Flow Structure and Heat Transfer in Stagnation Flow CVD Reactor

2010 ◽  
Author(s):  
Nasir Memon ◽  
Yogesh Jaluria
Keyword(s):  
Heat Transfer ◽  
Flow Structure ◽  
Atmospheric Pressure ◽  
Gas Flow ◽  
Flow Reactor ◽  
Chemical Vapor ◽  
Design Parameters ◽  
Stagnation Flow ◽  
Inlet Length ◽  
The Impact

An experimental study is undertaken to investigate the flow structure and heat transfer in a stagnation flow Chemical Vapor Deposition (CVD) reactor at atmospheric pressure. It is critical to develop models that predict flow patterns in such a reactor to achieve uniform deposition across the substrate. Free convection can negatively affect the gas flow as cold inlet gas impinges on the heated substrate, leading to vortices and disturbances in the normal flow path. This experimental research will be used to understand the buoyancy-induced and momentum-driven flow structure encountered in an impinging jet CVD reactor. Investigations are conducted for various operating and design parameters. A modified stagnation flow reactor is built where the height between the inlet and substrate is reduced when compared to a prototypical stagnation flow reactor. By operating such a reactor at certain Reynolds and Grashof numbers it is feasible to sustain smooth and vortex free flow at atmospheric pressure. The modified stagnation flow reactor is compared to other stagnation flow geometries with either a varied inlet length or varied heights between the inlet and substrate. Comparisons are made to understand the impact of such geometric changes on the flow structure and the thermal boundary layer. In addition, heat transfer correlations are obtained for the substrate temperature. Overall, the results obtained provide guidelines for curbing the effects of buoyancy and for improving the flow field to obtain greater film uniformity when operating a stagnation flow CVD reactor at atmospheric pressure.

Flow Structure and Heat Transfer in a Stagnation Flow CVD Reactor

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Nasir Memon ◽  
Yogesh Jaluria
Keyword(s):  
Heat Transfer ◽  
Flow Structure ◽  
Atmospheric Pressure ◽  
Gas Flow ◽  
Flow Reactor ◽  
Chemical Vapor ◽  
Design Parameters ◽  
Stagnation Flow ◽  
Inlet Length ◽  
The Impact

An experimental study is undertaken to investigate the flow structure and heat transfer in a stagnation flow chemical vapor deposition (CVD) reactor at atmospheric pressure. It is critical to develop models that predict flow patterns in such a reactor to achieve uniform deposition across the substrate. Free convection can negatively affect the gas flow as cold inlet gas impinges on the heated substrate, leading to vortices and disturbances in the normal flow path. This experimental research will be used to understand the buoyancy-induced and momentum driven flow structure encountered in an impinging jet CVD reactor. Investigations are conducted for various operating and design parameters. A modified stagnation flow reactor is built where the height between the inlet and substrate is reduced when compared with a prototypical stagnation flow reactor. By operating such a reactor at certain Reynolds and Grashof numbers, it is feasible to sustain smooth and vortex free flow at atmospheric pressure. The modified stagnation flow reactor is compared with other stagnation flow geometries with either a varied inlet length or varied heights between the inlet and substrate. Comparisons are made to understand the impact of such geometric changes on the flow structure and the thermal boundary layer. In addition, heat transfer correlations are obtained for the substrate temperature. Overall, the results obtained provide guidelines for curbing the effects of buoyancy and for improving the flow field to obtain greater film uniformity when operating a stagnation flow CVD reactor at atmospheric pressure.

Hydrogen Concentration Analysis in Pecvd and Rtcvd Silicon Nitride Thin Films and It's Impact on Device Performance

2001 ◽  
Vol 664 ◽  
Author(s):  
C. Y. Wang ◽  
E. H. Lim ◽  
H. Liu ◽  
J. L. Sudijono ◽  
T. C. Ang ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Threshold Voltage ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Gate Oxide ◽  
Nitride Film ◽  
Device Performance ◽  
Gas Flow Ratio ◽  
The Impact

ABSTRACTIn this paper the impact of the ESL (Etch Stop layer) nitride on the device performance especially the threshold voltage (Vt) has been studied. From SIMS analysis, it is found that different nitride gives different H concentration, [H] in the Gate oxide area, the higher [H] in the nitride film, the higher H in the Gate Oxide area and the lower the threshold voltage. It is also found that using TiSi instead of CoSi can help to stop the H from diffusing into Gate Oxide/channel area, resulting in a smaller threshold voltage drift for the device employed TiSi. Study to control the [H] in the nitride film is also carried out. In this paper, RBS, HFS and FTIR are used to analyze the composition changes of the SiN films prepared using Plasma enhanced Chemical Vapor deposition (PECVD), Rapid Thermal Chemical Vapor Deposition (RTCVD) with different process parameters. Gas flow ratio, RF power and temperature are found to be the key factors that affect the composition and the H concentration in the film. It is found that the nearer the SiN composition to stoichiometric Si3N4, the lower the [H] in SiN film because there is no excess silicon or nitrogen to be bonded with H. However the lowest [H] in the SiN film is limited by temperature. The higher the process temperature the lower the [H] can be obtained in the SiN film and the nearer the composition to stoichiometric Si3N4.

