Influence of Thermal Conductivity and 2-D Temperature Distribution of Liquid Water Saturation

Stochastic temperature distribution in a solid medium with random heat conductivity is investigated by the method of perturbation. The intrinsic randomness of the thermal conductivity k(x) is considered to be a distribution function with random amplitude in the solid, and several typical stochastic processes are considered in the numerical examples. The formulation used in the present analysis describes a situation that the statistical orders of the random response of the system are the same as those of the intrinsic random excitations, which is characteristic for the problem with extrinsic randomness. The maximum standard deviation of the temperature distribution from the mean value in the solid medium reveals the amount of unexpected energy experienced by the solid continuum, which should be carefully inspected in the thermal-failure design of structures with intrinsic randomness.

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Influence of Anisotropic Thermal Conductivity on Overall Cooling Effectiveness on a Film Cooled Leading Edge

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4051634 ◽

2021 ◽

pp. 1-22

Author(s):

Carol Bryant ◽

James L. Rutledge

Keyword(s):

Thermal Conductivity ◽

Temperature Distribution ◽

Film Cooling ◽

Leading Edge ◽

Ceramic Matrix Composites ◽

Internal Cooling ◽

Matrix Composites ◽

Edge Region ◽

Turbine Engine ◽

Anisotropic Thermal Conductivity

Abstract Increasing interest in the use of ceramic matrix composites (CMCs) for gas turbine engine hot gas path components requires a thorough examination of the thermal behavior one may expect of such components. Their highly anisotropic thermal conductivity is a substantial departure from traditional metallic components and can influence the temperature distribution in surprising ways. With the ultimate surface temperature dependent upon the internal cooling scheme, including cooling from within the film cooling holes themselves, as well as the external film cooling, the relative influence of these contributions to cooling can be affected by the directionality of the thermal conductivity. Conjugate heat transfer computational simulations were performed to evaluate the effect of anisotropy in the leading edge region of a turbine component. The leading edge region is modeled as a fully film-cooled half cylinder with a flat afterbody. The anisotropic directionality of the thermal conductivity is shown to have a significant effect on the temperature distribution over the surface of the leading edge. While structural considerations with CMC components are often paramount, designers should be aware of the thermal ramifications associated with the selection of the CMC layup.

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Predicting Liquid Water Saturation Through Differently Structured Cathode Gas Diffusion Media of a Proton Exchange Membrane Fuel Cell

Journal of Fuel Cell Science and Technology ◽

10.1115/1.4005617 ◽

2012 ◽

Vol 9 (2) ◽

Cited By ~ 2

Author(s):

N. Akhtar ◽

P. J. A. M. Kerkhof

Keyword(s):

Fuel Cell ◽

Liquid Water ◽

Proton Exchange Membrane ◽

Water Saturation ◽

Catalyst Layer ◽

Gas Diffusion ◽

Proton Exchange ◽

Diffusion Media ◽

Exchange Membrane

The role of gas diffusion media with differently structured properties have been examined with emphasis on the liquid water saturation within the cathode of a proton exchange membrane fuel cell (PEMFC). The cathode electrode consists of a gas diffusion layer (GDL), a micro-porous layer and a catalyst layer (CL). The liquid water saturation profiles have been calculated for varying structural and physical properties, i.e., porosity, permeability, thickness and contact angle for each of these layers. It has been observed that each layer has its own role in determining the liquid water saturation within the CL. Among all the layers, the GDL is the most influential layer that governs the transport phenomena within the PEMFC cathode. Besides, the thickness of the CL also affects the liquid water saturation and it should be carefully controlled.

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Study on Effective Radial Thermal Conductivity of Gas Flow through a Methanol Reactor

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2014-0065 ◽

2015 ◽

Vol 13 (1) ◽

pp. 103-112 ◽

Cited By ~ 1

Author(s):

Kun Lei ◽

Hongfang Ma ◽

Haitao Zhang ◽

Weiyong Ying ◽

Dingye Fang

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Reynolds Number ◽

Temperature Distribution ◽

Large Scale ◽

Gas Flow ◽

Fixed Bed ◽

Heat Transfer Model ◽

Transfer Model ◽

Particle Reynolds Number

Abstract The heat conduction performance of the methanol synthesis reactor is significant for the development of large-scale methanol production. The present work has measured the temperature distribution in the fixed bed at air volumetric flow rate 2.4–7 m3 · h−1, inlet air temperature 160–200°C and heating tube temperature 210–270°C. The effective radial thermal conductivity and effective wall heat transfer coefficient were derived based on the steady-state measurements and the two-dimensional heat transfer model. A correlation was proposed based on the experimental data, which related well the Nusselt number and the effective radial thermal conductivity to the particle Reynolds number ranging from 59.2 to 175.8. The heat transfer model combined with the correlation was used to calculate the temperature profiles. A comparison with the predicated temperature and the measurements was illustrated and the results showed that the predication agreed very well with the experimental results. All the absolute values of the relative errors were less than 10%, and the model was veriﬁed by experiments. Comparing the correlations of both this work with previously published showed that there are considerable discrepancies among them due to different experimental conditions. The influence of the particle Reynolds number on the temperature distribution inside the bed was also discussed and it was shown that improving particle Reynolds number contributed to enhance heat transfer in the fixed bed.

