Analysis Of Transfer Characteristics Research Articles

An in-silico analysis of hydrodynamics and gas mass transfer characteristics in scale-down models for mammalian cell cultures

Bioprocess scale-up and technology transfer can be challenging due to multiple variables that need to be optimized during process development from laboratory scale to commercial manufacturing. Cell cultures are highly sensitive to key factors during process transfer across scales, including geometric variability in bioreactors, shear stress from impeller and sparging activity, and nutrient gradients that occur due to increasing blend times. To improve the scale-up and scale-down of these processes, it is important to fully characterize bioreactors to better understand the differences that will occur within the culture environment, especially the hydrodynamic profiles that will vary in vessel designs across scales. In this study, a comprehensive hydrodynamic characterization of the Ambr® 250 mammalian single-use bioreactor was performed using time-accurate computational fluid dynamics simulations conducted with M-Star computational fluid dynamics software, which employs lattice-Boltzmann techniques to solve the Navier-Stokes transport equations at a mesoscopic scale. The single-phase and two-phase fluid properties within this small-scale vessel were analyzed in the context of agitation hydrodynamics and mass transfer (both within the bulk fluid and the free surface) to effectively characterize and understand the differences that scale-down models possess when compared to their large-scale counterparts. The model results validate the use of computational fluid dynamics as an in-silico tool to characterize bioreactor hydrodynamics and additionally identify important free-surface transfer mechanics that need to be considered during the qualification of a scale-down model in the development of mammalian bioprocesses.

Discrete element analysis of heating transfer characteristics of airport pavements by using electro thermal method for snow melting and deicing

This study presents a discrete element investigation on the internal temperature change characteristic and heat transfer efficiency in airport concrete pavement by using the carbon fiber electrothermal method for snow melting and deicing. A discrete element model for snow melting and deicing of airport concrete pavement by using the carbon fiber electrothermal method was generated. The temperature evolution on the surface of the pavement was captured and compared with the indoor experimental results. The numerical simulation results were in good agreement with the experimental results, which verified the applicability of the numerical model. On this basis, the effects of the heating temperature and heating paths on the internal heat conduction and temperature field distribution were investigated. The results showed that the temperature of the pavement surface and the temperature rise gradient are linearly related to the temperature of the carbon fiber heating wire. The initial heating time has little influence on the temperature rise path of the road surface layer after stopping heating and reheating. The temperature of the road surface layer rises slowly after the heating is stopped, and then decreases linearly at a rate of 0.4 °C/h not corresponding to the initial heating time.

Analysis of mass transfer characteristics in a planar solid oxide fuel cell with a chaotic flow channel

The flow channel design is crucial for the heat and mass transfer of reactants in a solid oxide fuel cell (SOFC), which ultimately affects the overall performance of the cell. To improve the gas transport characteristics and temperature uniformity, a chaotic flow channel with orthogonal corrugation is adopted for the design of a planar SOFC stack, and the influence of different wave parameters is evaluated. The results show that the chaotic flow channel induces secondary flow through the superposition of orthogonal waves, which reduces the low-oxygen region and enhances the local electrochemical reaction. The output power is improved in the chaotic flow channel by increasing the amplitude or decreasing the wavelength. The output power density with amplitude of 0.3 mm and wavelength of 1.2 mm at 0.5 V is increased by about 25.16 %. Meanwhile, the effective mass transfer coefficient and mass transfer efficiency is enhanced by 148 % and 378 %, respectively. Additionally, the chaotic structure improves the uniformity of oxygen and temperature. This study helps to improve the understanding of the gas transport processes within the flow channel and provides a basis for the design and optimization of SOFC flow channels.

Analysis of Mass Transfer and Shrinkage Characteristics of Chinese Cabbage (Brassica rapa L. ssp. pekinensis) Leaves during Osmotic Dehydration.

