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Numerical simulation results obtained for the effect of the discharge gap nonuniformity in a barrier-discharge ozone generator exerted on the operational characteristics thereof are presented. An ozonizer with a cylindrical shape of the electrodes is considered, the nonuniformity level is determined by displacing electrode axes with respect to each other. The volumetric flow rate distribution of the working gas and the active power released in the barrier discharge throughout the cross section of the ozone generator for several nonuniformity levels have been obtained, and their profound nonuniformity is shown. A mutually amplified negative effect of the obtained distributions exerted on the synthesis of ozone has been revealed. [ABSTRACT FROM AUTHOR]

The investigation of the couple stress fluid flow behaviour between two parallel plates under sudden stoppage of the pressure gradient is considered. Initially, a flow of couple stress fluid is developed between the two parallel plates under a constant pressure gradient. Suddenly, the applied pressure gradient is stopped, and the resulting unsteady flow is studied. This type of flow is known as run-up flow in the literature. Now the flow is expected to come to rest in a long time. Usually, these types of problems are solved by using the Laplace transform technique. There are difficulties in obtaining the inverse Laplace transform; hence, many researchers adopt numerical inversions of Laplace transforms. In this paper, the problem is solved by using the separation of variables method. This method is easier than the transform method. The velocity field is analytically obtained by applying the usual no-slip condition and hyper-stick conditions on the plates, and hence the volumetric flow rate is derived at subsequent times. The steady state solution before the withdrawal of the pressure gradient is matched with the initial condition on time. The rest time, i.e. the time taken by the fluid to come to rest after the pressure gradient is withdrawn is calculated. The graphs for the velocity field at different times and different couple stress parameters are drawn. In the special case when a couple stress parameter approaches infinity, couple stress fluid becomes a viscous fluid. Our results are in good agreement with this special case. [ABSTRACT FROM AUTHOR]

The battery plays a pivotal role in the electric vehicle (EV) sector, and the advancement of this industry hinges on enhancing the thermal performance and efficiency of batteries, especially in regions characterized by high-temperature extremes. The primary objective of this study is to propose a battery configuration capable of operating efficiently in hot regions. To achieve this goal, we have selected six battery materials, each possessing distinct physical characteristics, for an in depth investigation into their thermal behavior within a mini-channel Thermal Management System. Subsequently, we conducted a comparative analysis of various volumetric flow rates and flow directions to determine the optimal combination. Once the best configuration was identified, we conducted a case study using realistic ground-based meteorological data to evaluate the performance of the selected battery configuration under real conditions. The results of this study reveal that material which is characterized by the specific heat of 830J.kg-1.K-1, and a thermal conductivity of Kx = Ky = 34W.m-1.K-1 and Kz = 3.4W.m-1.K-1, exhibits the highest thermal performance. Taking into account the power required for the system, the most efficient volumetric flow rate is 0.05 L/min which requires a power of 3e-7W, with the same direction of fluid inlet and outlet in the minichannels. The selected material, volumetric flow rate, and flow direction in this study ensure that the maximum temperature of (Tmax) of the cell is maintained at 29.21 °C, with a temperature difference (Tdiff) of 1.56 °C. Regarding the case study, applying this optimal configuration under the climatic conditions of Benguerir, Morocco, results in a Tmax of 29.36 °C and a Tdiff of 1.58 °C, confirming the feasibility of the proposed battery configuration and its BTMS in high-temperature conditions.

ABSTRACTMaterial extrusion (MEX) 3D printing offers a promising avenue for fabricating metal and ceramic components, where highly loaded polymer filaments are 3D-printed and sintered. Achieving nearly 100% 3D-printed part density is critical in this process, as porosity during printing compromises part properties after sintering. However, challenges arise due to the unfavourable mechanical and rheological properties of MEX metal filaments, leading to slow print-speeds, filament breakage, and inconsistent extrusion. This work explores these process-property correlations by developing process maps for bound metal filaments and unfilled polymer systems. This study throws light on the significance of back-flow and back-pressure in calculating the pressure drop across the nozzle, especially in a diverse set of material systems represented by hard and stiff PLA, soft and flexible TPU, and brittle and fragile bronze filaments. Additionally, ANOVA identified the effect of print conditions on measured variables, while regression models helped predict the behaviour of a given material under different process conditions. Therefore, this study enables material design and discovery for bound-metal filaments while addressing critical knowledge gaps, thereby paving the way for high-density 3D-printed components.

