scholarly journals Climatic Issue in an Advanced Numerical Modeling of Concrete Carbonation

2021 ◽  
Vol 13 (11) ◽  
pp. 5994
Author(s):  
Viet Duc Ngo ◽  
Ngoc Tan Nguyen ◽  
Frédéric Duprat ◽  
Ngoc Tru Vu ◽  
Viet Phuong Nguyen
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Numerical Model ◽  
Relative Humidity ◽  
Research Work ◽  
Mass Conservation ◽  
Climatic Variables ◽  
Experimental Investigations ◽  
Concrete Carbonation ◽  
Wide Range

Damage in reinforced concrete structures is frequently caused by reinforcement corrosion due to carbonation. Although a wide range of literature contributed to the concrete carbonation consisting of experimental investigations and numerical simulations, research work on a complete numerical model for concrete carbonation prediction with integrated climatic variables (e.g., temperature, relative humidity) is still a challenge. The present paper aims to propose an advanced numerical model to simulate the penetration of carbon dioxide and moisture, diffusion of calcium ions, heat transfer, and porosity modification in concrete material using COMSOL Multiphysics software. Three coupled mass conservation equations of calcium, water, and carbon dioxide are solved together with additional equations regarding the heat transfer, variation of porosity, and content of portlandite and other hydrates and calcites. In this study, the actual temporal variabilities of temperature and relative humidity in Toulouse, France, are used as a case study. The predicted results of portlandite profiles and carbonation depth are compared with the experimental data and discussed to identify the effect of climatic variables on the concrete carbonation.

Measurement of Detailed Heat Transfer Coefficient and Film Cooling Effectiveness Distributions Using PSP and TSP

2009 ◽  
Author(s):  
Rebekah A. Russin ◽  
Daniel Alfred ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Optical Filters ◽  
Experimental Investigations ◽  
Transient Temperature ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Wide Range

This paper presents the development of a novel experimental technique utilizing both temperature and pressure sensitive paints (TSP and PSP). Through the combination of these paints, both detailed heat transfer coefficient and film cooling effectiveness distributions can be obtained from two short experiments. Using a mass transfer analogy, PSP has proven to be a powerful technique for measurement of film cooling effectiveness. This benefit is exploited to obtain detailed film cooling effectiveness distributions from a steady state flow experiment. This measured film cooling effectiveness is combined with transient temperature distributions obtained from a transient TSP experiment to produce detailed heat transfer coefficient distributions. Optical filters are used to differentiate the light emission from the florescent molecules comprising the PSP and TSP. Although two separate tests are needed to obtain the heat transfer coefficient distributions, the two tests can be performed in succession to minimize setup time and variability. The detailed film effectiveness and heat transfer enhancement ratios have been obtained for a generic, inclined angle (θ = 35°) hole geometry on a flat plate. Distinctive flow features over a wide range of blowing ratios have been captured with the proposed technique. In addition, the measured results have compared favorably to previous studies (both qualitatively and quantitatively), thus substantiating the use of the combined PSP / TSP technique for experimental investigations of three temperature mixing problems.

A Numerical Model for the Mist Dynamics and Heat Transfer at Various Ambient Pressures

2005 ◽  
Vol 127 (4) ◽  
pp. 631-639 ◽  
Author(s):  
Roy J. Issa ◽  
S. C. Yao
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Test Data ◽  
Model Simulation ◽  
Droplet Size Distribution ◽  
Atmospheric Conditions ◽  
Single Stream ◽  
Wide Range ◽  
Wall Interaction ◽  
Uniform Droplets

A numerical model is developed to simulate the dynamics of the droplet-wall interaction and heat transfer mechanisms at sub-atmospheric to elevated ambient pressures, and for surface temperatures ranging from nucleate to film boiling. This is the first time a general model is developed to study these phenomena over a wide range of ambient pressures. The model provides insight to the optimal flow conditions, and droplet size distribution for best heat transfer enhancement. Simulations are provided for single stream droplet impactions, and for full conical sprays using nozzles that dispense a spectrum of non-uniform droplets. The model simulation was compared against available test data for single stream of droplets at non-atmospheric conditions, and the simulation compared favorably well with the test data.

