Modeling of a Gallium Nitride Epitaxy Growth System

2004 ◽  
Author(s):  
D. Cai ◽  
B. Wu ◽  
L. L. Zheng ◽  
H. Zhang ◽  
W. J. Mecouch ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Gallium Nitride ◽  
Heterogeneous Reaction ◽  
Radiation Heat Transfer ◽  
Tubular Reactor ◽  
Nitride Layer ◽  
Operating Conditions ◽  
North Carolina State University ◽  
Design And Optimization

An iodine vapor phase epitaxy (IVPE) system has been designed and built at North Carolina State University to grow high quality thick gallium nitride layer at the growth rate up to 80 μm/h with the deposition temperature of 1010 °C and the pressure of 200 Torr. In order to optimize the growth process, a numerical model, which is capable of describing multi-component fluid flow, gas/surface chemistry, conjugate heat transfer, radiation heat transfer and multi-species transport, has been developed to help in design and optimization of the IVPE reactor. The gallium source weight reduce rate is converted into flow rate of gallium vapor and has been simulated as an inlet boundary condition of the tubular reactor. By matching predicted and experimental deposition rates, the heterogeneous reaction boundary condition is determined and applied to the substrate. Comprehensive two-dimensional computational simulations have been performed to study the temperature distribution, species mixing process and GaN deposition rate distribution on the substrate under different geometrical configurations and operating conditions; and the operating parameters have been optimized.

Simulation of Rapid Thermal Processing Equipment and Processes

1993 ◽  
Vol 303 ◽  
Author(s):  
Kun-Ho Lie ◽  
Tushar P. Merchant ◽  
Klavs F. Jensen
Keyword(s):  
Heat Transfer ◽  
Thermal Processing ◽  
Gas Flow ◽  
Transient Flow ◽  
Radiation Heat Transfer ◽  
Rapid Thermal Processing ◽  
Operating Conditions ◽  
Multiple Reflections ◽  
Design And Optimization ◽  
Process Gas

ABSTRACTWe present finite element simulations of fluid flow, heat transfer, and chemical reactions in axisymmetric rapid thermal processing (RTP) configurations. A new approach to simulating radiation heat transfer between lamps, substrates, and system walls is described. The method accounts for multiple reflections and readily allows the inclusion of temperature, radiation wavelength, and materials specific emissivity parameters. The influence of system geometry, lamp power profile, substrate and wall emissivity parameters, and process gas flow upon RTP performance characteristics is illustrated through examples. Transient flow and heat transfer simulations are used to identify operating conditions where flow recirculations are avoided. The further use of physically based models in the design and optimization of RTP systems is discussed.

Heat Transfer Modeling in a Counter-Current Moving-Bed Tubular Reactor for High-Temperature Thermochemical Energy Storage

2021 ◽  
Author(s):  
Wei Huang ◽  
Eric Million ◽  
Kelvin Randhir ◽  
Joerg Petrasch ◽  
James Klausner ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Tubular Reactor ◽  
Operating Conditions ◽  
Transfer Model ◽  
Reactor Performance ◽  
Low Oxygen ◽  
Moving Bed ◽  
Oxidation Reactor ◽  
Counter Current

Abstract An axisymmetric model coupling counter-current gas-solid flow, heat transfer, and thermochemical redox reactions in a moving-bed tubular reactor was developed. The counter-current flow enhances convective heat transfer and a low oxygen partial pressure environment is maintained for thermal reduction within the reaction zone by using oxygen depleted inlet gas. A similar concept can be used for the oxidation reactor which releases high-temperature heat that can be used for power generation or as process heat. The heat transfer model was validated with published results for packed bed reactors. After validation, the model was applied to simulate the moving-bed reactor performance, through which the effects of the main geometric parameters and operating conditions were studied to provide guidance for lab-scale reactor fabrication and testing.

Parametric height influence analysis on thermal radiation and convection applied to real ovens

2021 ◽  
pp. 095440892110375
Author(s):  
Sílvio Aparecido Verdério Júnior ◽  
Vicente Luiz Scalon ◽  
Santiago del Rio Oliveira ◽  
Elson Avallone ◽  
Paulo César Mioralli ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Numerical Models ◽  
Radiation Heat Transfer ◽  
Geometric Optimization ◽  
Operating Conditions ◽  
High Productivity ◽  
Order Of Magnitude ◽  
Lower Height ◽  
Heat Exchanges

Due to their greater flexibility in heating and high productivity, continuous tunnel-type ovens have become the best option for industrial processes. The geometric optimization of ovens to better take advantage of the heat transfer mechanisms by convection and thermal radiation is increasingly researched; with the search for designs that combine lower fuel consumption, greater efficiency and competitiveness, and lower costs. In this sense, this work studied the influence of height on heat exchanges by radiation and convection and other flow parameters to define the best geometric height for the real oven under study. From the dimensions and real operating conditions of continuous tunnel-type ovens were built five numerical models of parametric variation, which were simulated with the free and open-source software OpenFOAM®. The turbulent forced convection regime was characterized in all models. The use of greater heights in the ovens increased and intensified the recirculation regions, reduced the rates of heat transfer by thermal radiation, and reduced the losses of heat by convection. The order of magnitude of heat exchanges by radiation proved to be much higher than heat exchanges by convection, confirming the results of the main references in the technical-scientific literature. It was concluded that the use of ovens with a lower height provides significant increases in the thermal radiation heat transfer rates.

