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Abstract Proton exchange membrane fuel cells (PEMFCs) with a dead-ended anode and cathode can reach high hydrogen and oxygen utilization by a relatively simple system. Nevertheless, the accumulation of the water in the anode and cathode channels can lead to a local fuel starvation deteriorating the performance and the durability of PEMFCs. In this study, a novel design for a polymer electrolyte membrane (PEM) fuel-cell stack was presented which could achieve higher fuel utilization without using hydrogen and oxygen recirculation devices such as hydrogen pumps or ejectors that consume parasitic power and require additional control schemes. The basic concept of the innovatively proposed design was to divide the cells of a stack into several stages by conducting the outlet gas of each stage to a separator and reentering it into the next stage; thereby, a multistage anode and cathode system was prepared. In this relatively ingenious design, a higher gaseous flow rate was maintained at the cell outlet, even under dead-end conditions resulted in a reduced purge-gas emission by avoiding the accumulation of liquid water in the cells. The results revealed that proposed design had the same polarization curve as the open-end mode, leading to an enhanced PEMFC performance.

Abstract Thermal recovery in oil fields is an effective conventional method for extracting heavy oil. Steam injection is one of the main techniques in thermal recovery. Temperature reduction of the injected steam due to heat transfer from tubes to the reservoir environment is one of the essential problems in this method. Increasing the steam temperature or injection rate to overcome this energy loss and to provide the required temperature at the tube outlet considerably enhances the steam generation costs. Furthermore, increasing the injection temperature enhances the thermal stress to injection tubes that in turn brings irreparable damages to production units like casing breakage. In this study, an experimental setup used to simulate steam injection operation in order to decrease the heat transfer coefficient and reduce heat loss to conserve the injected steam temperature. This aim ascertained by using nano coatings as thermal insulator. Two types of thermal insulators including nano silica-based and nano ceramic-based insulators used in this study. Temperature, pressure, and injection rate of steam, and type and thickness of nano thermal insulators were the operating variables. Results show that increasing the injection temperature from 119 °C to 145 °C improves the heat transfer coefficient about twofold that in turn, causes rapid reduction of temperature in injection process. It was also shown that increasing the injection rate from 2.1 g/l to 6.3 g/l inside the bare tube improves the heat transfer coefficient up to 2.5-folds. Therefore, increasing the temperature or injection rate of steam could not be the suitable solution for compensating steam heat loss. The experimental results showed that using ceramic-based and silica-based nano insulation with 5 mm thickness reduces the heat loss up to 45% and 33% for injected steam at 145 °C, respectively.

Abstract Bitumen recovery by steam-solvent coinjection involves the coupled thermal/compositional mechanisms for reduction of bitumen viscosity. Reliable design of such processes requires reservoir flow simulation based on a proper phase-behavior model so that the oleic-phase viscosity near the steam-chamber edge can be modeled reliably. However, the effect of bitumen characterization (e.g., the number of pseudo components used) on steam-solvent coinjection simulation has not been studied in detail, and can be realized only after running multiple reservoir simulations, which is time consuming. There are two main objectives in this paper. One is to develop a reliable method for bitumen characterization by improving the fluid characterization method that was recently developed based on perturbation from n-alkanes (PnA). The other is to develop a novel analytical method for assessing the sensitivity of a particular coinjection simulation to bitumen characterization without having to perform reservoir simulations. A simulation case study is given to validate this analytical method. A proper number of pseudo components for bitumen characterization cannot be determined without considering the effect of phase behavior on the oleic-phase viscosity at chamber-edge conditions in steam-solvent coinjection simulation. Results show that the analytical method developed in this research can detect the sensitivity of recovery simulation to bitumen characterization without performing multiple flow simulations using different sets of fluid models. The PnA-based method developed for bitumen characterization gives reliable predictions of phase behavior for bitumen/solvent mixtures with a small amount of experimental data.

Abstract In the current study, an integrated renewable based energy system consisting of a solar flat plate collector is employed to generate electricity while providing cooling load and hydrogen. A parametric study is carried out in order to determine the main design parameters and their effects on the objective functions of the system. The outlet temperature of generator, inlet temperature to organic Rankine cycle turbine, solar irradiation intensity ( I ) , collector mass flow rate ( m ˙ c o l ) and flat plate collector area ( A P ) are considered as five decision variables. The results of parametric study show that the variation of collector mass flow rate between 3 kg/s and 8 kg/s has different effects on exergy efficiency and total cost rate of the system. In addition, the result shows that increment of inlet temperature to the ORC evaporator has a negative effect on cooling capacity of the system. It can lead to a decrease the cooling capacity from 44.29 kW to 22.6 kW, while the electricity generation and hydrogen production rate of the system increase. Therefore, a multi objective optimization is performed in order to introduce the optimal design conditions based on an evolutionary genetic algorithm. Optimization results show that exergy efficiency of the system can be enhanced from 1.72% to 3.2% and simultaneously the cost of the system can increase from 19.59 $/h to 22.28 $/h in optimal states.

Abstract Communication between vehicles and road infrastructure can enable more efficient use of the road network and hence reduce congestion in urban areas. This improvement can be enhanced by distributed control due to its lighter computational load and higher reliability. Despite favourable impacts on traffic, little is known about the effects of such systems on near-road air quality. In this study, an End-To-End (E2E) dynamic distributed routing algorithm in Connected and Automated Vehicles (CAVs) was applied in downtown Toronto, to identify whether benefits to network throughput were associated with lower near-road NO2 concentrations. We observe significant reductions in the emissions of Greenhouse Gases (GHGs) with increased penetration of CAVs. Nonetheless, at times, the emissions of nitrogen oxides (NOx) increased with higher CAVs. Besides, a higher frequency and severity of NO2 hot-spots were observed under a 100% CAV scenario. Impacts of the proposed system on electric energy consumption in a full electric vehicle network were also investigated, indicating that the addition of CAVs that are electric did not contribute to high energy savings. We propose that such new transformative technologies in transportation should be designed with air pollution and public health goals.

Abstract Conversion of carbon contained in the solid residues (tars + biochar) derived from urban biomass gasification named herein TC would allow enhancing the yield of carbon species (CO/CO2) in synthetic gas. For this purpose, three low cost materials have been tested as possible catalysts: iron species (reduced Fe), bone meal (BM), and ashes (ash) recovered from biochar complete oxidation. The parametric study used the following as variables: air GHSV, onset of reaction temperature, reaction time to optimize CO/CO2 molar ratio and tar content in the produced gas. Results showed an autocatalytic effect of biochar leading to the catalytic conversion of approximately 78% of tars by the native metals contained in TC. The catalytic effect was further enhanced by adding Fe, BM, and extra ash. Addition of Fe catalyst resulted in significant heat generation (temperature increase of ca. 500 °C) and a twofold decrease in reaction time to consume all the carbon. Use of ash and BM as catalysts exhibit heat generation comparable to Fe, along with an improved reaction time, complete tars conversion and a CO/CO2 molar ratio to above 1.3 in the produced gas.