The article presents an advanced two-dimensional (2D) computational fluid dynamics (CFD) model of an external gear pump which considers relief grooves. Relief grooves are limiting design features for the flow process of this type of pump, and their influence in existing studies is considered by a three-dimensional (3D) model only. The structural modification proposed by the authors is beyond the possibilities of real implementation, but it gives the possibility to precisely model the pump's design features. In contrast to the existing studies (using 3D CFD), the proposed advanced 2D model requires significantly fewer computing resources. Numerical experiments were carried out using the 2D model at different pump operating modes depending on the rotation frequency (950–1450 min−1) and pressure load (5–150 bar). The numerical results were validated by a real-world experiment for the same pump operating modes using an existing laboratory experimental setup. An analysis of the CFD model and real experiment results was carried out by determining a quantitative index of match (FIT), which varies in the range of 97.93–99.82%. This proves the performance of the proposed CFD model, which can be further used as a part of more complex hydraulic systems models. [ABSTRACT FROM AUTHOR]

The important aspects of increasing hydrodynamic efficiency, improving performance and technical characteristics of various heat and mass transfer equipment, as well as ensuring the required regime and flow conditions of fluids with different viscosities have been analyzed. Such heat transfer equipment includes radiators that contain tubes for circulating heat transfer medium. When solving related issues, in addition to studying the flow characteristics of various fluids in circular horizontal tubes (capillaries), it is necessary to determine the conditions, under which the flow of fluid inside capillaries and circular tubes of small diameter is laminar, so it can be described by the Poiseuille equation. The experimental data on determining water flow rates in horizontal circular tubes of various diameters are presented. The dependence of the volumetric flow rate on the pressure drop has been determined. It was shown that the basic parameters that determine the flow characteristics of fluids in horizontal tubes are the tube radius and fluid dynamic viscosity. A flow of distilled water in tubes with diameters of 0.95, 1.6 and 2.0 mm was analyzed at a gauge pressure ranging from 0.266 to 4.000 kPa. It was found that when using a 0.95 mm diameter tube, the dependence of the volumetric flow rate on the gauge pressure remains linear in the entire analyzed range of pressures. An increase in the tube radius increases the likelihood of flow velocity fluctuations and the appearance of a radial velocity component (i.e., the occurrence of the elements of a turbulent fluid flow structure). The water flow regime in tubes with diameters of 1.6 and 2.0 mm deviates from the laminar at pressures exceeding 1.3 and 1.0 kPa, respectively. The dependence of the volumetric flow rate on pressure for a 40% aqueous solution of calcium chloride, as well as transformer, transmission, and engine oils with dynamic viscosities ranging from 0.002 to 0.182 Pa · s remains linear up to the tube diameters of 5–6 mm. The results of studying fluids with different viscosities are presented in the form of a nomogram illustrating the ratio of the tube radius raised to the fourth power to the fluid viscosity as a function of the tube radius. By analyzing this relationship, it becomes possible to predict the flow characteristics of the studied fluid at given tube radius and dynamic viscosity values. The obtained results can be used when designing and operating various heat transfer devices, such as radiators with tubes for circulating a heat transfer medium. [ABSTRACT FROM AUTHOR]

In this article, a mathematical model is developed to study the effect of Non-Newtonian behavior of blood through stenosed artery considering Herschel-Bulkely fluid model. The constitutive equations of the model are solved analytically with the help of given boundary conditions to get different expression for flow rate. flow resistance and wall shear stress. It ix observed that the flow rate decreases with stenosis size. It has been shown that the resistance to flow and wall shear stress increases with the size of stenosis, but these increases is comparatively small due to Non-Newtonian type of blood and also comparison of these flow paraneters has been done for linear and quadratic variation of viscosity. [ABSTRACT FROM AUTHOR]

