A Numerical Study on the Slab Heating Characteristics in a Reheating Furnace With the Formation and Growth of Scale on the Slab Surface

2009 ◽  
Author(s):  
Dong Eun Lee ◽  
Jung Hyun Jang ◽  
Man Young Kim
Keyword(s):  
Heat Transfer ◽  
Present Model ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Radiant Heat ◽  
Transfer Model ◽  
Radiant Heat Transfer ◽  
Reheating Furnace ◽  
Combustion Gases ◽  
Scale Layer

In this work, the development of a mathematical heat transfer model for a walking-beam type reheating furnace is described and preliminary model predictions are presented. The model can predict the heat flux distribution within the furnace and the temperature distribution in the slab throughout the reheating furnace process by considering the heat exchange between the slab and its surroundings, including the radiant heat transfer among the slabs, the skids, the hot combustion gases and the furnace wall as well as the gas convection heat transfer in the furnace. In addition, present model is designed to be able to predict the formation and growth of the scale layer on the slab in order to investigate its effect on the slab heating. A comparison is made between the predictions of the present model and the data from an in situ measurement in the furnace, and a reasonable agreement is found. The results of the present simulation show that the effect of the scale layer on the slab heating is considerable.

Radiant Heat Transfer in Nitrogen-Free Combustion Environments

2018 ◽  
Vol 19 (2) ◽  
pp. 175-188
Author(s):  
A. Marzouk Osama
Keyword(s):  
Heat Transfer ◽  
Gaseous Mixture ◽  
Radiant Heat ◽  
Benchmark Problems ◽  
Radiant Heat Transfer ◽  
Discrete Ordinate ◽  
Combustion Gases ◽  
Directional Radiation ◽  
Equivalent Effect ◽  
Volume Method

AbstractWhen mathematically calculating the radiant heat flux during combustion, the radiant property of a gaseous mixture can be approximated as a weighted sum of the radiant properties of fictitious gases to give an equivalent effect of the actual gas mixture. This concept has been in use for many years. However, it was initially tailored to product gases in air-combustion environment. With the advent and progress in nitrogen-free combustion (particularly for environmental purposes), the chemical composition of the combustion gases is highly altered and existing models should be assessed for their suitability in these new environments. We carried out this task, which was motivated by our recent modeling work that revealed that a new model should be developed for nitrogen-free combustion environments. The model proposed here has four participating gases plus one transparent gas and its performance in predicting radiant heat transfer in 3D benchmark problems is evaluated in comparison with existing models, using the discrete-ordinate method for directional radiation domain combined with the finite-volume method of the spatial domain.

An improved model to analyze radiative heat transfer in flame-resistant fabrics exposed to low-level radiation

2016 ◽  
Vol 87 (16) ◽  
pp. 1953-1967 ◽  
Author(s):  
Yun Su ◽  
Jiazhen He ◽  
Jun Li
Keyword(s):  
Heat Transfer ◽  
Optical Properties ◽  
Thermal Energy ◽  
Thermal Exposure ◽  
Radiant Heat ◽  
Transfer Model ◽  
Radiant Heat Transfer ◽  
Flux Model ◽  
Fabric System ◽  
Improved Model

An improved heat transfer model, based on the two-flux model, in a multilayer flame-resistant fabric system with an air gap was proposed. The developed model considered the thermal radiation by absorbing, transmitting, emitting and reflecting in porous fabrics. The predicted results of the new model were compared with the previous Beer’s law model and the experimental results, and were found to be in good agreement with the experimental ones. The aim of this study is to investigate the mechanism of radiant heat transfer in the multilayer fabric system and the effects of the optical properties of flame-resistant fabric on heat transfer in the fabric system. The numerical results demonstrated that the self-emission in multilayer fabric system increases not only the rate of thermal energy transferred to human skin during thermal exposure, but also the rate of thermal energy transmitting to the ambience during cooling. The fabric’s optical properties have a complex influence on the transmitted and stored energy in multilayer protective clothing. The finding obtained in this study can provide references for the improvement of the thermal protective performance of flame-resistant fabrics.

