A Mathematical Solution for Gas-to-Surface Radiative Exchange Area for a Rectangular Parallelepiped Enclosure Containing a Gray Medium

1977 ◽  
Vol 99 (2) ◽  
pp. 203-207 ◽  
Author(s):  
H. B. Becker
Keyword(s):  
Rectangular Parallelepiped ◽  
Furnace Chamber ◽  
Zone Method ◽  
Present Contribution ◽  
Surface Exchange ◽  
Mathematical Solution ◽  
Graphical Data ◽  
Exchange Area ◽  
Adjacent Face ◽  
Gas Volume

The transfer of heat in a gas filled enclosure can be calculated by the zone method put forward by Hottel and Cohen [1, 2]. For a shape which can be divided into cylindrical or cubic zones, tabulated and graphical data on exchange areas are available, however, insufficient data exist for subdivision into rectangular zones. The present contribution provides a mathematical solution for the gas-to-surface exchange area between a rectangular parallelepiped gas volume and an adjacent face. The rules for manipulating and scaling of exchange areas are reviewed, and their application to the zoning of a rectangular furnace chamber into concentric rectangular volume elements is demonstrated.

The Application of Multi-Zone Thermal Radiation Models to Investigate the Energy Efficiency of a Metal Reheating Furnace Under Start Up Conditions

1999 ◽  
Author(s):  
John Ward ◽  
Sara A. C. Correia ◽  
João L. V. A. Sousa
Keyword(s):  
Combustion Products ◽  
Furnace Chamber ◽  
Zone Model ◽  
Two Dimensional ◽  
Heating Rates ◽  
Zone Method ◽  
Discharge Temperature ◽  
Start Up ◽  
Steel Bars ◽  
Industrial Heating

Abstract The zone method of radiation analysis has been widely used in mathematical models of a range of industrial heating processes. This paper is thus concerned with the use of a two-dimensional, multi-zone model to predict fuel consumptions, heating rates and load temperatures following the “cold start up” of a gas-fired furnace heating steel bars to a nominal discharge temperature of 1250°C. The model takes into account variations in the flows of the combustion products and in particular examines the influence of the re-circulation of these hot gases within the furnace chamber. The predictions of this complex two-dimensional model are compared with those of a one-dimensional so-called “long furnace model” to illustrate the differences resulting from the use of a more sophisticated multi-zone model.

scholarly journals Simulation of heat transfer in combustion chamber waterwall tubes of supercritical steam boilers

2016 ◽  
Vol 37 (2) ◽  
pp. 199-213 ◽  
Author(s):  
Sławomir Grądziel ◽  
Karol Majewski
Keyword(s):  
Combustion Chamber ◽  
Thermal Load ◽  
Fluid Pressure ◽  
Furnace Chamber ◽  
Zone Method ◽  
Left Hand ◽  
Right Hand ◽  
Steam Boilers ◽  
Difference Quotients ◽  
The Right

Abstract The paper presents the results of numerical computations performed for the furnace chamber waterwalls of a supercritical boiler with a steam output of 2400 × 103 kg/h. A model of distributed parameters is proposed for the waterwall operation simulation. It is based on the solution of equations describing the mass, momentum and energy conservation laws. The aim of the calculations was to determine the distribution of enthalpy, mass flow and fluid pressure in tubes. The balance equations can be brought to a form where on the left-hand side space derivatives, and on the right-hand side – time derivatives are obtained. The time derivatives on the right-hand side were replaced with backward difference quotients. This system of ordinary differential equations was solved using the Runge-Kutta method. The calculation also takes account of the variable thermal load of the chamber along its height. This thermal load distribution is known from the calculations of the heat exchange in the combustion chamber. The calculations were carried out with the zone method.

