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Made available in DSpace on 2021-06-25T11:56:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-14 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fluid flow in centrifugal compressors is complex and turbulent, making it difficult to achieve a robust equipment design. In this work, a computational fluid dynamics (CFD) analysis is conducted on the periodical domain of a CO2 centrifugal compressor impeller and vaneless diffuser, with a 2.85:1 pressure ratio, using ANSYS CFX. The fluid flow is assumed to be steady state, turbulent, and three dimensional. Since polar angles are not considered in the traditional one-dimensional analysis, eight polar angles on hub and shroud were considered for modeling, sensitivity analysis, and optimization. After numerical verification and validation, a sequential sensitivity analysis (SA) was performed to identify non-influential variables. From the same design of experiment (DoE) used by the Morris qualitative SA, a response surface (RS) was trained to perform a quantitative SA by the smoothing spline ANOVA (SS-ANOVA) method. The Morris method was found to be more conservative than SS-ANOVA, keeping more variables as influent for the analysis. Both methods agreed on influential variables ranking. Low computational effort was required to submit the RS to a constrained optimization procedure using the NSGA-II method. The polytropic efficiency of the optimal centrifugal compressor configuration increased 0.7%, keeping the pressure ratio above 2.85, and the required power and outlet temperature below the base compressor. The impact of the polar angles at trailing edge on output variables is higher than leading edge. The optimal centrifugal compressor found is submitted to different mass flow rates and the overall performance for the optimal angles of the trailing edge and leading edge of the impeller was higher than the base compressor. The strategy adopted herein related to qualitative and quantitative sensitivity analysis coupled with response surface and the constrained optimization was shown to be robust, which can be applied to high-dimensional CFD models to reduce the computational cost with suitable results regarding fluid flow phenomena. Sao Paulo State Univ, Ilha Solteira, SP, Brazil Univ Sao Paulo, Sch Engn, Sao Paulo, SP, Brazil Ctr Univ FEI, Sao Bernardo Do Campo, SP, Brazil Fed Univ ABC, Santo Andre, SP, Brazil Sao Paulo State Univ, Ilha Solteira, SP, Brazil CNPq: 306364/2020-4

The presence of heavy n-alkanes , together with CO2 and water, affects the accuracy of existing correlations used in equations of state. Moreover, they impact the performance of simulation software...

Oil and gas production in FPSOs (floating, production, storage, and offloading) faces a dual challenge: meeting variation in energy demand while decreasing its negative environmental impact. The present article integrates thermodynamic analysis of oil and gas processing plants and screening analysis to determine the most important operational parameters to lower energy demand and increase efficiency and production. Therefore, the main goals of this study are to identify the contribution of the total effect of the operating parameters in an FPSO with CCUS (CO2 capture, utilization, and storage). Twenty-seven thermodynamic and structural design variables are selected as input parameters for the sensitivity analyses. Four machine learning-based screening analysis algorithms such as smooth spline-analysis of variance (SS-ANOVA), PAWN, gradient boosting machine (GBM), and Morris are adapted to achieve the following objectives: (1) overall power consumption of FPSO, (2) CO2 removal efficiency of carbon capture and storage (CCS), (3) power consumption of CCS, and (4) total oil production. The influence of three real crude oil compositions with variations in gas–oil ratio (GOR) and CO2 content is assessed. The combination of thermodynamic and screening analyses showed that the optimal operating pressure parameters of CCS significantly reduce the energy consumption and exergy destruction of the key main and utility plants. Furthermore, the results indicated that total power consumption, CCS efficiency, and CCS power consumption are much more sensitive to the CO2 content of the fluid reservoir than GOR, while the total oil production is influenced only by the GOR content. Finally, for scenarios with high CO2 or GOR content, the effect of design variable interactions is decisive in changing the separation efficiency and/or the compression unit performance.

The air conditioning system of most commercial aircrafts consists of a main system, which operates on the principle of mix ventilation, and a personalized system called gasper. Field studies show that passengers prefer to keep gasper parcially open or redirect it away from the head due to the discomfort. Therefore, there is a demand to characterize the flow of this device for future improvements. In this way, the present work aims to experimentally study the gasper jet inside a real cabin mockup using PIV. The results indicate that passengers are subjected to a high speed jet and the air in their breathing zone is mostly supplied by the mixed ventilation system due to the large entrainment ratio.

