A Performance Study of a Horizontal-axis Micro-turbine in a Numerical Wave Flume

Numerical studies of performance of a 3-bladed Savonius type horizontal-axis wave energy converter are presented. Numerical simulations based on a volume of fluid (VOF) method coupled with a finite volume method (FVM) approach are performed in a numerical wave flume (NWF) for specified values of flow physics and turbine blade geometry conditions. Once validated against experimental data, the numerical simulations are extended to investigate the overall performance of the turbine over a very large range of wave height, wave frequency, and the submergence level for the same water depth in the context of optimization of a design of a small scale Savonius rotor. From the numerical results obtained and validated against the experimental data it can be concluded that the flow characteristics are strongly dependent upon differing wave propagation conditions and energy conversion rate can be increased with a proper combination of selected wave height and frequency for the investigated parametric value range

Numerical study of the pressure drop phenomena in wound woven wire matrix of a Stirling regenerator

Friction pressure drop correlation equations are derived from a numerical study by characterizing the pressure drop phenomena through porous medium of both types namely stacked and wound woven wire matrices of a Stirling engine regenerator over a specified range of Reynolds number, diameter and porosity. First, a finite volume method (FVM) based numerical approach is used and validated against well known experimentally obtained empirical correlations for a misaligned stacked woven wire matrix, the most widely used due to fabrication issues, for Reynolds number up to 400. The friction pressure drop correlation equation derived from the numerical results corresponds well with the experimentally obtained correlations with less than 5% deviation. Once the numerical approach is validated, the study is further extended to characterize the pressure drop phenomena in a wound woven wire matrix model of a Stirling engine regenerator for a diameter range from 0.080 to 0.110 mm and a porosity range from 0.472 to 0.638 within the same Reynolds number range. Thus, the new correlation equations are derived from this numerical study for different flow configurations of the Stirling engine regenerator. The results indicate flow nature and complex geometry dependent friction pressure drop characteristics within the present Stirling engine regenerator system. It is believed that the developed correlations can be applied with confidence as a cost effective solution to characterize and hence to optimize stacked and woven Stirling engine efficiency in the above specified ranges

Numerical study of the heat transfer in wound woven wire matrix of a Stirling regenerator

Nusselt number correlation equations are numerically derived by characterizing the heat transfer phenomena through porous medium of both stacked and wound woven wire matrices of a Stirling engine regenerator over a specified range of Reynolds number, diameter and porosity. A finite volume method (FVM) based numerical approach is proposed and validated against well known experimentally obtained empirical correlations for a random stacking woven wire matrix, the most widely used due to fabrication issues, for Reynolds number up to 400. The results show that the numerically derived correlation equation corresponds well with the experimentally obtained correlations with less than 6% deviation with the exception of low Reynolds numbers. Once the numerical approach is validated, the study is further extended to characterize the heat transfer in a wound woven wire matrix model for a diameter range from 0.08 to 0.11 mm and a porosity range from 0.60 to 0.68 within the same Reynolds number range. Thus, the new correlation equations are numerically derived for different flow configurations of the Stirling engine regenerator. It is believed that the developed correlations can be applied with confidence as a cost effective solution to characterize and hence to optimize stacked and wound woven wire Stirling regenerator in the above specified ranges

Adaptive coatings based on polyaniline for direct 2D observation of diffusion processes in microfluidic systems

Microfluidic devices are poised to dramatically influence the future of the process industry. Therefore the understanding and proper evaluation of the flow and mixing behaviour at microscale becomes a very important issue. In this study, the diffusion behaviour of two reacting solutions of HCl and NaOH were directly observed in a glass/polydimethylsiloxane microfluidic device using adaptive coatings based on the conductive polymer polyaniline that are covalently attached to the microchannel walls. The two liquid streams were combined at the junction of a Y-shaped microchannel, and allowed to diffuse into each other and react. The results showed excellent correlation between optical observation of the diffusion process and the numerical results. A numerical model which is based on finite volume method (FVM) discretisation of steady Navier-Stokes (fluid flow) equations and mass transport equations without reactions was used to calculate the flow variables at discrete points in the finite volume mesh element. The high correlation between theory and practical data indicates the potential of such coatings to monitor diffusion processes and mixing behaviour inside microfluidic channels in a dye free environment

