A Numerical Study of the Thermal Behaviour of Calibrators for Polymer Extrusion

2006 ◽  
Author(s):  
P. A. M. Lobarinhas ◽  
J. C. F. Teixeira ◽  
S. F. C. F. Teixeira
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Thermal Behavior ◽  
Numerical Study ◽  
Thermal Contact ◽  
Computer Code ◽  
Polymer Processing ◽  
Relevant Variables ◽  
Transient Case ◽  
Great Relevance

In polymer processing by extrusion, the thermal behavior of the components downstream of the extruder dye is of great relevance to the final characteristics of the product. In fact, the process productivity, the product dimensional quality and the physical/mechanical properties are strongly dependent upon the cooling process. In the present work, a numerical model adequate to describe the thermal behavior of the calibrator and the polymer profile is developed and implemented as a computer code. The model is fully 3D, transient and includes a formulation for the polymer movement inside the calibrator based upon the VOF method [1]. Although for practical purposes, a steady solution is desired, the model was implemented as a transient case, to enable its accurate validation with experimental data. The interface between the extrudate and the calibrator is described through a coefficient for the thermal contact resistance. The equations were discretized in a finite volume formulation [2] and the code implemented in Fortran. The good agreement between the model and the experimental data has vindicated the accuracy of the computer model and its subsequent application in the analysis and optimization of complete calibration units. A parametric analysis for the most relevant variables, such as polymer velocity and calibrator length, demonstrated the consistency of the numerical model.

scholarly journals Investigation of the effects of opening size and location on punching shear resistance of flat slabs using Abaqus

2021 ◽  
Vol 15 (4) ◽  
pp. 136-147
Author(s):  
Nguyen Tuan Trung ◽  
Pham Thanh Tung
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Numerical Study ◽  
Shear Resistance ◽  
Design Principles ◽  
Numerical Results ◽  
Punching Shear ◽  
Shear Reinforcement ◽  
Flat Slabs ◽  
Abaqus Model

The paper presents a numerical study on the effects of opening size and location on punching shear resistance of flat slabs without drop panels and shear reinforcement using ABAQUS. The study proposes an ABAQUS model that is enable to predict the punching shear resistance of flat slabs with openings. The model is validated well with the experimental data in literature. Using the validated numerical model, the effects of opening size and location on the punching shear resistance of flat slabs are then investigated, and the numerical results are compared with those predicted by ACI 318-19 and TCVN 5574:2018. The comparison between experimental and numerical results shows that the ABAQUS model is reliable. The punching shear resistances calculated by ACI 318-19 and TCVN 5574:2018 with different opening sizes and locations are agreed well to each other, since the design principles between two codes now are similar.

Numerical study of flow pattern around lateral intake in a curved channel

2019 ◽  
Vol 30 (11) ◽  
pp. 1950083 ◽  
Author(s):  
Hossien Montaseri ◽  
Hossein Asiaei ◽  
Abdolhossein Baghlani ◽  
Pourya Omidvar
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Flow Pattern ◽  
Numerical Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Curved Channel ◽  
Channel Bend ◽  
Outer Bank ◽  
Center Region

This paper deals with numerical study of flow field in a channel bend in presence of a lateral intake using three-dimensional numerical model SSIIM2. The effects of bend on the structure of the flow around the intake are investigated and compared with the experimental data. The tests are carried out in a U-shaped channel bend with a lateral intake. The intake is located at the outer bank of an 180∘ bend at position 115∘ with 45∘ diversion angle and the experimental data can be used to calibrate and validate numerical models. The results show that both the center-region and outer-bank cross-stream circulations are observed in the experiments while only the former is captured by the numerical model due to the limitations of the turbulence model. In the curved channel after the intake, both experimental and numerical results show another type of bi-cellular circulations in which clockwise center-region circulations and counterclockwise circulations near the inner bank and the free surface (inner-bank circulations) are captured. The study shows that the numerical model very satisfactorily predicts streamlines, velocity field and flow pattern in the channel and in vicinity of the intake. Investigation of flow pattern around lateral intake in channel bends shows that contrary to the case of flow diversion in straight channels, the width of the dividing stream surface near water surface level is greater than that of near bed level. Finally, the effects of position and diversion angle of the lateral intake, discharge ratio and upstream Froude number on the flow pattern are investigated.

