scholarly journals Coupled heat transfer between a viscous shock gasdynamic layer and a transversely streamlined anisotropic half-space

2020 ◽  
Vol 12 (S) ◽  
pp. 211-220
Author(s):  
Olga V. TUSHAVINA
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boundary Condition ◽  
Analytical Solution ◽  
Half Space ◽  
Stokes Equations ◽  
Conjugate Problem ◽  
Viscous Shock Layer ◽  
Boundary Layer Equations ◽  
Coupled Heat Transfer

The purpose of the article is to analytically solve the conjugate problem of heat transfer in a viscous shock layer on a blunt object and thermal conductivity in an anisotropic half-space. A feature of the flow around such bodies near the critical point is that in this case, the boundary layer equations are not satisfied and it is necessary to solve the Navier-Stokes equations together with the equations of continuity, state, and energy, however, in a stationary formulation of an incompressible flow. The problem of coupled heat transfer between a viscous shock gasdynamic layer and anisotropic half-space with the assumption of incompressibility of the gasdynamic flow behind the normal part of the shock wave is posed. An analytical solution to this problem is obtained with a boundary condition at the gas-solid object interface in the form of a parameter – temperature, as well as an analytical solution to the thermal conductivity problem in an anisotropic half-space with the same boundary condition.

Research on Heat Transfer Characteristics of Nano-Porous Silica Aerogel Material and its Application on Mars Surface Mission

2014 ◽  
Vol 924 ◽  
pp. 329-335 ◽  
Author(s):  
Cong Hang Li ◽  
Shi Chen Jiang ◽  
Zheng Ping Yao ◽  
Song Sheng ◽  
Xin Jian Jiang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Silica Aerogel ◽  
Thermal Environment ◽  
Porous Silica ◽  
Heat Transfer Model ◽  
Heat Radiation ◽  
Transfer Model ◽  
Ambient Conditions ◽  
Coupled Heat Transfer

Based on the nanoporous network structure features of silica aerogel, the gas-solid coupled heat transfer model of silica aerogel is analyzed, and the calculation formulas of the gas-solid coupled, the gas thermal conductivity and the heat radiation within the aerogel are derived. The thermal conductivity of pure silica aerogel is calculated according to the derived heat transfer model and is also experimentally measured. Moreover, measurements on the thermal conductivities of silica aerogel composites with different densities at ambient conditions are performed. And finally, a novel design of silica aerogel based integrated structure and thermal insulation used for withstanding the harsh thermal environment on the Martin surface is presented.

Analytical Solution for Solid Cylindrical Heat Source Model With Convective Boundary Condition

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Yang Zhou ◽  
Cheng Xu ◽  
David Sego ◽  
Dong-hai Zhang
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Analytical Solution ◽  
Heat Source ◽  
Groundwater Flow ◽  
Convective Boundary Condition ◽  
Convective Boundary ◽  
Energy Pile ◽  
Special Cases ◽  
Scs Model

Abstract The energy pile technology has been widely used, and the solid cylindrical heat source (SCS) model is usually adopted to describe the heat transfer process between the energy pile and the surrounding soil. This paper investigates the SCS model with a convective boundary condition (SCS-3 model), and realistic conditions such as transversely isotropic ground and groundwater flow are all included in the model. An analytical solution for the problem is established using Green's function method and the theory of moving heat sources. Solutions for the SCS model with a boundary condition of the first kind (SCS-1 model) and for the line source (LS) model with a convective boundary condition (LS-3 model) are recovered as special cases of the solution in this paper. Computational examples are presented, and comparisons between different models are made. First, the SCS-1 model is compared with the SCS-3 model, showing the error caused by neglecting the surface convective effect. Second, the LS-3 model is compared with the SCS-3 model, showing the error associated with neglecting the size of heat source. The effects of groundwater flow velocity and convective heat transfer coefficient on the temporal and spatial variations of these errors are also investigated.