EFFECT OF DIFFERENT WALL FUNCTIONS ON THE PREDICTION OF FLOW AND HEAT TRANSFER CHARACTERISTICS IN PLATE FIN AND TUBE HEAT EXCHANGERS

In the present study, effects of wall functions available in the Fluent software on the fluid flow and heat transfer characteristics of a plate fin and tube heat exchanger are investigated in the range of 6000Re500 ≤≤ for a non-dimensional fin spacing of 233.0=sF and the results are compared with experimental data. As it is well-known, wall functions are used to bridge the viscosity-affected region between the wall and the fully turbulent region in the flow domain. Both Standard k-ε and RNG k-ε turbulence models are employed in order to predict the flow and heat transfer characteristics inside the flow passage of the plate fin and tube heat exchanger comprised of four-row of staggered tube layout with wavy fin configuration. The test heat exchanger model is selected from the experimental work exists in the literature and the best wall function that has close agreement with the experimental data is chosen as Enhanced Wall Treatment

Kronik obstrüktif akciğer hastalığında nötrofil-lenfosit oranının öngörücü rolü]

Objective: Recently neutrophil-to-lymphocyte ratio (NLR) -the level of neutrophil reflecting the severity of inflammation and lymphocyte occurring after physiological stress has been gaining popularity, which was, along with other inflammatory markers, commonly accepted as an accurate marker of the inflammatory status. In this multi-centered study, an early, rapid, and low-cost diagnosis method was investigated. To this end, the correlation between chronic obstructive pulmonary disease and inflammation was planned to be utilized and whether neutrophil-to-lymphocyte ratio can be used as a valid tool in the diagnosis of acute exacerbations of chronic obstructive pulmonary disease was investigated. Method: We retrospectively enrolled the 467 patients. Control group included sex and age-matched healthy people. C-Reactive protein, forced expiratory volume-1, forced vital capacity, complete blood count and clinical data A receiver-operating characteristic curve analysis was performed to determine the best cut-off value of N/L ratio and C-Reaktif protein to predict the exacerbation. Two-sided p values <0.05 were considered statistically significant. Results: By spearman analysis, there was a strong correlation between. C-Reactive protein and N/L ratio in both stable group (r=0.436, p<0.001) and exacerbation group (r=0.534, p=0.001). Conclusion: Neutrophil/lymphocyte ratio may be a useful predictor of inflammation in chronic obstructive pulmonary disease and acute exacarbation of chronic obstructive pulmonary disease patients

Adaptive coatings based on polyaniline for direct 2d observation of diffusion processes in microfluidic systems

Microfluidic devices are poised to dramatically influence the future of the process industry. Therefore the understanding and proper evaluation of the flow and mixing behaviour at microscale becomes a very important issue. In this study, the diffusion behaviour of two reacting solutions of HCl and NaOH were directly observed in a glass/polydimethylsiloxane microfluidic device using adaptive coatings based on the conductive polymer polyaniline that are covalently attached to the microchannel walls. The two liquid streams were combined at the junction of a Y-shaped microchannel, and allowed to diffuse into each other and react. The results showed excellent correlation between optical observation of the diffusion process and the numerical results. A numerical model which is based on finite volume method (FVM) discretization of steady Navier-Stokes (fluid flow) equations and mass transport equations without reactions was used to calculate the flow variables at discrete points in the finite volume mesh element. The high correlation between theory and practical data indicates the potential of such coatings to monitor diffusion processes and mixing behaviour inside microfluidic channels in a dye free environment

Optimized CFD modelling and validation of radiation section of an industrial top-fired steam methane reforming furnace

[EN]The present study proposes an optimized computational fluid dynamics (CFD) modelling framework to provide a complete and accurate representation of combustion and heat transfer phenomena in the radiation section of an industrial top-fired steam methane reforming (SMR) furnace containing 64 reforming tubes, 30 burners and 3 flue-gas tunnels. The framework combines fully-coupled appropriate furnace-side models with a 1-D reforming process-side model. Experimental measurements are conducted in terms of outlet temperatures at the flue-gas tunnels, point-wise temperature distributions at the panel walls, and inside the reforming tube collectors which are placed at the refinery plant of Petronor. The final results are compared with the experimental data for validation purpose. The proposed fully coupled 3-D CFD modeling framework, which utilizes a detailed chemical-kinetic combustion mechanism, reproduces well basic flow features including pre-mixed combustion process, downward movement of flue-gas in association with large recirculation zones, radiative heat transfer to the reforming tubes, composition profiles along the reaction core of the reforming tubes, temperature non-uniformities, and fluctuating characteristics of heat flux. The reported non-uniform heat and temperature distributions might be optimized by means of the operating parameters in order to avoid a negative impact on furnace balancing and performance.This research is partially funded by Basque Industry 4.0 pro-gramme of Basque Government (BI00024/2019) and University-Company-Society 2019 call of UPV/EHU (US19/13) . Open access funding is provided by the University of the Basque Country (UPV/EHU)