The experimental data obtained proved that the effect of bed weight, flow rate and initial metal ion concentration plays a significant role on the removal of Cu (II) and Cd (II). The column performance calculation involves various parameters such as breakthrough time, saturation time, Volume treated at breakthrough point (ml), Volume treated at saturation point (ml), mads, mtotal, % removal have been calculated for both the metals using synthetic and industrial effluents. The detailed comparison studies have been reported in this paper along with explanation for both copper and cadmium. The cadmium metal % removal for synthetic solutions is better than industrial effluents at different bed heights and volumetric flow rates. The inverse trend for copper % removal is observed which shows that industrial effluent is better than the synthetic sample which may be due to more adsorbent dosage and influence of synergistic effect in the column. This trend is due to presence of Phenols, cresols, other heavy metals, sludge, major concentrations of adsorbates and impurities in industrial effluent. Overall in comparison with industrial effluents for cadmium, the synthetic solutions have proved to be more superior in terms of column total % removal and better performance was observed with synthetic solutions than industrial effluents. The adsorbent can be used for longer time before it needs replacement or regeneration. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main focus of this research is to modify the straight pipe of the Citronella essential oil distillation condenser using a helical coil pipe to shorten the distillation time. This study aims to obtain an effective shell-side fluid volumetric rate to shorten the distillation time. The volumetric rate of the shell side fluid varies from 0.72 to 3.66 LPM at a constant pitch ratio of 2.10. Recording of data in the form of temperature, volumetric rate of shell side water, and tube side steam after steady state is reached. The experimental results show that the effectiveness increases with the increase in the volumetric flow rate of the shell side fluid, where the maximum effectiveness at the volumetric flow rate of 3.66 LPM is 69.99%, while the minimum effectiveness at the volumetric flow rate of 0.72 LPM is 44.39%. The results of the validation of the effectiveness of the condenser show a trend curve that is identical to the previous research, with an average deviation of 5.67%. The maximum volumetric flow rate with a minimum distillation time of 120 minutes with a condensate volume of 8 ml or 240 minutes is smaller than the result of straight-pipe condenser distillation by UKM. The maximum effectiveness is due to an increase in the Reynolds number on the shell side, which results in an increase in the actual heat transfer. It can be concluded that the maximum condenser effectiveness at a maximum volumetric rate of 3.66 LPM could be used for refining Citronella essential oil by SMEs.

The article presents an advanced two-dimensional (2D) computational fluid dynamics (CFD) model of an external gear pump which considers relief grooves. Relief grooves are limiting design features for the flow process of this type of pump, and their influence in existing studies is considered by a three-dimensional (3D) model only. The structural modification proposed by the authors is beyond the possibilities of real implementation, but it gives the possibility to precisely model the pump’s design features. In contrast to the existing studies (using 3D CFD), the proposed advanced 2D model requires significantly fewer computing resources. Numerical experiments were carried out using the 2D model at different pump operating modes depending on the rotation frequency (950–1450 min−1) and pressure load (5–150 bar). The numerical results were validated by a real-world experiment for the same pump operating modes using an existing laboratory experimental setup. An analysis of the CFD model and real experiment results was carried out by determining a quantitative index of match (FIT), which varies in the range of 97.93–99.82%. This proves the performance of the proposed CFD model, which can be further used as a part of more complex hydraulic systems models.

