Les contraintes législatives, environnementales et économiques poussent les constructeurs automobiles à envisager toutes les solutions possibles pour optimiser au mieux la consommation de carburant des véhicules. La récupération d'énergie à l'échappement fait partie de ces solutions envisageable et le moteur à cycle de Rankine offre de nombreux avantages.Le choix de cette technologie de récupération d'énergie à l'échappement est justifié au moyen d'un état de l'art complet ainsi qu'au moyen d'une comparaison basée sur des simulations au moyen de modèles calibrés. Ces simulations ont permis également de donner un ordre de grandeurs des gains de consommation attendus sur différents cycles de conduite.L'expanseur du moteur à cycle de Rankine est un des éléments-clés du système. Aucun expanseur disponible sur le marché n'est adapté pour l'application véhicule. Dès lors, le dimensionnement d'un nouvel expanseur a été entrepris. Ce dimensionnement a nécessité le développement d'un modèle détaillé de l'expanseur scroll. Le moteur à cycle de Rankine fonctionne avec de l'eau et les expériences passées ont montré que la gestion d'un mélange eau-huile est particulièrement délicate. Le choix d'opérer sans lubrification a été réalisé et une attention particulière s'est portée sur la lubrification sèche des volutes de l'expanseur. Des essais expérimentaux ont permis de mettre en évidence les propriétés tribologiques de divers couples de matériaux. La définition des matériaux du joint radial et des volutes de l'expanseur a donc pu être réalisée.Finalement, cet expanseur a pu être testé sur un banc d'essais. Ce banc a également permis de tester plusieurs autres composants du moteur à cycle de Rankine. Les performances de ces composants ont pu être mesurées lors d'essais stabilisés et ils ont également permis de calibrer des modèles semi-empiriques. Ces modèles peuvent être utilisés dans l'évaluation des performances du système de récupération. / Automotive manufacturers seek every possibility to reduce passenger car fuel consumption due to several constraints such as legislative, environmental or economical ones. Waste heat recovery is one of those possibilities and, among the waste heat recovery solutions, Rankine cycle heat engines provide numerous advantages.A complete state of the art and a comparison based on calibrated semi-empirical models justified the choice of a Rankine cycle heat engine as the waste heat recovery technology to be investigated in this thesis. The simulation of different technologies also provided some orders of magnitude of the achievable fuel consumption reduction.The expander of the Rankine cycle heat engine is one of the key element of the system. No commercially available expander is suitable for a waste heat recovery application on passenger cars. Therefore, a new expander has been sized and manufactured. A detailed model of the scroll expander has been built in order to size the expander.The working fluid of the Rankine cycle heat engine is water and previous experimental works have shown that a mix of steam and lubricating oil is not easy to manage. Dry lubrication has therefore been chosen and experimental test have been run to study tribological properties of different couples of materials. Those tests allowed to choose the material of the involute and the tip seal of the expander.Finally, the expander has been tested in a Rankine cycle heat engine. Other components of the Rankine cycle heat engine have also been tested. Performances of those components have then been measured in steady conditions. These measurements allowed the calibration of semi-empirical models that can therefore be used to evaluate the performance of the system.

With the growth of energy consumption and the optimization of industrial processes worldwide, new energy sources have been explored and investigated. Waste heat is a potential source for the generation of electricity and heat. This heat can be reused at different stages of industrial processes by using absorption heat pumps, which transfer thermal energy from a location with a lower thermal potential to a location with a higher thermal potential. This research work is basically focused on the evaluation of different absorption heat pumps implemented in the SAKO Brno incineration plant. To carry out this purpose, a bibliographic review of this technology has been carried out worldwide, then the mass and energy balance in the compressor is presented, from which the waste heat to be recovered with the pump will be obtained. Using the EES software, the mass and energy balance of the selected pumps is performed, then the amount of heat and electrical energy generated by the plant when implementing each of the pumps is shown, and finally the economic analysis is presented The design and implementation of a heat exchanger in the system is also included as an essential part of improving operation. The best option arises from the highest operational efficiency at the lowest possible cost.

