Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 155-161).

A second law analysis of compression ignition engine was completed using a thermodynamic engine cycle simulation. The major components of availability destruction and transfer for an entire engine cycle were identified and the influence of mode of combustion, injection timing and EGR on availability balance was evaluated. The simulation pressure data was matched with the available experimental pressure data gathered from the tests on the Isuzu 1.7 L direct injection diesel engine. Various input parameters of the simulation were changed to represent actual engine conditions. Availability destruction due to combustion decreases with advanced injection timing and under premixed compression ignition (PCI) modes; but it is found to be insensitive to the level of EGR. Similarly, trends (or lack of trends) in the other components of availability balance were identified for variation in injection timing, EGR level and mode of combustion. Optimum strategy for efficient combustion processes was proposed based on the observed trends.

The purpose of the study was to compare the effectiveness of visualization of natural phenomena via computer simulation and manipulations of concrete objects, in a physics laboratory, on the development of students’ inquiry skills in mechanics. A quasi-experimental method that employed the 2 Learning Tools x 2 Time of learning split-plot factorial design was applied in the study. The sample consisted of 54 Grade 11 students from two physics classes of the university preparation section in the Ottawa-Catholic School Board. One class was assigned to interactive computer simulations (treatment) and the other to concrete objects in physics laboratory (control) as learning tools. Both tools were embedded in the general framework of the guided-inquiry cycle approach. The results showed that the interaction effect of the Learning Tools x Time of learning was not statistically significant. However, the results also showed a significant effect on the development of students’ inquiry skills (indicated by the pre- and post-inquiry skills test) regardless of the type of learning tool they had used. The findings suggested that these two strategies are effective in developing students’ inquiry skills in mechanics.

The purpose of the study was to compare the effectiveness of visualization of natural phenomena via computer simulation and manipulations of concrete objects, in a physics laboratory, on the development of students’ inquiry skills in mechanics. A quasi-experimental method that employed the 2 Learning Tools x 2 Time of learning split-plot factorial design was applied in the study. The sample consisted of 54 Grade 11 students from two physics classes of the university preparation section in the Ottawa-Catholic School Board. One class was assigned to interactive computer simulations (treatment) and the other to concrete objects in physics laboratory (control) as learning tools. Both tools were embedded in the general framework of the guided-inquiry cycle approach. The results showed that the interaction effect of the Learning Tools x Time of learning was not statistically significant. However, the results also showed a significant effect on the development of students’ inquiry skills (indicated by the pre- and post-inquiry skills test) regardless of the type of learning tool they had used. The findings suggested that these two strategies are effective in developing students’ inquiry skills in mechanics.

The purpose of the study was to compare the effectiveness of visualization of natural phenomena via computer simulation and manipulations of concrete objects, in a physics laboratory, on the development of students’ inquiry skills in mechanics. A quasi-experimental method that employed the 2 Learning Tools x 2 Time of learning split-plot factorial design was applied in the study. The sample consisted of 54 Grade 11 students from two physics classes of the university preparation section in the Ottawa-Catholic School Board. One class was assigned to interactive computer simulations (treatment) and the other to concrete objects in physics laboratory (control) as learning tools. Both tools were embedded in the general framework of the guided-inquiry cycle approach. The results showed that the interaction effect of the Learning Tools x Time of learning was not statistically significant. However, the results also showed a significant effect on the development of students’ inquiry skills (indicated by the pre- and post-inquiry skills test) regardless of the type of learning tool they had used. The findings suggested that these two strategies are effective in developing students’ inquiry skills in mechanics.

