Algorithm and Program for Simulating Heat Transfer in Cavities of Structural Members under Fire Conditions

2011 ◽  
Vol 90-93 ◽  
pp. 3227-3233
Author(s):  
Yong Jun Liu ◽  
Dong Wang ◽  
Xing Tao Ma
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Radiative Heat ◽  
Coefficient Matrix ◽  
System Of Equations ◽  
Structural Members ◽  
Finite Element Program ◽  
Heat Flows ◽  
Element Program ◽  
Fire Conditions

In this paper, an algorithm based on the network method suggested by Oppenheim for calculating the radiative heat flow in a cavity of structural members, say hollow core concrete slabs, exposed to fires is presented. It is assumed that the pressure in a cavity keeps atmospheric pressure through the whole cause of a fire, and the lost heat from the air due to expansion and immediate moving away from a cavity is neglected. The heat in a cavity is transfer via both heat conduction in air and thermal radiation among boundaries, and special regard is paid to modeling heat transfer by radiation. The effective radiative heat flow system of equations is derived and expressed in matrix form. The system of equations features a symmetric coefficient matrix, which can be stored in a one dimensional array, and can be solved using LDLT factorization. Node radiative thermal loads are calculated from effective radiative heat flows at edges of elements located on internal cavities. The nonlinear finite element program TFIELD written by first author has employed the new algorithm. Temperature distribution in two structural members with cavities are calculated using TFIELD, and numerical results demonstrate that the new algorithm is very effective and is useful for further study of structural behavior of structural members under fire conditions.

Shape and Size Optimization Design of Finned Brass Tube on the Central Air Conditioning

2012 ◽  
Vol 588-589 ◽  
pp. 1854-1857
Author(s):  
Shuang Chen ◽  
Bing Yan Zhang ◽  
Jian Hua Zhong
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Optimization Design ◽  
Heat Transfer Process ◽  
Finned Tube ◽  
Structure Parameters ◽  
Finite Element Program ◽  
Fin Efficiency ◽  
Heat Transfer Theory ◽  
Element Program

Finned tube heat transfer process was analyzed in this thesis, the optimal mathematical model of the fin efficiency and fin volume which was acted as the objective function is established based on the model of heat transfer theory. The heat exchanger numerical simulation of finned tube is taken by the ANSYS finite element program in heat transfer process, and the finned tube structure parameters ( fin spacing , fin thickness , fin height) were analyzed , the optimum structure parameters of a set of finned tube were obtained at the same time. These studies will have some guidance on the application of finned tubes.

COMMENT ON "FALSIFICATION OF THE ATMOSPHERIC CO2 GREENHOUSE EFFECTS WITHIN THE FRAME OF PHYSICS"

2010 ◽  
Vol 24 (10) ◽  
pp. 1309-1332 ◽  
Author(s):  
JOSHUA B. HALPERN ◽  
CHRISTOPHER M. COLOSE ◽  
CHRIS HO-STUART ◽  
JOEL D. SHORE ◽  
ARTHUR P. SMITH ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Radiative Heat ◽  
Second Law Of Thermodynamics ◽  
Heat Transfer Process ◽  
Second Law ◽  
Surface Cool ◽  
Radiative Balance ◽  
Heat Flows ◽  
Greenhouse Effects ◽  
Complete Process

In this journal, Gerhard Gerlich and Ralf D. Tscheuschner claim to have falsified the existence of an atmospheric greenhouse effect.1 Here, we show that their methods, logic, and conclusions are in error. Their most significant errors include trying to apply the Clausius statement of the Second Law of Thermodynamics to only one side of a heat transfer process rather than the entire process, and systematically ignoring most non-radiative heat flows applicable to the Earth's surface and atmosphere. They claim that radiative heat transfer from a colder atmosphere to a warmer surface is forbidden, ignoring the larger transfer in the other direction which makes the complete process allowed. Further, by ignoring heat capacity and non-radiative heat flows, they claim that radiative balance requires that the surface cool by 100 K or more at night, an obvious absurdity induced by an unphysical assumption. This comment concentrates on these two major points, while also taking note of some of Gerlich and Tscheuschner's other errors and misunderstandings.

Heat Transfer in Stepped Labyrinth Seals

1988 ◽  
Vol 110 (1) ◽  
pp. 63-69 ◽  
Author(s):  
S. Wittig ◽  
K. Jacobsen ◽  
U. Schelling ◽  
S. Kim
Keyword(s):  
Heat Transfer ◽  
Wall Friction ◽  
Leakage Flow ◽  
Test Rig ◽  
Transfer Coefficients ◽  
Labyrinth Seals ◽  
Finite Element Program ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Element Program

Leakage flow and heat transfer of scaled-up stepped labyrinth seals were investigated experimentally and numerically. The experiments were conducted in a test rig under steady conditions. For different geometries and pressure ratios a finite element program was used to determine the temperature distribution and subsequently the heat transfer coefficients. In verifying the experimental results, the flow field of the seals was calculated numerically by a finite difference program. Heat transfer coefficients were derived utilizing the well-known analogies between heat transfer and wall friction.