This thesis deals with the design of a Heat Recovery Steam Generator (HRSG). Theintroductory part is devoted to a brief description of the boiler, the specified parametersand the compilation of the temperature profile. The main computational part of thiswork is divided into 6 parts. The first contains preparatory calculations, including thecalculation of boiler eiciency. In the second part, a flue gas duct is designed. This isfollowed by a thermal calculation of the boiler for all heat exchange surfaces. The last 3parts deal with the design of the drum, piping and the loss of boiler draft calculation.

In der Dissertationsschrift wurden zwei Schwerpunkte untersucht, die sich zum einen mit der Entwicklung einer Bewertungsmatrix zur Erstabschätzung potenzieller Abwärmenutzungen und zum anderen mit der Integration thermoelektrischer Generatoren im Gießereiprozess auseinandersetzten. In der Matrix wurden 4 Modellabwärmequellen definiert, die sich jeweils in 9 verschiedene Betriebszustände unterteilen, um die vielfältigen Prozessbedingungen widerzuspiegeln. Weiterhin wurden 4 Modellwärmesenken festgelegt, die in Abhängigkeit der thermischen Leistung der Abwärmequellen, die Bewertungsreferenz darstellen. Im Ergebnis erfolgte eine Bewertung von 144 unterschiedlichen Abwärmenutzungskonzepten nach den Kriterien: Energieeffizienzsteigerung, Kaskadennutzung, wirtschaftlich maximal vertretbares Budget und erzielte CO2-Einsparung. Die Integration der thermoelektrischen Generatoren erfolgte am Pfannenfeuer, im Formkasten und an der Druckgussmaschine. Die höchsten Durchschnittswerte der elektrischen Leistung wurden mit 45mW im Formkasten erreicht. Damit können Sensornetzwerke energieautark versorgt, die Datenverfügbarkeit erhöht und die Prozesseffizienz gesteigert werden.

Research in sustainable energy sources has become the interest of many studies due to the increasing energy demand and the amount of wasted energy released from existing methods, along with their effect on climate change and environment sustainability. Thermo-Electric Generators (TEGs) are a potential solution that is being studied and implemented as they can convert low grade thermal energy to useful electrical energy at various operating conditions. The integration of a TEG within a heat exchanger (TEG/HX) system connected to an electrical DC micro-grid, using a Maximum Power Point Tracking (MPPT) system is the focus of this study. Using a numerical TEG/HX model from a previous study and a developed DC micro-grid model the interaction between the thermal and electrical aspects were investigated with the focus on the electrical performance of the system. The main concern of this study is to investigate the effect of the sub components of the DC micro-grid on the overall available energy. An analytic model was developed to estimate the power loss in the electrical circuit of the micro-grid, the model utilizes the equations for switching and conduction losses which have been used by several studies. Other variables such as the battery characteristics and electrical load profiles were also investigated by simulating several case studies including changing operating conditions. This study shows the effect of a TEG configuration on the power loss in an electrical system using power loss curves in comparison with the Open Circuit Voltage (OCV) of such configuration. It also covers important modes of operation for the battery, loads and MPPT for a stable and reliable operation of an isolated DC micro-grid system were TEGs are the only source of power. The result of the study presented is a system design that is able to maximize the electrical energy harvested from the TEGs to extend the operation of the dc-micro-grid first by applying a suitable TEG configuration and consequently a suitable electrical circuit. Secondly, by adapting to the changing operating conditions of the TEGs and the loads; and compensating for these changes using the battery storage system. / Thesis / Master of Applied Science (MASc)

