Numerical Simulations of the Fluid Flow and Heat Transfer during a Solidification Phase Change of a Polymer in a Die

2010 ◽  
Vol 97-101 ◽  
pp. 2736-2743
Author(s):  
Shi Xiong Ren ◽  
Sha Sha Dang ◽  
Tao Lu ◽  
Kui Sheng Wang
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Liquid Volume ◽  
Liquid Volume Fraction ◽  
Three Dimensional Models ◽  
Lower Temperature ◽  
Thermal Oil

Three-dimensional models of heat transfer have been established and numerically solved using a commercial software package, Fluent, in order to obtain distributions of temperature, velocity, pressure, and liquid volume fraction of the polymer. The influences of the boundary conditions on the phase change of the polymer and the temperature distribution in the die have been evaluated. The results show that the temperature of the region close to the pelletizing surface is relatively low due to the cooling effect of the cool water, while the temperature deeper inside the die is higher, with a lower temperature gradient, as a result of the heating effect of the hot thermal oil and the polymer. A solidification phase change of the polymer occurs near the polymer outlet due to heat loss from the polymer to the water, while deeper inside the hole the polymer remains fluid without solidification, due to heating by the thermal oil. Numerical simulation provides a reliable method to optimize the design of the die, the choice of metallic material for the die, and the operating conditions of the polymer pelletizing under water.

scholarly journals Computational characterization of the secondary droplets formed during the impingement of a train of ethanol drops

2019 ◽  
Vol 21 (2) ◽  
pp. 248-262 ◽  
Author(s):  
David Markt ◽  
Ashish Pathak ◽  
Mehdi Raessi ◽  
Seong-Young Lee ◽  
Roberto Torelli
Keyword(s):  
Volume Fraction ◽  
Direct Injection ◽  
Three Dimensional ◽  
Predictive Ability ◽  
Droplet Formation ◽  
Liquid Volume ◽  
Secondary Droplet ◽  
Liquid Volume Fraction ◽  
Secondary Droplets ◽  
Insight Into

This article uniquely characterizes the secondary droplets formed during the impingement of a train of ethanol drops, using three-dimensional direct numerical simulations performed under conditions studied experimentally by Yarin and Weiss. Our numerical results have been previously validated against experimental data demonstrating the ability to accurately capture the splashing dynamics. In this work, the predictive ability of the model is leveraged to gain further insight into secondary droplet formation. We present a robust post-processing algorithm, which scrutinizes the liquid volume fraction field in the volume-of-fluid method and quantifies the number, volume and velocity of secondary droplets. The high-resolution computational simulations enable secondary droplet characterization within close proximity of the impingement point at small length and time scales, which is extremely challenging to achieve experimentally. By studying the temporal evolution of secondary droplet formation, direct connections are made between liquid structures seen in the simulation and the instantaneous distribution of secondary droplets, leading to detailed insight into the instability-driven breakup process of lamellae. Time-averaged secondary droplet characteristics are also studied to describe the global distribution of secondary droplets. Such analysis is vital to understanding fuel drop impingement in direct injection engines, facilitating the development of highly accurate spray–wall interaction models for use in Lagrangian solvers.

scholarly journals Application of SLIPI-Based Techniques for Droplet Size, Concentration, and Liquid Volume Fraction Mapping in Sprays

2020 ◽  
Vol 10 (4) ◽  
pp. 1369 ◽  
Author(s):  
Yogeshwar Nath Mishra ◽  
Timo Tscharntke ◽  
Elias Kristensson ◽  
Edouard Berrocal
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Light Sheet ◽  
Calibration Procedure ◽  
Mie Scattering ◽  
Complete Characterization ◽  
Liquid Volume ◽  
Planar Imaging ◽  
Liquid Volume Fraction ◽  
Scanning Procedure