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Predicted Liquid Water Saturation in Unstructured Pore Networks Based on PEMFC GDL Porosity Profiles

ASME 2010 8th International Fuel Cell Science, Engineering and Technology Conference: Volume 1 ◽

10.1115/fuelcell2010-33097 ◽

2010 ◽

Cited By ~ 1

Author(s):

J. Hinebaugh ◽

Z. Fishman ◽

A. Bazylak

Keyword(s):

Liquid Water ◽

Water Saturation ◽

Pore Space ◽

Polymer Electrolyte Membrane ◽

Gas Diffusion ◽

Pore Network Model ◽

High Porosity ◽

Pore Networks ◽

Electrolyte Membrane ◽

Capillary Pressures

An unstructured, two-dimensional pore network model is employed to describe the effect of through-plane porosity profiles on liquid water saturation within the gas diffusion layer (GDL) of the polymer electrolyte membrane fuel cell. Random fibre placements are based on the porosity profiles of six commercially available GDL materials recently obtained through x-ray computed tomography experiments. The pore space is characterized with a Voronoi diagram, and invasion percolation-based simulations are performed. It is shown that water tends to accumulate in regions of relatively high porosity due to the lower associated capillary pressures. It is predicted that GDLs tailored to have smooth porosity profiles will have fewer pockets of high saturation levels within the bulk of the material.

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Modeling Surface Temperatures for Snow-Covered Roads: A Case Study for a Heated Pavement in Bærum, Norway

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198118772959 ◽

2018 ◽

Vol 2672 (12) ◽

pp. 220-231

Author(s):

Anne D. W. Nuijten ◽

Inge Hoff ◽

Knut V. Høyland

Keyword(s):

Thermal Conductivity ◽

Water Content ◽

Liquid Water ◽

Surface Condition ◽

Winter Season ◽

High Water ◽

Liquid Water Content ◽

High Water Content ◽

Snow Layer ◽

Snow Samples

Heated pavements are used as an alternative to removing snow and ice mechanically and chemically. Usually a heated pavement system is automatically switched on when snowfall starts or when there is a risk of ice formation. Ideally, these systems run based on accurate predictions of surface conditions a couple of hours ahead of time, for which both weather forecasts and reliable surface temperature predictions are needed. The effective thermal conductivity of the snow layer is often described as a function of its density. However the thermal conductivity of a snow layer can vary considerably, not only for snow samples with a different density, but also for snow samples with the same density, but with a variation in the liquid water content. In this paper a physical temperature and surface condition model is described for snow-covered roads. The model is validated for an entire winter season on a heated pavement in Norway. Two different models to describe the thermal conductivity through the snow layer were compared. Results show that the thermal conductivity of the snow layer can be best described as a function of the density for snow with a low liquid water content. For snow with a high water content, the thermal conductivity can be best described as a function of the volume fractions and thermal conductivity of ice, water, and air, in which air and ice are modeled as a series system and water and air/ice in parallel.

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Numerical modeling of microwave heating

Science of Sintering ◽

10.2298/sos1001099s ◽

2010 ◽

Vol 42 (1) ◽

pp. 99-124 ◽

Cited By ~ 15

Author(s):

A.K. Shukla ◽

A. Mondal ◽

A. Upadhyaya

Keyword(s):

Thermal Conductivity ◽

Numerical Modeling ◽

Temperature Distribution ◽

Microwave Heating ◽

Two Dimensional ◽

Conventional Furnace ◽

Microwave Furnace ◽

Simulation Results ◽

Heating Behavior ◽

Cylindrical Samples

The present study compares the temperature distribution within cylindrical samples heated in microwave furnace with those achieved in radiatively-heated (conventional) furnace. Using a two-dimensional finite difference approach the thermal profiles were simulated for cylinders of varying radii (0.65, 6.5, and 65 cm) and physical properties. The influence of susceptor-assisted microwave heating was also modeled for the same. The simulation results reveal differences in the heating behavior of samples in microwaves. The efficacy of microwave heating depends on the sample size and its thermal conductivity.

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