<p>The design, simulation, and analysis of a reference atrium using ComputationalFluid Dynamics (CFD) are presented. Atria geometries can be observed in manybuildings but their understanding from an energy perspective is not fully understood.Due to the many physical phenomena occurring within these atria, it is often difficult toassess the thermal comfort, energy consumption, and functionality of an atrium's design.The scale of an atrium’s structure coupled with dynamic physical phenomena creates acomplex problem to solve. One particular tool that is useful in solving for detailedenergy quantities is CFD. Validation studies have been conducted using previousexperimental atria data to ensure confidence in the predictions. These validation studieswere successful and also provided further insight on turbulence models, glazing systems,HVAC systems, thermal mass, and fluid flow and heat transfer behavior in atriageometries. A design for a reference atrium located in Toronto, Canada was thensimulated for typical summer and winter conditions using various configurations forglazing, solar heat flux, wall materials, occupant load, and HVAC. These simulationsprovide a realistic analysis of the reference atria and conclusions for the behavior of thereference atria are made.</p> / Master of Applied Science (MASc)

<p>A short, 30cm, test section was used to study the effect of electrohydrodynamic (EHD) forces on flow redistribution in a horizontal, shell and tube heat exchanger subject to both boiling and condensation. The use of a short test section allows for a consistent flow pattern across the test section length which provides further insight into the true effect of EHD.</p> <p>It was found that the voltage polarity of the applied voltages influences the flow distribution. For the current geometry studied, it was found that positive polarity voltages tend to pull liquid away from heat transfer surface and that negative voltages tended to repel more liquid toward the heat transfer surface. Using this knowledge we were able to show that positive voltages were more effective for convective condensation heat transfer enhancement, whereas negative voltages were more effective for convective boiling heat transfer enhancement. A twofold enhancement of convective boiling heat transfer was achieved for positive voltages and a 4fold enhancement was achieved for negative voltages. Similar pressure drop penalties were seen for both cases, approximately twice that of the no EHD case.</p> <p>Furthermore, the effect of DC level, peak to peak voltage, frequency and duty cycle waveform parameters on convective boiling enhancement were studied to explore the range of controllability for the current set of flow parameters. It was found that these various waveform parameters can induce different flow patterns and consequently different heat transfer and pressure drop configurations. In general the heat transfer is enhanced by EHD, but different pressure drop penalties can be achieved for a given enhancement ratio using different waveforms. High heat transfer for relatively low pressure drop was achieved using either negative DC signals or 50%duty cycle pulse waveforms. In some cases the enhancement is quite little compared to the pressure drop, for example the zero DC level, varying peak to peak voltage data. It is suggested that in a system where the heat exchanger pressure drop due to EHD is more dominant than the system pressure drop, it may be possible to use EHD as a method of retarding the system rather than enhancing it thereby broadening the scope of controllability.</p> <p>Finally we showed the proof of concept of using DC EHD as a rapid control mechanism for the load conditions. Using -8kVDC the water side heat flux could be varied by approximately ±3.2 kW/m² within 5 seconds. As a comparison, the same experiment was repeated using the refrigerant flow rate to control the load. Response times were similar for both experiments and although the power required for the flow rate control was less, the minimal variability in flow parameters for the EHD control make it a more attractive method of load control.</p> / Master of Applied Science (MASc)

<p>This research is concerned with CFD modelling of thermal energy storage tanks containing water with submerged phase change materials (PCM). Under appropriate operating conditions, the energy density of this hybrid system can be significantly increased (two to five times) relative to a system containing water only. However, due to low thermal conductivity of phase change materials, the geometry and configurations of the PCM capsules in the tank should be optimized. This research focused on the assessment of flat plate PCM modules submerged in a rectangular water tank. The encapsulation of the PCM within the slender flat plates resulted in a large PCM surface area and a reduction in the internal heat transfer resistance. The water was heated by coils placed at the bottom of the tank. The resulting natural convection currents acted to transfer heat from the hot coils to the PCM modules which were treated as isothermal at the PCM melt temperature. It is concluded that the charge rate of the system increases to 2.8 times by increasing the PCM volume percentage from 2.5% to 15%. However for PCM volume percentages of more than 15%, the area of the PCM became much more than the area of the coil (around 15 times) in a way that the charge rate of the system started to be controlled by the coil. In this stage, the charge rate of the system remained constant, and adding modules to the system only increased the heat capacity of the system. Therefore the charge rate of the system could only increase if the coil surface area was increased. The heat transfer coefficients of the PCM modules and coil tubes were higher than those evaluated by the experimental correlations for natural convection. This was due to the recirculation of the flow in the tank “pumping effect” created by the coil for PCM modules and by the PCM modules for the coil. It was also concluded that superheating of the PCM surface temperature decreases the heat transfer rate to the PCM significantly, and the charge rate of the system varies linearly with the temperature difference between the PCM modules and the coil.</p> / Master of Applied Science (MASc)