Cochlear implantation in inner ear malformations: Considerations related to surgical complications and communication skills

Introduction: There are particular challenges in the implantation of malformed cochleae, such as in cases of facial nerve anomalies, cerebrospinal fluid (CSF) leaks, erroneous electrode insertion, or facial stimulation, and the outcomes may differ depending on the severity of the malformation. The aim of this study was to assess the impact of inner ear malformations (IEMs) on surgical complications and outcomes of cochlear implantation. Methods: In order to assess the impact of IEMs on cochlear implant (CI) outcomes, 2 groups of patients with similar epidemiological parameters were selected from among 863 patients. Both the study group (patients with an IEM) and control group (patients with a normal inner ear) included 25 patients who received a CI and completed at least 1 year of follow-up. Auditory performance, receptive and expressive language skills, and production and use of speech were evaluated preoperatively and at least 1 year after implantation. Types of surgical complications and rates of revision surgeries were determined in each group. Results: In the study group, the most common malformation was an isolated enlarged vestibular aqueduct (EVA) (44.8%). Overall, the patients with IEMs showed significant improvement in auditory-verbal skills. In general, the patients who had normal cochleae scored significantly better compared to patients with IEMs (p < 0.05). The complication rate was significantly lower in the control group compared to the study group (p = 0.001), but the rate of revision surgeries did not differ significantly (p = 0.637). Conclusion: It is possible to improve communication skills with CIs in patients with IEMs despite the variations in postoperative performances. Patients with EVA, incomplete partition type 2, and cochlear hypoplasia type 2 were the best performers in terms of auditory-verbal skills. Patients with IEMs scored poorly compared to patients with normal cochleae. CSF leak (gusher or oozing) was the most common complication during surgery, which is highly likely in cases of incomplete partition type 3

Outcomes of high-risk breast lesions diagnosed using image-guided core needle biopsy: results from a multicenter retrospective study

PURPOSEThe clinical management of high-risk lesions using image-guided biopsy is challenging. This study aimed to evaluate the rates at which such lesions were upgraded to malignancy and identify possible predictive factors for upgrading high-risk lesions.METHODSThis retrospective multicenter analysis included 1.343 patients diagnosed with high-risk lesions using an image-guided core needle or vacuum-assisted biopsy (VAB). Only patients managed using an excisional biopsy or with at least one year of documented radiological follow-up were included. For each, the Breast Imaging Reporting and Data System (BI-RADS) category, number of samples, needle thickness, and lesion size were correlated with malignancy upgrade rates in different histologic subtypes. Pearson’s chi-squared test, the Fisher–Freeman–Halton test, and Fisher’s exact test were used for the statistical analyses.RESULTSThe overall upgrade rate was 20.6%, with the highest rates in the subtypes of intraductal papilloma (IP) with atypia (44.7%; 55/123), followed by atypical ductal hyperplasia (ADH) (38.4%; 144/375), lobular neoplasia (LN) (12.7%; 7/55), papilloma without atypia (9.4%; 58/611), flat epithelial atypia (FEA) (8.7%; 10/114), and radial scars (RSs) (4.6%; 3/65). There was a significant relationship between the upgrade rate and BI-RADS category, number of samples, and lesion size Lesion size was the most predictive factor for an upgrade in all subtypes.CONCLUSIONADH and atypical IP showed considerable upgrade rates to malignancy, requiring surgical excision. The LN, IP without atypia, pure FEA, and RS subtypes showed lower malignancy rates when the BI-RADS category was lower and in smaller lesions that had been adequately sampled using VAB. After being discussed in a multidisciplinary meeting, these cases could be managed with follow-up instead of excision