Numerical Simulation of Operating Parameters in a Methane Fueled Steam Reforming Reactor

2011 ◽  
Vol 8 (5) ◽  
Author(s):  
Joonguen Park ◽  
Joongmyeon Bae
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Wall Temperature ◽  
Steam Reforming ◽  
Space Velocity ◽  
Operating Parameters ◽  
Inlet Temperature ◽  
Fuel Conversion ◽  
Numerical Work ◽  
Wgs Reaction

This paper studies the heat and mass transfer characteristics in a steam reforming reactor using numerical simulation and investigates the operating parameters for effective hydrogen production. Simultaneous analysis of governing equations and chemical reaction equations is carried out in a multiphysical simulation. The major reactions are assumed to be the steam reforming, water-gas shift (WGS), and direct steam reforming reactions. The temperature and species concentrations measured for the experiment are compared with numerical results. After validation of the developed code, numerical work is carried out to study correlations between the performance and operating parameters, which are the wall temperature, the inlet temperature, the steam to carbon ratio (SCR), and the gas hourly space velocity (GHSV). The fuel conversion increases with the high wall temperature due to the increased heat transfer. The inlet temperature may not affect the fuel conversion, if the reformer length is long enough. However, the heat transfer limitation can occur near the inlet when the inlet temperature is over 300 °C. The concentration of carbon monoxide becomes lower with increasing SCR due to the decreased WGS reaction rate. The high GHSV causes the short residence time and it is the reason for the low fuel conversion.

A Method of Solving Three Temperature Problem of Turbine With Adiabatic Wall Temperature

2021 ◽  
Author(s):  
Zeyu Wu ◽  
Xiang Luo ◽  
Jianqin Zhu ◽  
Zhe Zhang ◽  
Jiahua Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Wall Temperature ◽  
Reference Temperature ◽  
Inlet Temperature ◽  
Adiabatic Wall ◽  
Rotating Cavity ◽  
Temperature Problem ◽  
Turbulence Parameters

Abstract The aeroengine turbine cavity with pre-swirl structure makes the turbine component obtain better cooling effect, but the complex design of inlet and outlet makes it difficult to determine the heat transfer reference temperature of turbine disk. For the pre-swirl structure with two air intakes, the driving temperature difference of heat transfer between disk and cooling air cannot be determined either in theory or in test, which is usually called three-temperature problem. In this paper, the three-temperature problem of a rotating cavity with two cross inlets are studied by means of experiment and numerical simulation. By substituting the adiabatic wall temperature for the inlet temperature and summarizing its variation law, the problem of selecting the reference temperature of the multi-inlet cavity can be solved. The results show that the distribution of the adiabatic wall temperature is divided into the high jet area and the low inflow area, which are mainly affected by the turbulence parameters λT, the rotating Reynolds number Reω, the high inlet temperature Tf,H* and the low radius inlet temperature Tf,L* of the inflow, while the partition position rd can be considered only related to the turbulence parameters λT and the rotating Reynolds number Reω of the inflow. In this paper, based on the analysis of the numerical simulation results, the calculation formulas of the partition position rd and the adiabatic wall temperature distribution are obtained. The results show that the method of experiment combined with adiabatic wall temperature zone simulation can effectively solve the three-temperature problem of rotating cavity.

Numerical Analysis of the Heat and Mass Transfer Characteristics in an Autothermal Methane Reformer

2010 ◽  
Vol 7 (5) ◽  
Author(s):  
Joonguen Park ◽  
Shinku Lee ◽  
Sunyoung Kim ◽  
Joongmyeon Bae
Keyword(s):  
Mass Transfer ◽  
Numerical Analysis ◽  
Heat And Mass Transfer ◽  
Steam Reforming ◽  
Space Velocity ◽  
Reaction Model ◽  
Operating Conditions ◽  
Local Thermal Equilibrium ◽  
Inlet Temperature ◽  
Transfer Characteristics

