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41.
A network approach was used to develop a thermofluid process model of a cross-flow primary superheater heat exchanger with complex flow arrangement in the convective pass of a coal-fired boiler. The model solves the transient one-dimensional forms of the conservation equations for mass, energy, and momentum, combined with the applicable closure relations, boundary values, and initial values. The dual-tube 12-pass superheater was discretized along the flue gas flow path as well as along the steam flow path. The model accounts for the convective thermal resistance on the steam side, the conductive thermal resistances of the tube wall, and scaling or fouling on the tube walls, as well as the convective and radiative thermal resistances on the flue gas side. The model was qualitatively validated using real plant data and for reference purposes also systematically compared to conventional lumped parameter models. The ability of the model to analyze the effect of the ramp rate during load changes on the tube metal temperature was demonstrated, as well as the ability to determine the maldistribution of flow and temperature on the steam and flue gas sides. Models such as this can be employed to study complex thermofluid process phenomena that may occur during intermittent, transient, and low-load operation of power plants. This could form the basis for improving operations and for the development of advanced tools for online process condition monitoring. 相似文献
42.
Crises are common in today's unpredictable environment rising the importance of crisis response strategies. Two societies in Europe are chosen: Finland, where trust in society is generalized to institutions, and Spain, where trust in society remains on the level of individuals. Using the results of the European Communication Monitor 2013 survey on crisis communication, we explored three hypotheses: “certain types of crises are often met with certain types of strategies,” “cultural context makes some crises more likely than others,” and “cultural context makes some response strategies more likely than others.” We find evidence for all three hypotheses and discuss our findings about perceived differences in the two societies. The results show that the cultural context plays an important role for crisis communication. 相似文献
43.
This paper presents a wind plant modeling and optimization tool that enables the maximization of wind plant annual energy production (AEP) using yaw‐based wake steering control and layout changes. The tool is an extension of a wake engineering model describing the steady‐state effects of yaw on wake velocity profiles and power productions of wind turbines in a wind plant. To make predictions of a wind plant's AEP, necessary extensions of the original wake model include coupling it with a detailed rotor model and a control policy for turbine blade pitch and rotor speed. This enables the prediction of power production with wake effects throughout a range of wind speeds. We use the tool to perform an example optimization study on a wind plant based on the Princess Amalia Wind Park. In this case study, combined optimization of layout and wake steering control increases AEP by 5%. The power gains from wake steering control are highest for region 1.5 inflow wind speeds, and they continue to be present to some extent for the above‐rated inflow wind speeds. The results show that layout optimization and wake steering are complementary because significant AEP improvements can be achieved with wake steering in a wind plant layout that is already optimized to reduce wake losses. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
44.
We study the design of two-level experiments with N runs and n factors large enough to estimate the interaction model, which contains all the main effects and all the two-factor interactions. Yet, an effect hierarchy assumption suggests that main effect estimation should be given more prominence than the estimation of two-factor interactions. Orthogonal arrays (OAs) favor main effect estimation. However, complete enumeration becomes infeasible for cases relevant for practitioners. We develop a partial enumeration procedure for these cases and we establish upper bounds on the D-efficiency for the interaction model based on arrays that have not been generated by the partial enumeration. We also propose an optimal design procedure that favors main effect estimation. Designs created with this procedure have smaller D-efficiencies for the interaction model than D-optimal designs, but standard errors for the main effects in this model are improved. Generated OAs for 7–10 factors and 32–72 runs are smaller or have a higher D-efficiency than the smallest OAs from the literature. Designs obtained with the new optimal design procedure or strength-3 OAs (which have main effects that are not correlated with two-factor interactions) are recommended if main effects unbiased by possible two-factor interactions are of primary interest. D-optimal designs are recommended if interactions are of primary interest. Supplementary materials for this article are available online. 相似文献
45.
Maarten Uyttebroek Pieter Vandezande Miet Van Dael Sam Vloemans Bart Noten Bas Bongers Wim Porto‐Carrero Maria Muñiz Unamunzaga Metin Bulut Bert Lemmens 《Journal of food process engineering》2018,41(1)
Apple pomace can be used as resource for the extraction of phenolic compounds with antioxidant properties. Pressing of apple in juice and pomace at lab scale in open air (aerobic) and under N2 atmosphere (anaerobic) showed a recovery of phenolic compounds of 85% in juice and pomace after anaerobic pressing, compared to 43% after aerobic pressing, indicating loss of phenolic compounds by oxidation and the advantage of anaerobic over aerobic pressing. After a membrane screening and concentration test at lab scale, the commercial nanofiltration membrane NFX was selected to concentrate phenolic compounds in an ethanol : water extract of apple pomace. At pilot scale, the concencentration of 10 selected phenolic compounds and quinic acid increased from 59.5 mg/L in the ethanol : water extract to 1256.1 mg/L in the final retentate, that is, by a factor 21.1. The volume of the crude extract was reduced by a factor of 28.5 during the filtration, indicating some loss of phenolic compounds during pilot testing due to membrane fouling or oxidation of polyphenols. The pilot concentration test using a spiral‐wound membrane module showed good flux and concentration of phenolic compounds, indicating the technical feasibility of membrane technology for efficient concentration of polyphenols in an ethanol : water extraction solvent. Unfortunately, the extraction and concentration process was not economically feasible under the assumptions made.
Practical applications
The valorization of food waste for the production of high‐added value products is an increasingly hot topic. Phytochemicals are present in relatively low concentration in the fruit matrix, and concentration in the extraction solvent is necessary to develop an industrially relevant process. In this study, membrane filtration was selected for concentration due to its low energy consumption and mild processing conditions compared to other technologies. Membrane screening and testing at lab and pilot scale with techno‐economic assessment can be used by food and nutraceutical industries to evaluate membrane technology for concentration of phytochemicals extracted from agroindustrial by‐products. 相似文献46.
47.
Thomas Frissen Erkan Toguslu Pieter Van Ostaeyen Leen d&#x;Haenens 《Telematics and Informatics》2018,35(2):491-503
The current study set out to investigate to what extent ISIS is bolstering its jihadist ideology on a ‘cut-and-paste’ or ‘cherry-picked’ version of Islam in their renowned online propaganda magazine Dabiq. The main objective was to examine in a systematic and quantitative way to what extent ISIS utilizes the Koran in an atomistic, truncated and tailored manner to bolster its religious legitimacy. A total of 15 issues of Dabiq and 700 Koranic references were scrutinized. By means of a quantitative analysis we developed an innovative taxonomy of Koranic chapters and verses (i.e. surahs and ayat, respectively) on the basis of their appearance in Dabiq. Our large-scale data analysis provide consistent empirical evidence for severe decontextualization practices of the Koran in three ways: (1) a thin, Medinan-dominated religious layer, (2) ayah mutilation, and (3) clustered versus exclusive mentions. Limitations and implications for future research, policy makers and CVE initiatives are discussed. 相似文献
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