Time Tf Research Articles

Numerical simulations of freezing behaviors of water droplets impacting cold hydrophobic surfaces

Freezing, as a prominent phase transition phenomenon, occurs frequently in nature and industry. This study employs a combination of the Volume of Fluid(VOF) model, solidification model, and a dynamic contact angle model to simulate the dynamics and solidification process of droplets impacting supercooled surfaces. Two distinct freezing morphologies, central-concave and central-convex, are observed. These different morphologies are attributed to the competition between the time scales associated with droplet impact dynamics and solidification (retraction time tr and solidification time tf,p). Thus, we propose a scaling law to predict the occurrence of different morphologies: when tr < tf,p, the final freezing morphology exhibits a central-convex shape, while when tr > tf,p, it exhibits a central-concave shape. In order to explore effects of nucleation on solidification, the classical nucleation theory is adopted to determine the nucleation time, and thus the freezing behaviors can be well captured. Furthermore, we examine the effect of volume expansion during phase transition on the freezing behaviors, and find that the increase in freezing time due to volumetric expansion can be well predicted by the scaling law tf ∼ Δ(H2)/ΔT.

Quantitative analysis of the density of states distribution in N-type polymer filed-effect transistor

In the advancement of polymer field-effect transistors, both p-type and n-type polymer transistors are indispensable because they are the basic components of complementary metal oxide semiconductor (CMOS) logic circuitry. The scarcity of research on the interface properties of n-type polymer transistors, particularly regarding their density of state (DOS) distribution hinders the device modeling and further optimization of n-type polymer transistor. Consequently, the focus on understanding and investigating n-type polymer transistors interface properties holds substantial value and relevance, as it fills a critical knowledge gap in the polymer transistors. In view of this, an n-type poly((N,N0-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-5,50-(2,29-bisthiophene)) (N2200) polymer transistor was fabricated and a dynamic quantitative measurement method was utilized to investigate the DOS distribution of polymer transistors. Comparative analyses were conducted on the drain current (ID), carrier charge (Q), and DOS with varying pulse fall times (Tf). Variations in pulse fall times revealed significant differences in the DOS near the edge of the lowest unoccupied molecular orbital (LUMO), with a maximum DOS of 8 × 1013 cm−2 eV−1 observed at Tf = 1000 μs and a maximum of 2 × 1013 cm−2 eV−1 at Tf = 100 μs. By using different Tf, an effective method was successfully utilized for analyzing the effects of water and oxygen molecules on the DOS distribution of n-type polymer transistors.

Influence factors and improvement scheme on the breakdown behavior of pseudospark switch

Abstract High-power pulse generators are widely used in civil and military fields. The main switch directly determines the output characteristics of the high-power pulse generators, such as the voltage front time (tf). Pseudospark switches (PSS) show a promising future for middle voltage, high repetitive frequency pulse power applications. However, how to further improve the breakdown behavior without reducing its advantages is a challenging task. In this paper, the influence of operating parameters (anode voltage UA and gas pressure p) and structural parameter (number of cathode holes) on the breakdown behavior are investigated, the related mechanism are explained, and specific improvement schemes are proposed. It is found that the tf of the single channel PSS (SCPSS) decreased significantly with increasing p, but hardly varied with UA under moderate p. However, it is not a sound solution to increase the p excessively to reduce tf. Besides, increasing the number of cathode holes can obtain a shorter tf at low pressures (which implies superior repetition frequency performance). However, at 25 Pa, the jitter (which is defined as the standard deviation of tf in multiple tests) of the 2-channel PSS is larger than that of the SCPSS. And the jitter of the 4-channel and 8-channel PSS is also greater than 6 ns and 2 ns, respectively. Through experimental and simulation analyses, it can be explained as the stepwise penetration of the virtual anode and the non-simultaneous ignition of the channels. A scheme to increase the trigger energy (ε) has been adopted to improve the simultaneous ignition probability, while shortening tf and reducing jitter. After optimization, the good ignition probability of the 4-channel PSS has been improved to 82% and the jitter has been reduced to less than 1 ns at 25 Pa and 14.7 mJ.

