GMT). No. of bitstreams: 1 PDF - Alexandre dos Santos Pascoal.pdf: 2352988 bytes, checksum: c311ea77167cf72630e47d718c89ef19 (MD5) Previous issue date: 2016-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / History and Philosophy of Science (HFC) has gained ground as an instrument to facilitate the teaching / learning for teachers and students of the sciences. This phenomenon can be explained by the degree of difficulty to explain / understand some scientific principles, when exposed out of context. The HFCs, to situate the scientific changes in the historical and philosophical context, at the same time it facilitates understanding, enables interdisciplinary practice in the academic environment. Our work is part of this new trend and the central idea was to create an innovative proposal of teaching from a problem that we see in the physical education field; the difficulty of understanding the Second Law of Thermodynamics. To this aim, starting from the HFC and the context of the Industrial Revolution, we conducted a literature search of exploratory and qualitative character on the subject and situate the importance of Carnot machine and its relation to our problem. As a result, in addition to academic text, we built a paradidactic and a proposal for practical application in the classroom and hope that these instruments contribute to the construction of an innovative teaching proposal. / A História e Filosofia da Ciência (HFC) tem ganhado espaço como um instrumento facilitador do processo de ensino/aprendizagem para professores e estudantes da área das ciências. Esse fenômeno pode ser explicado pelo grau de dificuldade encontrada para se explicar/entender alguns princípios científicos, quando expostos de maneira descontextualizada. A HFC, ao situar as mudanças científicas no contexto histórico e filosófico, ao mesmo tempo em que facilita o entendimento, possibilita a prática interdisciplinar no ambiente acadêmico. Nosso trabalho se insere nessa nova corrente e a ideia central foi à criação de uma proposta inovadora de ensino a partir de uma problemática que constatamos no campo do ensino da física; a dificuldade de compreensão da Segunda Lei da Termodinâmica. Para tal desiderato, partindo da HFC e do contexto da Revolução Industrial, realizamos uma pesquisa bibliográfica de caráter exploratória e qualitativa sobre a temática e situamos a importância da Máquina de Carnot e a relação desta com a nossa problemática. Como resultados, além do texto acadêmico, construímos um paradidático e uma proposta de aplicação prática em sala de aula e esperamos que estes instrumentos contribuam para a construção de uma proposta inovadora de ensino.

The rapidly expanding of the global population in the 21st-century forces people facing two serious problems: water scarcity and energy shortage. Enormous continuous studies focus on providing enough fresh water and energy in a sustainable way. This thesis aims at exploring novel membrane processes based on thermally responsive ionic liquids with the upper critical solution temperature (UCST ILs) for water desalination and energy conversion from low-grade heat energy to electricity. A UCST IL protonated betaine bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]) was first experimentally studied as a novel draw solute in a thermal forward osmosis (FO). A 3.2 M [Hbet][Tf2N] solution can be obtained via spontaneous phase separation from an IL and water mixture at room temperature. By heating and maintaining the temperature above 56°C, this solution can draw water from high-salinity solution up to 3.0 M, 5 times salty as the sea water. The IL draw solution can be easily regenerated by phase separation. Conducting the FO process at higher temperatures can also increase the water flux. According to the different choices of the freshwater polishing step, the electric energy consumption in this novel process was estimated as 26.3% to 64.2% of conventional one-step sea water reverse osmosis. Two UCST ILs with better performance, [Hbet][Tf2N] and choline bis(trifluoromethylsulfonyl)imide ([Choline][Tf2N]), were selected as the agents in a novel closed-loop thermally responsive IL osmotic heat engine (TRIL-OHE) to convert low-grade thermal energy to electricity. The specific energies of the [Hbet][Tf2N] system and the [Choline][Tf2N] system are 2500 kJ/t and 3700 kJ/t, which are 2.7 and 4.0 times of the seawater and river water system, respectively. The maximum power density measured from a commercial FO membrane is 1.5 W/m2 for the [Hbet][Tf2N] system and 2.3 W/m2 for the [Choline][Tf2N] system, leaving a big room to improve if highly permeable membranes are used. Another notable advantage of the TRIL-OHE is the heat released from the cooling stage can be largely recovered. A rigorous energy balance showed with a 70% heat recovery, the energy efficiency could be increased from around 20% to 70% of the Carnot efficiency in both UCST ILs systems.

Four problems in non-equilibrium statistical physics are investigated: 1. The thermodynamics of single-photon gas; 2. Energy of the ground state in Multi-electron atoms; 3. Energy state of the H2 molecule; and 4. The Condensation behavior in N weakly interacting Boson gas. In the single-photon heat engine, we have derived the equation of state similar to that in classical ideal gas and applied it to construct the Carnot cycle with a single photon, and showed the Carnot efficiency in this single-photon heat engine. The energies of the ground state of multi-electron atoms are calculated using the modi ed Bohr model with a shell structure of the bound electrons. The di erential Schrodinger equation is simpli ed into the minimization problem of a simple energy functional, similar to the problem in dimensional scaling in the H-atom. For the C-atom, we got the ground state energy -37:82 eV with a relative error less than 6 %. The simplest molecular ion, H+ 2 , has been investigated by the quasi-classical method and two-center molecular orbit. Using the two-center molecular orbit derived from the exact treatment of the H+ 2 molecular ion problem, we can reduce the number of terms in wavefunction to get the binding energy of the H2 molecule, without using the conventional wavefunction with over-thousand terms. We get the binding energy for the H2 with Hylleraas correlation factor 1 + kr12 as 4:7eV, which is comparable to the experimental value of 4:74 eV. Condensation in the ground state of a weakly interacting Bose gas in equilibrium is investigated using a partial partition function in canonical ensemble. The recursive relation for the partition function developed for an ideal gas has been modi ed to be applicable in the interacting case, and the statistics of the occupation number in condensate states was examined. The well-known behavior of the Bose-Einstein Condensate for a weakly interacting Bose Gas are shown: Depletion of the condensate state, even at zero temperature, and a maximum uctuation near transition temperature. Furthermore, the use of the partition function in canonical ensemble leads to the smooth cross-over between low temperatures and higher temperatures, which has enlarged the applicable range of the Bogoliubov transformation. During the calculation, we also developed the formula to calculate the correlations among the excited states.