Waste heat recovery is a multi-billion-dollar industry with a compound annual growth rate of 8.8% assessed between 2016 to 2024 and low-grade waste heat (< 230^oC ± 20^oC) makes up 66% of this ubiquitous resource. Thermoelectric generators are preferred for the recovery process because they are cheap and are well suited for this temperature range. They generate power by converting thermal potential to electric potential, known as the Seebeck effect. Since they have no moving parts, they are inherently immune to mechanical failure or an intermittent need for maintenance. However, the challenge has been to effectively harvest waste heat with these modules to generate power, using passive processes. This work is focused on designing a device for optimized harvesting of waste energy from the ambient with a custom, evaporatively-cooled heat sink. This heat sink is designed to passively handle the cooling of the other side of the thermoelectric module so as to enable the attainment of a minimum of 5V, which is the minimum voltage required to power small mobile devices. The heat sink model is similar to a loop heat pipe but engineered for compactness. To ensure this level of efficacy is attained, several studies are made to optimize the wick. Non-metal wicks were considered as they do not contribute to an increase in temperature of the compensation chamber in loop heat pipes. A non-metal wick integrated with nanoparticles is tested and results show a clear thermal management enhancement over similar but virgin non-metal wicks, at over 16%. The heat source section of the device is optimized for energy-harvesting in low grade temperature regimes by incorporating a near-black body coating on the metal heat source section. Experimental results show that both the heat source and sink sections were able to induce sufficient thermal potential for the thermoelectric modules to passively generate up to 5V using eight 40mm by 40mm Bismuth Telluride modules in 3.5 minutes. The prototype is relatively cheap, inherently reliable and presents the possibility of passively harvesting low-grade waste heat for later use, including powering small electronic devices.

Increasing the efficiency of conventional power plants is a crucial aspect in the quest of reducing the energy consumption of the world and to having sustainable energy systems in the future. Thus, within the scope of this thesis the possible efficiency improvements for the Wärtsilä 18V50DF model gas engine based combine power generation options are investigated by recovering waste heat of the engine via Organic Rankine cycle (ORC).  In order to this, four different ORC models are simulated via Aspen Plus software and these models are optimized for different objective functions; power output and price per unit of electricity generation. These ORC models are: regenerative Organic Rankine cycle (RORC), cascaded Organic Rankine cycle with an economizer (CORCE), cascaded Organic Rankine cycle with two heat sources (CORC2) and cascaded Organic Rankine cycle with three heat sources (CORC3). In the cascaded cycle models there are two loops which are coupled with a common heat exchanger that works as a condenser for the high temperature (HT) loop and as a preheater for the low temperature (LT) loop. By using this common heat exchanger, the latent heat of condensation of the HT loop is utilized. The engine’s hot exhaust gases are used as main heat source in all the ORC models. The engine’s jacket water is utilized in the CORC2 models as an additional heat source to preheat the LT working fluid. In the CORC3 models engine’s lubrication oil together with the jacket water are used as additional sources for preheating the LT loop working fluid. Thus, the suitability of utilizing these two waste heat sources is examined. Moreover, thermodynamic and economic analyses are performed for each model and the results are compared to each other. The effect of different working fluids, condenser cooling water temperatures, superheating on cycles performance is also evaluated. The results show that with the same amount of fuel the power output of the engine would be increased 2200 kW in average and this increases the efficiency of the engine by 6.3 %. The highest power outputs are obtained in CORC3 models (around 2750 kW) whereas the lowest are in the RORC models (around 1800 kW). In contrast to the power output results, energetic efficiencies of the RORC models (around 30 %) are the highest and CORC3 models (around 22 %) are the lowest. In terms of exergetic efficiency, the highest efficiencies are obtained in CORC2 (around 64.5 %) models whereas the lowest in the RORC models (around 63 %). All the models are found economically feasible since thermodynamically optimized models pay the investment costs back in average of 2 years whereas the economically optimized ones in 1.7. The selection of the working fluid slightly affects the thermodynamic performance of the system since in all the ORC configurations Octamethyltrisiloxane (MDM) working fluid cycles achieve better thermodynamic performances than Decamethyltetrasiloxane (MD2M) working fluid cycles. However, the choice of working fluid doesn’t affect the costs of the system since both working fluid cycles have similar price per unit of electricity generation. The CORC2 models obtain the shortest payback times whereas the CORC3 models obtain the longest Thus the configuration of the ORC does affect the economic performance. It is observed from the results that increasing the condenser cooling water temperature have negative impact on both thermodynamic and economic performances. Also, thermodynamic performances of the cycles are getting reduced with the increasing degree of superheating thus superheating negatively affects the cycle’s performances. The engine’s jacket water and lubrication oil are found to be sufficient waste heat sources to use in the ORC models.