Effect of temperature fluctuations during frozen storage on ice crystal distribution and quality of tilapia (Oreochromis mossambicus)

The study constructed a model of temperature fluctuation (TF, −20 °C ∼ -10 °C) during frozen status to build a link between the tilapia fillets muscle of ice crystal morphology, moisture distribution, protein oxidation index and the edible quality. When TF treatment more than 3 times, the brightness, color and hardness of frozen tilapia fillets decreased significantly, and the cooking loss and thawing loss increased significantly. The free and unconjugated water in frozen fish fillets exceeded 97 % and did not change much after 9 times TF. The K and TVB-N values were within the safety standards (K < 60 %, TVB-N < 30 mg N/100 g). The ice crystals in the tissues were significantly increased. Protein carbonyls and Ca2+-ATPase were significantly reduced, and secondary structures were irregular. Network correlation analysis showed that ice crystal morphology was significantly correlated with the color, texture and protein oxidation index of frozen tilapia fillets. The results would provide theoretical approach for the transportation and sales of tilapia industrial enterprises.

MODELLING ROUNDABOUT ENTRY CAPACITY FOR MIXED TRAFFIC FLOW USING ANN: A CASE STUDY IN INDIA

Roundabouts, as an unsignalized intersection, have an effective preventative measure designed to control straight-line crashes. Efficient traffic flow in cities depends upon appropriate capacity estimation of roundabouts. This study attempts to develop models for roundabout entry capacity by applying Artificial Neural Network (ANN) analysis for mixed traffic flow conditions. Data was gathered from 27 roundabouts spread across India. The influence area for gap acceptance (INAGA) concept was used as a graphical method to identify critical gap (Tc) of entry flow at roundabouts. This study indicated that the Bayesian Regularisation Neural Network (BRNN) based model has the best R2 and RMSE of 0.97 and 167.8. The connection weight approach and Garson algorithm evaluate the significance of each explanatory variable and identify follow-up time (Tf) as a critical parameter with values of 11.10 and 21.15%, respectively.

Arsenic uptake by Agrostis capillaris, as related to its genotypic diversity in the area of historical ore mining and processing

Common bentgrass Agrostis capillaris L. is known as tolerant to toxic elements. A hypothesis was examined that its ecotypes growing in historically polluted sites show a limited arsenic uptake and have genetic features that distinguish them from commercially available cultivars. The study was conducted in Złoty Stok, a historical area of arsenic mining. Additionally, two commercial cultivars were grown in pots with arsenic-rich soils. Based on arsenic concentrations in plant roots and shoots, bioconcentration and translocation factors BCF and TF were calculated. Commercial cultivars indicated many times higher BCF shoots and TF values compared to field plants. DNA analysis of leaf blades showed a clear distinction between the plants growing in some sites and patches in the field, and also a gene overlap between the plants in the field and commercial forms. The research did not allow for identification of ecotypes with exceptionally limited arsenic uptake. Moreover, there were no significant differences between the genotypic characteristics of plants growing in polluted sites and those poorly tolerant grown from commercially available seeds. Apparently, other factors, and not genetically determined features, are responsible for A. capillaris tolerance to arsenic in Złoty Stok.

Mind to move: Differences in running biomechanics between sensing and intuition shod runners.

