scholarly journals OPTIMIZATION OF A SMALL SOLAR CHIMNEY

2020 ◽  
Vol 60 (3) ◽  
pp. 225-234
Author(s):  
Janaina Oliveira Castro Silva ◽  
Cristiana Brasil Maia
Keyword(s):  
Exergy Efficiency ◽  
Small Scale ◽  
Conjugate Directions ◽  
Solar Chimney ◽  
Variable Metric ◽  
Optimization Study ◽  
Physical Variables ◽  
One Year ◽  
Tower Height ◽  
Hourly Basis

An optimization study to maximize the exergy efficiency of a small-scale solar chimney was carried out. Optimization variables include collector diameter (Dc), collector height (Hc), tower height (Ht), and tower diameter (Dt). Models from the literature were used to predict environmental and airflow parameters. Exergy efficiency and solar chimney efficiency were determined, on an hourly basis, for a one-year period. The model was simulated using the EES software. Two methods of optimization were used, the method of conjugate directions and the method of variable metric, both providing similar results. Results were compared to the results from an experimental prototype, and it was found that the energetic and exergetic efficiency were significantly improved. The analysis indicated that the height and diameter of the chimney and collector are the most important physical variables in the design of a solar chimney. For both methods, it was found that the maximum exergy efficiency was obtained with a collector height of 0.5 m, a collector diameter of 30 m, a tower diameter of 1 m, and a tower height of 17.8 – 18.8 m. The exergy efficiency was 44 %.

Small and Full-Scale Modeling for the Application of Wall Solar Chimneys

2016 ◽  
Author(s):  
David Park ◽  
Francine Battaglia
Keyword(s):  
Natural Ventilation ◽  
Velocity Ratio ◽  
Thermal Conditions ◽  
Ambient Air ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Solar Chimney ◽  
Window Position ◽  
Pi Theorem

A solar chimney is a natural ventilation technique that has a potential to save energy consumption as well as to maintain the air quality in the building. However, studies of buildings are often challenging due to their large sizes. The objective of the current study was to determine relationships between small- and full-scale solar chimney system models. In the current work, computational fluid dynamics (CFD) was utilized to model different building sizes with a solar chimney system, where the computational model was validated with the experimental study of Mathur et al. The window, which controls entrainment of ambient air, was also studied to determine the effects of window position. Correlations for average velocity ratio and non-dimensional temperature were consistent regardless of window position. Buckingham pi theorem was employed to further non-dimensionalize the important variables. Regression analysis was conducted to develop a mathematical model to predict a relationship among all of the variables, where the model agreed well with simulation results with an error of 2.33%. The study demonstrated that the flow and thermal conditions in larger buildings can be predicted from the small-scale model.

Development of a Predictive Equation for Ventilation in a Wall-Solar Chimney System

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
David Park ◽  
Francine Battaglia
Keyword(s):  
Mathematical Model ◽  
Relative Error ◽  
Natural Ventilation ◽  
Thermal Conditions ◽  
Ambient Air ◽  
Maximum Error ◽  
Scale Model ◽  
Small Scale ◽  
Maximum Relative Error ◽  
Solar Chimney

A solar chimney is a natural ventilation technique that has potential to save energy consumption as well as to maintain the air quality in a building. However, studies of buildings are often challenging due to their large sizes. The objective of this study was to determine the relationships between small- and full-scale solar chimney system models. Computational fluid dynamics (CFD) was employed to model different building sizes with a wall-solar chimney utilizing a validated model. The window, which controls entrainment of ambient air for ventilation, was also studied to determine the effects of window position. A set of nondimensional parameters were identified to describe the important features of the chimney configuration, window configuration, temperature changes, and solar radiation. Regression analysis was employed to develop a mathematical model to predict velocity and air changes per hour, where the model agreed well with CFD results yielding a maximum relative error of 1.2% and with experiments for a maximum error of 3.1%. Additional wall-solar chimney data were tested using the mathematical model based on random conditions (e.g., geometry, solar intensity), and the overall relative error was less than 6%. The study demonstrated that the flow and thermal conditions in larger buildings can be predicted from the small-scale model, and that the newly developed mathematical equation can be used to predict ventilation conditions for a wall-solar chimney.

