Numerical Predictions on the Soil Thermal Effect Under Surface Fire Conditions

1997 ◽  
Vol 7 (1) ◽  
pp. 51 ◽  
Author(s):  
LA Oliveira ◽  
DX Viegas ◽  
AM Raimundo
Keyword(s):  
Temperature Distribution ◽  
Flame Front ◽  
Radiation Effects ◽  
Control Volume ◽  
Ground Surface ◽  
Soil Surface ◽  
Heat Transfer Process ◽  
Maximum Temperature ◽  
Transient Temperature ◽  
Numerical Predictions

A control volume numerical method is used to predict the temperature distribution inside a soil extent, the surface of which has been swept by a two-dimensional flame front with pre-defined velocity and temperature distributions. Natural and forced convection, as well as radiation effects are included in the specification of the soil surface thermal boundary condition. The flame residence time and maximum temperature are identified as two major parameters to characterize the flame front. As expected, the heat penetration depth is confined to the near vicinity of the soil surface. Moreover, horizontal heat conduction throughout the soil has not always a significant effect on its global, transient temperature distribution. The influence of wind velocity and of soil thermal diffusivity upon its temperature distribution are analysed. Radiation is the dominant contribution in the whole heat transfer process between flame and ground surface.

Numerical and Experimental Investigation of Thermal Signatures of Buried Landmines in Dry Soil

2005 ◽  
Vol 128 (5) ◽  
pp. 484-494 ◽  
Author(s):  
F. Moukalled ◽  
N. Ghaddar ◽  
H. Kabbani ◽  
N. Khalid ◽  
Z. Fawaz
Keyword(s):  
Experimental Investigation ◽  
Numerical Model ◽  
Measurement Techniques ◽  
Infrared Camera ◽  
Soil Surface ◽  
Radiant Heat ◽  
Transient Temperature ◽  
Numerical Predictions ◽  
Soil Temperatures ◽  
Thermal Signature

This paper reports a numerical and experimental investigation conducted to study the thermal signature of buried landmines on soil surface. A finite-volume-based numerical model was developed to solve the unsteady three-dimensional heat transport equation in dry homogeneous soil with a buried mine. Numerical predictions of soil thermal response were validated by comparison with published analytical and numerical values in addition to data obtained experimentally. Experiments were performed inside an environmental chamber and soil temperatures were measured during cooling, using two measurement techniques, after exposing the soil surface to a radiant heat flux for a specified period. In the first technique, the temporal variation of the surface and internal soil temperatures were recorded using thermocouples. In the second technique, the soil surface temperature was measured using an infrared camera that revealed the thermal signature of the mine. The transient temperature profiles generated numerically agreed with measurements, and the difference between predicted and measured values was less than 0.3°C at both the soil surface and in depth. The accurate matching of numerical and IR images at the surfaces was found to strongly depend on the use of a smaller soil thermal conductivity at the surface than at greater depths. The numerical model was used to predict the dependence of the peak thermal contrast on time, depth, and heating period. The thermographic analysis, when combined with numerical predictions, holds promise as a method for detecting shallowly buried land mines.

Numerical Solution for a Transient Temperature Distribution on a Finite Domain Due to a Dithering or Rotating Laser Beam

2013 ◽  
Vol 4 (4) ◽  
pp. 22-38
Author(s):  
Tsuwei Tan ◽  
Hong Zhou
Keyword(s):  
Temperature Distribution ◽  
Laser Beam ◽  
Temperature Rise ◽  
Maximum Temperature ◽  
Finite Domain ◽  
Transient Temperature ◽  
Gaussian Laser Beam ◽  
Maximum Temperature Rise ◽  
Transient Temperature Distribution ◽  
Spatial Dimensions

The temperature distribution due to a rotating or dithering Gaussian laser beam on a finite body is obtained numerically. The authors apply various techniques to solve the nonhomogeneous heat equation in different spatial dimensions. The authors’ approach includes the Crank-Nicolson method, the Fast Fourier Transform (FFT) method and the commercial software COMSOL. It is found that the maximum temperature rise decreases as the frequency of the rotating or dithering laser beam increases and the temperature rise induced by a rotating beam is smaller than the one induced by a dithering beam. The authors’ numerical results also provide the asymptotic behavior of the maximum temperature rise as a function of the frequency of a rotating or dithering laser beam.

scholarly journals The Effect of Beam Intensity on Temperature Distribution in ADS Windowless Lead-Bismuth Eutectic Spallation Target