Copper processing plants involved in smelting, electro-refining and electro-winning are heat-intensive undertakings that provide extensive challenges for attainment of high energy efficiency. Literature has shown that most of these plants, especially smelters, operate at low overall energy efficiency due to the seemingly complex energy scenario where heat and electricity as forms of energy are treated distinctively from each other. Many copper processing plants have not yet explored both available and emerging waste heat recovery technologies hence remain operating at lower energy efficiencies. In the copper processing plants under study in particular the Nchanga tailings leach plant (TLP), plant operators hinted that some of the processes that ought to operate in heated environments operate at ambient temperatures because of lack of a heating mechanism. The project discusses possible heating mechanisms from available local resources and applicable technologies. As the competing options for providing the required heat at the Nchanga TLP present different carbon emission scenarios, the carbon emissions associated to the recommended installations shall be quantified against a suitable baseline. Flue gas waste heat from the nearby Nchanga smelter has been taken as the available local energy source on which the applicable heating scenarios at TLP are analyzed. The project analyzed waste heat scenarios for three furnaces at Nchanga smelter where it has been established that flue gases from the furnaces contain 37.31 MW of waste heat. Analysis for channeling the waste heat into heat recovery steam generators gave the steam turbine power generation potential of 7.06 MW. The project also demonstrated how energy efficiency undertakings can be used as a driver for carbon emission reduction measures and for participation to the available carbon trading mechanisms such as CDM. Selection of suitable baseline scenarios revealed a lot of potential for carbon finance undertakings in the three case study plants. At the Nchanga smelter, the 7.06 MW power generation capacity has an associated potential of 61,820 tCO2/year emission reductions that can be monetized through the available carbon trading markets. The research established that Nchanga TLP has a heating demand of 10.87MW. If this heating demand was to be met by using the smelter waste heat, the undertaking can be taken as CDM activity or other carbon trading platform with an associated potential of 95,183 tCO2/year.

Rising energy demands and the continual push to find more energy efficient technologies have been the impetus for the investigation of waste heat recovery techniques. Diesel engine exhaust heat utilization has the potential to significantly reduce the consumption of fossil fuels and reduce the release of greenhouse gases, because diesel engines are ubiquitous in industry and transportation. The exhaust energy can used to provide refrigeration by implementing an organic Rankine cycle coupled with a vapor-compression cycle. A critical component in this system, and in any waste heat recovery system, is the heat exchanger that extracts the heat from the exhaust. In this study, a cross-flow microchannel heat exchanger was geometrically examined and thermally tested under laboratory conditions. The heat exchanger, referred to as the Heat Recovery Unit (HRU), was designed to transfer diesel exhaust energy to a heat transfer oil. Two methods were developed to measure the geometry of the microchannels. The first was based on image processing of microscope photographs, and the second involved an analysis of profilometer measurements. Both methods revealed that the exhaust channels (air channels) were, on average, smaller in cross-sectional area by 11% when compared to the design. The cross-sectional area of the oil channels were 8% smaller than their design. The hydraulic diameters for both channel geometries were close to their design. Hot air was used to simulate diesel engine exhaust. Thermal testing of the heat exchanger included measurements of heat transfer, effectiveness, air pressure drop, and oil pressure drop. The experimental results for the heat transfer and effectiveness agreed well with the model predictions. However, the measured air pressure drop and oil pressure drop were significantly higher than the model. The discrepancy was attributed to the model's ideal representation of the channel areas. Additionally, since the model did not account for the complex flow path of the oil stream, the measured oil pressure drop was much higher than the predicted pressure drop. The highest duty of the Heat Recovery Unit observed during the experimental tests was 12.3 kW and the highest effectiveness was 97.8%. To examine the flow distribution through the air channels, velocity measurements were collected at the outlet of the Heat Recovery Unit using a hot film anemometer. For unheated air flow, the profile measurements indicated that there was flow maldistribution. A temperature profile was measured and analyzed for a thermally loaded condition. / Graduation date: 2012