<p>Electrohydrodynamics (EHD) was used to enhance the thermal performance of a latent heat thermal storage cell by reducing the charging time for a given amount of latent heat stored. Paraffin wax, which is an organic dielectric commercially available material was selected as the phase change material (PCM).</p> <p>Electric field was applied into the cell by using 9 electrodes kept at -8 kV in an effort to establish EHD forces inside the PCM. The EHD effect was studied in an originally conduction dominated melting environment. That was achieved by the cell design which promoted unidirectional melting downwards to prevent natural convection from occurring by assuring a thermally stratified molten phase. The target was to study the EHD mechanisms of enhancement with less interfering physics.</p> <p>Melting was studied under constant heat flux boundary condition. The temporal thermal profile of the surface heater and the melt front location were used to assess the EHD effect by comparing it to a 0 kV (no EHD) case.</p> <p>It was found that by using EHD (-8 kV), the time required to melt 7 mm thickness of the PCM can be reduced by 40 % when compared to 0 kV case. Through a four hour experiment time, the amount of molten PCM can be increased by 29 % by using EHD compared to 0 kV. The EHD power consumption was less than 0.17 W which is equivalent to 2.4 % of the thermal energy stored in the PCM.</p> <p>A new phenomena was discovered when applying EHD in the tested cell, which is Solid Extraction, where the solid dendrites within the mushy zone were extracted from the mushy zone into the liquid bulk towards regions of higher electric field.</p> <p>A new criteria was developed to quantify the EHD enhancement level and was called EHD enhancement factor. An enhancement factor up to 13 could be reached by using EHD. The effect of changing the heat flux on the enhancement factor was investigated, and it was found that the enhancement factor decreased by increasing the heat flux.</p> <p>Numerical simulations were performed in an effort to understand the EHD mechanisms of enhancement. The static electric field distribution, the interfacial extraction forces and the body forces acting on suspended dendrites were evaluated. The results of numerical simulations were supported by the high speed imaging and the experimental data to explain the EHD mechanisms of enhancement and the regions where solid dendrites extraction happened.</p> <p>Finally an analytical model was developed to estimate the energy stored in the different components of the tested latent heat storage cell and to estimate the amount of energy lost to the surroundings in order to quantify the accuracy of the experiment and a maximum of 18 % heat loss was estimated.</p> / Master of Applied Science (MASc)

Liquid fuel injection is a critical mechanism for the deliverance of liquid fuel in contemporary aircraft propulsion combustion systems due to its outsized influence in providing optimal combustion conditions and improving overall aircraft efficiency and performance. Despite this, these liquid jet in crossflow (LJIC) systems are highly variable due to conditions in the jet and the surrounding airflow, leading to variability in performance behavior and inconsistency in fuel mixing and combustion efficiency. This has prompted the introduction of solid pintile obstructions of novel designs to provide a more flow-independent fuel injection scheme and decrease variability of the jet properties against a range of crossflow conditions. This thesis will examine the effects of a solid pintile obstruction on the behavior of an LJIC injection in a typical ramjet combustion configuration, with a focus on the face angle variations of these pintiles. Two pintiles, with face angles of 60° and 120°, will be tested against a no-pintile control configuration under a range of relevant operating conditions and observed under a novel method of 3D-imaging in the x-z plane view. The investigation is designed to understand the effects of these pintiles in the context of broad shifts in the momentum flux ratio and Weber number across a broad range of vitiated and non-vitiated environments. Results demonstrate the significance of the pintiles on the trajectory and performance of an LJIC injection. Building upon previous investigations on the influence of various pintile dimensions, the face angle was found to play a similarly critical role in the influence of the LJIC injection. Overall, the 120° wider face angle appears to be most optimal in enhancing crossflow interaction and promoting flow-independence compared to the 60° face angle. Future research on narrower and wider face angles and the relationship between the face angle and other design parameters could further improve LJIC injection performance and flow-independence.

This diploma thesis is about an influence of technical gases CO2 and N2, that are present in a fuel, over overall combustion process and a flue gas emissions. The first part of this thesis discussed issues like heat transfer, basic process combustion utilities, used technical gases in experimental part and finally description of observed pollutants. Second part of thesis describes the experiments themselves. Experiments were trying to find how selected parameters were influenced by adding 40 mN3/h or 80 mN3/h of inert gases to a flow of natural gas. Observed parameters were namely emission volumes, flame parameters and maximal heat duty. Experiments took place in horizontal water-cooled combustion chamber and were performed on two different types of burners. Evaluation of results confirmed clear connection of inert gases on temperature of flame; the biggest temperature drop was observed while inert gas CO2 was present in fuel. Lowering of temperature spikes also highly influenced presence of NOx in hot flue gas during all performed trials.