The study of thermoacoustic effects is a relatively new area, particularly in application to thermoacoustic engines. For thermoacoustic engines to be commercially viable, there are still many aspects to be investigated, not only practical aspects but also at the fundamental level of physics. Particularly lacking is research on heat exchangers in thermoacoustic engines, despite the fact that this is one of the most important components, for which a design methodology does not yet exist. The primary aim of this work was to investigate the design methodology for heat exchangers in thermoacoustic devices to improve their efficiency. In this work, second law analysis was chosen as the design methodology and was applied to a simplified model of heat exchangers in thermoacoustic engines and its validity was examined. However, for the analysis to be useful to design practical devices, further knowledge of the heat transfer mechanism in oscillatory, compressible flow, and on the development of boundary layers under such conditions are required. This is not currently available for thermoacoustic devices. The commercial software PHOENICS was used to investigate this oscillatory heat transfer problem numerically. To test the capability of the software for simulating thermoacoustic phoenomena, two dimensional standing waves and thermoacoustic couples were simulated at various operating conditions and geometries, including conditions very close to those at heat exchangers in thermoacoustic engines. The results were compared with existing analytical solutions and the results of numerical simulations from others and showed that PHOENICS is capable of simulating thermoacoustic effects. However, the accuracy of second order effects, such as heat flux induced by thermoacoustic effects, was limited by the capability of PHOENICS and the results should be interpreted with this in mind. Energy and flow fields from thermoacoustic couple simulations were investigated from plots of energy vectors, energy lines, instantaneous velocity fields, particle traces and energy dissipation.The dependence of such quantities on plate spacing, plate length and Mach numbers are presented. One important result from these test which is relevant to the design of regenerators or heat exchangers in thermoacoustic engines was that a net heat pumping effect appears only near the edges of thermoacoustic couple plates, within about a particle displacement distance from the edges. Also it was observed that the energy dissipation near the plate is proportional to the plate surface area but increases quadratically as the plate spacing is reduced. The results also indicated the presence of larger scale vortical motion outside the plates which disappeared as the plate spacing was reduced. The presence of such vortical motion did not seem to influence the heat transfer to the plates. In order to simulate heat exchangers in thermoacoustic engines without simulating the whole device, boundary conditions representative of those near the ends of the regenerator plate were considered and tested. Although in some test cases, the simulation converged to a solution with minimal energy imbalances, there was a major discontinuity in the energy flux vectors near the boundary. Further investigations (both numerical and experimental) are required to provide further insight into the boundary conditions which need to be specified for future simulations of heat exchangers in thermoacoustic engines.

The purpose of the study was to compare the effectiveness of visualization of natural phenomena via computer simulation and manipulations of concrete objects, in a physics laboratory, on the development of students’ inquiry skills in mechanics. A quasi-experimental method that employed the 2 Learning Tools x 2 Time of learning split-plot factorial design was applied in the study. The sample consisted of 54 Grade 11 students from two physics classes of the university preparation section in the Ottawa-Catholic School Board. One class was assigned to interactive computer simulations (treatment) and the other to concrete objects in physics laboratory (control) as learning tools. Both tools were embedded in the general framework of the guided-inquiry cycle approach. The results showed that the interaction effect of the Learning Tools x Time of learning was not statistically significant. However, the results also showed a significant effect on the development of students’ inquiry skills (indicated by the pre- and post-inquiry skills test) regardless of the type of learning tool they had used. The findings suggested that these two strategies are effective in developing students’ inquiry skills in mechanics.

A detailed second law analysis of dual fuel LTC is not yet available in the open literature even though dual fuel low temperature combustion (LTC) has been studied before. To address this gap, a previously validated, closed-cycle, multi-zone, simulation of diesel-natural gas dual fuel LTC was used to perform a second law analysis. In the current study, a 2.4-liter single-cylinder research engine operating at a nominal load of 6 bar BMEP and 1700 rpm was used. Zone-wise thermodynamic irreversibilities as well as total cumulative entropy generated and lost available work over the closed cycle were quantified. Subsequently, two convenient second-law parameters were defined: (1) the “lost available indicated mean effective pressure” (LAIMEP), which can be interpreted as an engine-size-normalized measure of available work that is lost due to thermodynamic irreversibilities (analogous to the relationship between indicated mean effective pressure and indicated work); (2) fuel conversion irreversibility (FCI), which is defined as the ratio of lost available work to total fuel chemical energy input. Finally, parametric studies were performed to quantify the effects of diesel start of injection, intake manifold temperature, and intake boost pressure on LAIMEP and FCI. The results show that significant entropy generation occurred in the flame zone (52-61 percent) and the burned zone (31-39 percent) while packets account for less than 6 percent of the overall irreversibilities. Parametric studies showed LAIMEPs in the range of 645-768 kPa and FCIs in the range of 32.8-39.2 percent at different engine operating conditions. Although the present study focused on dual fuel LTC, the conceptual definitions of LAIMEP and FCI are generally applicable for comparing the thermodynamic irreversibilities of IC engines of any size and operating on any combustion strategy.