As an alternative to conventional mechanical fans, EHD fans and/or EHD gas pumps, which generate less noise, were investigated for cooling systems, such as in electronic equipment and automobiles. Wire-parallel plate electrode type EHD fans, which have greater design freedom and potential for practical application, have been suggested. This study clarifies the characteristics of a wire-partially insulated parallel plate electrode type EHD fan under DC positive applied voltage. In order to understand the characteristics of the EHD fan more deeply, visualizations of the air flow in the flow channel and the exit area were conducted by using PIV and CFD analyses. In the experiment, air at atmospheric pressure and room temperature was used as a working fluid. The experimental results for fan characteristics of the EHD fan, such as the velocity profile, cross-sectional average velocity, volumetric flow rate in the flow channel or at the exit area, power, and so on, are considered in detail. In addition, the flow visualization and the instantaneous and time-averaged velocity profiles from the PIV analysis are discussed. A comparison with the experimental results described above, and differences of flow regime for different locations, are also presented and discussed. Furthermore, a two-dimensional steady state flow simulation by means of CFD analysis was conducted and its experimental results analyzed. [ABSTRACT FROM AUTHOR]

Joule-Thomson cryo-refrigerators operating on mixed working fluids have significant advantages over chillers using pure refrigerants. When optimizing the composition of zeotropic refrigerant mixtures, it is necessary to take into account the peculiarities of the operation of volumetric compressors. It is known that the flow rate of a reciprocating compressor significantly depends on the compression ratio and the compressor suction pressure. Therefore, it is impractical to optimize the composition of zeotropic refrigerant mixtures at a fixed molar flow rate, as is done in many studies. This paper describes a method for optimizing the operation of a refrigeration machine operating on a five-component zeotropic mixture of refrigerants. The maximum cooling capacity of the unit at the temperature of 120 K, which is based on a hermetic compressor TAG 2513Z, was chosen as the objective function. The following parameters were varied during the optimization: compressor discharge and suction pressures, the composition of the five-component working mixture, as well as the temperature upstream of the throttle valve, and the temperature at the inlet to the phase separator. As a result of processing the results of the numerical experiment, an analytical expression was obtained that approximates the operation of the refrigeration unit depending on the eight varied parameters. This made it possible to find the optimal operating mode of the refrigeration machine, which achieves maximum cooling capacity. At the optimum operating mode of the refrigeration unit, the suction pressure is 2.35 bars, and the discharge pressure is 16.0 bars. With the optimal composition of the working substance, the maximum cooling capacity of 147.7 W with energy consumption by the compressor of 2.36 kW is achieved. [ABSTRACT FROM AUTHOR]

The localisation of leakages during the vacuum bagging process of a composite is currently time intensive and reliant on human labour. The purpose of this article is to explore four computational methods for leakage localisation using volumetric flow rate (VFR) data to increase the automation of the process. The data used in this article is based on experiments on a square vacuum bag with four vacuum ports. The first method is based on potential flow theory to simulate the flow. In the second method, numerical regression was applied to find a relation between the VFRs and port-leakage distances. The third method consisted of calculating the fractional VFRs for every point on a grid and finding the grid point whose values most closely correspond to the observed fractional VFRs. The last method involved training a machine learning algorithm with experimental data. After the development of the methods, their performance was tested over the entire single-leakage dataset and compared. The results were in the same order of magnitude for all methods, with an area of 10 5 mm 2 for the 95% confidence interval and a distance of 10 2 mm for the average error. Further research is required for application to different vacuum bag shapes and multiple leakages cases. The method with the highest adaptability and performance is the method based on potential-flow theory. Machine learning and the potential-flow method is further applicable to multiple leakage localisation. [ABSTRACT FROM AUTHOR]

