Study on the Range of Freeze-Thaw of Surrounding Rock from a Cold-Region Tunnel and the Effects of Insulation Material

2011 ◽  
Vol 399-401 ◽  
pp. 2222-2225 ◽  
Author(s):  
Peng Qi ◽  
Jing Zhang ◽  
Zhi Rong Mei ◽  
Yue Xiu Wu

A mathematical models for the coupled problem is established by considering heat and mass transfer and phase change for rock mass at low temperature, according to the theory of heat and mass transfer for porous media. It is considered of the influences of fluid transfer on the heat conduction and the temperature gradient on the seepage. By adopting the finite element method, the numerical simulation is done to study the range of frost-thaw of surrounding rock and the effects of insulation material in cold regions, which analysis the influence of tunnel depth and surrounding rock class on the range of frost-thaw, the change law of the frost-thaw area of different insulation material and the relationship between the frost-thaw area and the thickness of insulation material.

Author(s):  
Виктор Григорьевич Чеверев ◽  
Евгений Викторович Сафронов ◽  
Алексей Александрович Коротков ◽  
Александр Сергеевич Чернятин

Существуют два основных подхода решения задачи тепломассопереноса при численном моделировании промерзания грунтов: 1) решение методом конечных разностей с учетом граничных условий (границей, например, является фронт промерзания); 2) решение методом конечных элементов без учета границ модели. Оба подхода имеют существенные недостатки, что оставляет проблему решения задачи для численной модели промерзания грунтов острой и актуальной. В данной работе представлена физическая постановка промерзания, которая позволяет создать численную модель, базирующуюся на решении методом конечных элементов, но при этом отражающую ход фронта промерзания - то есть модель, в которой объединены оба подхода к решению задачи промерзания грунтов. Для подтверждения корректности модели был проделан ряд экспериментов по физическому моделированию промерзания модельного грунта и выполнен сравнительный анализ полученных экспериментальных данных и результатов расчетов на базе представленной численной модели с такими же граничными условиями, как в экспериментах. There are two basic approaches to solving the problem of heat and mass transfer in the numerical modeling of soil freezing: 1) using the finite difference method taking into account boundary conditions (the boundary, for example, is the freezing front); 2) using the finite element method without consideration of model boundaries. Both approaches have significant drawbacks, which leaves the issue of solving the problem for the numerical model of soil freezing acute and up-to-date. This article provides the physical setting of freezing that allows us to create a numerical model based on the solution by the finite element method, but at the same time reflecting the route of the freezing front, i.e. the model that combines both approaches to solving the problem of soil freezing. In order to confirm the correctness of the model, a number of experiments on physical modeling of model soil freezing have been performed, and a comparative analysis of the experimental data obtained and the calculation results based on the provided numerical model with the same boundary conditions as in the experiments was performed.


2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
Stanford Shateyi ◽  
Sandile Sydney Motsa

The unsteady heat, mass, and fluid transfer over a horizontal stretching sheet has been numerically investigated. Using a similarity transformation the governing time-dependent boundary layer equations for the momentum, heat, and mass transfer were reduced to a sets of ordinary differential equations. These set of ordinary differential equations were then solved using the Chebyshev pseudo-spectral collocation method, and a parametric analysis was carried out. The study observed, among other observations that the local Sherwood number increases as the values of the stretching parameter and the Schmidt number increase. Also the fluid temperature was found to be significantly reduced by increases in the values of the Prandtl number , the unsteadiness parameter , and the radiation parameter . The velocity and concentration profiles were found to be reduced by increasing values of the unsteadiness parameter .


2012 ◽  
Vol 459 ◽  
pp. 30-34 ◽  
Author(s):  
Feng Wen ◽  
Xiao Ping Yang

In order to get the perfect thermal protection materials and configuration of the electronic memory the relationship between the object temperature and time during heat transfer and the basic principles of heat and mass transfer for was analyzed. Several kinds of thermal protection structures and materials were simulated by ANSYS 10.0 and validated by experiments. The results demonstrated that nanometer aerogel is a kind of materials when placing it between memory and protective layer, 5 mm thick, makes sure the electronic memory works two hours normally in the environment at 125°C.


2013 ◽  
Vol 773 ◽  
pp. 561-565 ◽  
Author(s):  
Long Yu ◽  
Shu Rong Yu ◽  
Chun Ling Li

According to field synergy principle, analyzes the relationship of the effect for heat transfer with mass transfer in porous media. Using the divergence equation, express the degree of gas phase velocity vector and temperature gradient velocity in the process of heat and mass transfer, and the field synergy angleθplay an important role in heat and mass transfer either global or partial. In the result, the heat and mass transfer would be constrained by each other whileπθ>π/2, and be promoted whileπ/2>θ0, and be independency whileθ=π/2. The divergence equation of field synergy principle present the method of strengthen the heat and mass transfer in porous media.


1986 ◽  
Vol 108 (1) ◽  
pp. 132-140 ◽  
Author(s):  
K. Vafai ◽  
S. Whitaker

This paper analyzes the accumulation and migration of moisture in an insulation material. The problem is modeled as a two-dimensional, transient, multiphase flow in a porous slab. The local volume-averaging technique is used to arrive at a rigorous and fundamental formulation of the heat and mass transfer process in an insulation system. The controlling parameters and assumptions are presented in detail. The equations are solved by devising a two-phase numerical scheme to obtain the condensation regions and the factors which affect the temperature distribution. The phase change process and its effects on the temperature, vapor density, moisture content, liquid content, and the vapor pressure distributions are discussed in detail. The significant transport mechanisms are identified and a simplified formulation of heat and mass transfer, accompanied by phase change, in an insulation system is presented.


2021 ◽  
Vol 2096 (1) ◽  
pp. 012168
Author(s):  
A N Kovalenko ◽  
Yu P Zarichnyak ◽  
V A Ivanov ◽  
K N Bolshev

Abstract The relationship between the fractal self-organization of structural-phase inhomogeneity in nanostructured materials and the processes of heat and mass transfer in them is considered. It is characterized by a non-Euclidean relationship between the rate of increase in the number of the considered elements of the medium and an increase in the scale of their consideration and is described by the transfer equations in fractional derivatives with respect to coordinate and time.


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