Delving into the complexities of embodied cognition unveils the intertwined influence of mind, body, and environment. The connection of physical activity with cognition sparks a hypothesis linking motion and personality traits. Hence, this study explored whether personality traits could be linked to biomechanical variables characterizing running forms. To do so, 80 runners completed three randomized 50-m running-trials at 3.3, 4.2, and 5m/s during which their running biomechanics [ground contact time (tc), flight time (tf), duty factor (DF), step frequency (SF), leg stiffness (kleg), maximal vertical ground reaction force (Fmax), and maximal leg compression of the spring during stance (ΔL)] was evaluated. In addition, participants' personality traits were assessed through the Myers-Briggs Type Indicator (MBTI) test. The MBTI classifies personality traits into one of two possible categories along four axes: extraversion-introversion; sensing-intuition; thinking-feeling; and judging-perceiving. This exploratory study offers compelling evidence that personality traits, specifically sensing and intuition, are associated with distinct running biomechanics. Individuals classified as sensing demonstrated a more grounded running style characterized by prolonged tc, shorter tf, higher DF, and greater ΔL compared to intuition individuals (p≤0.02). Conversely, intuition runners exhibited a more dynamic and elastic running style with a shorter tc and higher kleg than their sensing counterparts (p≤0.02). Post-hoc tests revealed a significant difference in tc between intuition and sensing runners at all speeds (p≤0.02). According to the definition of each category provided by the MBTI, sensing individuals tend to focus on concrete facts and physical realities while intuition individuals emphasize abstract concepts and patterns of information. These results suggest that runners with sensing and intuition personality traits differ in their ability to use their lower limb structures as springs. Intuition runners appeared to rely more in the stretch-shortening cycle to energetically optimize their running style while sensing runners seemed to optimize running economy by promoting more forward progression than vertical oscillations. This study underscores the intriguing interplay between personality traits of individuals and their preferred movement patterns.

Feature statistics and analysis of transient overvoltage waveform measured from 220 kV substation

The electromagnetic transient overvoltage in the substation is an important factor that affects the life of insulation equipment. For evaluate the economy and reliability of the insulation design of substation equipment, it is necessary to study and analyze the actual measured overvoltage waveforms in the substation. In this paper, firstly, the 3018 pieces of overvoltage data monitored in the 220 kV substation from 2018 to 2019 are preprocessed to obtain the required overvoltage waveform. Next, by analyzing and classifying the overvoltage data, four typical overvoltage waveforms suffered by the insulation equipment in the substation are extracted. Combined with the IEC60060 standard, the time parameters of the overvoltage waveform are selected and defined: wave-front time (Tf), half-value time (Thalf), main oscillation frequency (f), and attenuation constant (α). Further, statistical analysis is performed on the parameters of each waveform. The distribution law, distribution characteristics and distribution range of the parameters are obtained. Finally, the parameters of four typical overvoltage waveforms are summarized and compared, the cumulative distribution functions are obtained. This results can guide and optimize the insulation design of the insulation equipment in the substation, reduce design errors. It provide data support for the economy and reliability of insulation design.

Effects of location of nano-enhanced PCM-packed bed on the process of heat transfer and phase transition in a nonuniform magnetic field

The phase change and thermal process intensification under nonuniform magnetic field (MGF) effects during hybrid nanofluid (NF) convection are investigated in this study using various arrangements of phase change material (PCM)-packed bed (PB) in a vented cavity. The PCM-PB is is considered as a triangular shape. The numerical research is done using the finite element method for different Reynolds numbers (Re between 200 and 600), inlet port sizes (between 0.5 and 2.5), Hartmann numbers (Ha between 0 and 60), nonuniform MGF component amplitudes (between 0 and 1), and different locations of the triangle PCM-PB zone. The process of phase change is accelerated by increasing the Re and port size, and the entire transition time (tf ) is reduced by 63% and 76%, respectively, when mix/max Re and min/max port sizes are considered. By using NF, the phase change is improved even further, and tf is further reduced by 17.6%–31.5%. When MGF strength and amplitude of the nonuniform component are increased, tf is reduced by about 13% and 6%. At the highest Ha, the average heat transfer (HT) drops by about 59%. The flow patterns, phase transition, and thermal performance are all significantly impacted by the placement of the PCM-PB zone. In terms of phase change process, configuration C2 by using NF at Ha = 60 is the best case while case at Ha = 0 by using only water is the worst case. The tf value is reduced by about 82.6% at the best case. When phase change and HT processes are considered, the optimal design of triangular PCM-PB zones alters.

Enhancing Pixel Charging Efficiency by Optimizing Thin-Film Transistor Dimensions in Gate Driver Circuits for Active-Matrix Liquid Crystal Displays.