Oil and gas industries have high carbon dioxide (CO2) emissions, which is a great environmental concern. Monoethanolamine (MEA) is widely used as a solvent in CO2 capture and storage (CCS) systems. The challenge is that MEA–CCS itself is an energy-intensive process that requires optimum configuration and operation, and numerous design parameters and heat demands must be considered. Thus, the current work evaluates the energy distributions and CO2 removal efficiency of a CCS installed in floating production storage and offloading units under different operating conditions of a power and heat generation hub. The optimization procedures are implemented using highly accurate surrogate models for the following responses: (1) overall power consumption of CCS, (2) CCS separation performance, and (3) CCS heating and cooling demands. The input variables considered in the present research include the following: (1) the exhaust gas compositions and mass flowrate, (2) the operating pressure and temperature parameters of CCS and the injection compression unit, (3) the structural parameters of absorber and stripper columns, and (4) MEA solution parameters. The optimum CCS configuration significantly reduces the total heating and cooling demands by 62.77% (7 × 106 kW) and the overall power consumption by 8.65% (1.8 MW), and it increases the CCS separation performance by 4.46% (97.46%) and mitigates the CO2 emissions of proper CCS by 1.02 t/h compared with conventional operating conditions.

Made available in DSpace on 2019-10-04T12:41:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-08-27 National Agency of Petroleum, Natural Gas and Biofuels (ANP) Shell Brazil Ltda. Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Universidad Tecnologica de Pereira Petrobras Floating production storage and offloading (FPSO) platforms are great energy consumers. Reservoir fluid composition and operating parameters of FPSOs are known to be important parameters for the total energy demand, and also for enhancing overall oil production. In the current research paper, the contribution of eight thermodynamic input parameters of a typical Brazilian FPSO operating on a pre-salt field is quantified by the Smoothing Spline ANOVA method for two responses: (i) energy consumption of the plant and; (ii) overall oil production. Three operation modes are considered in the analysis: Mode 1 (maximum oil/gas content), Mode 2 (50% BS&W) and Mode 3 (maximum water/CO2 content). The input parameters considered in the present research are: output pressure of the first control valve (P-1), output pressure of the second stage of separation train (P-2), input pressure of the third stage of separation train (P-3), output pressure of dilution water pump (P-4), output pressure of the main gas compressor (P-c), petroleum temperature of the first heat exchanger (T-1), petroleum temperature of the second heat exchanger (T-2), and dilution water temperature of heat exchanger (T-3) are considered as input parameters. In terms of energy consumption, parameters P-3 and P-c are always relevant for all operation modes. Furthermore, P-3, P-2, and T-2 are the most important parameters for overall oil production for all operation modes. Univ Sao Paulo, Sch Engn, Dept Mech Engn, Sao Paulo, Brazil Fed Univ ABC, Energy Engn, Santo Andre, Brazil Sao Paulo State Univ, Dept Mech Engn, Ilha Solteira, Brazil Sao Paulo State Univ, Dept Mech Engn, Ilha Solteira, Brazil CNPq: 304935/2016-6 CNPq: 309214/20173

Made available in DSpace on 2019-10-04T12:37:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The present work aims to perform a parametric study of heat transfer enhancement and the associated pressure loss applied to louvered fins with rectangular winglet vortex generators (RWL). The contributions of a set of design variables on heat transfer and pressure drop are evaluated for two geometry types, L1 and L2. The procedure to investigate the relative importance of the geometrical design variables on thermal-hydraulic performance is enabled by a Design of Simulations (DOS) method called Latin Hypercube Sampling (LHS) in association with a modern non-parametric statistical method (Smoothing Spline ANOVA method) and Computational Fluid Dynamics. Outcomes from the screening analyses turned out that the louver angle is the unique contributor to friction factor for both geometry types and this behaviour is independent of Reynolds number. With respect to heat transfer, the contributions of the input variables are different for both geometry types and Reynolds numbers. For Re-Dh = 120, no important two-factor interaction effects were observed for both L1 and L2, in the same way as occurred in terms of friction factor. Conversely, for Re-Dh = 240 one relevant interaction effect was observed. Fed Univ ABC, Energy Engn, Santo Andre, SP, Brazil Univ Sao Paulo, Polytech Sch, Dept Mech Engn, Sao Paulo, SP, Brazil Univ Munich, Angew Mech, Munich, Germany Sao Paulo State Univ, Dept Mech Engn, Ilha Solteira, SP, Brazil Sao Paulo State Univ, Dept Mech Engn, Ilha Solteira, SP, Brazil FAPESP: 2017/06978-3 FAPESP: 2016/14620-9 CNPq: 307421/2014-7

