Browsing by Author "Collier-Reed, Brandon"

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    A biomass-fueled combined steam and sCO2 heat and power cycle for Southern African conditions
    (2025) Haffejee, Rashid Ahmed; Collier-Reed, Brandon
    Biomass is a renewable, cost-efficient, carbon-neutral fuel obtained from agricultural waste streams or energy crops that can be combusted in a furnace to co-generate electricity and heat. Integrating a supplementary high efficiency cycle, such as the supercritical-CO2 (sCO2) Brayton cycle, with an existing industrial Rankine cycle and a biomass fired boiler may be an economical option to increase overall thermal efficiency and net generation. However, the integration of sCO2 heaters within the biomass boiler presents challenges related to operating philosophies and component specifications. The focus of this research was to investigate the integration of a sCO2 Brayton cycle with a combined heat and power steam cycle with a modular biomass boiler firing typical Southern African bagasse fuel. A quasi-steady state 1D thermofluid network-based process model of the sCO2, steam and flue gas cycles was developed for nominal and partial load analysis. It accounts for the detailed component characteristics for the Rankine and Brayton cycles, as well as the biomass boiler, together with the complex interactions between all of the components in the different cycles. To facilitate the analysis of these intricate systems, a sophisticated simulation code was developed to allow for necessary customization and enforcement of required boundary conditions and control parameters. The network model solves the mass, energy, momentum, and species balance equations for the various fluid streams, accounting for radiative and convective heat transfer phenomena in the boiler. Due to the novelty of the proposed integrated cycle, high-fidelity 3D CFD modelling was then also used to validate the heat uptakes for the sCO2 heaters in the biomass boiler. Two configurations with the sCO2 heater/s situated within the flue gas flow path were investigated, namely a single convective-dominant heater, and a dual heater configuration with a radiative and a convective heater. At nominal load, the network model results show the required rate of overfiring for the sCO2 configurations, with a 15.3% increase in fuel flow rate resulting in an additional 21.2% in net power output. The impact of the sCO2 heaters situated in the gas flow path was quantified, with reduced heat uptakes for downstream steam heat exchangers offset by increased furnace waterwall heat transfer. At partial loads, between 100%-60%, inventory control proves to be the better performing control strategy for load following, maintaining high thermal efficiency across partial loads. Notably, at 60% load, the sCO2 compressor inlet conditions are near the pseudo-critical point, which requires careful management of inventory control. The boiler CFD modelling highlighted lower heat uptakes for sCO2 heaters compared to the 1D model, exacerbated at lower loads, particularly for the dual heater configuration. The 1D model was consequently calibrated based on these results. The single sCO2 heater configuration is recommended as the preferred configuration to minimise adverse impacts on the Rankine cycle superheaters. Further iterations between the 1D process model and CFD model are recommended.
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    Enabling 'growth mindsets' in engineering students
    (University of Cape Town, 2020) Campbell, Anita; Craig, Tracy; Collier-Reed, Brandon
    Student failure is often attributed to a lack of work by students. While this view has some merit, it implies that only students need to change and reduces the incentive for lecturers, curricula, assessment practices to be interrogated. In this thesis, I take a comprehensive look into why students do not work. Firstly, I place social psychology factors in context with other factors that impact student success and show how beliefs about academic ability underpin the academic behaviour that leads to success. By placing a learning theory lens on six characteristics of fixed mindsets (beliefs that ability can only be developed to an individually pre-determined level) and growth mindsets (beliefs that that effective effort will lead to unlimited self-improvement), I develop a theoretical framework that explains how both fixed and growth mindsets can be encouraged by teaching practices. As students with fixed mindsets may be more vulnerable to dropping out of university, lecturers should be aware of the mindset messages they are sending to students through their words, actions and choice of activities and assessment practices. To address the question of how growth mindsets can be developed, I present results from a systematic literature review of growth mindset interventions aimed at engineering students, drawing on databases in education, engineering, and psychology. The findings show that most interventions involved informing students about mindsets and asking students to reflect on or teach others about mindsets, using personal examples. An intervention was devised to develop growth mindsets in engineering students through tutoring groups on the social media platform WhatsApp. Poor group functioning was addressed using a design-based research approach for the establishment of effective groups. Unexpectedly, assessments of engineering students' mindsets through surveys and interviews showed very low numbers of students with fixed mindset views. Reasons for this result are explained by categorizing growth mindset enablers identified from literature and comparing the literature findings with interview data from engineering students. The thesis culminates by contributing a critique on mindset assessment and a framework for creating learning environments conducive to student success.