Flat panel displays are electronic displays that are thin and lightweight, making them ideal for use in a wide range of applications, from televisions and computer monitors to mobile devices and digital signage. The Thin-Film Transistor (TFT) layer is responsible for controlling the amount of light that passes through each pixel and is located behind the liquid crystal layer, enabling precise image control and high-quality display. As one of the important parameters to evaluate the display performance, the faster response time provides more frames in a second, which benefits many high-end applications, such as applications for playing games and watching movies. To further improve the response time, the single-pixel charging efficiency is investigated in this paper by optimizing the TFT dimensions in gate driver circuits in active-matrix liquid crystal displays. The accurate circuit simulation model is developed to minimize the signal's fall time (Tf) by optimizing the TFT width-to-length ratio. Our results show that using a driving TFT width of 6790 μm and a reset TFT width of 640 μm resulted in a minimum Tf of 2.6572 μs, corresponding to a maximum pixel charging ratio of 90.61275%. These findings demonstrate the effectiveness of our optimization strategy in enhancing pixel charging efficiency and improving display performance.

Convection and phase change in a lid-driven trapezoidal vented cavity with encapsulated PCM under non-uniform magnetic field by using ternary nanofluid

In this study, a novel configuration of lid-driven vented cavity system equipped with encapsulated phase change materials is studied where applications are relevant in drying, material processing, and electronic cooling. For controlling the convective heat transfer and phase transition, combined utilization of non-uniform magnetic field with ternary nanofluid is offered. Upper wall is inclined and moving with constant speed while ternary nanofluid up to a loading of 0.03 is used. Galerkin weighted residual finite element method is considered as the solution technique. A range of parameters for Reynolds number (Re, 200–1000), wall velocity (Rep, 0–1500), Hartmann number (Ha, 0–30), inclination parameter (yd, 0–0.4H), non-uniform amplitude (Af, 0–0.3), and nanoparticle loading (ϕ, 0–0.03) are considered in the analysis. When Re is increased, transition time (tf) is generally reduced for moving wall case. Reduction of tf up to 65% is obtained at the highest Re when moving wall is used at Rep=1000. For stationary wall case, the behavior of tf with Re is non-monotonic while at the highest Re, tf is reduced. The phase transition process is strongly influenced by the moving wall velocity while first increment and decrement of tf with wall velocity is observed. Thermal performance rises by around 58% and 22%, respectively by using the highest Re for stationary and moving walls. There is a significant increase in heat transfer, of around 211%, as wall velocities rise from Rep=0 (stationary) to Rep=1500. The tf for the moving wall is decreased by around 43.7% at the highest Ha. According to the stationary scenario, tf rises by around 33% until Ha=15 and falls by roughly 39.2% between Ha=15 and Ha=30. Amplitude of non-uniform magnetic field results in variation of tf between 4.5% and 19%. When imposing magnetic field at maximum strength, thermal performance is improved by 44.75% with a moving wall while it is just 5% in a stationary scenario. While raising the value of upper wall’s inclination (yd) increases the thermal performance, it also influences the phase change process. More loading of nanoparticles in base fluid results in a faster transition; the corresponding decreases in tf are 24.5% and 12.7% for stationary and moving wall setups, respectively. The increases in thermal performance for stationary and moving wall cases are 36.3% and 33.7%, respectively.

Evaluation of different Starch Binders on physical quality of fish feed pellets.