The Influence of Radiation Model on the Distribution of Heat Flux in the Pusher Furnace / Wpływ Modelu Promieniowania Na Rozkład Gęstości Strumienia Ciepła W Piecu Przepychowym

2012 ◽  
Vol 57 (4) ◽  
pp. 1143-1149 ◽  
Author(s):  
A. Gołdasz ◽  
Z. Malinowski ◽  
T. Telejko ◽  
M. Rywotycki ◽  
A. Szajding
Keyword(s):  
Heat Exchange ◽  
Three Dimensional ◽  
Radiation Energy ◽  
Furnace Chamber ◽  
Radiative Heat Exchange ◽  
Heating Process ◽  
Zone Method ◽  
Atmosphere Temperature ◽  
A Charge ◽  
Pusher Furnace

A three dimensional numerical model of the heat exchange during a charge heating process in a pusher furnace, using the finite element method, was used in this study. The radiative heat exchange in the furnace chamber was carried out based on two methods: the zone method and the method of basing on the average configuration ratio. In the zone method the flux of radiation energy reaching the surface of the heated charge was determined by performing calculations of brightness in a multi-surface closed system which is the pusher furnace chamber filled with an emitting-absorbing medium. In the second case an average configuration ratio was used by setting the radiation energy flux through linking the walls temperature with the furnace atmosphere temperature.

High-resolution observations of metastable γ’ precipitation in Al-15at.%Ag

1996 ◽  
Vol 54 ◽  
pp. 1004-1005
Author(s):  
N. V. Larcher ◽  
I. G. Solorzano
Keyword(s):  
Discontinuous Precipitation ◽  
Equilibrium Phase ◽  
Quantitative Description ◽  
Present Contribution ◽  
Α Phase ◽  
The Matrix ◽  
Aging Sequence ◽  
Matrix Precipitation ◽  
Considerable Detail ◽  
Kinetics Of

It is currently well established that, for an Al-Ag alloy quenched from the α phase and aged within the metastable solvus, the aging sequence is: supersaturated α → GP zones → γ’ → γ (Ag2Al). While GP zones and plate-shaped γ’ are metastable phases, continuously distributed in the matrix, formation of the equilibrium phase γ takes place at grain boundaries by discontinuous precipitation (DP). The crystal structure of both γ’ and γ is hep with the following orientation relationship with respect to the fee α matrix: {0001}γ′,γ // {111}α, <1120>γ′,γ, // <110>α.The mechanisms and kinetics of continuous matrix precipitation (CMP) in dilute Al-Ag alloys have been studied in considerable detail. The quantitative description of DP kinetics, however, has received less attention. The present contribution reports the microstructural evolution resulting from aging an Al-Ag alloy with Ag content higher than those previously reported in the literature, focusing the observations of γ' plate-shaped metastable precipitates.

WET BURNING – THE MODERN TREND IN ENVIRONMENTAL BENIGN FUEL COMBUSTION AND IN SOLUTION TO THE PROBLEM OF SUSTAINABLE DEVELOPMENT OF THE POWER GENERATION

2018 ◽  
pp. 96-117 ◽  
Author(s):  
B. S. Soroka
Keyword(s):  
Numerical Simulation ◽  
Nitrogen Oxides ◽  
Chemical Kinetics ◽  
Fuel Combustion ◽  
Transport Processes ◽  
Cfd Modeling ◽  
Furnace Chamber ◽  
Modern Trend ◽  
Atmospheric Air ◽  
No Formation