Made available in DSpace on 2022-04-28T19:44:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-10-01 Agência Nacional do Petróleo, Gás Natural e Biocombustíveis Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The injection of CO2 into oil reservoirs is used by the oil and gas industry for enhanced oil recovery (EOR) and/or the reduction of environmental impact. The compression systems used for this task work with CO2 in supercritical conditions, and the equipment used is energy intensive. The application of an optimization procedure designed to find the optimum operating conditions leads to reduced energy consumption, lower exergy destruction, and reduced CO2 emissions. First, this work presents two thermodynamic models to estimate the amount of power necessary for a multi-stage CO2 compression system in floating production storage and offloading (FPSO) using accurate polytropic relationships and equations of state. Second, a thermodynamic analysis using the first and second laws of thermodynamics is conducted to identify possible improvements in energy consumption and the sources of the compression unit’s irreversibilities. In the final step, optimization procedures, using two methods with different approaches, are implemented to minimize the total power consumption. As the number of stages and the pressure drop between them influence the total power required by the compressors, these are considered as the input parameters used to obtain the inlet pressure at each stage. Three different compositions with variations in CO2 content, i.e., pure CO2, pure CH 4, and 70% CO2 + 30% CH 4, are also investigated as three different operating scenarios. The optimal configurations and pressure ratios result in a reduction in power consumption of up to 9.65%, mitigation of CO2 emissions by up to 1.95 t/h, and savings in exergy loss of up to 23.9%, when compared with conventional operating conditions. Department of Mechanical Engineering Polytechnic School University of São Paulo Centro Universitário FEI Energy Engineering Federal University of ABC Department of Mechanical Engineering São Paulo State University Department of Mechanical Engineering São Paulo State University CNPq: 306364/2020-4

This work aims to develop a mathematical model for computing the distribution of temperature, O2, and CO2 in the human body, depending on the ambient conditions. The body is divided into segments, including layers of tissues and blood compartments, where mass and energy balances are applied. The inclusion of O2 and CO2 transfer mechanisms throughout all segments and tissues of the human body is one of the great novelties of this work. It also includes the exothermic metabolic reactions in the tissues, the transportation of O2 and CO2 by the blood, and the energy exchanged with the environment through the skin and by ventilation. The model also includes the regulation of metabolism, circulation, ventilation, and sweating, depending on the body temperature and the concentrations of O2 and CO2 in the blood. The lungs are represented by alveolar and blood compartments, with diffusion between them. Comparisons with experimental data from the existing literature show that the proposed model is suitable for representing transient exposure to cold and warm ambient temperatures, low concentration of O2, and high concentrations of CO2. In the end, some results demonstrate the effect of ambient temperature on the distribution of temperature, O2, and CO2 across segments, blood, and tissues. Shivering in a cold environment reduces the concentration of O2 and increases the concentration of CO2 in the muscles, which results in increased ventilation and blood circulation. The concentration of gases in the skin depends mainly on variations in the skin's circulation with the environment, which alters the availability of O2 and the elimination of CO2. Small variations were found in the concentrations of O2 and CO2 in the brain and lungs.

The purpose of this work was to know the characteristics of tricuspid bioprosthetic mitral valves in terms of velocity fields and valve aperture areas for some instants concerning the diastole. A left heart simulator was used as an in vitro platform for the bioprostheses. A particle image velocimetry (PIV) system was applied for characterizing instantaneous 2D-velocity fields within the left ventricular model (LVM), and also for detection of mitral bioprostheses aperture areas. The ventricular states were established for 60, 70 and 90 bpm (beats per minute) and a blood analog fluid based on glycerol was employed at 36.5±0.5oC. Two mitral bioprostheses (nominal diameter of 27 and 31 mm) and an aortic bileaflet mechanical valve (27 mm diameter) were used. Instantaneous two-dimensional velocity fields at the upper part of the LVM, for two sections (in the middle of the LVM, and also in a section at 7 mm of distance from that) were obtained. Averaged velocity vector maps (N = 50) were calculated for some instants of interest. According to different heart rates, bioprostheses and sections within the LVM, the velocity fields were presented, as well the bioprostheses aperture areas. In conclusion, the experimental scope including different ventricular states showed how the inflow characteristics of the LVM change according to the chosen variables. This information will aid the validation of a numeric model for the LVM operation, which has been elaborated (some specific methods are presented in the Appendix).