Structured laser illumination planar imaging (SLIPI)-based techniques have been employed during the past decade for addressing multiple light scattering issues in spray imaging. In this article, SLIPI droplet sizing based on the intensity ratio of laser-induced fluorescence (LIF) over Mie scattering (SLIPI-LIF/Mie) and SLIPI-Scan for extinction-coefficient (µe) mapping are applied simultaneously. In addition, phase Doppler anemometry (PDA) and numerical calculations based on the Lorenz–Mie theory are also employed in order to extract the droplets Sauter mean diameter (SMD), the droplets number density (N), and the liquid volume fraction (LVF) in a steady asymmetric hollow cone water spray. The SLIPI-LIF/Mie ratio is converted to droplets SMD by means of a calibration procedure based on PDA measurements. The droplet SMD for the investigated spray varies from 20 µm to 60 µm, the N values range from 5 to 60 droplets per mm3, and the LVF varies between 0.05 × 10−4 and 5.5 × 10−4 within the probed region of the spray. To generate a series of two-dimensional images at different planes, the spray scanning procedure is operated in a “bread slicing” manner by moving the spray perpendicularly to the light sheet axis. From the resulting series of images, the procedure described here shows the possibility of obtaining three-dimensional reconstructions of each scalar quantity, allowing a more complete characterization of droplet clouds forming the spray region.

Two-Phase Heat Transfer in a Wall-Driven Cubical Heat Sink

2016 ◽  
Author(s):  
Majid Molki
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Sink ◽  
Volume Fraction ◽  
Turbulent Heat Transfer ◽  
Liquid Volume ◽  
Turbulent Heat ◽  
Fluid Temperature ◽  
Complex Flow ◽  
Liquid Volume Fraction

Turbulent heat transfer for flow of water-air mixture driven by moving walls in a cubical heat sink is investigated. One wall is maintained at an elevated temperature, while the vertical walls are at a low temperature. The cubical enclosure functions as a heat sink using water-air mixture with no phase change. Different arrangements for wall motion are considered, which include 1 to 4 moving walls. As the number of moving walls increases, the flow and heat transfer become more complex. In general, the flow reveals complex and multi-scale structures with an unsteady and evolving nature. The larger structure of the flow is resolved using Large Eddy Simulation, while the sub-grid scales are captured by the dynamic k-equation eddy-viscosity model. The focus of this work is on thermal field and heat transfer as affected by the complex flow field generated by multiple moving walls. The results indicate that the Nusselt number for the heat sink varies from 5202.8 to 7356.1, depending on the number of moving walls. Contours of fluid temperature, liquid volume fraction, local and average values of Nusselt number are among the results presented in this paper.

CFD Investigation of Hydrodynamic and Heat Transfer Phenomena around Trilobe Particles in Hydrocracking Reactor

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Mohammad Reza Bandari ◽  
Yaghoub Behjat ◽  
Shahrokh Shahhosseini
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Film Formation ◽  
Liquid Volume ◽  
Liquid Volume Fraction

In this work, computational fluid dynamics (CFD) has been employed to compute local convection heat transfer coefficient (h) that is the key parameter in calculation of heat transfer rate between the particle and fluids in packed bed reactors. In addition, the relation between Reynolds number and Nusselt number for spherical and trilobe catalyst particles have been investigated. Moreover, the parameters of Ranz-Marshall (R-M) correlation have been estimated in order to use it for trilobe catalyst particle. The heat transfer coefficients of the spherical and trilobe particles were compared and the effect of particle shape and configuration on heat transfer rate has been investigated. Eulerian-Eulerian approach was employed in order to investigate gas-liquid hydrodynamic especially liquid film formation around trilobe particles. The effects of liquid film around a trilobe particle and liquid volume fraction on heat transfer coefficient have also been studied. The CFD simulation results indicate that increasing inlet liquid volume fraction raises the liquid film thickness around the particles leading to reduction of heat transfer coefficient. In addition, the results revealed that flow field and temperature profiles around the particles became more complicated as a result of liquid film formation and gas-liquid interactions.

Application of a Multifield Model to Reflooding of a Hot Vertical Tube: Part II—Analysis of Experimental Results

1988 ◽  
Vol 110 (3) ◽  
pp. 710-720 ◽  
Author(s):  
M. Kawaji ◽  
S. Banerjee
Keyword(s):  
Heat Transfer ◽  
Volume Fraction ◽  
Fluid Model ◽  
Constitutive Relations ◽  
Strong Dependence ◽  
Sensitivity Study ◽  
Experimental Results ◽  
Liquid Volume ◽  
Liquid Volume Fraction ◽  
Dispersed Flow