This paper discusses a numerical analysis of the heat and mass transfer characteristics in an autothermal methane reformer. Assuming local thermal equilibrium between the bulk gas and the surface of the catalyst, a one-medium approach for the porous medium analysis was incorporated. Also, the mass transfer between the bulk gas and the catalyst’s surface was neglected due to the relatively low gas velocity. For the catalytic surface reaction, the Langmuir–Hinshelwood model was incorporated in which methane (CH4) is reformed to hydrogen-rich gases by the autothermal reforming (ATR) reaction. Full combustion, steam reforming, water-gas shift, and direct steam reforming reactions were included in the chemical reaction model. Mass, momentum, energy, and species balance equations were simultaneously calculated with the chemical reactions for the multiphysics analysis. By varying the four operating conditions (inlet temperature, oxygen to carbon ratio (OCR), steam to carbon ratio, and gas hourly space velocity (GHSV)), the performance of the ATR reactor was estimated by the numerical calculations. The SR reaction rate was improved by an increased inlet temperature. The reforming efficiency and the fuel conversion reached their maximum values at an OCR of 0.7. When the GHSV was increased, the reforming efficiency increased but the large pressure drop may decrease the system efficiency. From these results, we can estimate the optimal operating conditions for the production of large amounts of hydrogen from methane.

Numerical Simulation Of A Microchannel For Microelectronic Cooling

2012 ◽  
Author(s):  
Wai Hing Wong ◽  
Normah Mohd. Ghazali
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Large Temperature ◽  
Rectangular Microchannel ◽  
Numerical Work ◽  
Solid Region ◽  
Wall Interaction

Kertas kerja ini membincangkan simulasi berangka ke atas sinki haba saluran mikro dalam penyejukan alatan mikroelektronik. Model Dinamik Bendalir Berkomputer (CFD) tiga dimensi dibina menggunakan pakej komersil, FLUENT, untuk mengkaji fenomenon aliran bendalir dan pemindahan haba konjugat di dalam suatu sinki haba segi empat yang diperbuat daripada silikon. Model ditentusahkan dengan keputusan daripada uji kaji dan pengkajian berangka yang lepas untuk lingkungan nombor Reynolds kurang daripada 400 berdasarkan diameter hidraulik 86 mm. Kajian ini mengambil kira kesan kelikatan bendalir yang bersandaran dengan suhu dan keadaan aliran pra–membangun dari segi hidrodinamik dan haba. Model memberi maklumat tentang taburan suhu dan fluks haba yang terperinci di dalam sinki haba saluran mikro. Kecerunan suhu yang tinggi dicatat pada kawasan pepejal berdekatan dengan sumber. Fluks haba paling tinggi didapati pada dinding tepi saluran mikro diikuti oleh dinding atas dan bawah. Purata pekali pemindahan haba yang lebih tinggi bagi silikon menjadikan ia bahan binaan sinki haba saluran mikro yang lebih baik berbanding dengan kuprum dan aluminium. Peningkatan nisbah aspek saluran mikro yang bersegi empat memberi kecekapan penyejukan yang lebih tinggi kerana kelebaran saluran yang berkurangan memberi kecerunan halaju yang lebih tinggi dalam saluran. Nisbah aspek yang optimum yang diperoleh adalah dalam lingkungan 3.7 – 4.1. Kata kunci: Saluran mikro, CFD, FLUENT, simulasi berangka, penyejukan mikroelektron The paper discusses the numerical simulation of a micro–channel heat sink in microelectronics cooling. A three–dimensional Computational Fluid Dynamics (CFD) model was built using the commercial package, FLUENT, to investigate the conjugate fluid flow and heat transfer phenomena in a silicon–based rectangular microchannel heatsink. The model was validated with past experimental and numerical work for Reynolds numbers less than 400 based on a hydraulic diameter of 86 mm. The investigation was conducted with consideration of temperaturedependent viscosity and developing flow, both hydrodynamically and thermally. The model provided detailed temperature and heat flux distributions in the microchannel heatsink. The results indicate a large temperature gradient in the solid region near the heat source. The highest heat flux is found at the side walls of the microchannel, followed by top wall and bottom wall due to the wall interaction effects. Silicon is proven to be a better microchannel heatsink material compared to copper and aluminum, indicated by a higher average heat transfer. A higher aspect ratio in a rectangular microchannel gives higher cooling capability due to high velocity gradient around the channel when channel width decreases. Optimum aspect ratio obtained is in the range of 3.7 – 4.1. Key words: Microchannel, CFD, FLUENT, numerical simulation, microeletronics cooling

scholarly journals The numerical simulation of enhanced heat transfer on a Linear Fresnel molten salt-type receiver tube filled with porous media