Today, the estimation of physical parameters has become very important; for instance, the water flow rate (RWFR) estimation is one of the types that will gain considerable significance among the others performed in this way. The forecasting of RWFR plays a crucial role in planning and building of new water dams, or operating the ones that were previously built. This study proposes machine learning algorithms to estimate a one-day ahead short-term RWFR. The estimation models were developed, using historical RWFR data, in order to obtain the future RWFR values. For the purpose of RWFR predictions, long short-term memory (LSTM) neural network, adaptive neuro-fuzzy inference system (ANFIS) with fuzzy c-means (FCM), ANFIS with subtractive clustering (SC), as well as the ANFIS with grid partition (GP) were advanced. A measurement station (MS), named as Harmanli MS, located on the Maritsa River and at the border of Turkey and Bulgaria, was selected as the study region. A total of 102 models were constructed by these four algorithms. The forecasting outcomes were compared with the real measured data. The comparisons were conducted using the statistical error results obtained from mean absolute error (MAE), root mean square error (RMSE), and the correlation coefficient (R). The predictions of the daily average volumetric flow rate (VFR) data have indicated that ANFIS-FCM model had generated the best statistical error results. Namely, statistical error results of 2.54 m3/s MAE, 4.35 m3/s RMSE, and 0.9981 R have been obtained with the utilization of the ANFIS-FCM algorithm. On the other hand, when the averages of three statistical error parameters are considered, it was shown that averages of the statistical error results of the ANFIS-SC algorithm including cumulative of 48 models to be slightly better than the average statistical error results of the ANFIS-FCM. Accordingly, it was concluded and demonstrated in this study that FCM and SC tools of the ANFIS can be two useful methods in VFR predictions. Finally, as in the case of RWFR data which usually has random distributions, it has been reported and shown that both algorithms can be simply accomplished to any type of randomly distributed data. [ABSTRACT FROM AUTHOR]

The article presents the experimental results of the calibration of the typical check structure with sluice gates installed in a trapezoidal irrigation channel. Hydraulic experiments on sluice gate discharge capacity were performed on a model made in a 1:2 scale. It has been explained how the method of measuring the downstream water depth below the sluice gate in the check structures installed in a trapezoidal irrigation channels affects the measured depth values. On the basis of hydraulic measurements, regression relationships were developed for the discharge coefficients for submerged outflow through the sluice gate in two types of sluice gates installed in irrigation channels. The formulas allow to calculate the volumetric flow rate below the submerged sluice gate after determining the water depth upstream and below the sluice gate and the gate opening height. The differences in volumetric flow rates calculated from regression relationships and measured values do not exceed 10%, which confirms their practical suitability for calculating the discharge through a sluice gate mounted in a trapezoidal channel. The values of the discharge coefficients determined in the channels with rectangular cross-sections are not useful for the discharge coefficients of sluice gates check structures installed in trapezoidal channels. Nomograms and relationships for discharge coefficients of the analysed sluice gate were developed. [ABSTRACT FROM AUTHOR]

As an alternative to conventional mechanical fans, EHD fans and/or EHD gas pumps, which generate less noise, were investigated for cooling systems, such as in electronic equipment and automobiles. Wire-parallel plate electrode type EHD fans, which have greater design freedom and potential for practical application, have been suggested. This study clarifies the characteristics of a wire-partially insulated parallel plate electrode type EHD fan under DC positive applied voltage. In order to understand the characteristics of the EHD fan more deeply, visualizations of the air flow in the flow channel and the exit area were conducted by using PIV and CFD analyses. In the experiment, air at atmospheric pressure and room temperature was used as a working fluid. The experimental results for fan characteristics of the EHD fan, such as the velocity profile, cross-sectional average velocity, volumetric flow rate in the flow channel or at the exit area, power, and so on, are considered in detail. In addition, the flow visualization and the instantaneous and time-averaged velocity profiles from the PIV analysis are discussed. A comparison with the experimental results described above, and differences of flow regime for different locations, are also presented and discussed. Furthermore, a two-dimensional steady state flow simulation by means of CFD analysis was conducted and its experimental results analyzed.

Transport of suspension particles over porous media occurs in many industrial and environmental processes such as filtering and sedimentation. Among these applications, flow of red blood cells over EGL has received considerable attention in the recent years. In this paper, by considering EGL as a porous mesh, we present the fundamental physics of suspensions of particles at various suspension concentrations over porous layers. We quantitatively examine the flow of mono-disperse non-colloidal suspensions over a porous medium by developing an analytical framework to model the flow in a channel where the lower surface was replaced by various porous media. The model validated by comparing the predictions of the flow at low suspension concentrations with the flow of pure Newtonian fluid over a porous layer and a good agreement was found. We showed that the volumetric flow rate induced by the presence of porous media depends on the values of the permeability parameter α = L K , the thickness ratio δ = H L , and the concentration of the suspension flow ϕ where L is the half-thickness of the free flow region, H is the thickness of the porous layer, and K is the permeability of the porous layer. Furthermore, the velocity and shear stress profiles for the flow over the permeable layer were examined for the limiting cases of α → 0 and α → ∞. [ABSTRACT FROM AUTHOR]