scholarly journals Displacement and Stress Function-based Linear and Quadratic Triangular Elements for Saint-Venant Torsional Problems

2018 ◽  
Vol 20 (2) ◽  
pp. 70 ◽  
Author(s):  
Joko Purnomo ◽  
Wong Foek Tjong ◽  
Wijaya W.C. ◽  
Putra J.S.
Keyword(s):  
Cross Sections ◽  
Stress Function ◽  
Torsional Rigidity ◽  
Structural Members ◽  
Finite Element Program ◽  
Element Program ◽  
Standard Linear ◽  
Triangular Elements ◽  
Displacement Based ◽  
High Degree

Torsional problems commonly arise in frame structural members subjected to unsym­metrical loading. Saint-Venant proposed a semi inverse method to develop the exact theory of torsional bars of general cross sections. However, the solution to the problem using an analytical method for a complicated cross section is cumbersome. This paper presents the adoption of the Saint-Venant theory to develop a simple finite element program based on the displacement and stress function approaches using the standard linear and quadratic triangular elements. The displacement based approach is capable of evaluating torsional rigidity and shear stress distribution of homogeneous and nonhomogeneous; isotropic, orthotropic, and anisotropic materials; in singly and multiply-connected sections.  On the other hand, applications of the stress function approach are limited to the case of singly-connected isotropic sections only, due to the complexity on the boundary conditions. The results show that both approaches converge to exact solutions with high degree of accuracy.

scholarly journals REPLY TO "COMMENT ON 'FALSIFICATION OF THE ATMOSPHERIC CO2 GREENHOUSE EFFECTS WITHIN THE FRAME OF PHYSICS' BY JOSHUA B. HALPERN, CHRISTOPHER M. COLOSE, CHRIS HO-STUART, JOEL D. SHORE, ARTHUR P. SMITH, JÖRG ZIMMERMANN"

2010 ◽  
Vol 24 (10) ◽  
pp. 1333-1359 ◽  
Author(s):  
GERHARD GERLICH ◽  
RALF D. TSCHEUSCHNER
Keyword(s):  
Heat Transfer ◽  
Radiative Heat ◽  
Second Law Of Thermodynamics ◽  
Heat Transfer Process ◽  
Trace Gas ◽  
Second Law ◽  
Heat Flows ◽  
The Earth ◽  
Greenhouse Effects ◽  
Fundamental Physical

It is shown that the notorious claim by Halpern et al. recently repeated in their comment that the method, logic, and conclusions of our "Falsification Of The CO2 Greenhouse Effects Within The Frame Of Physics" would be in error has no foundation. Since Halpern et al. communicate our arguments incorrectly, their comment is scientifically vacuous. In particular, it is not true that we are "trying to apply the Clausius statement of the Second Law of Thermodynamics to only one side of a heat transfer process rather than the entire process" and that we are "systematically ignoring most non-radiative heat flows applicable to Earth's surface and atmosphere". Rather, our falsification paper discusses the violation of fundamental physical and mathematical principles in 14 examples of common pseudo-derivations of fictitious greenhouse effects that are all based on simplistic pictures of radiative transfer and their obscure relation to thermodynamics, including but not limited to those descriptions (a) that define a "Perpetuum Mobile Of The 2nd Kind", (b) that rely on incorrectly calculated averages of global temperatures, (c) that refer to incorrectly normalized spectra of electromagnetic radiation. Halpern et al. completely missed an exceptional chance to formulate a scientifically well-founded antithesis. They do not even define a greenhouse effect that they wish to defend. We take the opportunity to clarify some misunderstandings, which are communicated in the current discussion on the non-measurable, i.e., physically non-existing influence of the trace gas CO2 on the climates of the Earth.

Improvement of the Calculation of Hydrodynamic Systems by Considering the Dynamic Deformation Caused by Vibration

2011 ◽  
Author(s):  
Sebastian Kukla ◽  
Tim Sadek
Keyword(s):  
Reynolds Equation ◽  
Coefficient Matrix ◽  
Influence Coefficient ◽  
Finite Element Program ◽  
Hydrodynamic System ◽  
Element Program ◽  
Dynamic Components ◽  
Stiffness And Damping ◽  
Hydrodynamic Systems ◽  
Surface Dynamic

In order to improve the calculation of stiffness and damping coefficients (SDC) for hydrodynamic systems, this paper proposes the consideration of both static and dynamic deformations of the running surface. Dynamic deformations are caused by rotor vibration and corresponding unbalanced forces. A lubrication wedge was used to exemplify the significant influence of these dynamic deformations in SDC calculations. This basic hydrodynamic system was calculated considering material elasticity. First of all, an influence coefficient matrix, which describes the correlation of pressure and deformation, was calculated with the finite element program ANSYS. Using this matrix, small dynamic deformations of the running surface were considered in solving the Reynolds equation for the lubrication wedge. The analysis of the vibration response of this basic hydrodynamic system considering elastic material deformation demonstrated that both static and dynamic components of deflection significantly affect the SDC. These coefficients were also proved to be highly dependent on the stimulation frequency.