Made available in DSpace on 2019-10-04T12:39:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-08-15 National Agency of Petroleum, Natural Gas and Biofuels (ANP) Shell Brazil Ltda. Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) A Floating, Production Storage and Offloading (FPSO) plant is a high-energy consumer (from a few to several hundreds of megawatts). Since a number of parameters have effects on the FPSO plant performance, screening analysis procedure could be used to select the most important parameters affecting a given output and an optimization procedure being applied to maximize/minimize an objective function. Thus, optimization procedures focused on fuel consumption and hydrocarbon liquids recovery can improve the energy efficiency, product recovery, and sustainability of the plant. In the present work, optimization procedures are used for an FPSO plant operating at three different conditions of the Brazilian deep-water oil field in pre-salt areas to investigate: (1) Maximum oil/gas content (Mode 1); (2) 50% BS&W oil content (Mode 2) and; (3) High water/CO2 content in oil (Mode 3). In order to reduce the computational efforts, we investigate the contribution of eight thermodynamic input parameters to the fuel consumption of the FPSO plant and hydrocarbon liquids recovery by using the Smoothing Spline ANOVA (SS-ANOVA) method. From SS-ANOVA, the input parameters that presented the major contributions (main and interaction effects) to the fuel consumption and hydrocarbon liquids recovery were selected for the optimization procedure. The optimization procedure consists of a Hybrid method, which is a combination of Non-dominated Sorting Genetic Algorithm (NSGA-II) and AfilterSQP methods. The results from the optimized case indicate that the minimization of fuel consumption is 4.46% for Mode 1, 834% for Mode 2 and 2.43% for Mode 3, when compared to the baseline case. Furthermore, the optimum operating conditions found by the optimization procedure of hydrocarbon liquids recovery presented an (C) 2019 Elsevier Ltd. All rights reserved. Univ Sao Paulo, Sch Engn, Dept Mech Engn, Sao Paulo, Brazil Fed Univ ABC, Energy Engn, Sao Paulo, Brazil Sao Paulo State Univ, Dept Mech Engn, Ilha Solteira, Brazil Sao Paulo State Univ, Dept Mech Engn, Ilha Solteira, Brazil CNPq: 304935/2016-6 CNPq: 309214/2017-3

Continuous settlers are present in the treatment of effluents and domestic water. They have low operational and maintenance cost; however, they can reach high separation efficiency. In this work, the fluid dynamic characteristics of the settler in bench scale, with no-concentric axial inlet in the feedwell were precisely evaluated, using both experimental and numeric approach. The velocity fields were experimentally obtained by PIV (Particle Image Velocimetry). Numerically, the three-dimensional flow was studied using the ANSYS CFX package. For more adequate representation of velocities, the RNG κ-e, SST κ-ω, and BSL-RSM turbulence models were analyzed. After the validation of fluid dynamics, it was possible to perform multiphase simulations, analyzing the efficiency of solid particles removal. The Eulerian-Eulerian multiphase model was applied, along with the particle interfacial transfer model. The profiles of axial U and radial V velocity components allowed observing that the BSL-RSM model showed consistent results when compared to the experimental data. In relation to the separation efficiency, smaller particles (10 μm) were verified to tend to be more evenly distributed in the settler, while larger particles are quickly deposited on the bottom. From the diameter of 100 μm, there was no difference between the separation efficiency values obtained.

Surrogate-based optimization procedure is used to maximize the heat transfer of multilouvered fin compact heat exchangers with delta-winglet vortex generators (DWL). Five input parameters, such as louver angle and DWL angles of attack and positions, were chosen. The heat transfer enhancement performance of two distinct geometries, GEO1 and GEO2, with two rows of delta-winglets were considered on this research. Reynolds numbers of 120 and 240, based on hydraulic diameter, were investigated. The surrogate-based optimization procedure uses the NSGA-II (Non-Dominated Sorting Genetic Algorithm) combined with artificial neural networks. Compared with the respective baseline geometry (louvered fin without DWLs), the results showed that GEO1 optimized solutions increased the heat transfer by 21.27% and 23.52% with associated pressure loss increase of 24.66% and 36.67% for the lower and the higher Reynolds numbers, respectively. For GEO2 optimized solutions, the heat transfer was increased by 13.48% and 15.67% with an increase of the pressure drop by 20.33% and 23.70%, for the lower and the higher Reynolds numbers, respectively. The optimized solutions showed that heat transfer behind the second row of delta-winglets are as high as that behind the first row, for both Reynolds numbers. The flow patterns and heat transfer characteristics from optimized solutions presented some particular behavior, differently from the findings when louvered fin and DWLs are applied separately.