Assessment of GRACE-FO Laser Ranging Interferometer measurements

2021 ◽  
Author(s):  
Athina Peidou ◽  
Felix Landerer ◽  
David Wiese ◽  
Matthias Ellmer ◽  
Eugene Fahnestock ◽  
...  
Keyword(s):  
High Frequency ◽  
Signal To Noise Ratio ◽  
Small Scale ◽  
Laser Ranging ◽  
High Signal ◽  
Measurement Sensitivity ◽  
One Year ◽  
Mass Transfers ◽  
Gravity Recovery ◽  
System Errors

<p>The performance of Gravity Recovery and Climate Experiment Follow‐On (GRACE-FO) laser ranging interferometer (LRI) system is assessed in both space and frequency domains. With LRI’s measurement sensitivity being as small as 0.05 nm/s<sup>2</sup> at GRACE-FO altitude we perform a thorough assessment on the ability of the instrument to detect real small-scale high-frequency gravity signals. Analysis of range acceleration measurements along the orbit for nearly one year of daily solutions suggests that LRI can detect signals induced by mass perturbation up to 26 mHz, i.e., ~145 km spatial resolution. Additionally, high frequency signals that are not adequately modeled by dealiasing models are clearly detected and their magnitude is shown to reach 2-3 nm/s<sup>2</sup>. The alternative K‐band microwave ranging system (KBR) is also examined and results demonstrate the inability of KBR to retrieve signals above 15mHz (i.e., shorter than ~200 km) as the noise of the KBR range acceleration increases rapidly. Overall, the first stream of LRI measurements shows that the high signal to noise ratio allows for detection of mass transfers in finer scales, however the ability to fully exploit the high-quality signal measured by the LRI in Level 2 products is still constrained by noise of background models and other onboard instrumentation and measurement system errors.</p><p>Copyright Acknowledgment: This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Science Program.</p>

Cost-Effectiveness of Solar-Powered LED Reading Lamps in Burkina Faso

2013 ◽  
pp. 203-221
Keyword(s):  
Cost Effectiveness ◽  
Burkina Faso ◽  
Small Scale ◽  
Small Community ◽  
Reading Habits ◽  
Education Interventions ◽  
Solar Powered ◽  
Reading Test Scores ◽  
One Year ◽  
6Th Graders

A small-scale project to induce more reading among 5th and 6th graders in rural Burkina Faso by providing them with solar-powered LED lamps indeed increased reading for students in villages without preexisting libraries, but did not affect reading capabilities. The research aimed to establish the magnitude of effects after one year when 10-14 year-olds in rural African villages with small community libraries were given solar-powered lamps for night reading. The effects measured were reading habits (how much did students read?) and reading capabilities (how well could students read and comprehend what they read?). Once village effects were controlled, the lamps had statistically significant effects on reading habits for students in villages without preexisting libraries. The effect sizes were modest, ranging from .20 to .25. There were no effects on reading test scores. A cost-effectiveness metric to use for comparing with other studies of education interventions then is that expenditure of $1 per student on a solar-powered LED reading lamp distribution program generated about a 1% increase in reading, with no apparent effect on reading capabilities.

scholarly journals Optimization and Economic Analysis for Small-Scale Movable LNG Liquefaction Process with Leakage Considerations

2020 ◽  
Vol 10 (15) ◽  
pp. 5391
Author(s):  
Sang Hyun Lee ◽  
Dong-Ha Lim ◽  
Kyungtae Park
Keyword(s):  
Sensitivity Analysis ◽  
Economic Analysis ◽  
Cost Analysis ◽  
Exergy Efficiency ◽  
Small Scale ◽  
Product Cost ◽  
Quantitative Results ◽  
Liquefaction Process ◽  
Lng Liquefaction ◽  
The Cost

In this study, exergy and economic analysis were conducted to gain insight on small-scale movable LNG liquefaction considering leakage. Optimization and comparison were performed to demonstrate the quantitative results of single mixed refrigerant, dual nitrogen expansion, and the propane pre-cooling self-refrigeration processes. For the optimization, exergy efficiency was used as the objective function; the results showed that exergy efficiencies are 38.85%, 19.96%, and 13.65%, for single mixed refrigerant, dual nitrogen expansion, and propane pre-cooling self-refrigeration, respectively. Further, the cost analysis showed that the product cost of each process is 4002.3 USD/tpa, 5490.2 USD/tpa, and 9608.5 USD/tpa. A sensitivity analysis was conducted to determine parameters that affect exergy and cost. The SMR process is the most competitive in terms of exergy efficiency, product cost, and operability, without considering makeup facilities.