The mass transfer and shrinkage characteristics of Chinese cabbage (CC) during osmotic dehydration (OD) were investigated. The leaves were grouped into four sections and analyzed based on their morphological characteristics (i.e., maturity, width, and thickness). The sections were immersed in 2.0 mol/m3 NaCl for 120 h at 25 ± 2 °C. The diffusion coefficient (D) of the leaf blade was not significantly different with respect to the sections that were formed, but it was significantly different in the midrib in the increasing order of P1, P4, P3, and P2, with values of 1.12, 1.61, 1.84, and 2.06 (× 10-6), respectively, after a 1 h soaking period due to the different characteristics in morphology and structure, such as porosity (0.31, 0.41, 0.42, and 0.38 for positions 1, 2, 3, and 4, respectively) and fiber contents. Numerical simulation (NS) for CC was conducted with and without the consideration of shrinkage during OD. The shrinkage effect on the NaCl uptake analyzed using NS indicated no significant difference between 0 to 48 h for both models. However, changes in the NaCl concentration were observed from 48 h onwards, with a lesser concentration in the model with shrinkage for all sections. The difference in NaCl concentration for the models with and without shrinkage was within the standard error range (±0.2 mol/m3) observed during experimental analysis. This implies that the shrinkage effect can be overlooked during the modeling of CC to reduce computational power.

Calculation and Analysis of Load Transfer Characteristics of Tensile Anchors for Geotechnical Anchoring Systems

In order to explore the problems of load transfer and anchorage mechanisms of tensile anchors under pull-out load for geotechnical anchoring systems, a step-wise mathematical model is established which considers the linear–nonlinear shear stress and shear displacement of the anchorage segment, using an elasto-plastic constitutive model. The displacement, axial force, and shear stress of the anchorage interface in different stages (elastic, plastic, and debonding) are analyzed and solutions are derived. And the theoretical solutions for the ultimate pull-out load of the anchor at each stage are also presented. Two in situ pull-out tests are used to verify and apply these findings in engineering. The results show that the stepwise composite model could reflect the bonding, softening and residual characteristics of the anchoring interface. In the process of the pull-out load increasing, the pulling end of the anchor initially enters the plastic stage and the debonding stage, respectively, and the failure of the anchor occurs at the pulling end, and as the axial force transfers down deeper, the damage gradually spreads deeper. The axial force distribution of the anchorage section is a monotonically decreasing curve, and the peak point of the shear stress gradually moves deeper. The calculation results of the axial force distribution curve and load–displacement curve of the anchor are in good agreement with the measured values, which verifies the rationality and reliability of the theoretical prediction method. This method can provide a theoretical reference for the load transfer analysis and design of tension anchors for geotechnical anchoring systems.

Preparation and steady-state heat transfer characteristics analysis of building insulation phase change composite material

The compatibility of Ba(OH)2?8H2O with aluminum alloy and copper after 50 heating cycles was studied using SEM and high power X-ray diffraction technique. Analyze the effect of temperature on thermal stability. The results show that Ba(OH)2?8H2O has some corrosion resistance to aluminum alloys and is similar with copper. The Ba(OH)2?8H2O/foam copper phase transition composites were prepared by a simple vacuum adsorption filling method. The experimental process of phase change energy storage device with and without copper foam was established, and the continuous heat transfer and transformation of Ba(OH)2?8H2O/foam copper phase change composites were carried out at room temperature. The results show that compared with pure Ba(OH)2?8H2O, Ba(OH)2?8H2O/foam copper phase converter has faster heat transfer and better thermal conductivity, effectively reducing the supercooling effect of Ba(OH)2?8H2O. Heat transfer experiment at high temperature shows that the heat capacity of Ba(OH)2?8H2O/foam copper phase changes with the increase of temperature. When the temperature of the zone is higher than the material phase changes in temperature, some insulation measures should be taken for phase shifting components.