Purpose Besides ventricular parameters, the design and angular orientation of a prosthetic heart valve induce a specific flow field. The aim of this study was to know the inflow characteristics of a left ventricular model (LVM), investigating the behavior of tricuspid bioprosthetic mitral valves in terms of velocity profiles and related valve aperture areas at the beginning of diastole, under different conditions. Methods 3 heart rates (HRs) were established in the LVM and each mitral bioprosthesis (27 and 31 mm diameter) was installed in 2 orientations, rotated by 180°. For each experimental setup, 2-dimensional particle image velocimetry (2D PIV) measurements and simultaneous mitral valve (MV) area detection were obtained from 50 samples. Results The results from the velocity profiles immediately downstream of mitral bioprostheses showed the influence of valve orientation for moderate HRs, although for a similar magnitude of mean velocity vectors. The geometries of MV open areas for each HR were similar regardless of valve orientation, except for the 27-mm valve at 90 beats per minute (bpm), and for the 31-mm valve at 60 bpm. Moreover, for each HR, similar percentages of valve open area were obtained regardless of MV nominal diameters. Conclusions In conclusion, the experimental setup for the 2D PIV measurements synchronized with the MV area detection was a useful tool for knowing the inflow characteristics of the LVM.

Optimization is now recognized as essential in the design of modern compact heat exchanger since the augmentation of heat transfer applying longitudinal vortex generator depends on different interacting parameters, such as its streamwise and spanwise locations, and attack and roll angles and shape. For this work, an optimization procedure based on the SIMPLEX method was conducted through a fluid–solid conjugated heat transfer modeling considering a fin-tube compact heat exchanger with two rows of tubes in staggered and inline arrangements, in order to find an optimum configuration of the vortex generators for two objective functions related to Colburn factor (j) and Friction factor (f). Two Reynolds numbers (250 and 650), performing as a function of fin-pitch, were evaluated. Moreover, a simple approach based on trigonometric decomposition to treat the constraints is presented, which allows great flexibility to vortex generators to cover the design space solution. Seven independent input parameters for each vortex generator in optimization procedure were considered, totaling fourteen independent variables. The results indicate that this work-optimized configuration for the vortex generators achieved higher heat transfer augmentation than those in previous works in the open literature, for both objective functions, Reynolds number and tube arrangements, and it is more pronounced for staggered tube arrangement than for inline tube arrangement. Moreover, suitable vortex generator shapes to maximize the objective functions are more similar to rectangular-winglet type than delta-winglet type, and the optimum ratio between the vortex generator height and fin-pitch is 0.6. Although several trends could be defined for the optimum points, optimized configurations of the vortex generators were found to be different for each Reynolds number, tube arrangement and objective functions, indicating strong asymmetry between the vortex generators to achieve higher heat transfer augmentation.

The demand for LNG (liquefied natural gas) increases each year, and relevant studies have been developed in order to reduce both power consumption and greenhouse gas emissions of LNG plants. Multistream plate-fin heat exchangers (MPFHE) are widely used in these plants due to their large heat transfer surface area per unit volume for multi-phase flows. The thermal-hydraulic performance of heat exchangers also impacts on compressor shaft work of liquefaction plants. In this study, an automated optimization procedure is performed for commonly used MPFHE in a three-stage propane pre-cooling cycle to maximize the coefficient of performance (COP) of liquefaction plants. Four geometric input parameters (fin type, fin height, fin thickness, and fin frequency) have been selected for the optimization. The optimal heat exchangers and operating conditions of the entire refrigeration cycle and their feasibility are taken into account. The optimal fin designs of the heat exchangers affect the cycle operating conditions, which results in COP improvements of 18.9%, 2.5%, and 9.4%, and ranging from 7% to 32% of mitigation in CO2 emission when compared to the literature cases. Compared with the baseline case, the COP is improved by 9.4%, compressor shaft power is reduced by 7.1% (about 11.2 MW), heat transfer is augmented by 1.5% (3.8 MW), and CO2 emission is reduced by 6.3 t/h, which result in more efficient and sustainable LNG production.

The combination of multi-louvered fins and delta-winglet vortex generators is a promising strategy to enhance heat transfer in flat-tube compact heat exchangers. This paper focuses on screening analysis and, pressure drop and heat transfer characteristics of some parameters of multi-louvered heat exchangers combined with delta-winglets. Two rows of delta-winglets were considered for this research. The thermal-hydraulic performance of two distinct geometries, GEO1 and GEO2, were evaluated. The main differences between those two geometries are the louver height and delta-winglet frontal area. The contribution of the input parameters such as louver angle, angle of attack of the delta-winglet and streamwise position of the delta-winglet are also investigated in order to understand which of these parameters strongly influences heat transfer and pressure drop. Reynolds numbers of 120 and 240, based on hydraulic diameter, were investigated. The Smoothing Spline ANOVA model was used to investigate main and interaction effects among the input parameters. The randomly sample generation is performed by the Latin Hypercubes Sampling (LHS) method. The results indicate that the louver angle is the main contributor to increase the Friction factor for GEO1 and GEO2 for both Reynolds numbers. At the lower Reynolds number, the most important heat transfer parameter was the louver angle for both geometries, while at the higher Reynolds number, the angles of attack of the first row of delta-winglets mostly contributed to GEO1, and the angle of attack of the first row of delta-winglets was as important as the louver angle for GEO2. Although those specific geometries can be considered a kind of compound enhancement technique, relevant interactions were not verified between louvers and delta-winglet vortex generators parameters, i.e., the main effects were predominant in heat transfer and pressure drop.