Designing, Setting Up, and Facilitating a Knowledge Sharing Virtual Community of Practice, between Social Work Lecturers in the UK and India

2012 ◽  
Vol 8 (4) ◽  
pp. 22-49 ◽  
Author(s):  
Isabel Williams
Keyword(s):  
Social Work ◽  
Action Research ◽  
Knowledge Sharing ◽  
Community Of Practice ◽  
Virtual Community ◽  
Online Discussions ◽  
Small Scale ◽  
Virtual Community Of Practice ◽  
One Year ◽  
The Uk

The purpose of this research is to evaluate the effectiveness of a virtual Community of Practice (vCoP) which was developed between social work lecturers in two University settings – one in the UK and the other in India. The design and methodology draws on qualitative data collected from online discussions and semi-structured questionnaires arising from the involvement of twelve participants over a one year period. An Action Research method was adopted which allowed the shift of power from the designer to the participants over the year. This paper illustrates how a vCoP can be an ideal tool to aid communication and knowledge sharing between universities within an international context. It adds value by increasing the knowledge of participant lecturers to more than local perspectives and gives a greater understanding of social work from an international, cross-country, perspective. Although one of the limitations is that this is a small scale study, it does raise important considerations necessary for ensuring the success for vCoP’s and offers a model to aid successful online collaboration as well as important messages for those who are developing online courses and teaching within an international environment. It further gives insight into adopting Action Research as a research methodology that can be usefully used for online collaborative research.

scholarly journals The Impact of Tides on the Bay of Biscay Dynamics

2020 ◽  
Vol 8 (8) ◽  
pp. 617
Author(s):  
John Karagiorgos ◽  
Vassilios Vervatis ◽  
Sarantis Sofianos
Keyword(s):  
Vertical Mixing ◽  
Ocean Model ◽  
Open Ocean ◽  
Small Scale ◽  
Bay Of Biscay ◽  
English Channel ◽  
Tidal Forcing ◽  
Freshwater Transport ◽  
One Year ◽  
The Impact

The impact of tides on the Bay of Biscay dynamics is investigated by means of an ocean model twin-experiment, consisted of two simulations with and without tidal forcing. The study is based on a high-resolution (1/36∘) regional configuration of NEMO (Nucleus for European Modelling of the Ocean) performing one-year simulations. The results highlight the imprint of tides on the thermohaline properties and circulation patterns in three distinct dynamical areas in the model domain: the abyssal plain, the Armorican shelf and the English Channel. When tides are activated, the bottom stress is increased in the shelf areas by about two orders of magnitude with respect to the open ocean, subsequently enhancing vertical mixing and weakening stratification in the bottom boundary layer. The most prominent feature reproduced only when tides are modelled, is the Ushant front near the entrance of the English Channel. Tides appear also to constrain the freshwater transport of rivers from the continental shelf to the open ocean. The spectral analysis revealed that the tidal forcing contributes to the SSH variance at high frequencies near the semidiurnal band and to the open ocean mesoscale and small-scale features in the presence of summer stratification pattern.

Principals’ experiences of changes in relationships with newly qualified teachers resulting from a teacher registration reform

2019 ◽  
Vol 33 (4) ◽  
pp. 556-568
Author(s):  
Anneli Frelin ◽  
Göran Fransson
Keyword(s):  
Instructional Leaders ◽  
Small Scale ◽  
Structured Interviews ◽  
Content Type ◽  
Qualified Teachers ◽  
One Year ◽  
Teachers Perspectives ◽  
Academic Year ◽  
Newly Qualified Teachers

Purpose The purpose of this paper is to understand, from principals’ points of view, how a teacher registration reform is enacted by examining the potential changes in the relationships between principals and newly qualified teachers (NQTs). The reform entailed principals performing an aptitude assessment of new teachers in their probationary year. Design/methodology/approach Semi-structured interviews were conducted with five principals from two Swedish municipalities on three occasions in one academic year. A third follow-up interview was conducted one year later with four of the principals, the fifth no longer being in post. Findings The assessment appears to be downplayed by the principals, whereas the supportive dimension and the facilitation of NQTs’ professional development seem to be acknowledged and made explicit. For some of the principals, their creative translation of the reform’s intentions transformed these relations and strengthened their leadership. Research limitations/implications The study is small-scale and was carried out in a specific period of policy implementation from the principals’ perspectives. Future studies would benefit from involving both principals’ and teachers’ perspectives. Practical implications Policymakers appear to have underestimated the structural aspects of the reform, even though in general the reform enactments had some kind of positive effect on these relations. Social implications For some principals, their creative translation of the reform’s intentions transformed relations and strengthened their leadership. Originality/value The data are from a unique period when a reform was implemented and later partly withdrawn. The study deepens the understanding on how principals tries to enact and balance their roles as evaluators of NQTs and pedagogical and instructional leaders.

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