No description available.

As hybrid and electric vehicles continue to evolve there is a need for better battery thermal management systems (BTMS), which maintain uniformity of operating temperature of the batteries in the vehicles. This thesis investigates the use of an indirect liquid cooled system, which can be applied to hybrid and electric vehicles. The design is modeled as part of the UOIT EcoCAR. The predominant focus of this indirect liquid cooled system is the entropy generation in each of the components within the system, as well as a total system analysis. Four main components of the system are the battery module, heat exchanger, pump, and throttle. The battery module coolant tubes and the entire heat exchanger model are developed. Various parameters are changed in each component, leading to a decrease in entropy generation depending on the variable changed. Of the four components identified, the heat exchanger produced the majority of entropy generation, which leads to an overall increase in system entropy generation. There are many factors to consider when designing a liquid cooled BTMS. The new model shows a unique ability to improve system performance by reducing the entropy generation in the BTMS. / UOIT

In this thesis, fuel cell systems are analysed thermodynamically and electrochemically. Thermodynamic relations are applied in order to determine the change of first law and second law efficiencies of the cells, and using the electrochemical relations, the irreversibilities occuring inside the cell are investigated. Following this general analysis, two simple solid oxide fuel cell systems are examined. The first system consists of a solid oxide unit cell with external reformer. The second law efficiency calculations for the unit cell are carried out at 1273 K and 1073 K, 1 atm and 5 atm, and by assuming different conversion ratios for methane, hydrogen, and oxygen in order to investigate the effects of temperature, pressure and conversion ratios on the second law efficiency. The irreversibilities inside the cell are also calculated and graphed in order to examine their effects on the actual cell voltage and power density of the cell. Following the analysis of a solid oxide unit cell, a simple fuel cell system is modeled. Exergy balance is applied at every node and component of the system. First law and second law efficiencies, and exergy loss of the system are calculated.

Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Sept. 2, 2009). Includes bibliographical references (p. 63-65).

In this study, the use of robotics was explored in a Grade 12 Technical Sciences class, to further understand it as an emerging pedagogy that allows learners to apply creative thinking and produce innovative solutions to problems in Newton’s Second law of motion. The study's conceptual framework was underpinned by constructivism, constructionism and the Cognitive Refinement Instructional Approach (CRIA), which supports the notion that through assimilation and accommodation, Lego Mindstorms robotics tools can be used as manipulatives to develop new knowledge. The learners participating in this mixed-method procedure of enquiry were randomly assigned to an experimental group (n = 21) that took part in the robotics intervention and a control group (n = 21) that continued with conventional extra classes. It was evident in the qualitative results that learner’s knowledge improved regarding the concepts of acceleration and net force, but misconceptions persisted in the concepts of frictional force and tension force. In the analysis of the quantitative results, the independent-samples t-test showed that there was a significant difference in the post-test scores between the control group (M= 3.19, SD= 1.16) and experimental group (M=4.57, SD= 1.43); t(40)= 3.42, p = 0.001. The study found that robotics does have a significant effect on the academic test scores of Technical Sciences learners than the traditional intervention in Newton’s Second Law. The scientific merit and significance of this study will contribute to teaching methods and learning of science in the technical-academic schooling stream. / Dissertation (MEd)--University of Pretoria, 2021. / Science, Mathematics and Technology Education / MEd / Unrestricted

This thesis examines the effects of product composition, reactant temperature, reactant pressure, fuel-air equivalence ratio, diluent addition, and fuel composition on entropy generation in a constant internal energy/constant volume combustion process. Equilibrium product composition is shown to produce less combustion-generated entropy than frozen product composition. Using methane as the fuel, it is found that increasing reactant temperature by 100 K decreases entropy generation by 6 to 9 percent, while reactant pressure has little effect on entropy generation. Total entropy generation is increased with excess air and increased diluent addition. For the three fuels considered in this analysis (CH4, C2H5OH, C8H18), iso-octane uniformly exhibits the highest entropy generation, indicating the strong effect of fuel type and structure on combustiongenerated entropy.

Many industrial processes have low-temperature waste heat sources that cannot be efficiently recovered. Low grade waste heat has generally been discarded by industry and has become an environmental concern because of thermal pollution. This has led to the lookout for technologies which not only reduce the burden on the non-renewable sources of energy but also take steps toward a cleaner environment. One approach which is found to be highly effective in addressing the above mentioned issues is the Organic Rankine Cycle (ORC), which can make use of low- temperature waste heat to generate electric power. Similar in principle to the conventional cycle, ORC is found to be superior performance-wise because of the organic working fluids used in the cycle. The focus of this study is to examine the ORC using different types of organic fluids and cycle configurations. These organic working fluids were selected to evaluate the effect of the fluid boiling point temperature and the fluid classification on the performance of ORCs. The results are compared with those of water under similar conditions. In order to improve the cycle performance, modified ORCs are also investigated. Regenerative ORCs are analyzed and compared with the basic ORC in order to determine the configuration that presents the best thermal efficiency with minimum irreversibility. The evaluation for both configurations is performed using a combined first and second law analysis by varying certain system operating parameters at various reference temperatures and pressures. A unique approach known as topological method is also used to analyze the system from the exergy point of view. Effects of various components are studied using the exergy-wheel diagram. The results show that ORCs using R113 as working fluid have the best thermal efficiency, while those using Propane demonstrate the worse efficiency. In addition, results from these analyses demonstrate that regenerative ORCs produce higher efficiencies compared to the basic ORC. Furthermore, the regenerative ORC requires less waste heat to produce the same electric power with a lower irreversibility.