Simulation of gas quenching

2004 ◽  
Vol 120 ◽  
pp. 727-735
Author(s):  
F. Frerichs ◽  
Th. Lübben ◽  
U. Fritsching ◽  
H. Lohner ◽  
A. Rocha ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Treatment ◽  
Strain Hardening ◽  
Mechanical Behaviour ◽  
Mechanical Response ◽  
Temperature Dependent ◽  
Finite Element Program ◽  
Element Program ◽  
Gas Quenching

The prediction of mechanical behaviour of specimen during heat treatment by means of numerical simulation requires numerous modules e.g. for heat transfer and mechanical behaviour. The quality of predictions depend on the quality of the applied models within the modules. In this paper the strain hardening model used in the mechanical module will be investigated. For simulation of mechanical behaviour during gas quenching it is first of all necessary to calculate the interaction between gas and specimen. Using simulated flow field and temperature distribution within the gas, the heat transfer coefficient is calculated from computational fluid dynamics. The cooling and further the mechanical behaviour e.g. residual stresses and distortion of the specimen are simulated by a commercial Finite Element program. To investigate strain hardening it is helpful to choose in a first step a material that will not show phase transformations due to heat treatment. Therefore simulation of mechanical behaviour of austenitic cylinders (SAE30300) is investigated. The required thermo-physical properties such as thermal conductivity, density, and specific heat are taken from literature. With the exception of Poisson’s ratio the mechanical properties are measured and calculated by own investigations. For description of the temperature dependent stress strain curves the Ramberg-Osgood model is used. The simulated results are compared with experimental data in order to decide which model better describes the mechanical response, whether the kinematic or isotropic strain hardening.

Meshed Photonic Crystals for Manipulating Near-Field Thermal Radiation Across Variable Nano/Micro Gap

2017 ◽  
Author(s):  
Mahmoud Elzouka ◽  
Sidy Ndao
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Photonic Crystals ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Near Field ◽  
Far Field ◽  
Memory Devices ◽  
Gap Size

The ability to manipulate heat flow can result in wonderful applications such as thermal logic and memory devices. Thermal logic and memory devices are similar to their electronic counterparts, however, they are powered solely by heat. In addition, thermal logic and memory devices can operate in harsh environments where electronics typically fail. Despite our understanding of various mechanisms of heat transfer, controlling heat (in a sense of switching heat flow on or off) is more challenging than controlling electricity due to the lack of perfect thermal insulators. One possible solution is to control the near-field thermal radiation heat transfer between hot and cold terminals by manipulating the size of the vacuum gap separating the two. Unlike far-field thermal radiation, near-field thermal radiation intensity increases exponentially with decreasing the gap size. There are however challenges in manipulating the nano/micro vacuum gaps to achieve enough contrast in heat transfer between the high and low heat transfer cases. In this paper, we present a prototype of a microdevice with a controllable micro gap of size 3 μm (initial gap size) between the hot and cold terminals; this configuration achieves a contrast in near-field radiative heat transfer at temperatures as high as 600 K. Furthermore, we present numerical analysis for meshed photonic crystals to achieve even higher contrast in radiative heat transfer with enhancement in heat transfer as high as 26 times in comparison to far-field.

Finite element program for moisture and heat transfer in heated concrete

1982 ◽  
Vol 68 (1) ◽  
pp. 61-70 ◽  
Author(s):  
Zdeněk P. Bažant ◽  
Jenn-Chuan Chern ◽  
Werapol Thonguthai
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Finite Element Program ◽  
Element Program ◽  
Heated Concrete

scholarly journals THERMOFILLER EFFECT ON HEAT-STRESSED MULTILAYERED ENCLOSING STRUCTURES

2018 ◽  
pp. 155-169
Author(s):  
A. N. Kozlobrodov ◽  
E. A. Ivanova ◽  
A. V. Golovko
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Thermal Properties ◽  
Heat Exchange ◽  
Quantitative Assessment ◽  
Thermal Conditions ◽  
Finite Element Program ◽  
Transfer Processes ◽  
Negative Effect ◽  
Element Program

The article deals with spatial heat-stressed elements that influence the thermal properties of multilayered enclosing structures. Using the ANSYS finite element program, the effect of thermofiller location on heat transfer processes is studied nearby the heat-stressed elements. A quantitative assessment is given to thermal conditions of heat-stressed elements of enclosing structure under extreme heat exchange conditions. Specific conditions are created to raise the temperature nearby the heat-stressed elements and reduce their negative effect.  

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