Study on Flow and Heat Transfer Characteristics and Anti-Clogging Performance of Tree-Like Branching Microchannels

In this paper, a tree-like branching microchannel with bifurcating interconnections is designed for gas turbine blade cooling. A theoretical analysis, experimental study, and numerical simulation of the heat transfer and hydrodynamic characteristics of the tree-like branching microchannel is performed, and the influence of the total number of branching levels m on the anti-clogging performance is also studied. The results indicate that the total heat transfer ratio and pressure drop ratio are closely related to the structur ne parameters. The comprehensive thermal performance increase with an increase in the ratio of Lb/L0 and fractal dimension D. Nu/Nus, f/fs, and η are increased as m increases from 3 to 5. Furthermore, the tree-like microchannel network exhibits robustness for cooling gas turbine blades. A greater total number of branching levels and a higher Re number are advantageous for enhancing the anti-clogging performance of the tree-like branching microchannel.

Two-Phase Flow Visualization and Heat Transfer Characteristics Analysis in Ultra-Long Gravity Heat Pipe

The ultra-long gravity heat pipe has a long heat transfer distance and narrow working fluid flow channel within its tube. Due to these unique design features, the vapor–liquid counter-flow and heat transfer characteristics of these heat pipes are more complex than those found in conventional-size heat pipes. This paper innovatively proposes the design of a segmented visualization window structure of an ultra-long gravity heat pipe, which successfully overcomes the challenge of visualizing the internal flow during operations. A visualization experimental platform, measuring 40 m in height with an inner diameter of 7 mm and the aspect ratio up to 5714, was built to investigate the evolving characteristics of two-phase flows with an increasing heat input and the impact of the phase change flow characteristics on the thermal performance of ultra-long gravity heat pipes. The results obtained can provide guidance for the development of the internal structure of ultra-long gravity heat pipes that are being applied in exploiting geothermal energy. The results show that, at low heat input (200 W, 250 W), there are separate flow paths between the condensate return and the steam, but the high hydrostatic pressure due to the height of the liquid injection results in the presence of an unsaturated working fluid with a higher temperature in the liquid pool area, which has a lower evaporation rate, limiting the heat transfer through the heat pipe. It is found that if increasing the heat input up to 300 W, the evaporative phase change in the heating section becomes intense and stable. At the same time, despite the intermittent formation of liquid columns in the adiabatic section due to the vapor–liquid rolls, which increases the resistance to the vapor–liquid counter-flow, the liquid columns are blocked for a short period of time, and the path of steam rises and the condensate return is smooth, which does not seriously affect the steam condensation and liquid return evaporation. At this point, the overall temperature of the heat pipe is evenly distributed along the tube and the heat transfer performance is optimal. When the heat input further increases (350 W, 400 W), a large amount of condensate is trapped in the upper part of the adiabatic section and the condensing section by long liquid plugs for a long time. At this point, the condensate flow back to the heating section is significantly reduced, and the steam is seriously prevented from entering the condensation section, resulting in a significant increase in the temperature gradient between the lower part of the evaporating section and the upper part of the adiabatic section and deterioration of the heat transfer performance.

3D computational fluid dynamics-based analysis of water transfer characteristics of hollow fiber membrane for gas-to-gas membrane humidifier

Water in a proton exchange membrane fuel cell is the main factor determining its performance and durability. A humidifier provides water vapor to regulate the humidity of the fuel cell and enable proper operation. The water transfer properties of membranes are investigated through experiments, and simulations enable faster prediction and optimization of various operating conditions. In this study, a numerical simulation model using the diffusion coefficient empirical formula was developed to calculate the water vapor transport. User-defined function codes are applied to predict mass transfer using the concentration difference between the wet and dry surfaces of the membrane. The results were analyzed by the water transfer rate, mass fraction, and pressure characteristics of the influence of flow rate, pressure, temperature, humidity, and the number of membranes of 9 or 21. The analysis model predicted the experimental results with high reliability of R-square 0.96. It was confirmed that a high flow rate increased the outlet water transfer flux, and an increase in the tube decreased the water transfer flux.