A CFD Assessment of Engine Core Zone Casing Heat Transfer

2019 ◽  
Author(s):  
Zixiang Sun ◽  
Nicholas J. Hills ◽  
Richard Scott
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Convection Heat Transfer ◽  
Aircraft Engine ◽  
Operating Conditions ◽  
Steady Flows ◽  
Radiation Heat ◽  
Core Zone ◽  
The Public ◽  
The Core

Abstract A systematic CFD investigation was conducted to assess the core zone (CZ) casing heat transfer of a large civil aircraft engine. Three key engine operating conditions, maximum takeoff (MTO), cruise (CRZ) and ground idle (GI) were analyzed. Steady flows were assumed. Turbulence was simulated using the realizable k-epsilon model in conjunction with the scalable wall function. Buoyancy effect was taken into account. Radiation was calculated using the discrete ordinate (DO) model. It was shown that the forced convection heat transfer dominates in most of the casing surface in the core zone, and radiation is of second importance in general. However, in some areas where both convection and radiation heat transfer are weak but the latter is relatively greater in magnitude than the former, radiation heat transfer could thus become dominant. In addition, the overall impact of radiation on casing heat transfer increases from MTO to CRZ and GI conditions, as the strength of engine load decreases. The overall effect of buoyancy on casing heat transfer is small, but could be noticeable in some local areas where flow velocity is low. The insight into heat transfer features on the engine core zone casing supported by quantified CFD evidences is the first in the public domain, as far as authors are aware.

Effect of Sub-Micron Thin Film on Surface Temperature During Chemical Vapor Deposition

2005 ◽  
Author(s):  
Wei Huang ◽  
Weixue Tian ◽  
Wilson K. S. Chiu
Keyword(s):  
Heat Transfer ◽  
Chemical Vapor Deposition ◽  
Optical Fiber ◽  
Vapor Deposition ◽  
Film Growth ◽  
Radiation Heat Transfer ◽  
Carbon Film ◽  
Chemical Vapor ◽  
Operating Conditions ◽  
Effective Emissivity

In this paper, we investigated the effect of the film thickness on heat transfer and subsequent film temperature distribution of an optical fiber as it traverses through a chemical vapor deposition (CVD) reactor. A 50 nm thick carbon coating is applied on the optical fiber as it moves through the CVD reactor. In this process, the only heat source is the hot optical fiber entering the CVD reactor from the draw furnace. Radiation heat transfer from the optical fiber as it is being coated plays an important role during CVD carbon film growth. The carbon film will change the effective emissivity of the optical fiber as it traverses through the CVD reactor. This study will calculate the effective emissivity of this film-fiber structure based on wave theory, and evaluate the optical fiber’s resulting temperature field and rate of heat transfer loss during chemical vapor deposition. Results are correlated to operating conditions.

Heat Transfer Analysis in a Blast Furnace Tuyere Nose

2005 ◽  
Author(s):  
David Roldan ◽  
Clifford Tetrault ◽  
Yongfu Zhao ◽  
Mark Atkinson ◽  
Chenn Q. Zhou
Keyword(s):  
Heat Transfer ◽  
Blast Furnace ◽  
Radiation Heat Transfer ◽  
Cooling Water ◽  
Chemical Reactor ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Large Area ◽  
Fuel Gas ◽  
Hot Air

The Blast furnace process is a counter current moving bed chemical reactor to reduce iron oxides to iron for iron/steel making. In the process, tuyeres are used to introduce hot air (blast) and fuel (gas or pulverized coal) into the furnace for combustion. The nose of a tuyere, composed of copper material, that is exposed to a high temperature environment and a cooling water pipe is embedded to prevent melting of the material. In this work, heat transfer and temperature distributions have been analyzed using the computational fluid dynamics commercial software, FLUENT®. The computations have included the cooling water flow and conjugate heat transfer in the tuyere nose. Both convection and radiation heat transfer on the surfaces are included. Different geometry and operating conditions were considered. The results have indicated that insufficient cooling in a large area between the nose inlet and outlet pipe can cause failures of the tuyere nose.

scholarly journals Numerical and experimental analysis for simulating fuel reactor in chemical looping combustor system

2020 ◽  
Vol 7 (3) ◽  
pp. 551-559 ◽  
Author(s):  
Tamer M. Ismail ◽  
Lu Ding ◽  
Khaled Ramzy ◽  
M. Abd El-Salam
Keyword(s):  
Heterogeneous Reaction ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Chemical Looping ◽  
Design And Optimization ◽  
Particle Combustion ◽  
Fuel Reactor ◽  
Power Direction ◽  
Particle Velocities ◽  
Capture Techniques