Effective Thermal Conductivity of Ordered Mesoporous Carbon CMK-3

2013 ◽  
Author(s):  
Daili Feng ◽  
Yanhui Feng ◽  
Xinxin Zhang ◽  
Ge Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Mesoporous Carbon ◽  
Two Dimensional ◽  
Hexagonal Array ◽  
Coupled Heat Transfer ◽  
Ordered Mesoporous ◽  
Carbon Rods ◽  
Conductivity Models

CMK-3 is a typical of carbon rods which are arranged in relatively regular two-dimensional hexagonal array. In our study, the effective thermal conductivity of CMK-3 composite is investigated. For the thermal conductivity of carbon rods, the equilibrium molecular dynamics (EMD) is performed with Tersoff potential. The influences of porosity and temperature are also considered. For the thermal conductivity of air confined in mesoporous can be estimated by the frequently used Kaganer model. Then, the effective thermal conductivity models developed for coupled heat transfer of air and solid are obtained by the unit cell method. ETCs along the X and Y directions are extremely poor, due to the overwhelming effect of air thermal resistance. However, in the Z direction, the ETC improves almost linearly as the porosity decreases, and the value is much higher than those of X and Y directions. This study is in attempts to explore the possibility of CMK-3 being a proper substrate for thermal usage.

scholarly journals MATHEMATICAL MODELS OF HEAT TRANSFER IN ELEMENTS OF TURBO GENERATORS (CONTINUED)

2020 ◽  
Vol 2 (1) ◽  
pp. 21-28
Author(s):  
V. I. Havrysh ◽  
◽  
B. O. Bilinskyi ◽  
O. S. Korol ◽  
R. R. Shkrab ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Temperature Distribution ◽  
Mathematical Models ◽  
Half Space ◽  
Analytical Solutions ◽  
Internal Heat ◽  
Normal Operation ◽  
Cylindrical Shape ◽  
Temperature Regimes

Previously developed [8] and presented new mathematical models for the analysis of temperature regimes in individual elements of turbo generators, which are geometrically described by isotropic half-space and space with an internal heat source of cylindrical shape. Cases are also considered for half-space, when the fuel-releasing cylinder is thin, and for space, when it is heat-sensitive. For this purpose, using the theory of generalized functions, the initial differential equations of thermal conductivity with boundary conditions are written in a convenient form. To solve the obtained boundary value problems of thermal conductivity, the integral Hankel transformation was used, and as a result, analytical solutions in the images were obtained. The inverse Hankel integral transformation was applied to these solutions, which made it possible to obtain the final analytical solutions of the initial problems. The obtained analytical solutions are presented in the form of improper convergent integrals. Computational programs have been developed to determine the numerical values ​​of temperature in the above structures, as well as to analyze the heat transfer in the elements of turbo generators due to different temperature regimes due to heating by internal heat sources concentrated in the cylinder volume. Using these programs, graphs are presented that show the behavior of curves constructed using numerical values ​​of the temperature distribution depending on the spatial radial and axial coordinates. The obtained numerical values ​​of temperature indicate the correspondence of the given mathematical models for determining the temperature distribution to the real physical process. The software also allows you to analyze media with internal heating, concentrated in the spatial figures of the correct geometric shape, in terms of their heat resistance. As a result, it becomes possible to increase it, to determine the allowable temperatures of normal operation of turbo generators, to protect them from overheating, which can cause the destruction of not only individual elements but also the entire structure.

scholarly journals Modeling the conjugate problem of heat transfer at hot jet impingement onto a cooled surface

2021 ◽  
Vol 2119 (1) ◽  
pp. 012157
Author(s):  
V V Lukashov ◽  
V S Naumkin
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Flat Plate ◽  
Gas Flow ◽  
Jet Impingement ◽  
Conjugate Problem ◽  
Heat Fluxes ◽  
The Other ◽  
Local Maxima ◽  
The Impact

Abstract The paper solves the problem of thermal conductivity inside a flat plate under the impact of a hot jet of nitrogen impinging from one side and cooled by a gas flow from the other side. In this formulation of the problem, there may be local maxima and minima of the temperature inside the plate, caused by an uneven distribution of heat fluxes along the plate.