Analysis of Power Transfer Characteristics of IPT System With Near Field Magnetic Coupling

This article investigates the working principle of the inductive power transfer (IPT) system from the perspectives of electromagnetic field distribution. According to the limitations of frequency and transmission distance, it is proved in this paper that the IPT system works in the near field, where the energy density of the magnetic field is much stronger than that of the electric field. Therefore, only the magnetic field in the IPT system needs to be considered in approximate power analysis. The mutual inductance model of the IPT system is an approximate and simplified form of the electromagnetic field model. The complex form of the Poynting vector of the IPT system is integrated over an intermediate infinite plane of the two coils to reveal the power transfer characteristics including the active and reactive power. When the system is in full resonance, only active power is transferred without reactive power, which is consistent with the results obtained from the circuit model. This article is useful to provide an insight into the power flow and energy distribution of the IPT system.

Optimal structure design and heat transfer characteristic analysis of X-type air-cooled battery thermal management system

This paper develops an X-type double inlet and outlet symmetrical air-cooled battery thermal management system (BTMS) that overcomes the high temperature, large temperature difference, and high power dissipation problems. The proposed method extends previous symmetrical BTMSs, i.e., single inlet and outlet BTMS, single inlet and double outlet BTMS, and double inlet and single outlet BTMS. However, compared with the existing symmetrical BTMS, the suggested X-type BTMS improves performance and reduces the maximum temperature, maximum temperature difference, and maximum power dissipation by 4.33 K, 74 %, and 62.9 %, respectively. Additionally, the inlet and outlet parameters of the X-type BTMS are optimized with orthogonal analysis, and the optimum settings defined as 71 mm near the outlet, 135 mm near the inlet, 90° for the outlet angle, and 150° for the inlet angle, among which the outlet position and inlet angle significantly affect the performance of the BTMS. The original X-type BTMS is optimized to reduce the maximum temperature and maximum temperature difference by 4 K and 76.5 %, respectively. Furthermore, the heat transfer correlation expression for the X-type BTMS is obtained through theoretical analysis within an 8 % deviation, providing a reference for the design of BTMS.

A high temperature wear-resistant Ni-based alloy coating for coppery blast furnace tuyere application

With the aim to improve the high temperature wear resistance of copper, a Ni-based coating was fabricated on its surface by plasma cladding. The coating has no crack defects and forms a metallurgical bonding with copper substrate (dilution rate 13.3 %). The γ-(Cu, Fe, Ni), Cr23C6, CrB, Fe3Ni and Ni3Si phases make the coating have strong bearing and plastic shear resistance, resulting in significantly higher wear resistance than the copper substrate. As the temperature increases, the wear resistance of the coating shows a trend of increasing first (about 400 °C and 500 °C) and then decreasing (above 600 °C). NiO oxide layer on the coating surface plays an important role in the transformation of wear resistance and wear mechanism. Heat transfer characteristics analysis results (based on the service conditions of blast furnace tuyere) show that manufacturing the coating on the inner wall of tuyere has no obvious effect on the overall temperature field distribution. The maximum temperature of the coating surface is only about 191.06 °C, which is far below its allowable temperature (600 °C). Therefore, the Ni-based coating can be applied to the surface strengthening for the inner wall of blast furnace tuyere.

Analysis of power flow transfer characteristics and stability improvement method of DC grid considering converter’s safety boundary

In order to analyze the impact of power flow transfer of the DC grid on safe operation, this paper studies the calculation methods of power flow transfer of the DC grid under master–slave control and droop control, including the calculation of power flow transfer in line disconnection situation and converter power changing situation. Through the proposed calculation methods, by considering the safety boundary constraints of the converter station based on the PQ power domain, the impact on the safe operation of a complex DC grid when power flow transferring is analyzed. Finally, to solve instability caused by the power flow transfer, a virtual impedance-based method is introduced to increase the safety boundary and enhances the stable operation ability of the system. Finally, the simulations of an 11-terminal CIGRE DC system established in PSCAD/EMTDC software verify the correctness of the proposed method. 11This work is supported by Cloud energy storage framework-based AI dispatching strategy of renewable energy integration and contingency response (5100-202199274A-0-0-00).