Heat Transfer in Chemical Vapor Deposited Optical Fiber Coatings

2001 ◽  
Author(s):  
Patricia O. Iwanik ◽  
Wilson K. S. Chiu
Keyword(s):  
Heat Transfer ◽  
Optical Fiber ◽  
Gas Flow ◽  
Convection Heat Transfer ◽  
Fiber Surface ◽  
Chemical Vapor ◽  
Temperature Changes ◽  
Flow And Heat Transfer ◽  
Chemical Vapor Deposited ◽  
Fiber Coatings

Abstract A fundamental understanding of how reactor parameters influence the fiber surface temperature is essential to manufacturing high quality optical fiber coatings by chemical vapor deposition (CVD). In an attempt to better understand this process, a finite volume model has been developed to study the gas flow and heat transfer of an optical fiber as it travels through a CVD reactor. This study showed that draw speed significantly affects fiber temperature inside the reactor, with temperature changes up to 45% observed under the conditions studied. Multiple heat transfer modes contribute to this phenomena, with convection heat transfer dominating the process.

Numerical Investigation of the Effect of Diffuser and Volute Design Parameters on the Performance of a Centrifugal Compressor Stage

2016 ◽  
Author(s):  
Lei Yu ◽  
William T. Cousins ◽  
Feng Shen ◽  
Georgi Kalitzin ◽  
Vishnu Sishtla ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Gas Flow ◽  
Pressure Rise ◽  
Design Parameters ◽  
Compressor Stage ◽  
Flow Distortion ◽  
Cross Sectional ◽  
Centrifugal Stage ◽  
And Performance ◽  
The Impact

In this effort, 3D CFD simulations are carried out for real gas flow in a refrigeration centrifugal compressor. Both commercial and the in-house CFD codes are used for steady and unsteady simulations, respectively. The impact on the compressor performance with various volute designs and diffuser modifications are investigated with steady simulations and the analysis is focused on both the diffuser and the volute loss, in addition to the flow distortion at impeller exit. The influence of the tongue, scroll diffusion ratio, diffuser length, and cross sectional area distribution is examined to determine the impact on size and performance. The comparisons of total pressure loss, static pressure recovery, through flow velocity, and the secondary flow patterns for different volute designs show that the performance of the centrifugal compressor depends upon how well the scroll portion of the volute collects the flow from the impeller and achieves the required pressure rise with minimum flow losses in the overall diffusion process. Finally, the best design is selected based on compressor stage pressure rise and peak efficiency improvement. An unsteady simulation of the full wheel compressor stage was carried out to further examine the interaction of impeller, diffuser and the volute. The unsteady flow interactions are shown to have a major impact on the performance of the centrifugal stage.

scholarly journals Investigation of aerodynamics and heat transfer of the modular jet recuperator

2021 ◽  
Vol 2039 (1) ◽  
pp. 012001
Author(s):  
P D Alekseev ◽  
Yu L Leukhin
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Annular Channel ◽  
Secondary Flows ◽  
Cocurrent Flow ◽  
Outlet Section ◽  
Entire Cross Section ◽  
Staggered Arrangement ◽  
Perforated Pipe ◽  
The Impact

Abstract A study of the aerodynamics and heat transfer of a jet modular recuperator with a change in its geometric characteristics has been carried out. The influence of the in-line and staggered arrangement of the blowing holes, as well as the diameter of the perforated pipe is considered. In all considered variants, the number of holes, their diameter and gas flow rate through the recuperator remained unchanged. Numerical modeling of the problem was carried out in a three-dimensional setting using the ANSYS Fluent 15.0 software package. It was found that with the in-line arrangement of the blowing holes, secondary flows are formed between their longitudinal rows in the form of swirling jets of opposite rotation directed towards the outlet section of the recuperative device, through which the main part of the heated air flows out. With the staggered arrangement of the blowing holes, the formation of spiral vortices is disturbed, the air flow is carried out along the entire cross section of the annular channel, increasing the drift effect of the flow on the impact jets, which leads to a decrease in the intensity of heat transfer and its uniformity along the length of the working surface. An increase in the diameter of the inner perforated pipe leads to a decrease in the drift effect of the cocurrent flow on the jets, an increase in the distribution uniformity of the heat flux along the length of the heat transfer surface, and an increase in the heat transfer coefficient.