scholarly journals Analytical Solution of Heat Conduction for Hollow Cylinders with Time-Dependent Boundary Condition and Time-Dependent Heat Transfer Coefficient

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Te-Wen Tu ◽  
Sen-Yung Lee
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Analytical Solution ◽  
Transfer Coefficient ◽  
Time Dependent ◽  
Physical Parameters ◽  
Expansion Theorem ◽  
Present Solution ◽  
Hollow Cylinders

An analytical solution for the heat transfer in hollow cylinders with time-dependent boundary condition and time-dependent heat transfer coefficient at different surfaces is developed for the first time. The methodology is an extension of the shifting function method. By dividing the Biot function into a constant plus a function and introducing two specially chosen shifting functions, the system is transformed into a partial differential equation with homogenous boundary conditions only. The transformed system is thus solved by series expansion theorem. Limiting cases of the solution are studied and numerical results are compared with those in the literature. The convergence rate of the present solution is fast and the analytical solution is simple and accurate. Also, the influence of physical parameters on the temperature distribution of a hollow cylinder along the radial direction is investigated.

Impact of Layered Soil on Foundation Heat Transfer for Slab-On Grade Floors

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Nizar Khaled ◽  
Khaled Rouissi ◽  
Moncef Krarti
Keyword(s):  
Heat Transfer ◽  
Analytical Solution ◽  
Soil Temperature ◽  
Soil Properties ◽  
Heat Loss ◽  
Layered Soil ◽  
Soil Medium ◽  
Coupled Heat Transfer ◽  
Building Foundation ◽  
The Impact

This paper presents an analytical solution associated with the steady-periodic heat transfer for a typical slab-on-grade floor building foundation in contact with a nonhomogeneous soil medium. In particular, the solution accounts for the impact of the above-grade wall thickness on the ground-coupled heat transfer. The interzone temperature estimation profile (ITPE) technique is utilized to obtain the analytical solution to determine soil temperature distributions and to estimate foundation heat loss/gain from slab-on-grade floors. In this paper, the impact of the nonhomogeneous soil properties on the transient foundation heat transfer is investigated for various slab configurations and soil thermal properties. The presented solution presents the first ITPE analytical solution for building foundation coupled with layered soil medium. The results indicate that nonhomogeneous soil properties have a significant effect on soil temperature distribution and on total slab heat loss. In particular, it is found that an error of up to 20% in estimating total slab heat transfer can be incurred if homogeneous soil medium is considered instead of a two-layered ground.

scholarly journals Natural Convection Flow from an Isothermal Sphere with Temperature Dependent Thermal Conductivity

1970 ◽  
Vol 2 (2) ◽  
pp. 53-64 ◽  
Author(s):  
Md Mamun Molla ◽  
Azad Rahman ◽  
Lineeya Tanzin Rahman
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Convection Flow ◽  
Temperature Dependent ◽  
Boundary Layer Equations ◽  
Wide Range ◽  
Conductivity Parameter ◽  
Marine Engineering ◽  
Temperature Dependent Thermal Conductivity

Laminar free convection flow from an isothermal sphere immersed in a fluid with thermal conductivity proportional to linear function of temperature has been studied. The governing boundary layer equations are transformed into a non-dimensional form and the resulting nonlinear system of partial differential equations is reduced to local non-similarity equations, which are solved numerically by very efficient implicit finite difference method together with Keller box scheme. Numerical results are presented by velocity and temperature distribution of the fluid as well as heat transfer characteristics, namely the heat transfer rate and the skin-friction coefficients for a wide range of thermal conductivity parameter γ (= 0.0, 0.5, 1.0, 2.0, 3.0, 5.0) and the Prandtl number Pr (= 0.7, 1.0, 3.0, 5.0, 7.0).   Keywords: Natural convection, temperature dependent thermal conductivity, isothermal sphere.    doi:10.3329/jname.v2i2.1872  Journal of Naval Architecture and Marine Engineering 2(2005) 53-64

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