There has been some work put into the production of a numerical model to research the impact that an attractive field has on the progression of blood through a slanted different atherosclerotic corridors. It has been concluded that the Casson condition will be utilized to mirror the non-Newtonian nature of blood. Logically and graphically, the impacts of the reaction of attractive field, yield stresses, shape boundary, and tendency of supply route on speed, volumetric stream rate in stenotic segment, and divider shear pressure at the outer layer of stenosis are shown. [ABSTRACT FROM AUTHOR]

Featured Application: The proposed application could be exploited for the design of a desalination device at various scales, depending on the desired flow rate of clean water. An array of ion separation cells is presented in this work, to propose a novel desalination device. Molecular Dynamics simulations have been incorporated to establish the theoretical background and calculate all parameters that could lead the manufacturing step. The main system component is an ion separation cell, in which water/NaCl solution flows due to an external pressure difference and ions are directed towards the non-permeable walls under the effect of an electric field, with direction perpendicular to the flow. Clean water is gathered from the output, while the remaining, high-concentration water/ion solution is re-cycled in the cells. The strength of the electric field, cell dimensions, and wall/fluid interactions are investigated over a wide range, and shear viscosity and the volumetric flow rate are calculated for each case. [ABSTRACT FROM AUTHOR]

In this paper, we have considered a two-phase flow in a groovy curved channel. The fluid contains a uniformly distributed small particles and the flow is generated by a transient pressure gradient along the grooves. The governing equations describing the flow in the groovy curved domain are developed and the analytical solution of the complex flow field is determined using domain perturbation method. The effect of the particles on the flow is discussed through the particle relaxation time relative to the flow characteristic time. It is found that the fluid and particle velocities depend on the magnitude of particle relaxation time relative to the flow characteristic time. The effect of the grooves on the transient flow is examined in the presence of the fluid-particle interactions, and the associated results have been reported. The results are further compared with those of a two-phase flow in a smooth curved channel and a particle-free flow in a groovy curved channel, which are special cases of the present study. • A transient two-phase flow in a groovy domain is studied. • Fluid-particle interactions are examined in the flow domain. • The flow is bounded by groovy curved boundaries aligned with phase shift. • Small wavenumber grooves have enhancing effect on the flow compared to smooth curved boundaries with no grooves. • Large wavenumber grooves decrease the flow. [ABSTRACT FROM AUTHOR]

Characterization of two-phase flows is a common problem in the process industry. Due to complexity of flows, having accurate measurements of velocity fields, phase fractions, and the volumetric flow rates is challenging. Even though several approaches have been developed, accurate measurements of the flow quantities remain a challenge. Metering volumetric flow rate requires information on the local phase fraction and velocity field in the pipe cross section to be imaged. These data are commonly obtained using two individual measurement systems, the so-called dual-modality system. This article considers a dual-modality consisting of electromagnetic flow tomography (EMFT) and electrical tomography (ET) imaging, which provide information on the velocity field and electrical conductivity distribution, respectively; the combination of EMFT and ET reconstruction can be further used for inferring the volumetric flow rate. The aim of this article is to improve the accuracy of the EMFT and ET reconstructions—and the resulting flow rate estimate—by enhanced modeling of the unknown velocity and conductivity fields. More specifically, the proposed approach is based on modeling the joint statistics of the velocity and conductivity with a cross-covariance matrix which is based on a representative ensemble of velocity–conductivity image pairs obtained, for example, from fluid dynamical modeling or empirically. The cross-covariance matrix is incorporated in the joint reconstruction within the Bayesian inverse problems framework as an additional prior model. The proposed image reconstruction approach is tested with a set of numerical simulations. The results show that the joint reconstruction approach (JRA) with a cross-covariance model is capable of improving the accuracy of the estimates compared to the approaches that are currently in use. [ABSTRACT FROM AUTHOR]