The flow patterns of a prosthetic heart valve in the aortic or mitral position can change according to its type and orientation. This work describes the use of 2D particle image velocimetry (PIV) applied to the in vitro flow fields characterization inside the upper part of a left ventricular model at various heart rates and as a function of two orientations of stented tricuspid mitral bioprostheses. In the ventricular model, each mitral bioprosthesis (27 and 31 mm diameter) was installed in two orientations, rotated by 180°, while the aortic bileaflet mechanical valve (27 mm diameter) remained in a fixed orientation. The results (N = 50) showed changes in the intraventricular flow fields according to the mitral bioprostheses positioning. Also, changes in the aortic upstream velocity profiles were noticed as a function of mitral orientations.

The optimized use of ethanol in current and new vehicles requires detailed information on atomization, evaporation, mixing and combustion processes of this fuel. In this work, laser diagnostic tools are applied to analyze ethanol combustion in pulsed spray flames. Fuel droplet diameter and velocity distributions are measured by Phase Doppler Interferometry (PDI) across the flame. The evolution of droplets dispersion at early stages of the injection event is visualized in a diametral plane at exit of the injector by high repetition rate Mie scattering. The burner is formed by a swirler mixer and an automotive port fuel injector both positioned at the top exit of a vertical cylinder. Three injection frequencies (100 Hz, 250 Hz, and 400 Hz) are analyzed in depth. The increase in the injection frequency induced a transition from higher to lower density spray patterns impacting the combustion process of the droplets. The higher density spray presented droplet dispersion similar to a cloud in group combustion mode, promoting a mono-modal droplet diameter distribution across the flame centerline and produced an elongated flame with a visible reaction zone down to the injection plane of the burner. The lower density spray suggests droplets in the internal group combustion mode, being highly susceptible to swirling flow structures and promoting a bi-modal diameter distribution at the centerline, mainly produced by residual droplets with high axial velocity and preferential evaporation of small droplets. Furthermore, the lowest density spray led to a shorter flame presenting similarities to a lifted flame.

Augmentation of heat transfer has been an important research topic for many years. Although many heat transfer enhancement techniques have been proposed over the years, few researches deal with thermal optimization considering vortex generators (VG). This work is related to optimization of VG position and angles in a fin-tube compact heat exchanger using the Genetic Algorithm (GA). Two approaches were evaluated: Response Surface Methodology (RSM) applying Neural Networking method, and Direct Optimization (DO). Numerical analyses based on the finite-volume methodology was performed to analyze heat transfer and pressure drop of a fin-tube heat exchanger with two row of tubes in staggered tube arrangement applying two delta winglet type longitudinal vortex generators with aspect ratio 2. Turbulent flow simulation was performed for Reynolds number 1400 (based on fin pitch). Four vortex generator parameters which impact heat exchanger performance were analyzed: longitudinal vortex generator position in x–y directions, attack angle (θ) and roll angle (φ). The present work is the first to study the influence of VG roll angle on heat transfer enhancement. Therefore, eight independent input parameters were considered, four VG parameters for each tube. Four performance evaluation criteria (PEC) based on Colburn factor (j) and Friction factor (f) were chosen as objective function. The optimized VG configurations led to heat transfer enhancement rates higher than reported in the literature. Direct Optimization reported better results than Response Surface Methodology for all objective functions. Important flow interactions were found between vortices generated by VG1 and VG2, which influenced the results of Colburn factor (j) and Friction factor (f). The best results for each objective functions were achieved when VG1 was not symmetrical to VG2. Regarding global pressure drop, VG1 does not contribute to its mitigation, whereas VG2 is very important to flow separation delay in tube 2. The main contribution of VG1 is to increase the heat transfer rate, whereas VG2 increases the heat transfer rate and decreases the pressure drop. Roll angle has a strong influence on friction factor (f), especially for VG1.