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    From Gatekeepers to Gateways: Courses Impeding Graduation Annual Report 2019
    (University of Cape Town, 2020) Shay, Suellen; Collier-Reed, Brandon; Hendry, Jane; Marquard, Stephen; Kefale, Kende; Prince, Robert; Steyn, Sanet; Mpofu-Mketwa, Tsitsi; Carstens, Rondine
    The Courses Impeding Graduation (CIG) Project is a research and development initiative of the Centre for Higher Education Development (CHED) addressing the problem of high failure rates in courses that are obstacles to student retention and progression. This report report lays out the background, aims, objectives, and outcomes of the project in 2019, with a particular focus on first-year Mathematics courses in the Faculty of Science, examining which students are at higher risk of failing these courses. The report includes student perspectives gathered through focus groups.
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    Numerical optimisation and theoretical analysis of complex microchannel heat exchangers
    (2025) Godi, Nahum Yustus; Collier-Reed, Brandon; Ngoepe, Malebogo
    The purpose of this study is to evaluate the performance of the geometries in forced convective heat transfer and steady state laminar incompressible fluid flow. Microchannel heat sinks used were numerically modelled from highly conductive (aluminium) solid material substrate. ANSYS FLUENT Response Surface Optimisation Tool (RSO) was used to numerically optimise and compare the performance of combined microchannel heat sinks with perforated, solid, half-hollow and hollow fins. The simulation began by optimising a typical microchannel heat sink geometry before fin-bars were inserted into the cooling channel to augment heat transfer. Furthermore, solid and perforated fins were modelled and added on the top of the typical heat sink. The performance of the various configurations was then compared. A novel combined microchannel design with circular micro fins was modelled with a circular flow channel. Additionally, a hybrid model was developed, incorporating circular fins on a microchannel heat sink with a rectangular flow channel. The third design featured rectangular fins mounted on a microchannel with a rectangular flow channel. The combined microchannels, featuring circular and rectangular fins, were cooled by water flowing through the channels and internally along the fin inner surface walls to dissipate heat. These designs were then integrated into the computational domain and subjected to cooling using both water and an air stream. The water flows through the flow channel while air flows over the vertical fins to remove excess heat from the external wall surfaces of the fins in forced convection laminar flow condition. Theoretical analysis (intersection of asymptotes method) was carried out in the cooling channels (circular and rectangular). The theoretical analysis results indicated the presence of an optimal geometry among the various cross-sectional shapes, effectively cooling a volume with a uniformly distributed heat flux. A comparison of the analytic findings with the numerical results demonstrates that an optimal design is possible. The numerical cooling processes were carried out in parallel and counter flows. These findings demonstrate that an optimal design can be realised with a combination of Computational Fluid Dynamics and geometric modelling techniques.
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    Workplace learning through structured interactions
    (2009) Seth, Aileen; Shaw, Corrinne; Collier-Reed, Brandon
    Individuals need to keep learning to stay employable and compete in today’s job market, and organisations need to keep learning in order to maintain a competitive advantage in the economy. The workplace is thus being recognised as a legitimate environment for learning new skills and knowledge, through participation in everyday work activities. This recognition has led to numerous studies that connect learning and the workplace, giving rise concepts such as ‘the learning organisation’, ‘organisational learning’, ‘workplace learning’ and ‘informal learning’. All of which have created confusion, uncertainty and complexity in understanding how learning takes place. In order to understand how individuals learn in the workplace, and thus understand how organisations can enhance such learning, this study investigates individuals’ perceptions of their workplace as a learning environment and their experiences of learning through participation in work activities.