The two-fluid model equations developed for reflood calculations and discussed in Part I (Kawaji and Banerjee, 1987) are solved numerically with appropriately formulated constitutive relations to analyze the Inconel tube reflood experiments involving inverted annular and dispersed flow regimes downstream of the quench front. Constitutive relations are formulated separately for individual transfer mechanisms that are considered to be phenomenologically significant. For inverted annular flow, phasic pressure difference is incorporated into the momentum equations to predict the interfacial waves which enhance film boiling heat transfer. For dispersed flow, a size distribution of drops is considered and both single and multifield equations of motion are solved to calculate the droplet transport. Most of the important heat transfer and hydrodynamic aspects of the experimental results are predicted reasonably well, indicating the adequateness of the mechanisms considered. In particular, a wall–drop interaction heat transfer mechanism is determined to be essential in explaining the experimentally observed strong dependence of heat transfer rate on liquid volume fraction in the dispersed flow region. A sensitivity study is made to identify the weaknesses in the constitutive relations, but no single relation could be accounted for areas in need of further improvement. In comparison with the predictions of the single-field model, those of the multifield model showed improvement for some but not all experiments.

Three-Dimensional Numerical Study on Freezing Phase Change Heat Transfer in Biological Tissue Embedded With Two Cryoprobes

2011 ◽  
Author(s):  
Fang Zhao ◽  
Zhenqian Chen ◽  
Mingheng Shi
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Biological Tissue ◽  
Numerical Study ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Freezing Process ◽  
Ice Crystal ◽  
Obvious Effect ◽  
Phase Change Heat Transfer

A mathematical model for phase change heat transfer in cryosurgery was established. In this model, a fractal tree-like branched network was used to describe the complicated geometrical frame of blood vessel. The temperature distribution and ice crystal growth process in biological tissue including normal tissue and tumor embedded with two cryoprobes were numerically simulated. The effects of cooling rate, initial temperature and distance of two cryoprobes on freezing process of tissue were also studied. The results show that the ice crystal grows more rapidly in the initial freezing stage and then slows down in the following process, and the pre-cooling of cryoprobes has no obvious effect on freezing rate of tissue. It also can be seen that the distance of 10 mm between two cryoprobes is the most appropriate choice for operation effect in the range of operating conditions presented in this study.

scholarly journals Numerical Exploration of Influence of Phase Changing Material in Heat Transfer Augmentation in the Double Tube Heat Exchanger

2018 ◽  
Vol 7 (3.27) ◽  
pp. 162
Author(s):  
C Gnanavel ◽  
R Saravanan ◽  
M Chandrasekaran
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Volume Fraction ◽  
Heat Transfer Fluid ◽  
Storage Device ◽  
Liquid Volume ◽  
Inlet Temperature ◽  
Transition Flow ◽  
Liquid Volume Fraction ◽  
Tube Heat Exchanger

The double tube heat exchanger is a device in which the inner tube carries the hot fluid.  Phase Changing Material is the energy storage device is used for Solar heater applications to maintain the constant temperature, in the present study of this work is CFD Analysis of plain tube heat exchanger with Phase Changing Material (PCM) and without Phase Changing Material (PCM), Charging time, liquid volume fraction with the various Heat Transfer Fluid (HTF) inlet temperature 70, 75, 80 deg Celsius and various flow conditions of laminar flow of 2000 Re, Transition flow of 4000 Re and Turbulent flow of 10,000 Re  

scholarly journals Detailed Simulation of Complex Hydraulic Problems with Macroscopic and Mesoscopic Mathematical Methods

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Chiara Biscarini ◽  
Silvia Di Francesco ◽  
Fernando Nardi ◽  
Piergiorgio Manciola
Keyword(s):  
Free Surface ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Free Surface Flows ◽  
Urban Setting ◽  
Liquid Volume ◽  
Small Scale ◽  
Mathematical Methods ◽  
Liquid Volume Fraction ◽  
Advantages And Disadvantages

The numerical simulation of fast-moving fronts originating from dam or levee breaches is a challenging task for small scale engineering projects. In this work, the use of fully three-dimensional Navier-Stokes (NS) equations and lattice Boltzmann method (LBM) is proposed for testing the validity of, respectively, macroscopic and mesoscopic mathematical models. Macroscopic simulations are performed employing an open-source computational fluid dynamics (CFD) code that solves the NS combined with the volume of fluid (VOF) multiphase method to represent free-surface flows. The mesoscopic model is a front-tracking experimental variant of the LBM. In the proposed LBM the air-gas interface is represented as a surface with zero thickness that handles the passage of the density field from the light to the dense phase and vice versa. A single set of LBM equations represents the liquid phase, while the free surface is characterized by an additional variable, the liquid volume fraction. Case studies show advantages and disadvantages of the proposed LBM and NS with specific regard to the computational efficiency and accuracy in dealing with the simulation of flows through complex geometries. In particular, the validation of the model application is developed by simulating the flow propagating through a synthetic urban setting and comparing results with analytical and experimental laboratory measurements.