Thermodynamic Analysis of Latent Heat Storage in a Shell-and-Tube Heat Exchanger

1992 ◽  
Vol 114 (2) ◽  
pp. 93-99 ◽  
Author(s):  
Ch. Charach ◽  
A. Zemel
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Entropy Generation ◽  
Gas Flow ◽  
Heat Storage ◽  
Cylindrical Tube ◽  
Design Parameters ◽  
Storage Process ◽  
Latent Heat Storage ◽  
Tube Heat Exchanger

This work addresses the entropy generation aspects of a latent heat storage in which the energy delivered by a hot gas flowing through a cylindrical tube induces melting of the material surrounding the tube. The heat transfer for conduction-dominated melting is analyzed, taking into account the two-dimensional effects. The storage process irreversibilities associated with both the gas flow and the heat transfer (including entropy generation in the melted layer) are considered. The number of entropy generation units, which is a measure of the thermodynamic imperfection of the energy storage process, is expressed as a function of the main design parameters of the system. Analytic bounds and simplified asymptotic expressions for this quantity are derived. The results are compared with earlier one-dimensional studies.

Influence of the Time-Temperatur-Profile on Powder Characteristics of Nanocrystalline Anatase (TiO2) produced by Chemical Vapor Synthesis

2007 ◽  
Vol 1056 ◽  
Author(s):  
Ruzica Djenadic ◽  
Sankhanilay Roy Chowdhury ◽  
Marina Spasova ◽  
Andreas Gondorf ◽  
Erdal Akyildiz ◽  
...  
Keyword(s):  
Gas Flow ◽  
Flow Reactor ◽  
Chemical Vapor ◽  
Titanium Isopropoxide ◽  
Degree Of Crystallinity ◽  
Chemical Vapor Synthesis ◽  
Nanocrystalline Particles ◽  
Powder Characteristics ◽  
Gas Flow Reactor ◽  
Nanocrystalline Anatase Tio2

ABSTRACTChemical Vapor Synthesis (CVS) is the conversion of molecular species into nanocrystalline particles by chemical reactions in a gas flow reactor. Pure anatase nanoparticles are generated in a hot wall reactor from titanium isopropoxide using different time-temperature-profiles. The time-temperature-profile (T(t)-profile) in the gas phase of the reactor has a profound influence on the particle characteristics such as particle microstructure and surface chemistry and, therefore, on the quality of the powder consisting of nanocrystalline particles. In this study a simple reaction-coagulation-sintering model (CVSSIN) was used to predict influence of the T(t)-profile on the powder characteristics. The as-synthesized anatase powders show a very high degree of crystallinity, primary particle of about 10 nm sizes and a low degree of agglomeration.

scholarly journals Experimental research of incipient turbulent flow frequency spectra in hydrodynamic unsteadiness

2021 ◽  
Vol 13 (2) ◽  
pp. 91-102
Author(s):  
Viacheslav KRAEV
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Flow Structure ◽  
Experimental Research ◽  
Gas Flow ◽  
Frequency Spectra ◽  
Flow Acceleration ◽  
Aerospace Systems ◽  
Acceleration And Deceleration ◽  
Unsteady Conditions

Hydraulic and heat transfer processes play a very important role in the design and prototyping of aerospace technology. Unsteady conditions are the peculiarity of mostly aerospace systems. Flow acceleration and deceleration may significantly affect the heat transfer and hydrodynamic process in channels of aerospace systems. For unsteady process modeling, a fundamental research of unsteady hydrodynamic turbulent flow structure., Moscow Aviation Institute National Research University (MAI) has been building unsteady turbulent flow structures since 1989. An experimental facility was designed to provide gas flow acceleration and deceleration. Experimental data of a turbulent gas flow structure during flow acceleration and flow deceleration are presented. The frequency spectra of axial and radial velocity pulsations are based on experimental data. The results of experimental turbulent flow research demonstrate the fundamental hydrodynamic unsteadiness influence on the flow structure. The main results of the flow acceleration and deceleration experimental research show that there are tangible differences from the steady flow structure. The analysis of unsteady conditions influence on the turbulent pulsations generation and development mechanisms is presented. The results show the unsteady conditions influence onto turbulent vortexes disintegration tempo. The present paper describes a method of experimental research, methodology of data processing and turbulent accelerated and decelerated flow spectra results.

scholarly journals Modeling the conjugate problem of heat transfer at hot jet impingement onto a cooled surface

2021 ◽  
Vol 2119 (1) ◽  
pp. 012157
Author(s):  
V V Lukashov ◽  
V S Naumkin
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Flat Plate ◽  
Gas Flow ◽  
Jet Impingement ◽  
Conjugate Problem ◽  
Heat Fluxes ◽  
The Other ◽  
Local Maxima ◽  
The Impact

Abstract The paper solves the problem of thermal conductivity inside a flat plate under the impact of a hot jet of nitrogen impinging from one side and cooled by a gas flow from the other side. In this formulation of the problem, there may be local maxima and minima of the temperature inside the plate, caused by an uneven distribution of heat fluxes along the plate.

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