The article considers the role and place of water and water vapor in combustion processes with the purpose of reduction the effluents of nitrogen oxides and carbon oxide. We have carried out the complex of theoretical and computational researches on reduction of harmful nitrogen and carbon oxides by gas fuel combustion in dependence on humidity of atmospheric air by two approaches: CFD modeling with attraction of DRM 19 chemical kinetics mechanism of combustion for 19 components along with Bowman’s mechanism used as “postprocessor” to determine the [NO] concentration; different thermodynamic models of predicting the nitrogen oxides NO formation. The numerical simulation of the transport processes for momentum, mass and heat being solved simultaneously in the united equations’ system with the chemical kinetics equations in frame of GRI methane combustion mechanism and NO formation calculated afterwards as “postprocessor” allow calculating the absolute actual [CO] and [NO] concentrations in dependence on combustion operative conditions and on design of furnace facilities. Prediction in frame of thermodynamic equilibrium state for combustion products ensures only evaluation of the relative value of [NO] concentration by wet combustion the gas with humid air regarding that in case of dry air – oxidant. We have developed the methodology and have revealed the results of numerical simulation of impact of the relative humidity of atmospheric air on harmful gases formation. Range of relative air humidity under calculations of atmospheric air under impact on [NO] and [CO] concentrations at the furnace chamber exit makes φ = 0 – 100%. The results of CFD modeling have been verified both by author’s experimental data and due comparing with the trends stated in world literature. We have carried out the complex of the experimental investigations regarding atmospheric air humidification impact on flame structure and environmental characteristics at natural gas combustion with premixed flame formation in open air. The article also proposes the methodology for evaluation of the nitrogen oxides formation in dependence on moisture content of burning mixture. The results of measurements have been used for verification the calculation data. Coincidence of relative change the NO (NOx) yield due humidification the combustion air revealed by means of CFD prediction has confirmed the qualitative and the quantitative correspondence of physical and chemical kinetics mechanisms and the CFD modeling procedures with the processes to be studied. A sharp, more than an order of reduction in NO emissions and simultaneously approximately a two-fold decrease in the CO concentration during combustion of the methane-air mixture under conditions of humidification of the combustion air to a saturation state at a temperature of 325 K.

Verbi a supporto nel latino tardo: il caso di facio

2020 ◽  
Vol 59 (1-4) ◽  
pp. 145-160
Author(s):  
Giovanbattista Galdi
Keyword(s):  
Direct Object ◽  
Late Period ◽  
Present Contribution ◽  
Verbal Noun ◽  
Verb Constructions ◽  
History Of ◽  
Semantic Evolution

SummarySupport verb constructions are documented throughout the history of Latin. These syntagms are characterized by the presence of a support verb with a more or less reduced semantic force, and a predicative (abstract or verbal) noun that often constitutes its direct object. The present contribution deals, specifically, with the use of facio as a support verb (as in bellum facere, iter facere, insidias facere etc.), focussing on the post-classical and late period. Two main questions shall be discussed: (a) whether, and if so, how facio becomes more productive in later centuries in both non-Christian and Christian sources; (b) what type of semantic evolution the verb undergoes in later Latin and whether, in this respect, continuity or rupture should be assumed with regard to the earlier period. This last point will enable us to suggest a more convincing explanation of an often-quoted passage of Cicero (Phil. 3. 22), in which the expression contumeliam facere is found.

Relation of the Saccasa?khepa??k? Called S?ratthas?lin? to the Vinayavinicchaya??k? Called Vinayas?ratthasand?pan?

2018 ◽  
Vol 35 (1-2) ◽  
pp. 189-223
Author(s):  
Petra Kieffer-Pülz
Keyword(s):  
Thirteenth Century ◽  
Present Contribution ◽  
The Common ◽  
Literary Histories ◽  
High Degree ◽  
Parallel Texts

The present contribution suggests the common authorship of three P?li commentaries of the twelfth/thirteenth centuries CE, namely the Vinayavinicchaya??k? called Vinayas?ratthasand?pan? (less probably Vinayatthas?rasand?pan?), the Uttaravinicchaya??k? called L?natthappak?san?, and the Saccasa?khepa??k? called S?ratthas?lin?. The information collected from these three commentaries themselves and from P?li literary histories concerning these three texts leads to the second quarter of the thirteenth century CE as the period of their origination. The data from parallel texts explicitly stated to having been written by V?cissara Thera in the texts themselves render it possible to establish with a high degree of probability V?cissara Thera as their author.

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