Prandtl Number Effect on the Laminar Convective Heat Transfer From a Rotating Disk

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Christian Helcig ◽  
Stefan aus der Wiesche ◽  
Igor V. Shevchuk
Keyword(s):  
Heat Transfer ◽  
Prandtl Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rotating Disk ◽  
Ratio Method ◽  
Experimental Investigations ◽  
Wide Range ◽  
Experimental Apparatus ◽  
Similar Solutions

Convective heat transfer in rotating disk systems is of great importance in many engineering applications. Despite the high practical relevance, there have been only a small number of experimental investigations regarding the influence of the Prandtl number larger than unity. Ever since Dorfman's pioneering work more than 50 years ago, various analytical works about the heat transfer of a rotating disk have been published. However, this study is a novelty because measurements of the laminar convective heat transfer over a free rotating disk for a wide range of Prandtl number up to Pr=5000 are presented. The accuracy of the employed experimental apparatus was assessed by heat transfer measurements in air, for which reliable literature data are widely available. Natural convection effects and temperature-dependent physical properties have been taken into consideration using the property-ratio method. The experimental results are in excellent agreement with analytical self-similar solutions and the theoretical correlation of Lin and Lin. The applicability of frequently used heat transfer correlations is assessed by the means of the new experimental data.

scholarly journals Modelling investigation of water droplet evaporative freezing in artificial snowmaking

2019 ◽  
Vol 128 ◽  
pp. 06013
Author(s):  
Georges El Achkar ◽  
Aiqiang Chen ◽  
Rachid Bennacer ◽  
Bin Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Relative Humidity ◽  
Air Temperature ◽  
Water Droplet ◽  
Theoretical Models ◽  
Comsol Multiphysics ◽  
Initial Diameter ◽  
Air Space ◽  
Mass And Heat Transfer

In this paper, a modelling investigation of water droplet evaporative freezing was conducted in order to better understand the snowmaking process and hence to optimise the design of the artificial snowmaking device. To this end, mass and heat transfer theoretical models of a single water droplet cooling in an air space were established and implemented in a numerical model developed using the software COMSOL Multiphysics. The effects of the air temperature, relative humidity and velocity and the water droplet initial diameter and temperature on this process were identified and analysed, and their appropriate ranges for the snowmaking were determined.

scholarly journals A contribution on versatile process chains: joining with adaptive joining elements, formed by friction spinning

2021 ◽  
Author(s):  
Christian Wischer ◽  
Werner Homberg
Keyword(s):  
Current Knowledge ◽  
Research Work ◽  
Sheet Thickness ◽  
Experimental Investigations ◽  
Initial Material ◽  
Ongoing Research ◽  
Mechanical Joining ◽  
Process Chains ◽  
Wide Range ◽  
Joining Process

AbstractNowadays, manufacturing of multi-material structures requires a variety of mechanical joining techniques. Mechanical joining processes and joining elements are used to meet a wide range of requirements, especially on versatile process chains. Most of these are explicitly adapted to only one, specific application. This leads to a less flexibility process chain due to many different variants and high costs. Changes in the boundary conditions like sheet thickness, or layers, lead to a need of re-design over the process and thus to a loss of time. To overcome this drawback, an innovative approach can be the use of individually manufactured and application-adapted joining elements (JE), the so-called Friction Spun Joint Connectors (FSJC). This new approach is based on defined, friction-induced heat input during the manufacturing and joining of the FSJC. This effect increases the formability of the initial material locally and permits them to be explicitly adapted to its application area. To gain a more detailed insight into the new process design, this paper presents a detailed characterization of the new joining technique with adaptive joining elements. The effects and interactions of relevant process variables onto the course and joining result is presented and described. The joining process comprises two stages: the manufacturing of FSJC from uniform initial material and the adaptive joining process itself. The following contribution presents the results of ongoing research work and includes the process concept, process properties and the results of experimental investigations. New promising concepts are presented and further specified. These approaches utilize the current knowledge and expand it systematically to open new fields of application.