Abstract The greenhouse problem has a significant effect on our communities such as, health and climate. Carbon dioxide is one of the main gases that cause global warming. Therefore, CO2 capture techniques have been the focus of attention these days. The chemical looping combustion technique adopted the air reactor and fuel reactor to recycle heat energy. This study presents a numerical and experimental investigation on a fuel reactor in chemical looping combustor (CLC) system. The present numerical model is introduced by the kinetic theory of granular flow and coupled with gas–solid flow with chemical reactions to simulate the combustion of solids in the CLC. The k–ε turbulent model was used to model the gas phase and the particle phase. The developed model simplify the prediction of flow patterns, particle velocities, gas velocities, and composition profiles of gas products and the distribution of heterogeneous reaction rates under the same operating conditions. The predicted and experimental results were compared according to the basis of determination coefficient (R2). In addition the results showed that there is a good agreement between the predicted and experimental data. The value of (R2) for CO, CO2 and CH4 was 0.959, 0.925 and 0.969 respectively. This shows that the present model is a promising simulation for solid particle combustion and gives the power direction for the design and optimization of the CLC systems.

Experimental Study on the Effect of Low Acute Side Angles on Heat Transfer in Rhombic Shaped Microchannel

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Sunil K. Dwivedi ◽  
Sandip K. Saha
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Experimental Study ◽  
Heat Flux ◽  
Nusselt Number ◽  
Three Dimensional ◽  
Constant Heat Flux ◽  
Numerical Results ◽  
Transfer Model ◽  
Design And Optimization

This experimental study on rhombic shaped microchannels was conducted to understand the effect of a low acute side angle on the Nusselt number and compare the results with the published numerical results for H1 (axially constant heat flux and circumferentially constant temperature) and H2 (constant axial and circumferential wall heat flux) boundary conditions. The hydraulic and heat transfer characteristics of the rhombic geometry with a side angle of 30 deg for different mass flow rates and heat flux inputs are obtained using a three-dimensional (3D) conjugate heat transfer model, which is validated with the experimental results. It is found that the average Nusselt number obtained from the experimental and numerical results can be approximated closely with that computed using the H1 boundary condition. The local Nusselt number of hydrodynamically and thermally developed regions obtained from the numerical analysis is compared with a correlation for the H1 boundary condition. These results will be useful in design and optimization of a rhombic shaped microchannel for electronic cooling applications.

Investigation of Spectral Radiation Heat Transfer and NOx Emission in a Glass Furnace

2000 ◽  
Author(s):  
B. Golchert ◽  
C. Q. Zhou ◽  
S. L. Chang ◽  
M. Petrick
Keyword(s):  
Heat Transfer ◽  
Glass Furnace ◽  
Radiation Heat Transfer ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Transfer Model ◽  
Radiation Heat ◽  
Spectral Radiation ◽  
Radiation Emission ◽  
The Impact

Abstract A comprehensive radiation heat transfer model and a reduced NOx kinetics model were coupled with a computational fluid dynamics (CFD) code and then used to investigate the radiation heat transfer, pollutant formation and flow characteristics in a glass furnace. The radiation model solves the spectral radiative transport equation in the combustion space of emitting and absorbing media, i.e., CO2, H2O, and soot and emission/reflection from the furnace crown. The advanced numerical scheme for calculating the radiation heat transfer is extremely effective in conserving energy between radiation emission and absorption. A parametric study was conducted to investigate the impact of operating conditions on the furnace performance with emphasis on the investigation into the formation of NOx.

Effect of Dilute and Dense Phase Conditions on Bed-to-Wall Heat Transfer Mechanism in the Riser Column of a Circulating Fluidized Bed Combustor

2005 ◽  
Author(s):  
G. Nirmal Vijay ◽  
B. V. Reddy
Keyword(s):  
Heat Transfer ◽  
Circulating Fluidized Bed ◽  
Radiation Heat Transfer ◽  
Transfer Mechanism ◽  
Operating Conditions ◽  
Wall Heat Transfer ◽  
Heat Transfer Mechanism ◽  
Dense Phase ◽  
Radiation Heat ◽  
Bed Temperature

The bed-to-wall heat transfer in the riser column of a circulating fluidized bed (CFB) combustor depends on the contributions of particle convection, gas convection and radiation heat transfer. The percentage contribution of each of these components depends on the operating conditions i.e., dilute and dense phase bed conditions and bed temperature in the riser column. In the present paper, the contribution of particle convection, gas convection and radiation heat transfer components with operating conditions is estimated using the cluster renewal mechanistic model. The present results contribute some fundamental information on bed-to-wall heat transfer mechanism under dilute and dense phase conditions with bed temperature. The results will further aid for better understanding of heat transfer mechanism to water-wall surfaces in the upper region of the riser column.

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