This paper describes the design, manufacturing, and testing of a novel controllable hypoxic incubator with fully functional oxygen gas control and temperature control in a humid environment. On the current market, a majority of the few hypoxic incubators use pre-mixed gas that does not offer precise control over gas concentration. The objective for this project was to create a chamber that allows the user to set the O2 concentration to varying set points of % O2 while maintaining the chamber at a constant body temperature, CO2 level, humidity, and sterility. To start the project, multiple concepts were developed for the chamber design and the control system. These concepts were compared against developed engineering specs and were evaluated amongst the team and sponsor. From there, a detailed CAD model was developed and utilized to design the structure and was used as a guide for manufacturing. The control system was prototyped on breadboards via Arduino. This breadboard testing served as the map to solder perf boards, which are utilized as the final structure for the control system. Once all parts were sourced, machined, and assembled for the final chamber and the control system, these subassemblies were integrated together with a regulated gas system via various tubing. The integrated final design underwent a variety of testing to validate the incubator design and control system. Testing was performed throughout the course of this project: material testing, gas leak testing, cell test, temperature control test, and gas control system optimization; however, the most important of these tests were those relating to the environmental control of the incubator. These tests confirmed whether the incubator design was functional as a practical incubator. Testing confirmed that O2 and temperature control maintained in spec over a short and long period of time while maintaining a humid environment. CO2 control optimization had more complications than the O2 hypoxia system. During testing CO2 concentration would typically overshoot the set point, likely due to a lack of precise control over the gas flow. CO2 variability was reduced due to optimization in the code, but not fully mitigated. Future iterations of this chamber could improve upon the CO2 control and streamline the user interface.

The subject of this study is the effect of in-cylinder selective non-catalytic reduction (SNCR) of NOx emissions in diesel exhaust gas by means of direct injection of aqueous urea ((NH2)2CO) into the combustion chamber. A single cylinder diesel test engine was modified to accept an electronically controlled secondary common rail injection system to deliver the aqueous urea directly into the cylinder during engine operation. Direct in-cylinder injection was chosen in order to ensure precise delivery of the reducing agent without the risk of any premature reactions taking place. Unlike direct in-cylinder injection of neat water, aqueous urea also works as a reducing agent by breaking down into ammonia (NH3) and Cyanuric Acid ((HOCN)3). These compounds serve as the primary reducing agents in the NOx reduction mechanism explored here. The main reducing agent, aqueous urea, was admixed with glycerol (C3H8O3) in an 80-20 ratio, by weight, to function as a lubricant for the secondary injector. The aqueous urea injection timing and duration is critical to the reduction of NOx emissions due to the dependence of SNCR NOx reduction on critical factors such as temperature, pressure, reducing agent to NOx ratio, Oxygen and radical content, residence time and NH3 slip. From scoping engine tests at loads of 40 percent and 80 percent at 1500 rpm, an aqueous urea injection strategy was developed. The final injection strategy chosen was four molar ratios, 4.0, 2.0, 1.0 and 0.5 with five varying injection timings of 60, 20, 10, 0, and -30 degrees after top dead center (ATDC). In addition to the base line and aqueous urea tests, water injection and an 80-20 water-glycerol solution reduction agent tests were also conducted to compare the effects of said additives as well. The comparison of baseline and SNCR operation was expected to show that the urea acted as a reducing agent, lowering NOx emissions up to 100% (based on exhaust stream studies) in the diesel exhaust gas without the aid of a catalyst. The data collected from the engine tests showed that the aqueous urea-glycerol solution secondary had no effect on the reduction of NOx and even resulted in an increase of up to 5% in some tests. This was due to the low average in-cylinder temperature as well as a short residence time, prohibiting the reduction reaction from taking place. The neat water and water-glycerol solution secondary injection was found to have a reduction effect of up to 59% on NOx production in the emissions due to the evaporative cooling effect and increased heat capacity of the water.

This work deals with the determination of the operational efficiency of solid fules boilers for their inclusion in the relevant emission class according to ČSN EN 303-5. Two steel boilers of the same manufacturer, type and performance but of different ages, were measured. The experimental measurments in the real operation of the boilers were carrien out during the combustion of two types of fuels, namely brown coal and spruce wood.The operational efficiency of the monitored sources was calculated from the measured data using both direct and undirect methods. The found efficiency of the boilers corresponds to the expected values, due to their construction, age and the way of using individual components and regulations. In the project part of this work there is a proposal of heating of the family house for the condition of the building before and after the insulation. The calculation was made for the solid fuel boiler and heat pump. The building is heated by radiators and floor heating. The design of the whole system, technical report and project documentation were prepared for each variant.

This work thoroughly analyzes a previously created computational model for predicting characteristic properties of the combustion process in an experimental combustion chamber. Any found shortcomings of the original model are removed and the model is further improved prior to its application on 11 real cases of combustion tests performed at various conditions and with various fuels. Data provided by the model are confronted with the data obtained during the combustion tests and the model accuracy is evaluated, based on local heat flux along the length of the combustion chamber. Finally, the overall usefulness of the model is determined by the means of evaluating the acquired accuracy values, and further possibilities of model improvement and use are presented.