Exergy analysis is applied to assess the quality of the energy conversion processes that take place in the human body, aiming at developing indicators of thermal comfort based on the concepts of destroyed exergy rate, exergy transfer rate to the environment and exergy efficiency. In literature only destroyed exergy has been used to evaluate thermal sensation. To perform the exergy balance it is necessary to calculate the exergy variation of the body over time which is a composition of metabolic exergy and the exergy variation due to transient environmental conditions. The exergy transfer to the environment is calculated as the sum of the terms associated with radiation, convection, evaporation and respiration. The thermal behavior of the human body is simulated by a model composed of 15 cylinders, naked and dressed for winter seasons, as a function of the air temperature, mean radiant temperature and relative humidity. The energy equation is solved to obtain transitory response of the body due to a variation in environmental conditions and the energy transfer to the environment. For relative humidities between 40% and 60%, results indicate that the destroyed exergy is minimal for thermal comfort conditions. Nevertheless, for low relative humidities and high temperatures the destroyed exergy is also minimal, indicating the necessity of another physical quantity to evaluate thermal comfort conditions. At this point the exergy transfer to environment is high, showing that the body may not be at thermal comfort condition. This article proposes is to use two terms of the exergy analysis to evaluate the thermal comfort condition: destroyed exergy and exergy transfer to environment.

The aim of this work is to apply performance indicators for individuals under physical activity based on the concepts of exergy destroyed and exergy efficiency. The cardiopulmonary exercise test is one of the most used tests to assess the functional capacity of individuals with varying degrees of physical training. To perform the exergy analysis during the test, it is necessary to calculate heat and mass flow rates, associated with radiation, convection, vaporization and respiration, determined from the measurements and some relations found in the literature. The energy balance allowed the determination of the internal temperature over time and the exergy variation of the body along the experiment. Eventually, it was possible to calculate the destroyed exergy and the exergy efficiency from the exergy analysis. The exergy rates and flow rates are dependent of the exercise level and the body metabolism. The results show that the relation between the destroyed exergy and the metabolism is almost constant during the test, furthermore its value has a great dependence of the subject age. From the exergy analysis it was possible to divide the subjects according to their training level, for the same destroyed exergy, subjects with higher lactate threshold can perform more work.

A steady state multi-segmented heat transfer model of the human upper limbs was developed. The main purpose was to evaluate the impact of blood flow through superficial veins and subcutaneous vascular structures in the palm of the hands over the heat transfer between the limbs and the environment. The distinguishing feature of the model is the inclusion of a detailed circulatory network composed of vessels with diameter larger than 1 mm. The model was validated by comparing its results from exposures to a hot, a neutral, and a cold environment to experimental data presented in the literature.

A two-dimensional numeric simulator is developed to predict the nonlinear, convective-reactive, oxygen mass exchange in a cross-flow hollow fiber blood oxygenator. The numeric simulator also calculates the carbon dioxide mass exchange, as hemoglobin affinity to oxygen is affected by the local pH value, which depends mostly on the local carbon dioxide content in blood. Blood pH calculation inside the oxygenator is made by the simultaneous solution of an equation that takes into account the blood buffering capacity and the classical Henderson-Hasselbach equation. The modeling of the mass transfer conductance in the blood comprises a global factor, which is a function of the Reynolds number, and a local factor, which takes into account the amount of oxygen reacted to hemoglobin. The simulator is calibrated against experimental data for an in-line fiber bundle. The results are: (i) the calibration process allows the precise determination of the mass transfer conductance for both oxygen and carbon dioxide; (ii) very alkaline pH values occur in the blood path at the gas inlet side of the fiber bundle; (iii) the parametric analysis of the effect of the blood base excess (BE) shows that (.)V(CO₂) is similar in the case of blood metabolic alkalosis, metabolic acidosis, or normal BE, for a similar blood inlet P(CO₂), although the condition of metabolic alkalosis is the worst case, as the pH in the vicinity of the gas inlet is the most alkaline; (iv) the parametric analysis of the effect of the gas flow to blood flow ratio (QG/QB) shows that (.)V(CO₂) variation with the gas flow is almost linear up to QG/QB = 2.0. (.)V(O₂) is not affected by the gas flow as it was observed that by increasing the gas flow up to eight times, the (.)V(O₂) grows only 1%. The mass exchange of carbon dioxide uses the full length of the hollow-fiber only if Q(G) /Q(B)> 2.0, as it was observed that only in this condition does the local variation of pH and blood P(CO₂) comprise the whole fiber bundle.

The objective of the present work is to propose a numerical and statistical approach, using computational fluid dynamics, for the study of the atmospheric pollutant dispersion. Modifications in the standard k – e turbulence model and additional equations for the calculation of the variance of concentration are introduced to enhance the prediction of the flow field and scalar quantities. The flow field, the mean concentration and the variance of a flow over a two-dimensional triangular hill, with a finite-size point pollutant source, are calculated by a finite volume code and compared with published experimental results. A modified low Reynolds k – e turbulence model was employed in this work, using the constant of the k – e model C μ =0.03 to take into account the inactive atmospheric turbulence. The numerical results for the velocity profiles and the position of the reattachment point are in good agreement with the experimental results. The results for the mean and the variance of the concentration are also in good agreement with experimental results from the literature.