Measuring the mobility of charge carriers in samples with low conductivity by the field effect transistor method using output characteristics

FET-based charge carrier mobility measurements in low-conductivity materials, as well as semiconductor materials with a high density of trapping states, such as nanocrystals and polycrystalline films, are highly distorted due to charge accumulation in the transistor structure. In this work, a comparative study of the measurement of the mobility of charge carrier in conductive polymers, nanocrystals and polycrystalline films, using the analysis of output and transfer characteristics, was carried out. It is shown that using output characteristics instead of transfer characteristics for calculating the charge carrier mobility helps to avoid a systematic error in the measurement. Keywords: field-effect transistor, FET, charge carrier mobility, output characteristics, transfer characteristics, charge accumulation, nanocrystals.

Effect of Pulsed Electric Field on the Electrodialysis Performance of Phosphate-Containing Solutions.

A comparative analysis of mass transfer characteristics and energy consumption was carried out for the electrodialysis recovery of PV from of NaH2PO4 solutions and multicomponent (0.045 M NaxH(3-x)PO4, 0.02 M KCl, 0.045 M KOH, 0.028 M CaCl2, and 0.012 M MgCl2, pH 6.0 ± 0.1) solution in conventional continuous current (CC) and pulsed electric field (PEF) modes. The advantages of using PEF in comparison with CC mode are shown to increase the current efficiency and reduce energy consumption, as well as reduce scaling on heterogeneous anion-exchange membranes. It has been shown that PEF contributes to the suppression of the "acid dissociation" phenomenon, which is specific for anion-exchange membranes in phosphate-containing solutions. Pulse and pause lapse 0.1 s-0.1 s and duty cycle 1/2 were found to be optimal among the studied PEF parameters.

S–CO2 heat transfer characteristics analysis in PCHE and vertical channel

Numerical simulations are applied to investigate supercritical carbon dioxide (S–CO2) and heat transfer characteristics in the case of uniform/nonuniform heating conditions in the straight vertical channel and printed circuit heat exchanger (PCHE). The proposed S–CO2 heat transfer correlation agrees well with the experimental values. Results show that high heat flux let S–CO2 heat transfer deterioration likely to occur. Heat transfer deterioration effect will be enhanced as S–CO2 is in area of the gas-like region. Heat transfer enhancement effect will be more significant when S–CO2 is in the area of the liquid-like region. The concept of total length is proposed which is the channel length affected by heat transfer deterioration and entrance effect together. The affected length is 55–70 times of the equivalent diameter in the case of 140 kW/m2 heat flux; the affected length is 85–125 times of the equivalent diameter in the case of 300 kW/m2 heat flux. Changes in dominance of h and λ of PCHE suggest that the convective heat transfer and heat conduction resistance strength of the fluid layer is changing. This study provides guidance for PCHE design and heat transfer enhancement.

Error estimation and cross-coupled control based on a novel tool pose representation method of a five-axis hybrid machine tool