Binders are the products that are used to bind, glue or hold the various feed ingredients together in order to maintain pellet integrity. For aqua-culturists, feed manufacturing is an expensive exercise due to the high cost of ingredients along with traditional artificial binders. The use of grain starches as aqua feed binders have advantages which include availability of that binder, nutritional contribution, and minimization of feed cost. A research trial was conducted to test physical properties such as palatability, water stability, dustiness, friability, settling velocity and floatation time of locally available starch i.e. wheat gluten, pea starch and guar gum and to assist their incorporation in on-farm aqua feed. Results revealed that among these three starch, the starch from pea source was proved superior over other two (wheat gluten and guar gum) as all physical quality parameters (dustiness, water stability and friability) revealed better performance of pea starch except pelletability in which guar gum performed best. Although not a single diet proved best in case of flotation time (Tf) and settling velocity (Vset) at varying lengths (6mm, 9mm and 12 mm). This finding indicates the significance of suitable binders for optimal water pollution and sustainable aquaculture. The use of these binders i.e. wheat gluten, pea starch and guar gum in fish feed pellets may also reduce dependence on synthetic binders and minimizes cost.

Effect of the crack layer theory parameters on the discontinuous slow crack growth of high density polyethylene under fatigue loading

For engineering thermoplastics, particularly high density polyethylene (HDPE), the crack layer (CL) theory is an effective proposition for modeling slow crack growth and predicting their lifetime. Nevertheless, the associated excessive input parameters needed in its implementation sets a difficulty for its use. Therefore, an understanding of the role of each parameter and how they affect the CL growth is needed. The effect of the parameters has been studied in the past, however, under creep conditions only. Their effects under other loading conditions, e.g., fatigue, and geometries, e.g., compact tension (CT) specimen, is still unclear. For instance, increasing the natural drawing ratio λ was found to non-linearly reduce failure time tf, whereas a rise in the drawing stress σdr increased tf which correlates logarithmically with the loading frequency f. Furthermore, tf was found to increase with the transformation energy γtr, specimen thickness B, plane stain elastic modulus E′, drawing stress σdr, characteristic time t∗, and the specific fracture energy γ0. Therefore, outcomes of this work extend the applicability of the CL theory in the design and lifetime prediction of various industrial products within oil and gas, nuclear, automotive, and aerospace.

Study on long front time wave switching impulse of rod-plane air gap

In long-distance transmission lines, the switching overvoltage waveform differs from that of ordinary lines. The wave front time is primarily distributed above 1000 μs. And the switching overvoltage waveform has an important influence on the design of external insulation. This paper aims to deeply study the effect of various factors on the discharge of air gaps under the long front switching impulse voltage. This paper selects three kinds of rod-plane air gaps, and the switching impulse discharge experiments with different front lengths and absolute humidity under positive polarity are carried out. The effects of front time Tf, absolute humidity h, and gap distance d on the discharge characteristics of the air gap are analyzed. The results show that the U50% of an air gap is positively correlated with absolute humidity, front time, and gap distance. When considering the additional influence of humidity, the humidity additional influence factor c and the atmospheric parameter influence index n at different front times are almost unchanged. With the increase in gap distance, the influence of front time on U50% is more obvious. With the growth of the operating wave front time, the rising rate of U50% tends to slow down. The discharge time of the air gap under different conditions is mainly determined by the front time. The research results can provide a theoretical and experimental reference for the influence of front time Tf and atmospheric parameters on the discharge characteristics of air gaps under long front switching impulse.

Quantum field theory of physical and purely virtual particles in a finite interval of time on a compact space manifold: diagrams, amplitudes and unitarity

We provide a diagrammatic formulation of perturbative quantum field theory in a finite interval of time τ, on a compact space manifold Ω. We explain how to compute the evolution operator U(tf, ti) between the initial time ti and the final time tf = ti + τ, study unitarity and renormalizability, and show how to include purely virtual particles, by rendering some physical particles (and all the ghosts, if present) purely virtual. The details about the restriction to finite τ and compact Ω are moved away from the internal sectors of the diagrams (apart from the discretization of the three-momenta), and coded into external sources. Unitarity is studied by means of the spectral optical identities, and the diagrammatic version of the identity U†(tf, ti)U(tf, ti) = 1. The dimensional regularization is extended to finite τ and compact Ω, and used to prove, under general assumptions, that renormalizability holds whenever it holds at τ = ∞, Ω = ℝ3. Purely virtual particles are introduced by removing the on-shell contributions of some physical particles, and the ghosts, from the core diagrams, and trivializing their initial and final conditions. The resulting evolution operator Uph(tf, ti) is unitary, but does not satisfy the more general identity Uph(t3, t2)Uph(t2, t1) = Uph(t3, t1). As a consequence, Uph(tf, ti) cannot be derived from a Hamiltonian in a standard way, in the presence of purely virtual particles.