The objective of this work is to develop an improved model of the human thermal system. The features included are important to solve real problems: 3D heat conduction, the use of elliptical cylinders to adequately approximate body geometry, the careful representation of tissues and important organs, and the flexibility of the computational implementation. Focus is on the passive system, which is composed by 15 cylindrical elements and it includes heat transfer between large arteries and veins. The results of thermal neutrality and transient simulations are in excellent agreement with experimental data, indicating that the model represents adequately the behavior of the human thermal system.

The aim of this work is to analyze the carbon monoxide (CO) transport in the human body submitted to several physical activity levels. A complete mathematical model of the human respiratory system was developed, considering the exchanges of CO, oxygen (O2) and carbon dioxide (CO2) in the lung, blood and tissues. The human body was divided in the following compartments: alveolar, pulmonary capillaries, arterial, venous, tissue capillary and tissues. The gas transport in the blood and tissues is represented by empirical equations. The physiological parameters were described in function of physical activity. The model was validated by comparing its results with experimental data of controlled CO exposition. The agreement was excellent. CO concentration curves for critical days of São Caetano do Sul city (SP, Brazil) atmosphere were used as model input. The simulation results for some physical activities show that the more intense the activity, the larger the blood carboxyhemoglobin (COHb) level variations. The COHb level was compared with a CO quality air criteria, which showed to be adequate for low and moderate physical activity levels.

The combination of multi louvered fins and delta-winglet vortex generators is a promising strategy to enhance heat transfer in fin-tube compact heat exchangers. The present paper focuses on the thermal-hydraulic performance optimization of such heat exchangers. The contribution of parameters such as Reynolds number, louver angle, angle of attack of the delta-winglet and streamwise position of the delta-winglet is also investigated in order to know which of these parameters strongly influences heat transfer and pressure drop. Reynolds numbers of 120 and 240, based on hydraulic diameter, were investigated. A semi parametric function estimation based on ANOVA type decomposition was applied to determine the effects of the input parameters on Colburn and Friction factors. The surrogate-based optimization procedure uses a NSGA-II method (Non-Dominated Sorting Genetic Algorithm) combined with artificial neural networks. The results indicated that the louver angle is the main contributor to increase the Friction factor increase for both Reynolds numbers. At the lower Reynolds number, the most important parameter to heat transfer was the louver angle, and at the higher Reynolds number, the angle of attack of delta winglet resulted in the highest influence on heat transfer. By comparison with baseline geometry (multi-louvered heat exchanger without vortex generator), the results from the optimization procedure showed that the addition of delta winglets increased the heat transfer by 22.45% with associated pressure loss penalty of 32.83% for the lower Reynolds number, while for the higher Reynolds number, the heat transfer and the pressure loss were increased by 23.91% and 49.34%, respectively.

The objective of this work is to study the primary control system of a hydropower plant operating isolated. The plant is modeled by differential equations and the results are compared with field data from an actual hydropower plant, with deviations lower than 1.0%. The study of the primary control system is conducted in order to define optimal parameters for the controllers. Four controllers are studied: traditional, PI, PID and PI-PD. The controllers’ performances are evaluated by stability criteria and a performance index. For the hydropower plant studied, the PI controller has the best performance.

The effects of operational and geometrical parameters on pressure distribution and flow pattern in Y-jet atomizers were studied using an experimental apparatus working with air and water. The results show that the mixing point pressure is very dependent on the diameter ratio of the mixing duct and the air port and the water supply pressure ratio. A correlation to predict the mixing point pressure was developed and showed good agreement with the experimental data. With this correlation, it is possible to predict the occurrence of the critical condition for the air flow at the exit of its port. In a second group of results, the influence of geometrical and operational parameters on the pressure distribution inside the mixing duct was analyzed. The main result found was that for air liquid ratio between 0.1 and 0.2, this pressure distribution can be taken as linear. This information about air liquid ratio and the correlation to predict the occurrence of chocked flow at the exit of the air port may give useful guidelines for atomizer designers. Finally, using a two-phase map, the flow pattern inside Y-jet atomizers was found to be a transition between the annular flow and the wispy-annular flow.

The main purpose of this paper is to present a numerical calculation procedure for transient heat conduction in a 3D elliptical cylinder. A non-orthogonal analytical transformation converting an elliptical cylinder into a parallelepiped was developed. The finite-volume method was applied to the transformed partial differential equations. The resulting algebraic equations were solved by a technique similar to the alternating-direction-implicit scheme.