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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. [ABSTRACT FROM AUTHOR]

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, resulting in flawed calculations. In this work, the most used correlations for predicting the properties of heavy n-alkanes are analyzed. Calculations were made using commercial software packages for two compositions of pre-salt reservoirs, and considering the Peng-Robinson and the Soave-Redlich-Kowng equations of state. The properties of the estimated C20+fraction affected the numerical stability, and the calculated PT diagrams are unexpected. The reasons for the observed pitfalls are discussed. [ABSTRACT FROM AUTHOR]

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 (P1), output pressure of the second stage of separation train (P2), input pressure of the third stage of separation train (P3), output pressure of dilution water pump (P4), output pressure of the main gas compressor (Pc), petroleum temperature of the first heat exchanger (T1), petroleum temperature of the second heat exchanger (T2), and dilution water temperature of heat exchanger (T3) are considered as input parameters. In terms of energy consumption, parameters P3 and Pc are always relevant for all operation modes. Furthermore, P3, P2, and T2 are the most important parameters for overall oil production for all operation modes. [ABSTRACT FROM AUTHOR]

Production in FPSO (Floating Production Storage and Offloading) is challenging due to its energy demand, operating cost, and environmental impact. In particular, the composition of the reservoir fluid, which varies along with the life of a well, greatly affects the operation and production of the FPSO. Any optimization study aiming at reducing energy consumption, sustainability, and operating costs during the life span of a well should take this fluid variability into account. Additionally, a typical FPSO operating in the Brazilian deep-water oil regions requires process fluid with high CO 2 content. Therefore, a new FPSO process plant configuration comprises a membrane-based CCU (Carbon Capture and Utilization) system integrated with an MEA-based CCS (Carbon Capture and Storage) system and a CO 2 compression unit with fewer compressors and one injection unit is proposed. Subsequently, automated optimization procedures consisting of a hybrid algorithm (NSGA-II + AfilterSQP) are implemented to optimize the energy efficiency, sustainability, and operation costs of the FPSO under consideration. More than 25 thermodynamic and structural design variables are considered as input variables in the optimization procedures. The results presented a significant reduction of up to 10.1% (2.9 MW) in overall power consumption, mitigation of CO 2 emissions of up to 47 kg/h, a decrease of up to 3.9% (2.4 million USD/year) in operating cost, and an improvement of up to 53.5% in total heating and cooling demand of the FPSO, which means a reduction of 3.8 × 109 (kJ/h). In a proposed system with one CO 2 injection unit, optimization results in the mitigation of total power consumption of up to 1.4 MW, a decrease in capital cost of 10 million USD, a reduction in operating cost of 50 million USD/year, and an increase of 4.4% in CO 2 removal efficiency. [Display omitted] • Twenty-seven thermodynamic and structural design input parameters for optimization. • A proposal system for the integration of a membrane CCU system with an MEA CCS. • A significant reduction of up to 10.1% (2.9 MW) in overall power consumption. • An improvement of up to 53.5% (3.8 × 109 kJ/h) in total heating and cooling demand. • A decrease in capital cost of 10 million USD for using a unique compression unit. [ABSTRACT FROM AUTHOR]

In the recent years some papers have dealt with heat exchangers with non-circular tube geometry and vortex generators. Parametric studies with vortex generators applied on heat exchangers models are necessary. The present work consists of an experimental investigation about the influence of combining a plate-finned elliptical tube with vortex generators mounted on the fin surface. The objective is to search for the best position to place the vortex generators just considering heat transfer enhancement. The experimental technique for Nussel tnumber determination was the naphthalene sublimation and mass transfer analogy. A visualization was implemented spreading wetted chalk on fin surface, as a color sensitive evaporation material. The better position obtained is useful for future investigations involving heat exchanger formed by a higher number of tube rows. Additionally was studied the influence of Reynolds number and angle of attack on the average Nusselt number. [ABSTRACT FROM AUTHOR]

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/CO 2 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, 8.34% 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 increase of 4.36% for Mode 1, 3.79% for Mode 2 and 1.75% for Mode 3 in total exportation oil. • For the first time, a lifetime FPSO optimization is performed considering three operation modes. • The fuel consumption of the FPSO plant is reduced by 8.34%. • The hydrocarbon liquids recovery is increased by up to 4.36%. • Real data of an FPSO operating in the Brazilian pre-salt basin has been used. [ABSTRACT FROM AUTHOR]

Abstract FPSO (Floating, Production, Storage and Offloading) units are used for primary petroleum processing. The FPSO units have a technical advantage for short-lived well exploration and for remote marginal fields, where building a pipeline is cost-prohibitive. Considering the relevance of the FPSOs for the Brazilian petroleum market, the main goal of this paper is to present an optimization procedure to find the best operating conditions of a primary petroleum platform processing crude oil with high gas-oil ratio (GOR) and moderate CO 2 content. Seven input parameters related to operating pressures of plant are selected for the optimization procedure aiming to minimize the total fuel consumption (FUE) of the FPSO. For the optimization procedure, the processing plant of the FPSO is modeled and simulated by using Aspen HYSYS®, and the Genetic Algorithm is used for minimizing the objective function. The optimum operating condition found by the optimization procedure presented a reduction in fuel consumption by 4.6% when compared to a conventional operating condition. Moreover, because of the fuel consumption optimization, a significant reduction by 6.3% in the power consumption of the plant and an improvement in the recovery of the volatile components were verified, in comparison with the baseline case. Highlights • A FPSO processing crude oil with high GOR and moderate CO2 content was modeled and optimized. • Real performance data of an offshore gas turbine was considered. • The integration of Aspen HYSYS with an external optimizer based on Genetic Algorithm was conducted. • Significant reductions of fuel consumption and CO 2 emission were achieved by optimization. • Real data of a FPSO operating in the Brazilian pre-salt basin was used. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]