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Jie Liu ◽  
Lei Gao ◽  
Wen-qiang Lu
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Temperature Distribution ◽  
Heat Transfer Process ◽  
Beam Intensity ◽  
Maximum Temperature ◽  
Flow Process ◽  
Large Power ◽  
Spallation Target ◽  
Lead Bismuth Eutectic

The spallation target is the component coupling the accelerator and the reactor and is regarded as the “heart” of the accelerator driven system (ADS). Heavy liquid metal lead-bismuth eutectic (LBE) is served as core coolant and spallation material to carry away heat deposition of spallation reaction and produce high flux neutron. So it is very important to study the heat transfer process in the target. In this paper, the steady-state flow pattern has been numerically obtained and taken as the input for the nuclear physics calculation, and then the distribution of the extreme large power density of the heat load is imported back to the computational fluid dynamics as the source term in the energy equation. Through the coupling, the transient and steady-state temperature distribution in the windowless spallation target is obtained and analyzed based on the flow process and heat transfer. Comparison of the temperature distribution with the different beam intensity shows that its shape is the same as broken wing of the butterfly. Nevertheless, the maximum temperature as well as the temperature gradient is different. The results play an important role and can be applied to the further design and optimization of the ADS windowless spallation target.

scholarly journals Transient temperature distribution on the corneal endothelium during ophthalmic phacoemulsification: a numerical simulation using the nodeless variable element

2010 ◽  
Vol 4 (6) ◽  
pp. 885-892 ◽  
Author(s):  
Wiroj Limtrakarn ◽  
Somporn Reepolmaha ◽  
Pramote Dechaumphai
Keyword(s):  
Numerical Simulation ◽  
Temperature Distribution ◽  
Anterior Chamber ◽  
Heat Generation ◽  
Corneal Endothelium ◽  
Temperature Response ◽  
Maximum Temperature ◽  
Transient Temperature ◽  
Cataract Operation ◽  
Transient Temperature Distribution

Abstract Background: During cataract operation (phacoemulsification), a phaco needle-tip is inserted into the anterior chamber of eye. Then, heat is generated by the oscillation of the phaco needle, which may injury the corneal endothelial cells. There are no data available for temperature responses at the corneal endothelium to heat from the phaco needle during phacoemulsification. Objective: Investigate temperature distribution on the corneal endothelium during ophthalmic phacoemulsification using numerical simulation, and compare the transient temperature response to heat between balanced salt solution (BSS) and ophthalmic viscoelastic device (OVD), Viscoat®. Methods: Heat flux from a phaco needle was measured with thermal properties of BSS and AVS in an experimental setting. Then, nodeless variable finite element method was applied to predict temperature changes in the eye by the phaco needle inserted into the anterior chamber. The transient temperature distribution on the corneal endothelium was calculated at 10, 20, and 30 seconds after heat generation by the needle. Results: The heat generation of phaco needle without sleeve cover was 1.6 kW/m2. The numerical simulation showed that the maximum temperature occurs on the wound location at all times after heat generation by the phaco needle. Especially, at time 30 seconds, it was 49.2 and 41.7°C in BSS and OVD, respectively. The temperature elevation by the phaco needle was lower in OVD than BSS. Conclusion: Phacoemulsification is a heat-generating procedure performed between the anterior chamber structures of eye. During this procedure, OVD may protect the corneal endothelium against heat better than BSS.

Numerical and Experimental Investigation of Thermal Signatures of Buried Landmines in Dry Soil

2005 ◽  
Author(s):  
F. Moukalled ◽  
N. Ghaddar ◽  
H. Kabbani ◽  
N. Khaled ◽  
Z. Fawaz
Keyword(s):  
Experimental Investigation ◽  
Numerical Data ◽  
Soil Surface ◽  
Radiant Heat ◽  
Balance Model ◽  
Transient Temperature ◽  
Numerical Predictions ◽  
Dry Soil ◽  
The Difference ◽  
Thermal Signature

This paper reports a numerical and experimental investigation conducted to study the surface thermal signature of buried landmines. Numerical predictions are obtained by solving an unsteady three-dimensional energy balance model for heat transport in dry soil with a buried mine using the conservative finite-volume method. The model is validated by comparing generated results against published analytical and numerical data in addition to indoor measurements performed on dry soil inside an environmental chamber. The thermal signatures are observed while cooling takes place after exposing the soil surface to a radiant heat flux for a specified period. Transient temperature profiles produced numerically agree well with thermocouple measurements recorded at shallow soil depths and with surface IR images. The difference between predicted and measured surface temperatures is less than 0.4°C and the difference in thermal signature is less than 0.3°C. Sit in. The numerical model is also used to predict perturbations of the expected thermal signatures that are compared to the real (measured) ones from the IR images. The thermographic analysis shows good promise as a method for detecting shallowly buried land mines where not only the temperature difference or contrast images generated by the thermal signatures are matched between the IR images and the simulation images with high accuracy, but also the absolute temperatures for many images generated at discrete time intervals.