scholarly journals A magnetic resonance study of temperature-dependent microstructural evolution and self-diffusion of water in Arctic first-year sea ice

2005 ◽  
Vol 40 ◽  
pp. 179-184 ◽  
Author(s):  
C. Bock ◽  
H. Eicken
Keyword(s):  
Magnetic Resonance ◽  
Sea Ice ◽  
Microstructural Evolution ◽  
Volume Fraction ◽  
Bulk Liquid ◽  
Liquid Volume ◽  
Liquid Volume Fraction ◽  
Cross Sectional ◽  
Pore Connectivity ◽  
Pore Number

AbstractThe microstructural evolution of brine inclusions in granular and columnar sea ice has been investigated through magnetic resonance imaging (MRI) for temperatures between –28 and –3˚C. Thin-section and salinity measurements were completed on core samples obtained from winter sea ice near Barrow, Alaska, USA. Subsamples of granular (2–5cm depth in core) and columnar sea ice (20–23 cm depth) were investigated with morphological spin-echo and diffusion-weighted imaging in a Bruker 4.7T MRI system operating at field gradients of 200 mTm–1 at temperatures of approximately –28, –15, –6 and –3˚C. Average linear pore dimensions range from 0.2 to 1 mm and increase with bulk liquid volume fraction as temperatures rise from –15 to –3˚C. Granular ice pores are significantly larger than columnar ice pores and exhibit a higher degree of connectivity. No evidence is found of strongly non-linear increases in pore connectivity based on the MRI data. This might be explained by shortcomings in resolution, sensitivity and lack of truly three-dimensional data, differences between laboratory and field conditions or the absence of a percolation transition. Pore connectivity increases between –6 and –3˚C. Pore-number densities average at 1.4±1.2mm–2. The pore-number density distribution as a function of cross-sectional area conforms with power-law and lognormal distributions previously identified, although significant variations occur as a function of ice type and temperature. At low temperatures (< –26˚C), pore sizes were estimated from 1H self-diffusivity measurements, with self-diffusivity lower by up to an order of magnitude than in the free liquid. Analysis of diffusional length scales suggests characteristic pore dimensions of <1 μm at < –26˚C.

Numerical Simulation of Gas Flow and Heat Transfer in Cross-Wavy Primary Surface Channel for Microtubine Recuperators

2005 ◽  
Author(s):  
H. X. Liang ◽  
Q. W. Wang ◽  
L. Q. Luo ◽  
Z. P. Feng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Gas Turbine ◽  
Numerical Study ◽  
High Reliability ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
The Cross

Three-dimensional numerical simulation was conducted to investigate the flow field and heat transfer performance of the Cross-Wavy Primary Surface (CWPS) recuperators for microturbines. Using high-effective compact recuperators to achieve high thermal efficiency is one of the key techniques in the development of microturbine in recent years. Recuperators need to have minimum volume and weight, high reliability and durability. Most important of all, they need to have high thermal-effectiveness and low pressure-losses so that the gas turbine system can achieve high thermal performances. These requirements have attracted some research efforts in designing and implementing low-cost and compact recuperators for gas turbine engines recently. One of the promising techniques to achieve this goal is the so-called primary surface channels with small hydraulic dimensions. In this paper, we conducted a three-dimensional numerical study of flow and heat transfer for the Cross-Wavy Primary Surface (CWPS) channels with two different geometries. In the CWPS configurations the secondary flow is created by means of curved and interrupted surfaces, which may disturb the thermal boundary layers and thus improve the thermal performances of the channels. To facilitate comparison, we chose the identical hydraulic diameters for the above four CWPS channels. Since our experiments on real recuperators showed that the Reynolds number ranges from 150 to 500 under the operating conditions, we implemented all the simulations under laminar flow situations. By analyzing the correlations of Nusselt numbers and friction factors vs. Reynolds numbers of the four CWPS channels, we found that the CWPS channels have superior and comprehensive thermal performance with high compactness, i.e., high heat transfer area to volume ratio, indicating excellent commercialized application in the compact recuperators.

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