A Numerical Study of the Effect of Blind Opening on Laminar-to-Turbulent Transition in the Flow Over a Simple Recessed Window-Plane Blind System

2010 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Turbulent Flow ◽  
Numerical Study ◽  
Plane Surface ◽  
Radiant Heat ◽  
Approximate Model ◽  
Radiant Heat Transfer ◽  
Buoyancy Forces ◽  
Open Plane

Most numerical studies of convective heat transfer between a window-blind system and a room are based on the assumption that the flow remains laminar. However, in the case of larger windows it is to be expected that transition to turbulent flow will occur in the system. The aim of the present study was to numerically determine when transition to turbulent flow occurs in a recessed window system and the effect of a simple partially open plane blind on when transition occurs. An approximate model of a recessed window that is covered by a partially open plane blind has been considered. The inner surface of the window is modeled as a plane vertical isothermal surface and the blind as a thin plane surface that offers no resistance to heat transfer. The fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being dealt with using the Boussinesq approach. Radiant heat transfer effects have been neglected. The k-epsilon turbulence model with the full effects of the buoyancy forces being accounted for has been used in obtaining the solution. The governing equations have been solved using the commercial finite-volume based cfd code FLUENT. The solution has as parameters: (1) the Rayleigh number, (2) the Prandtl number, (3) the dimensionless ‘window’ recess depth, (4) the dimensionless blind opening, and (5) whether the ‘window’ surface is at a higher or lower temperature than the room air. Because of the application being considered results have only been obtained for Pr = 0.7 and for the case where the ‘window’ surface is at a higher temperature than the room air. The effect of transition on the mean Nusselt number variation with Rayleigh number with various blind openings for various dimensionless window recess depths has in particular been studied.

scholarly journals PERPINDAHAN PANAS HYBRID PHOTOVOLTAIC DAN THERMOELEKTRIC GENERATOR DENGAN HOT MIRROR

Foristek ◽  
2021 ◽  
Vol 11 (2) ◽  
Author(s):  
Ardiansyah Ardiansyah ◽  
Mustofa Mustofa ◽  
Iskandar Iskandar ◽  
Andi Idhan ◽  
Yuli Asmi Rahman
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Convection Heat Transfer ◽  
Radiant Heat ◽  
Fresnel Lens ◽  
Radiant Heat Transfer ◽  
Convection Heat ◽  
Solid Objects ◽  
Free Convection Heat ◽  
Wasted Heat

Heat transfer is the transfer of energy from one area to another due to the temperature difference between these areas. Wasted heat energy can be converted into electricity using (TEG) between the hot and cold sides. If the temperature difference is more significant, the efficiency may increase along with the operating temperature of the TEG-type material. So in this study, the author will calculate the heat transfer that occurs in Photovoltaic (PV), Thermoelectric Generator (TEG), and Hot Mirrors by utilizing thermal energy light produced from Muxindo LED bulbs with 10 Watt, 15 Watt, and 20 Watt power. The results of this study indicate that by using 10, 15, and 20 Watt LED bulbs for free convection heat transfer, the power generated from each point increases because it passes through several obstacles from objects that experience a decrease in temperature to PV and TEG, with the characteristics of the displacement. The movement of molecules from the medium importance follows convection heat at every point of transfer in the intermediate substance. The most significant power generated from radiant heat transfer is about 0.1873 Watt. It occurs on the surface of the fresnel lens using a 20 Watt LED bulb with the characteristic that the radiation propagates in a straight line and does not require an intermediate medium to transfer heat from one substance to another. The most significant conduction heat transfer power, 0.2453 Watt, occurs in Fresnel Lens using a 20 Watt LED bulb with heat transfer characteristics in solid objects.

Radiant Heat Transfer From Isothermal Dispersions With Isotropic Scattering

1967 ◽  
Vol 89 (4) ◽  
pp. 300-308 ◽  
Author(s):  
R. H. Edwards ◽  
R. P. Bobco
Keyword(s):  
Heat Transfer ◽  
Approximate Solutions ◽  
Radiant Heat ◽  
Second Order ◽  
Isotropic Scattering ◽  
Radiant Heat Transfer ◽  
Approximate Methods ◽  
First Order ◽  
Order Solution ◽  
Radiant Transfer

Two approximate methods are presented for making radiant heat-transfer computations from gray, isothermal dispersions which absorb, emit, and scatter isotropically. The integrodifferential equation of radiant transfer is solved using moment techniques to obtain a first-order solution. A second-order solution is found by iteration. The approximate solutions are compared to exact solutions found in the literature of astrophysics for the case of a plane-parallel geometry. The exact and approximate solutions are both expressed in terms of directional and hemispherical emissivities at a boundary. The comparison for a slab, which is neither optically thin nor thick (τ = 1), indicates that the second-order solution is accurate to within 10 percent for both directional and hemispherical properties. These results suggest that relatively simple techniques may be used to make design computations for more complex geometries and boundary conditions.

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