A Computer-Aided Cooling-Line Design System for Injection Molds

1990 ◽  
Vol 112 (2) ◽  
pp. 161-167 ◽  
Author(s):  
L. S. Turng ◽  
K. K. Wang
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Cooling System ◽  
Transient Heat Conduction ◽  
Heat Transfer Process ◽  
Design System ◽  
Cavity Surface ◽  
Transient Temperature ◽  
Numerical Predictions ◽  
Line Design

This paper presents a methodology for analyzing the heat-transfer process during the injection molding of plastics as an aid to mold design. A numerical scheme using the Boundary Element Method (BEM) with “zonal” approach has been developed to solve the quasi-steady temperature field and its normal derivative over the entire surface of the mold plates including the cavity wall as well as parting surface. In order to obtain a solution for the temperature field, a cycle-averaged heat-transfer coefficient is introduced from a transient heat-conduction analysis and applied as the boundary condition at the cavity surface. The numerical predictions as compared with the experimental data have shown that the cycle-averaged solution used in this study gives a reasonable representation of the transient temperature variation over the cavity surface. Based on the numerical predictions, the mold designer will be able to design a proper cooling-system for a mold to achieve better part quality and high productivity through more uniform cooling and shorter cycle time, respectively.

Boundary Condition Design to Heat a Moving Object at Uniform Transient Temperature Using Inverse Formulation

2004 ◽  
Vol 126 (3) ◽  
pp. 619-626 ◽  
Author(s):  
Hakan Ertu¨rk ◽  
Ofodike A. Ezekoye ◽  
John R. Howell
Keyword(s):  
Boundary Condition ◽  
Temperature Distribution ◽  
Design Problem ◽  
Manufacturing Industry ◽  
Three Dimensional ◽  
Chemical Deposition ◽  
Iterative Solution ◽  
Conveyor Belt ◽  
Temperature History ◽  
Transient Temperature

The boundary condition design of a three-dimensional furnace that heats an object moving along a conveyor belt of an assembly line is considered. A furnace of this type can be used by the manufacturing industry for applications such as industrial baking, curing of paint, annealing or manufacturing through chemical deposition. The object that is to be heated moves along the furnace as it is heated following a specified temperature history. The spatial temperature distribution on the object is kept isothermal through the whole process. The temperature distribution of the heaters of the furnace should be changed as the object moves so that the specified temperature history can be satisfied. The design problem is transient where a series of inverse problems are solved. The process furnace considered is in the shape of a rectangular tunnel where the heaters are located on the top and the design object moves along the bottom. The inverse design approach is used for the solution, which is advantageous over a traditional trial-and-error solution where an iterative solution is required for every position as the object moves. The inverse formulation of the design problem is ill-posed and involves a set of Fredholm equations of the first kind. The use of advanced solvers that are able to regularize the resulting system is essential. These include the conjugate gradient method, the truncated singular value decomposition or Tikhonov regularization, rather than an ordinary solver, like Gauss-Seidel or Gauss elimination.

Temperature Distribution and Fluid Flow Modeling of Electron Beam Melting® (EBM)

2012 ◽  
Author(s):  
M. Jamshidinia ◽  
F. Kong ◽  
R. Kovacevic
Keyword(s):  
Electron Beam ◽  
Fluid Flow ◽  
Temperature Distribution ◽  
Molten Pool ◽  
Electron Beam Melting ◽  
Control Volume ◽  
Thermal Analyses ◽  
Scanning Speed ◽  
Flow Modeling ◽  
Fluid Flow Modeling

A three-dimensional (3D) numerical model is developed by using control volume method to analyze the effects of the electron beam scanning speed on the temperature distribution and fluid flow of the liquid phase in the electron beam melting® (EBM) of Ti-6Al-4V powder. The numerical calculations are performed by Fluent codes, in which thermal analyses with and without considering fluid flow in the molten pool are compared. A series of experiments are performed with an Electron Beam Melting® machine to verify the numerical accuracy. Compared to thermal analysis without considering convection in the molten pool, a closer numerical prediction of geometrical size of molten pool to the experimental data can be achieved by using thermal and fluid flow modeling. The difference between the melt pool geometry in the two models is due to the consideration of the effects of the outward flow in the fluid flow model caused by surface tension.

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