In order to improve the metrological characteristics of a standard nozzle under actual operating conditions, an improved model of a steady-state gas flow in the varying-cross-section channels was used to refi ne the estimates of two methodological errors when reproducing a volumetric flow rate of gas. The first methodological error is caused by the selection of a gas flow model, accounting for the initial kinetic energy of the flow at the nozzle inlet, and the second – by the variation in humidity of the process air. It is shown that these methodological errors should be considered when operating standard volumetric air flow rate measuring devices, containing critical nozzles. [ABSTRACT FROM AUTHOR]

The aim – to determine the optimal value of the angle between the graft and the coronary artery, which can ensure maximum volumetric blood flow through the created coronary anastomosis. Materials and methods. The study was carried out with porcine vessels. Coronary anastomoses were created between grafts and coronary arteries located in porcine myocardium with angles of 30°, 45° and 90°. A total of 81 coronary anastomoses were created – 27 comparison triples. To assess the volumetric blood flow through the coronary anastomosis, the transit-time volume flowmeter was used. A special solution was passed through the graft at constant pressure. This solution was a 7.5 : 7 mixture of distilled water and glycerin to achieve a relative viscosity equal to that of blood – 4.5. All anastomoses compared with each other were created with the same vessels for the purity of the experiment. Anastomoses were also investigated using X-ray contrast imaging in lateral and antero-posterior projections. Using angiography, the internal diameters of the anastomoses were measured. Results. Anastomoses with an angle of 30° and 45° revealed greater values ​​of volumetric blood flow compared with a 90° angle. The results of the X-ray contrast study confirmed an increase in both (longitudinal and transverse) diameters of the anastomoses with an angle of 45°. Conclusions. The angle of 45° is considered to be the most optimal for anastomosis regarding the feasibility and the capacity of those anastomoses to provide higher velocity of blood flow, as well as by increasing the size of the anastomosis, which corrects possible unevenness of the suture line

With the rapid development of microelectronic devices, efficient thermal management in narrow spaces faces significant challenges. Two-phase heat transfer technology is proposed as a breakthrough in this field; however, big challenges, especially in designing a high-performance wick within limited space, are urgent to be addressed before ultrathin two-phase heat transfer devices (TPHTDs) can be further applied. In this study, a multilayer composite micromesh wick (MCMW), comprised of coarse and fine meshes with different layer combinations, is proposed to enhance the wicking capability, which is promising to further enhance the thermal performance of ultrathin TPHTDs. Capillary rise rate experiments are conducted to evaluate the comprehensive wicking capability. The results show that MCMW structures yield a significant wicking capability enhancement when compared with multilayer single mesh wick (MSMW) structures. The MCMW, consisted of 3 layers of 100-mesh and 3 layers of 300-mesh, exhibits an optimum volumetric flow rate of 14.44 mm3/s and an equilibrated wicking height at 55.98 mm. MCMW structure provides a convenient and effective alternative in enhancing the wicking capability of mesh wicks and the thermal performance of ultrathin TPHTDs. • Multilayer composite micromesh wicks exhibit a significant enhancement in wicking capability. • Optimum layer number combination parameters of multilayer composite micromesh wicks were obtained. • Multilayer composite micromesh wicks are highly promising for ultrathin two-phase heat transfer devices. [ABSTRACT FROM AUTHOR]

Unsteady flow through a curved channel with roughness in the form of sinusoidal corrugations is examined. The flow is generated by a time periodic pressure gradient. The fluid velocity is both time and space periodic, as a result of the oscillatory pressure gradient and the geometry of the curved channel. The effects of the inherent parameters; physical and geometrical, on the velocity field and the volumetric flow rate are determined analytically. For low frequency of the oscillatory pressure gradient, the flow is essentially similar in characteristics to that of the steady flow driven by a constant pressure gradient, but for high frequency, the flow is substantially modified, when compared with the steady flow. The corrugations increase the total flow rate for small corrugation wavenumber, and further enhancement is obtained when the phase difference between the corrugated curved walls is increased. For large corrugation wavenumber, a contrary effect of the corrugations is found; the flow rate decreases irrespective of the phase difference. However, we have shown that for sufficiently high corrugation wavenumber and oscillation frequency, the effect of the phase difference would be negligible. [ABSTRACT FROM AUTHOR]

