Energy demands are projected to continue increasing over the next decade, which is prompting a change towards higher efficiencies and better utilization of the current energy supply. Thermal waste energy, a prominent inefficiency during any process, can be converted to electrical energy or re-purposed for low-grade energy needs, such as hot water and space heating/cooling. Naturally ventilated chimneys, driven by buoyancy differences between the exhaust gases and the surrounding air, prove to be a source of waste heat. The challenge of waste heat recovery from naturally ventilated exhaust networks is the reduction in buoyancy effects and increase in flow restrictions within the network. This research study will focus on understanding the effects of waste heat recovery and the associated exhaust control devices on the performance of a naturally ventilated exhaust network and the accompanying appliance(s). To investigate the effects, a nodal network methodology using mass and energy conservation principles was adapted for exhaust networks to develop a one-dimensional computational model. In contrast to previous exhaust flow design methodologies, this method solves for the thermal input of the appliance and the associated flow rates, temperature, and pressures via the appliance set point temperature and exterior conditions, such as outside temperature and pressure. Using empirical correlations for heat transfer and pressure loss coefficients of appliance and exhaust components, the computational model was validated through experimental testing of an exhaust network used in the development of a waste heat recovery system called TEG POWER (Thermal Electrical Generator Pizza Oven Waste Energy Recovery). The experimental facility was constructed to investigate the exhaust network with and without the TEG POWER system, along with exhaust control devices. These devices included an exhaust throttling valve and a draft hood to induce dilution air into the chimney. To investigate the individual effects of the devices, experimental testing was conducted at an oven temperature of 300°F (148.9°C), 500°F (260°C), and 600°F (315.6°C) with varying degrees of throttling and/or dilution air. The mass flow measurements were calculated using an energy balance technique validated against a two-way energy balance and well-established heat transfer and pressure loss correlations of the heat exchanger. The experimental mass flow, temperature, and draft pressure results were compared against the respective computational predictions and found to be within a ±10% agreement. The application of the exhaust control techniques with and without waste heat recovery is highly dependent on the objective(s), such as reducing natural gas consumption, and the constraint(s), such as a minimum chimney temperature, placed on the exhaust network design. Using the computational model, a design methodology was proposed to meet the objective(s) within the constraints of the exhaust network. To test the design methodology, a case study was performed with the objective to minimize oven natural gas consumption with a TEG POWER system in relation to a baseline appliance solely fitted with a draft hood. Within the constraints, the methodology was able to identify the appropriate degree of throttling and dilution air intake to minimize natural gas consumption. With the inclusion of the TEG POWER system, the case study showed a potential reduction in natural gas consumption by up to 18% (1.7 L/min) and 13% (3 L/min) at 300 and 600°F oven operating temperatures, respectively. The implementation of the control technique allowed the oven to minimize the intake of dilution air by up to 70% and maintain operational stability during exterior fluctuations in temperature and pressure. The implementation of the waste heat recovery device captured up to 1.0 and 2.7 kW, or a natural gas equivalent of 1.9 and 5 L/min, at 300 and 600°F oven operating temperatures respectively. Implemented into the 8,000 pizza restaurants across Canada, the TEG POWER system would reduce total natural gas consumption by up to 65.5 million cubic meters, which is enough to heat 24,000 Canadian homes, and reduce CO2 output by 112,000 metric tonnes. / Thesis / Master of Applied Science (MASc)

Afin de contrôler l’émission totale des NOx dans l’échappement automobile, un capteur potentiométrique à base de zircone stabilisée à l’yttrium a été développé par la technique de sérigraphie. Il est montré que l’utilisation d’un filtre catalytique, déposé directement sur l’élément sensible, permet d’éliminer les interférences venant d’autres gaz réducteurs dans l’échappement, en particulier monoxyde de carbone (CO), hydrogène (H2), hydrocarbures (CxHy) et ammoniac (NH3). En plus, il est possible de fixer avec le filtre catalytique le rapport NO/NO2 correspondant à l’équilibre thermodynamique. Par conséquent la réponse du capteur n’est plus dépendante du rapport NO/NO2, mais seulement de la température. De plus, la sensibilité et la sélectivité du capteur à NO2 peut considérablement être améliorée en appliquant un courant de polarisation. / In order to monitor the total NOx emission in car exhausts, a potentiometric gas sensor based on yttria-stabilized zirconia (YSZ) has been developed by screen-printing technology. It is shown that the use of a catalytic filter directly deposited on the sensing element can successfully eliminate the interferences coming from other reducing gas species in the automotive exhaust such as carbon monoxide (CO), hydrogen (H2), hydrocarbons (CxHy) and ammoniac (NH3). Furthermore, another advantage of the catalytic filter is its capacity to fix the NO/NO2 ratio according to the thermodynamic equilibrium. In that way, the sensor response is no longer dependent on the NO/NO2 ratio in the exhaust, but only dependent on the temperature. Finally, the application of a polarisation current can enhance considerably the selectivity and sensitivity of the sensor towards NO2.