The biorefinery concept is attractive. Increasing international concerns over issuessuch as climate change have led to political as well as social pressures for a shift fromfossil fuels to renewable resources and biomass is one abundant renewable resource.Biomass has the potential of supplying many of the fuels and chemicals which arecurrently dependent on petroleum. Much development is still needed in the field ofbiorefineries and a systematic approach to evaluate and compare process technologiesand to suggest optimizations seems necessary.The objective of this thesis is to develop entropy analysis as a possible evaluation toolfor optimization of biorefinery processes. This is a new application of entropyanalysis which is rarely discussed in the literature. The scientific basis of the entropyanalysis is described and the proposed methodology is explained. The position ofentropy analysis among other system analysis tools such as exergy analysis and lifecycle assessment is discussed along with entropy analysis earlier applications.A case study is introduced which is the IBUS (Integrated Biomass Utilization System)project in Denmark. The idea in IBUS is to integrate the biomass plant with a powerplant to utilize the surplus steam from the power plant for the internal use of thebiorefinery. The suggested method of entropy analysis is applied to this case study tocompare different processes for production of ethanol along with solid biofuel andanimal feed from Danish wheat straw. The evaluation is a gate to gate analysis inwhich production of energy carriers are also included in addition to biorefining ofwheat straw. A parallel life cycle assessment study with equivalent system boundariesis also carried out to compare the results with a conventional environmental systemsanalysis method.The results from the entropy analysis of the IBUS case study show that fermentationof C5 and C6 sugars by yeast is the most efficient process thermodynamically whilefermentation of only C6 sugars by yeast is the least efficient among the three casesstudied. Integration of the biorefinery with a coal fired CHP plant is identified as awise choice by the results of the entropy analysis method.For the IBUS process alternatives investigated in this study, the entropy results andthe LCA results (aggregated environmental load) are in correlation; entropy results areconsistent with weighting results based on two different weighting methods namelyEco indicator 99 and EPS 2000. Entropy generation is also in correlation withproduction cost for the processes analyzed in this evaluation. Another observation isthat cooling in the biorefining process contributes highly in the generation of entropy.This potential improvement option is not surfaced by the LCA conducted.The potential for further investigation and development of the tool is recognizedreflecting on some interesting observations in the results. Improvement of the tool ishighly possible for example by supplementing other implications of entropy inprocess design such as "waste potential entropy" concept which is developed as aneco-toxicity measure. / Uppsatsnivå: D

This research is focused on formulating a new model of entropy production for two-phase flow, including cavitating turbulent flow. In particular, it focuses on the following aspects of the fluid dynamics and the potential contribution of the model to fluid device design. It includes (i) developing a new turbulent entropy model, (ii) a new formula of entropy production rate for two-phase flow including cavitating turbulent flow based on the second law, (iii) applying the technique to study a NACA hydrofoil, and (iv) conducting associated performance analysis of a propeller using post-processing of the CFD results and demonstrating that entropy production of two-phase cavitating flow around the propeller can be correlated to the loss of power output. The first stage consists of formulating the entropy production for laminar channel flow using Gibb’s free energy. This model is validated through the analytically solved Navier-Stokes equations. Subsequently, the single-phase turbulent flow is formulated in a similar manner, but the validations are carried out by comparing the prediction of the model with DNS results. Then, the model of entropy production for two-phase turbulent flow is derived from Gibb’s equation and a version of the Reynolds averaged Navier-Stokes (RANS) equations. The k- ε model is employed to represent the turbulent properties of single phase and two phase flows. A developed inter-phase slip algorithm mixture model is applied to control over coupling of phases. The Rayleigh-Plesset equation is used to model the rate of mass generation of vapour at the inter phase. The standard k-ε turbulence equations are used to describe turbulence in the cavitation flow. The validations of CFD predictions include exploring the force and cavitation characteristics of the NACA 4412 hydrofoil section. The application of this entropy production model in engineering design is presented via the comparisons between CFD results and the experimental data for the velocity distributions behind propeller P5168.

This dissertation aims at addressing two important theoretical questions which are still debated in the statistical mechanical community. The first question has to do with the outstanding problem of how to reconcile time-reversal asymmetric macroscopic laws with the time-reversal symmetric laws of microscopic dynamics. This problem is addressed by developing a novel mechanical approach inspired by the work of Helmholtz on monocyclic systems and the Heat Theorem, i.e., the Helmholtz Theorem. By following a line of investigation initiated by Boltzmann, a Generalized Helmholtz Theorem is stated and proved. This theorem provides us with a good microscopic analogue of thermodynamic entropy. This is the volume entropy, namely the logarithm of the volume of phase space enclosed by the constant energy hyper-surface. By using quantum mechanics only, it is shown that such entropy can only increase. This can be seen as a novel rigorous proof of the Second Law of Thermodynamics that sheds new light onto the arrow of time problem. The volume entropy behaves in a thermodynamic-like way independent of the number of degrees of freedom of the system, indicating that a whole thermodynamic-like world exists at the microscopic level. It is also shown that breaking of ergodicity leads to microcanonical phase transitions associated with nonanalyticities of volume entropy. The second part of the dissertation deals with the problem of the foundations of generalized ensembles in statistical mechanics. The starting point is Boltzmann's work on statistical ensembles and its relation with the Heat Theorem. We first focus on the nonextensive thermostatistics of Tsallis and the associated deformed exponential ensembles. These ensembles are analyzed in detail and proved (a) to comply with the requirements posed by the Heat Theorem, and (b) to interpolate between canonical and microcanonical ensembles. Further they are showed to describe finite systems in contact with finite heat baths. Their mechanical and information-theoretic foundation, are highlighted. Finally, a wide class of generalized ensembles is introduced, all of which reproduce the Heat Theorem. This class, named the class of dual orthodes, contains microcanonical, canonical, Tsallis and Gaussian ensembles as special cases.