Heat actuated adsorption heat pumps offer the opportunity to improve overall energy efficiency in waste heat applications by eliminating shaft work requirements accompanying vapor compression cycles. The coefficient of performance (COP) in adsorption heat pumps is generally low. The objective of this thesis is to model the adsorption system to gain critical insight into how its performance can be improved. Because adsorption heat pumps are intermittent devices, which induce cooling by adsorbing refrigerant in a sorption bed heat/mass exchanger, transient models must be used to predict performance. In this thesis, such models are developed at the adsorbent particle level, heat/mass exchanger component level and system level. Adsorption heat pump modeling is a coupled heat and mass transfer problem. Intra-particle mass transfer resistance and sorption bed heat transfer resistance are shown to be significant, but for very fine particle sizes, inter-particle resistance may also be important. The diameter of the adsorbent particle in a packed bed is optimized to balance inter- and intra-particle resistances and improve sorption rate. In the literature, the linear driving force (LDF) approximation for intra-particle mass transfer is commonly used in place of the Fickian diffusion equation to reduce computation time; however, it is shown that the error in uptake prediction associated with the LDF depends on the working pair, half-cycle time, adsorbent particle radius, and operating temperatures at hand. Different methods for enhancing sorption bed heat/mass transfer have been proposed in the literature including the use of binders, adsorbent compacting, and complex extended surface geometries. To maintain high reliability, the simple, robust annular-finned-tube geometry with packed adsorbent is specified in this work. The effects of tube diameter, fin pitch and fin height on thermal conductance, metal/adsorbent mass ratio and COP are studied. As one might expect, many closely spaced fins, or high fin density, yields high thermal conductance; however, it is found that the increased inert metal mass associated with the high fin density diminishes COP. It is also found that thin adsorbent layers with low effective conduction resistance lead to high thermal conductance. As adsorbent layer thickness decreases, the relative importance of tube-side convective resistance rises, so mini-channel sized tubes are used. After selecting the proper tube geometry, an overall thermal conductance is calculated for use in a lumped-parameter sorption bed simulation. To evaluate the accuracy of the lumped-parameter approach, a distributed parameter sorption bed simulation is developed for comparison. Using the finite difference method, the distributed parameter model is used to track temperature and refrigerant distributions in the finned tube and adsorbent layer. The distributed-parameter tube model is shown to be in agreement with the lumped-parameter model, thus independently verifying the overall UA calculation and the lumped-parameter sorption bed model. After evaluating the accuracy of the lumped-parameter model, it is used to develop a system-level heat pump simulation. This simulation is used to investigate a non-recuperative two-bed heat pump containing activated carbon fiber-ethanol and silica gel-water working pairs. The two-bed configuration is investigated because it yields a desirable compromise between the number of components (heat exchangers, pumps, valves, etc.) and steady cooling rate. For non-recuperative two-bed adsorption heat pumps, the average COP prediction in the literature is 0.39 for experiments and 0.44 for models. It is important to improve the COP in mobile waste heat applications because without high COP, the available waste heat during startup or idle may be insufficient to deliver the desired cooling duty. In this thesis, a COP of 0.53 is predicted for the non-recuperative, silica gel-water chiller. If thermal energy recovery is incorporated into the cycle, a COP as high as 0.64 is predicted for a 90, 35 and 7.0°C source, ambient and average evaporator temperature, respectively. The improvement in COP over heat pumps appearing in the literature is attributed to the adsorbent particle size optimization and careful selection of sorption bed heat exchanger geometry.