This paper presents a CFD analysis of three types of axial-flow magnesium-based automotive cooling fans. The numerical modeling was conducted for geometrically modified fan designs: one with no-beads, the second one with beads at the suction-side of the fan namely reverse-beads fan, and the third one with beads installed at the pressure-side of the fan namely forward-beads fan. The effect of geometric modifications of the fan blades on the volumetric flow rate, fan efficiency, and energy efficiency was investigated using Reynolds-averaged Navier-Stokes (RANS) equations following the multiple reference frame methodology. The fan with no-beads was fabricated using 3D printing technology and tested to measure the flow velocity. Subsequently, the fans with beads along with the no-beads fan designs were numerically analyzed. The volumetric flow rate, fan efficiency, and energy efficiency were quantified as a function of fan rotating speed. The results show that the reverse-beads fan produced a relatively more volumetric flow rate and energy-efficient compared to the forward-beads fan. Moreover, to further improve the performance of the reverse-beads fan, the location and size of the bead structure were varied along the radial direction of the fan blade. The optimized reverse-beads fan significantly improves the fan performance. [ABSTRACT FROM AUTHOR]

Accurate estimates for ground thermal parameters and borehole thermal resistance are important to improve the design of borehole heat exchangers (BHEs) in ground-coupled heat pump systems(GCHPs). In order to improve the estimating accuracy of borehole thermal resistance, this paper presents a simple analytical method for evaluating the actual averaged –over-the –depth mean fluid temperature (MFT) in the U-pipe of BHE to calculate borehole thermal resistance R b. Furthermore, the effects of borehole depth and volumetric flow rate on the calculating RMSE distribution between borehole thermal resistance R b and effective borehole thermal resistance R b ∗ are investigated. The conclusion shows that the relative deviation between the two borehole thermal resistances corresponding to the volumetric flow rate 1.5e-4m3/s increases from 4.2% to 29.7% when borehole depth changes from 50 m to 200 m. Finally, the borehole depths corresponding to different volumetric flow rate are optimized to find the boundary line where R b are nearly equal to R b ∗ in the operating time, and the impacts of grout thermal conductivity and heat rate per unit depth of BHE on the boundary line are quantitatively analyzed. Volumetric flow rate has more effect on R b with the higher grout thermal conductivity, the relative error between the two R b corresponding to V = 1.5e-4m3/s and V = 3e-4 m3/s is 10.8% for k g = 2.3 W/(m.°C). The effect of heat rate per unit depth of BHE on R b is very limited, the relative error between the two R b corresponding to q 1 = 50 W/m and q 1 = 80 W/m is 5.4% under V = 1.5e-4m3/s, and it is only 3.7% under V = 3e-4 m3/s. • A simple analytical method is proposed to evaluate the mean fluid temperature of BHE. • Effects of depth and fluid flow rate on borehole thermal resistance are investigated. • The boundary line where R b are nearly equal to R b ∗ is found by parameter optimization. [ABSTRACT FROM AUTHOR]

An array of ion separation cells is presented in this work, to propose a novel desalination device. Molecular Dynamics simulations have been incorporated to establish the theoretical background and calculate all parameters that could lead the manufacturing step. The main system component is an ion separation cell, in which water/NaCl solution flows due to an external pressure difference and ions are directed towards the non-permeable walls under the effect of an electric field, with direction perpendicular to the flow. Clean water is gathered from the output, while the remaining, high-concentration water/ion solution is re-cycled in the cells. The strength of the electric field, cell dimensions, and wall/fluid interactions are investigated over a wide range, and shear viscosity and the volumetric flow rate are calculated for each case.