Mass transfer of water vapor, carbon dioxide and oxygen on modified cellulose fiber-based materials

2012 ◽  
Vol 27 (2) ◽  
pp. 409-417 ◽  
Author(s):  
Alemayehu H. Bedane ◽  
Qinglin Huang ◽  
Huining Xiao ◽  
Mladen
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Water Vapor ◽  
Relative Humidity ◽  
Transmission Rate ◽  
The Other ◽  
Paper Sample ◽  
Coated Paper ◽  
Wide Range ◽  
Transfer Properties

Abstract Mass transfer properties of fibre network and coated paper are essential for understanding the barrier properties of the products and further advance in their application. In this study, different unmodified and coated papers, e.g., (Poly lactic acid (PLA), zein grafted paper) were prepared and characterized with regard to mass transfer properties. Water vapor, carbon dioxide (CO2) and oxygen (O2) transmission rates through the cellulose paper films were measured and the results discussed. The effects of sample film thickness and samples were found to be strongly dependent on the temperature and the relative humidity difference (mass transfer driving force). On the other hand water vapor permeabilities relative humidity. Water vapor diffusivities of the samples were also measured from the uptake rate measurements using Fickian diffusion slab model for a wide range of relative modified samples were found to be generally low compared to unmodified (reference) paper sample. Among the investigated samples, PLA/polyhedral oligomeric silsesquioxane POSS-bentonite modified paper sample showed higher mass transfer resistance to water vapour and the gases investigated in this study (CO2and O2). It showed lower water transmission rate (104 g/m2.day) compared to PLA-coated paper (130 g/m2.day), zein coated paper (179 g/m2.day) and control sample (359 g/m2.day) at the relative humidity gradient RH=74% and temperature of 25 oC. The oxygen transmission rate for PLA/(POSS-Bentonite) coated paper was found to be lower than for the other modified papers. Zein grafted paper showed better barrier property for water vapor than oxygen. Water vapor permeation through paper films shows an Arrhenius type of dependency with temperature, indicating activated process. The activation energies reveal diffusion dominated process for all paper samples investigated in this study, according to the solution-diffusion mechanism used to describe the permeation processes.

Modeling of Intensified Heat Exchangers with Different Fluid Viscosities

2021 ◽  
Vol 628 (6) ◽  
pp. 44-50
Author(s):  
A. G. Laptev ◽  
◽  
E. A. Lapteva ◽  
A. A. Akhmitshin ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mathematical Model ◽  
Heat Exchangers ◽  
Transformer Oil ◽  
Design Parameters ◽  
Experimental Investigations ◽  
Industrial Enterprises ◽  
Wide Range ◽  
Momentum And Heat Transfer

Equations are derived for mean friction and heat transfer coefficients to solve problems of updating industrial plants for getting oil fractions based on application of approximate method of modeling momentum and heat transfer in heat exchangers with surface intensifiers. The Dyssler and Van-Driest turbulent boundary-layer model is used for the turbulent viscosity function for a flat smooth wall. An equation for the Stanton number is written using Chilton-Colborne hydrodynamic analogy and agreement with the known analogy is shown. Identical local properties of turbulent motion in a boundary layer on a plate and in a near-wall layer of a tube and the conservative properties of the laws of friction and heat transfer to turbulences, which are taken account of parametrically, are used for modeling momentum and heat transfer in channels with surface intensifiers. An equation for mean tangential stress in channels with intensifiers and, further, an equation for the Nusselt number is derived using a dissipative model. The results of calculations and comparison with the known experimental investigations are given for tubes with surface wire inserts, with spiral finning and rectangular projections for transformer oil at Reynolds numbers 200 < Re <2000. Thus, the adequacy of the developed mathematical model is proved in a wide range of operating and design parameters and thermophysical properties of fluids and gases. Further, the hydraulic resistance of the channel is the key experimental information about the object of modeling. Examples of use of mathematical model for designing and commissioning heat exchangers in petroleum fuels fractionating plants at industrial enterprises in the Russian Federation and abroad are given.

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