Subcritical crack growth models for SiC fiber in air and steam: Low temperature data and possible effects of residual stress

Failure times (tf) and brittle creep strain rates (ἑ) for static fatigue of Hi-Nicalon™-S fiber tows were measured at 500 and 600 °C. These measurements added to those done previously at 700–1100 °C. Subcritical crack growth (SCG) based models developed to predict tf and ἑ from the 700–1100 °C data were modified to include the additional data. Parameters for two SCG laws were determined for air and Si(OH)4 saturated steam environments, and an additional parameter for effective room-temperature residual stress (σRo) along the crack path was introduced. Tow failure was modelled as sequential filament failure by SCG from weakest to strongest in a Weibull distribution. The increase in stress on intact filaments as they oxidized and as other filaments failed caused brittle creep strain. SCG-based models for both surface and interior cracks were considered. Orthogonal direction regression (ODR) was used to find the best parameter fits to data. Faster numerical methods to find the global parameter-space minima and avoid local minima were developed. New model parameters were determined using the entire 500–1100 °C tf and ἑ data set, done at initial applied stresses from 260 to 1526 MPa. In air, measured tf and ἑ at 500 and 600 °C follow the trends previously observed for higher temperatures. However, beneath 700 °C in steam, tf are longer and ἑ are much slower than expected. They are similar to values measured for air, suggesting an SCG mechanism change between 700° and 600 °C in steam. An atomistic SCG law-based model with activation energy (Q) of 310 kJ/mol and σRo of ∼200 MPa compression is suggested to be appropriate for static fatigue in air. An atomistic SCG law-based model with Q of 360 kJ/mol and σRo of ∼0 MPa best fit data measured in steam. However, differences in data fit quality between models were small, so firm conclusions about the correct model, residual stress effects, and associated crack paths could not be made. As stress approaches zero, the model converges to tow failure times that are the times for complete fiber oxidation. As failure times approach zero and temperatures decrease, the model converges to tow strengths predicted by fiber bundle theory at room temperature. The sources of error in data fit, the merit of different SCG models, and the possible roles of residual stress in SCG for Hi-Nicalon™-S fibers are discussed.

Assessment of the Feasibility of Implementing a Flash Flood Early Warning System in a Small Catchment Area

The occurrence of flash floods is an increasingly common phenomenon. In many parts of the world, it is associated with an increase in the intensity of rainfall. Reducing the financial and social losses caused by the occurrence of local urban floods is possible through the use of hydrodynamic modeling and real-time flood forecasting. The purpose of this study is to assess the ability of the modeling technique to simulate the flow in a small catchment area and to determine the time remaining to reach the set warning and danger levels. SWMM 5.2 and QuantumGIS software were used in the study. The analysis showed that for the considered catchment area with a short length of the main stream (1612 m), the time possible for implementing countermeasures and evacuating the population is 70 to 120 min. The study also confirmed that short-term rainfall requires less depth to reach high stormwater elevations than long-term rainfall. In addition, a relationship was noted between the preceding rainfall and the height of stormwater and the forecast time. There was an unfavorable reduction in forecasting time as the depth of rainfall increased and its duration shortened. In the case of the analyzed catchment, the maximum elevation of stormwater (Esw,max) is generated by rainfall that is characterized by the highest intensity in the final phase of their duration. Similarly, the longest forecast time (tf) for the maximum stormwater elevation is caused by rainfall, which is characterized by the highest intensity in its final phase. The results of the study can significantly assist local governments when developing a catchment management plan and when trying to implement practices to minimize the negative effects of flash floods.