Experimental and Numerical Study of Cavitation in Centrifugal Pumps

2010 ◽  
Author(s):  
Erfan Niazi ◽  
M. J. Mahjoob ◽  
Ardeshir Bangian
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Mass Flow Rate ◽  
Computer Simulations ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Numerical Results ◽  
Centrifugal Pumps ◽  
Cavitation Threshold

Cavitation in pumps is one of the most important causes of damage to pumps impellers/inducers. A numerical model is developed here to simulate the pump hydraulics in different conditions. Experiments are also conducted to validate the computer simulations. To verify the numerical model, the h–m˙ (head versus mass flow rate) of the model is compared with the experimental data. The system is then run under cavitation state. Two methods are applied to monitor the cavitation threshold: first by using stroboscope and observing cavitation bubbles through the transparent casing of the pump and second by checking the NPSHA value for cavitation based on ISO3555. The paper then compares the experimental and numerical results to find the strengths and weaknesses of the numerical model.

TEHD Lubrication of Mechanical Face Seals in Stable Tracking Mode: Part 1—Numerical Model and Experiments

2003 ◽  
Vol 125 (3) ◽  
pp. 608-616 ◽  
Author(s):  
Noe¨l Brunetie`re ◽  
Bernard Tournerie ◽  
Jean Fre^ne
Keyword(s):  
Numerical Model ◽  
Thermal Behavior ◽  
Stokes Equations ◽  
Numerical Models ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Computer Code ◽  
Three Dimensional Model ◽  
Face Seals ◽  
Improved Model

After a short presentation of state-of-the-art experimental studies on the thermal behavior of non-contacting face seals, the literature about numerical models for thermal effects is investigated. Next, the geometry, kinematics and dynamics of a steady state three-dimensional model are developed. Simplified Navier-Stokes equations, a generalized Reynolds equation and an energy equation with proper boundary conditions are established for flow regimes, varying from laminar to turbulent. The numerical computer code for solving the governing equations is presented and representative results are shown. It is demonstrated that face distortions strongly modify the seals’ thermal behavior. An original test rig has been developed in order to ensure full fluid film conditions. This apparatus and the experimental procedure are described. The ability of the numerical model to simulate real configurations is also illustrated. Theoretical and experimental results are in good agreement. Yet an improved model of heat transfer on boundaries is still needed.

Combined Experimental and Numerical Study for Multiple Microchannel Heat Transfer System

2010 ◽  
Author(s):  
Jingru Zhang ◽  
Yogesh Jaluria ◽  
Tiantian Zhang ◽  
Li Jia
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Steady State ◽  
Numerical Model ◽  
Initial Conditions ◽  
Numerical Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Variation Versus ◽  
Heat Transfer System

Multiple microchannel heat sinks for potential use for electronic chip cooling are studied experimentally and numerically to characterize their thermal performance. The numerical simulation is driven by experimental data, which are obtained concurrently, to obtain realistic, accurate and validated numerical models. The ultimate goal is to design and optimize thermal systems. The experimental setup was established and liquid flow in the multiple microchannels was studied under different flow rates and heat influx. The temperature variation versus time was recorded by thermocouples, from which the time needed to reach steady state was determined. Temperature variations under steady state conditions were compared with three-dimensional steady state numerical simulation for the same boundary and initial conditions. The experimental data served as input parameters for the validation of the numerical model. In case of discrepancy, the numerical model was improved. A fairly good agreement between the experimental and simulation results was obtained. The numerical model also served to provide input that could be employed to improve and modify the experimental arrangement.

A numerical study of thermal behavior of CASTOR RBMK-1500 cask under fire conditions

2021 ◽  
Vol 376 ◽  
pp. 111131
Author(s):  
Robertas Poškas ◽  
Povilas Poškas ◽  
Kęstutis Račkaitis ◽  
Renoldas Zujus
Keyword(s):  
Thermal Behavior ◽  
Numerical Study ◽  
Fire Conditions

scholarly journals Investigation of the Thickness Differential on the Formability of Aluminum Tailor Welded Blanks

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 875
Author(s):  
Jie Wu ◽  
Yuri Hovanski ◽  
Michael Miles
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Model ◽  
Plastic Strain ◽  
Finite Element Model ◽  
Equivalent Plastic Strain ◽  
Element Model ◽  
Dome Height ◽  
Tailor Welded Blanks ◽  
Simulation Results

