Building a MATLAB applicaton for preliminary design and optimization of shell and tube heat exchangers

Designing shell and tube heat exchangers is a complex and time-consuming procedure. Since they are one of the most common process units in process industry, great effort should be made to improve their design and to facilitate the design procedure. Therefore, in this study, an easy-to-use MATLAB application for shell and tube heat exchanger preliminary design and optimization was developed. The application enables users to select operating parameters manually and test their effect on heat transfer area and pressure drop. Moreover, the application helps users to optimize the preliminary design, in terms of finding the minimal heat transfer area required to meet the process requirements. The validity of the application was tested on the example from the literature, where the heat transfer area was 61.91 m2. During the proposed optimization procedure, different parameter values were tested and an optimal combination of parameters was found within 5 seconds (for all combinations), resulting in the heat transfer area of 53.27 m2. The application has a great feature of displaying the impact of baffle cut value and baffle spacing on most important design parameters: heat transfer area, tube-side pressure drops and shell-side pressure drops. Also, new correlations were developed for the calculation of the Colburn heat transfer factor and friction factor as a function of Reynolds number and baffle cut value. Overall, the application has proven to be useful for the preliminary design of shell and tube heat exchangers, and can represent the foundation for the development of advanced heat exchanger design applications

Stochastic optimization of microgrids with renewable and storage energy systems

The microgrids can function as a single controllable system in a grid-connected or islanded operation mode. The transition from grid-connected mode to islanded mode can result in microgrid excess generation or demand, which must be spilled or curtailed. This paper proposes an optimization model for optimizing the microgrid operations accounting for distributed energy resources (stochastic generation and time-varying demand), as well as microgrid operation constrains. The objective is to minimize the microgrid operational costs considering the classical generation capacities and exchanged power with the upstream grid, as well the operational constraints. The analyzed microgrid is composed of a thermal engine, a photovoltaic system, an electrochemical storage system, critical and interruptible loads. The deterministic and stochastic optimization model were formulated, and each optimization model is tested in various case studies considering the different operational states of the microgrid

A Novel Approach for Simulation and Optimization of Rubber Vulcanization

The kinetic model, encompassing the curing and reversion phenomena of the NR/SBR rubber vulcanization process, was developed by means of the finite element method simultaneously with heat transfer equations, including heat generation due to curing reactions. The vulcanization simulation was conducted for three spheres of different diameters (1, 5 and 10 cm) and two rubber wheels, one of which was a commercial product of the rubber industry. The proposed advanced simulation model, based on products’ two-dimensional axisymmetry, includes cooling after vulcanization, during which the crosslinking reactions continue to take place as a result of the products’ heated interiors. As a criterion for removing the product from the mold, an average vulcanization degree of 0.9 was set, whereby, during cooling, the vulcanization degree increases, due to crosslinking reactions. Based on the minimal difference between the maximal and minimal vulcanization degrees, which did not exceed a value of 0.0142, the optimal process parameters for each product were determined, achieving homogeneity and obtaining high-quality rubber products, while simultaneously ensuring a more efficient vulcanization process and enhanced cost effectiveness for the rubber industry

Flicker propagation in power systems supplying wind farms

In the last years, the conducted studies for connecting renewable energy sources with small installed capacity to the electrical grid highlighted the importance of the grid characteristics and on the technical conditions required for the equipments. The operation of wind farms in the electrical system is restricted by its capacity to absorb the produced power and to ensure the required adequacy. The propagation of voltage fluctuations in the electrical system, where wind farms are connected, is of high importance in order to assess their power quality impact

Effects of the LPA1 Receptor Deficiency and Stress on the Hippocampal LPA Species in Mice

Lysophosphatidic acid (LPA) is an important bioactive lipid species that functions in intracellular signaling through six characterized G protein-coupled receptors (LPA1-6). Among these receptors, LPA1 is a strong candidate to mediate the central effects of LPA on emotion and may be involved in promoting normal emotional behaviors. Alterations in this receptor may induce vulnerability to stress and predispose an individual to a psychopathological disease. In fact, mice lacking the LPA1 receptor exhibit emotional dysregulation and cognitive alterations in hippocampus-dependent tasks. Moreover, the loss of this receptor results in a phenotype of low resilience with dysfunctional coping in response to stress and induces anxiety and several behavioral and neurobiological changes that are strongly correlated with mood disorders. In fact, our group proposes that maLPA1-null mice represent an animal model of anxious depression. However, despite the key role of the LPA-LPA1-pathway in emotion and stress coping behaviors, the available information describing the mechanisms by which the LPA-LPA1-pathway regulates emotion is currently insufficient. Because activation of LPA1 requires LPA, here, we used a Matrix-Assisted Laser Desorption/ Ionization mass spectrometry-based approach to evaluate the effects of an LPA1 receptor deficiency on the hippocampal levels of LPA species. Additionally, the impact of stress on the LPA profile was also examined in both wild-type (WT) and the Malaga variant of LPA1-null mice (maLPA1-null mice). Mice lacking LPA1 did not exhibit gross perturbations in the hippocampal LPA species, but the LPA profile was modified, showing an altered relative abundance of 18:0 LPA. Regardless of the genotype, restraint stress produced profound changes in all LPA species examined, revealing that hippocampal LPA species are a key target of stress. Finally, the relationship between the hippocampal levels of LPA species and performance in the elevated plus maze was established. To our knowledge, this study is the first to detect, identify and profile LPA species in the hippocampus of both LPA1-receptor null mice and WT mice at baseline and after acute stress, as well as to link these LPA species with anxiety-like behaviors. In conclusion, the hippocampal LPA species are a key target of stress and may be involved in psychopathological conditions.This study was supported by Consejeria de Economia, Innovacion, Ciencia y Empleo, Junta de Andalucia (SEJ-1863 to CP; CTS-643 to GE-T), Ministerio de Economia y Competitividad and the European Regional Development Fund (PSI2017-83408-P to CP), Ministerio de Educacion, Cultura y Deporte (FPU14/01610 to RM-F and FPU16/05308 to AN-Q), and Consejeria de Economia, Innovacion, Ciencia y Empleo, Junta de Andalucia (SEJ-1863, FPI to ST)

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)