CFD analysis and optimization of nano-enhanced phase change process in multiple port vented cavity equipped with encapsulated PCM under the combined effects of triple rotating cylinders and inclined magnetic field

In this study, phase change process dynamics in a multiple vented cavity system equipped with encapsulated phase change materials (PCM) are analyzed under the combined utilization of multiple rotating cylinders and magnetic field. The applications can be found in electronic cooling, rotating type heat exchangers where PCMs are immersed in between and for control purpose of the thermal management. The numerical work is conducted for different values of rotational Reynolds number (Rew, between 0 and 10000), distance between the cylinders (sn between 0.05H and 0.2H), strength of magnetic field (Hartmann number-Ha between 0 and 50) and size of the inlet port (w between 0.075H and 0.25H, H as the cavity size). The phase change process is found to be slower for Rew up to Rew=6000 after which it becomes fast. The full transition time (tF) rises by about 170% at Rew=6000 and then reduces 62% at Rew=10000. At the highest magnetic field, the process intensifies and up to Ha=20, it becomes slower. When magnetic field is active up to Ha=20, the value of tF rises by about 46.5% as compared to case without magnetic field while a reduction of the value by 43.8% is achieved by using magnetic field at the highest strength (Ha=50). Increasing the distance between the triple cylinders and port size of the vented cavity have negative impact on the process both with and without magnetic field. The phase completion time increases by about 124% in the absence of magnetic field when port size is increased from w=0.075H to w=0.25H while the value is 33% with magnetic field at Ha=50. Optimization studies are conducted to find the optimum set of parameter at two different port sizes (w). At w=0.1H, the optimum values are found as (Ha, Rew, sn)=(49.24,4073,0.094H) and at w=0.25H, the values are (Ha, Rew, sn)=(50,2296,0.068H).

Experimental study on the dispersed phase droplet formation process in a circumferential shear flow in dripping regime

A simplified experimental device was designed to simulate the shear flow in a liquid-liquid cyclone reactor. And the dispersed phase droplet formation process in the shear flow in dripping regime was investigated. Four characteristic parameters, droplet growth time (Tg), shrink time (Ts), formation time (Tf) and size (d) were used to describe the formation process. All the parameters presented fluctuation with different serial droplet numbers. Therefore, the effect of dispersed phase inlet flow rate (vd) on the value and uniformity of the parameters are analyzed. The results indicate that with the increase of vd, Tg, Ts, Tf decrease firstly and then increase, while the droplet size gradually increases. Meanwhile, the uniformity of Tg decreases first and then basically tends to be stable, while that of Ts, Tf and d decreases firstly and then increases. Eventually, the optimal range of vd under different continuous phase inlet flow rate is provided.

Thermal and Phase Change Process in a Locally Curved Open Channel Equipped with PCM-PB and Heater during Nanofluid Convection under Magnetic Field

Thermal performance and phase-change dynamics in a channel having a cavity equipped with a heater and phase-change material (PCM)-packed bed (PB) region are analyzed during nanoliquid convection under an inclined magnetic field. Curvature of the upper wall above the PCM zone is also considered by using the finite element method. Impacts of curvature of the upper wall (between 0.01H and 0.6H, H-channel height), strength of magnetic field (MGF) (Hartmann number between 0 and 40), height (between 0.1H and 0.4H) and number (between 5 and 17) of heaters on the thermal performance and phase-change dynamics are studied. In the interior and wall near regions of the PCM-PB, the curvature effects become opposite, while phase completion time (tF) rises by about 42% at the highest radius of the curvature. Imposing MGF and increasing its strength has positive impacts on the phase change and thermal performance. There is a reduction in tF by about 45.2% and 41.8% when MGF is imposed at Ha = 40 for pure fluids and nanofluids. When thermal performance for all different cases is compared, using MGF+nanofluid+PCM provides the most favorable case. When the reference case (only pure fluid without MGF and PCM) is used, including nanoparticles results in an improvement of 33.7%m while it is further increased to 71.1% when PCM-PB is also installed. The most favorable case by using MGF, nanofluid and PCM-PB results in thermal performance improvement of about 373.9% as compared to the reference configuration.