A finite element model is proposed to investigate the effect of thickness differential on Limiting Dome Height (LDH) testing of aluminum tailor-welded blanks. The numerical model is validated via comparison of the equivalent plastic strain and displacement distribution between the simulation results and the experimental data. The normalized equivalent plastic strain and normalized LDH values are proposed as a means of quantifying the influence of thickness differential for a variety of different ratios. Increasing thickness differential was found to decrease the normalized equivalent plastic strain and normalized LDH values, this providing an evaluation of blank formability.

scholarly journals Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 125
Author(s):  
Eduardo Freitas ◽  
Pedro Pontes ◽  
Ricardo Cautela ◽  
Vaibhav Bahadur ◽  
João Miranda ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Heat Dissipation ◽  
Numerical Study ◽  
Pool Boiling ◽  
Temperature Drop ◽  
Surface Cooling ◽  
Average Temperature ◽  
Gold Silver

This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanoparticles), in order to evaluate the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. To study the nucleation of a single bubble in pool boiling condition, a numerical model was also implemented. The results show an evident benefit of using biphilic patterns with well-established distances between the superhydrophobic regions. This can be observed in the resulting plot of the dissipated heat flux for a biphilic pattern with seven superhydrophobic spots, δ = 1/d and an imposed heat flux of 2132 w/m2. In this case, the dissipated heat flux is almost constant (except in the instant t* ≈ 0.9 when it reaches a peak of 2400 W/m2), whilst when using only a single superhydrophobic spot, where the heat flux dissipation reaches the maximum shortly after the detachment of the bubble, dropping continuously until a new necking phase starts. The biphilic patterns also allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic spacing between the superhydrophobic regions, which clearly contributes to cool down the surface. This effect is noticeable in the case of employing the Ag 1 wt% nanofluid, with an imposed heat flux of 2132 W/m2, where the coalescence of the drops promotes a surface cooling, identified by a temperature drop of 0.7 °C in the hydrophilic areas. Those areas have an average temperature of 101.8 °C, whilst the average temperature of the superhydrophobic spots at coalescence time is of 102.9 °C. For low concentrations as the ones used in this work, the effect of the nanofluids was observed to play a minor role. This can be observed on the slight discrepancy of the heat dissipation decay that occurred in the necking stage of the bubbles for nanofluids with the same kind of nanoparticles and different concentration. For the Au 0.1 wt% nanofluid, a heat dissipation decay of 350 W/m2 was reported, whilst for the Au 0.5 wt% nanofluid, the same decay was only of 280 W/m2. The results of the numerical model concerning velocity fields indicated a sudden acceleration at the bubble detachment, as can be qualitatively analyzed in the thermographic images obtained in this work. Additionally, the temperature fields of the analyzed region present the same tendency as the experimental results.

scholarly journals Experimental and Numerical Study on Water Filling and Air Expelling Process in a Pipe with Multiple Air Valves under Water Slow Filling Condition

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2511
Author(s):  
Jintao Liu ◽  
Di Xu ◽  
Shaohui Zhang ◽  
Meijian Bai
Keyword(s):  
Numerical Model ◽  
Stokes Equations ◽  
Numerical Study ◽  
Practical Method ◽  
Navier Stokes ◽  
Physical Processes ◽  
Two Phase ◽  
Saint Venant Equations ◽  
Water Filling ◽  
Air Valve

This paper investigates the physical processes involved in the water filling and air expelling process of a pipe with multiple air valves under water slow filling condition, and develops a fully coupledwater–air two-phase stratified numerical model for simulating the process. In this model, the Saint-Venant equations and the Vertical Average Navier–Stokes equations (VANS) are respectively applied to describe the water and air in pipe, and the air valve model is introduced into the VANS equations of air as the source term. The finite-volume method and implicit dual time-stepping method (IDTS) with two-order accuracy are simultaneously used to solve this numerical model to realize the full coupling between water and air movement. Then, the model is validated by using the experimental data of the pressure evolution in pipe and the air velocity evolution of air valves, which respectively characterize the water filling and air expelling process. The results show that the model performs well in capturing the physical processes, and a reasonable agreement is obtained between numerical and experimental results. This agreement demonstrates that the proposed model in this paper offers a practical method for simulating water filling and air expelling process in a pipe with multiple air valves under water slow filling condition.

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