Five-axis hybrid machine tools combine the advantages of series and parallel mechanisms; however, the time-varying, non-linear, and strong coupled characteristics of parallel mechanisms cause contour control difficulties, particularly during high-speed motion. To solve this problem, this study explores the error-transfer laws between the five feed axes, tool centre position (TCP), and tool orientation (TO). It proposes a new tool-pose representation method, called ‘TP’, for five-axis machine tools; and designs a cross-coupled controller taking TP as the control target. Moreover, a kinematic model of the hybrid machine tool is established, and the error transfer law is solved through the first-order differentiation of the kinematic model. Subsequently, two points are taken on the tool axis, the redundancy of coordinates is removed by coordinate transformation, and TP is achieved. Finally, a cross-coupled controller is designed. The input of the controller are the tracking errors obtained according to the five feed-axes commands and encoder feedbacks. In the controller, according to the laws of error transfer, the TP contour error is estimated in real time, and the control variables are assigned to the feed axes. Finally, taking a five-axis hybrid machine tool as an example, the error transfer characteristic analysis as well as error estimation and cross-coupled control (CCC) experiments are performed. The experimental results obtained through the numerical control (NC) program feedback of the computer numerical control (CNC) system verify the correctness of the theory and validity of the method.

Mass Transfer Characteristic Analysis and Optimization of Flow Field for Neutral Organic Redox Flow Battery Based on 1‐DPAQCl

AbstractA novel negative electrolyte for organic redox flow battery has been synthesized, which has higher solubility in neutral solution. In order to promote the commercialization of the novel electrolyte(1‐DPAQCl), a series of optimization should be carried out, in which the first is the operating conditions and mass transfer. A 3D steady state finite element model was established, which was compared with a lot of experimental data. The effects of only increasing the positive concentrations and only increasing the negative concentrations on the battery behaviors have been analyzed and the results showed that the setting of only increasing the positive concentrations can improve the discharge voltage up to 1.8 % and decrease the charging voltage by 1.21 %. The battery performances under four flow fields were investigated based on this model and the concentration uniformity factor of the four flow design were obtained. The results presented that the charge‐discharge voltages of the interdigital flow field (IFF) was the best, which was followed by the rotary flow field (RFF) and serpentine flow field (SFF), the parallel flow field (PFF) was worst. The uniformity factors of IFF were 23.5 % higher than that of PFF and 12.5 % higher than that of SFF.

Unclamped inductive stressing of GaN and SiC Cascode power devices to failure at elevated temperatures

In this paper, the ruggedness performance of GaN HEMT and SiC JFET devices in cascode configuration with a low voltage silicon power MOSFET has been evaluated experimentally. The impact of the bus voltage on the drain current and avalanche energy are investigated as well as the temperature sweep to enable analysis of the alternation of these parameters on the Unclamped Inductive Switching (UIS) ruggedness of cascode devices. The experimental measurements show that the GaN cascode devices have lower avalanche energy rating when compared with the closely rated SiC cascode devices just before the failure. SiC cascode devices can also withstand higher bus voltage in comparison to GaN cascode devices when under electrothermal stress by unclamped inductive switching. The analysis of transfer characteristics and leakage current of SiC JFET & GaN HEMT cascode structures following UIS stress have also been performed together with Computed Tomography (CT) Scan imaging to determine the per-area avalanche energy density.

Global fluid flow and heat transfer characteristics analysis of an open air-cooled drive motor for drilling application

The stator winding temperature rise of variable frequency induction motor (VFIM) with high current density may be too high during operation, which properly causes motor breakdowns. Therefore, it is essential to conduct thermal management for VFIM. In this paper, a 600kW VFIM with the open air-cooling is studied at the point of thermal. A compact cooling improvement structure, axial ventilation guide vane, is proposed to strengthen the heat dissipation capacity of the motor. The global numerical model based on the multi-physics bidirectional coupling method is established to provide a comprehensive understanding of fluid-thermal characteristics in the motor. Based on simulation results, the cooling improvement is analyzed and discussed from multiple perspectives, such as temperature, flow, vortex, etc. It is concluded that the proposed structure can reduce the maximum and average temperature rise of the stator winding by 1.4K and 0.7K, respectively. Moreover, the effect of installation location on the cooling effect is investigated. When the proposed structure is installed on both sides, the overall heat dissipation power rises to 42299.7W. The experiment was also conducted to verify the simulation results. The relative error between simulation results and experimental data is 4.4%.