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In India, the expansion of industries and two-fold increase in motor vehicles over the last decade are posing a serious environmental crisis in the form of urban air pollution. Common pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs), and nitrogen oxides produced by industry and motor vehicles. Air pollution results from a variety of sources. The natural sources include volcanoes, forest fire, scattering soil, biological decay, lightning strikes, dust storms etc. and man-made sources include thermal power plants, vehicular exhausts, incinerators and various other industrial emissions. More than 60% of the air pollution is contributed by these man-made sources. Amongst the gaseous pollutants, the major concern and a challenging task is to control oxides of nitrogen, commonly referred to as NOx. In case of diesel engines, despite the modification in engine design and improvement in after treatment technologies, large amount of NOx continues is get emitted and attempts to develop new catalyst to reduce NOx have so far been less successful. Further, with the emission standards becoming more stringent, estimates are that NOx and particulate matter emission must be reduced by as much as 90%. In this context, the emergence of electrical discharge plasma technique in combination with the few existing technologies is providing to be economically viable and efficient technology. In this thesis emphasis has been laid on the discharge based non-thermal plasma for NOx removal. NOx from simulated gas mixture and actual diesel engine exhaust has been treated. The thesis mainly addresses the following issues. . • Performance evaluation of pipe-cylinder and wire-cylinder reactor for NOx removal . • Study of effect of plasma assisted adsorbent reactor on NOx removal . • Study of effect of adsorption and plasma based desorption using different adsorbent material and electrode configuration The first chapter provides introduction about the air pollutants and the existing NOx control technologies, a brief history of electric discharge plasma, a detailed literature survey and scope of the work. A detailed experimental setup consisting of voltage sources, gas system (simulated flue gas and diesel exhaust), gas analyzers, adsorbent materials are discussed in the second chapter. In the third chapter, NOx is treated by three different methods and are described in separate parts. In first part we have done a comparative study of NO/NOx removal using two different types of dielectric barrier discharge electrodes: a) wire-cylinder reactor, b) pipe-cylinder reactor. Investigations were first carried out with synthetic gases to obtain the baseline information on the NO/NOx removal with respect to the two geometries studied. Further, experiments were carried out with raw diesel exhaust under loaded condition. A high NOx removal efficiency 90% was observed for pipe-cylinder reactor when compared to that with wire-cylinder reactor, where it was 53.4%. In second part an analysis has been made on discharge plasma coupled with an adsorbent system. The cascaded plasma-adsorbent system may be perceived as a better alternative for the existing adsorbent based abatement system in the industry. During this study the exhaust is sourced from a diesel generator set. It was observed that better NO removal in a plasma reactor can be made possible by achieving higher average fields and subsequent NO2 removal can be improved using an adsorbent system connected in cascade with the plasma system. This part describes the various findings pertaining to these comparative analyses. The third and last part of chapter 3 consists of gas desorption from an adsorbent by non-thermal plasma, which is an alternative to conventional thermal desorption, has been studied in relation to diesel engine exhaust. In this process saturated adsorbent material is regenerated using high energetic electrons and excited molecules produced by non thermal plasma. The last Chapter lists out the major inferences drawn from this study.