In the process of electricity generation, water is used as the working fluid to transport energy from the fuel to the turbine. This water has to be ultrapure in order to reduce maintenance cost on the boilers. For the production of ultrapure water, a desalination process is used. This process consists of an ultrafiltration pretreatment section, two reverse osmosis stages and a continuous electrodeionisation stage. Reverse osmosis desalination plants are, however, inherently inefficient with a high specific energy consumption. In an attempt to improve the efficiency of low recovery seawater applications, energy recovery devices are installed on the brine outlet of the reverse osmosis stages. The energy recovery device recovers the energy that is released through the high pressure brine stream and reintroduces it to the system. The investigated desalination process has a fresh water feed with a salinity of 71 ppm and is operated at recoveries above 85%. The plant produces demineralised water at a salinity lower than 0.001ppm for the purpose of high pressure boiler feed. A thermodynamic analysis determined the Second Law efficiencies for the first and second reverse osmosis sections as 3.85% and 3.68% respectively. The specific energy consumption for the reverse osmosis plants is 353 Wh/m3 and 1.31 Wh/m3. This was used as the baseline for the investigation. An exergy analysis determined that energy is lost through the brine throttling process and that a pressure exchanging system can be installed on all reverse osmosis brine streams. Energy recovery devices are untested in high recovery fresh water applications due to the low brine pressure and low brine flow. It was determined that pressure exchanging systems can reduce the specific energy consumption of the first reverse osmosis stage with 12.2% whereas the second RO stage energy consumption can be improved with 7.7%. The Second Law efficiency can be improved by 25.6% for the first reverse osmosis stage while the efficiency is improved with 18.1% for the second stage. The optimal operating recovery for the PES is between 80% and 90%. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

In the process of electricity generation, water is used as the working fluid to transport energy from the fuel to the turbine. This water has to be ultrapure in order to reduce maintenance cost on the boilers. For the production of ultrapure water, a desalination process is used. This process consists of an ultrafiltration pretreatment section, two reverse osmosis stages and a continuous electrodeionisation stage. Reverse osmosis desalination plants are, however, inherently inefficient with a high specific energy consumption. In an attempt to improve the efficiency of low recovery seawater applications, energy recovery devices are installed on the brine outlet of the reverse osmosis stages. The energy recovery device recovers the energy that is released through the high pressure brine stream and reintroduces it to the system. The investigated desalination process has a fresh water feed with a salinity of 71 ppm and is operated at recoveries above 85%. The plant produces demineralised water at a salinity lower than 0.001ppm for the purpose of high pressure boiler feed. A thermodynamic analysis determined the Second Law efficiencies for the first and second reverse osmosis sections as 3.85% and 3.68% respectively. The specific energy consumption for the reverse osmosis plants is 353 Wh/m3 and 1.31 Wh/m3. This was used as the baseline for the investigation. An exergy analysis determined that energy is lost through the brine throttling process and that a pressure exchanging system can be installed on all reverse osmosis brine streams. Energy recovery devices are untested in high recovery fresh water applications due to the low brine pressure and low brine flow. It was determined that pressure exchanging systems can reduce the specific energy consumption of the first reverse osmosis stage with 12.2% whereas the second RO stage energy consumption can be improved with 7.7%. The Second Law efficiency can be improved by 25.6% for the first reverse osmosis stage while the efficiency is improved with 18.1% for the second stage. The optimal operating recovery for the PES is between 80% and 90%. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015