2019 ◽  
Vol 118 ◽  
pp. 01041
Author(s):  
Chenggang Yang ◽  
Yuning Zhang ◽  
Fenghe Yan ◽  
Wenguang Zhang ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Porous Media ◽  
Molten Salt ◽  
Temperature Difference ◽  
Wall Temperature ◽  
Three Dimensional ◽  
Heat Transfer Fluid ◽  
Filling Rate

In this paper, three-dimensional numerical simulation was taken on a Linear Fresnel solar receiver tube using molten salt as heat transfer fluid (HTF), in which the porous media was filled to enhance the heat transfer efficiency. The simulation was to analyze the influence of the different conditions (filling rate, porosity and thermal conductivity) on heat transfer effect and wall temperature difference. The results revealed that the Nu (Nusselt number) increased firstly and then decreased with the increasing filling rate in both center filling and annular filling types. The optimal thermal performance were obtained when filling rate were 0.8 and 0.2 in center filling and annular filling, respectively. The Nu were about 1.7 and 1.5 times as the clear receiver. The circumferential temperature difference decreased firstly and then increased with filling rate increasing in both center filling and annular filling types. The lowest circumferential temperature differences were achieved at the filling rate 0.8 and 0.4 in center filling and annular filling types, and temperature difference decreased 15.88°C and 22°C compared with clear receiver, respectively. The Nu and PEC both decreased with porosity increasing. However, the thermal conductivity of porous media had little influence to the Nu and circumferential wall temperature.

Optimization of Operating Parameters of Liquid-Liquid Circulation Fluidized Bed for Ice-Making Based on Exergy Method

2011 ◽  
Vol 236-238 ◽  
pp. 600-603
Author(s):  
Kun Feng Liang ◽  
Chun Yan Gao ◽  
Lin Wang
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Droplet Diameter ◽  
Storage System ◽  
Second Law Of Thermodynamics ◽  
Operating Parameters ◽  
Inlet Temperature ◽  
Contact Heat ◽  
Novel Method

A novel method of dynamic ice forming, liquid-liquid circulating fluidized bed, was studied using direct contact heat transfer between drops and the coolant for ice storage system. In order to model multiphase flows and heat transfer in circulating fluidized bed, a numerical model was developed. Exergy discharge was discussed for liquid-liquid circulating fluidized bed based on the second law of thermodynamics. Numerical method was used to study the influence of operating parameters, such as the droplet diameter and the inlet temperature or velocity average of liquid phase, on the ice-making performance and total exergy discharge in the dynamic ice-making process.

The Numerical Simulation Research on Heat Exchanging Enhancement and Structural Optimization of the Flue Gas Heat Transfer of Mixed Arrangement Irregular Heat-Pipe

2013 ◽  
Vol 781-784 ◽  
pp. 2770-2774
Author(s):  
De Fan Qing ◽  
Deng Qiang Yan
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Pipe ◽  
Flue Gas ◽  
Simulation Method ◽  
Inlet Temperature ◽  
Equivalent Diameter ◽  
The Third ◽  
Heat Transfer Efficiency ◽  
Line Spacing

The mixed arrangement irregular heat-pipe flue gas heat transfer was researched, using numerical simulation method. The irregular heat-pipe: triangle heat pipe; square heat pipe. The heat pipe equivalent diameter of flue gas heat transfer is 20 mm, the speed of inlet flue gas is 11 m/s, the inlet temperature of flue gas is 500 K. the results show mixed arrangement irregular heat-pipe can enhance heat exchanging, the optimal parameters of mixed arrangement structure in the condition of given working condition: the first row is triangle heat pipe, the second row is circular heat pipe, the third row is triangle heat pipe, row 4 is square heat pipe, the line spacing of the first row and second is 40 mm, the line spacing of the second and third row is 40 mm, the line spacing of the third row and the fourth row is 35 mm, and the row spacing of the tube is 40 mm. the heat transfer efficiency of the optimized irregular heat-pipe-exchanger raised 40 ~ 60%.

Uncertainty Analysis of Heat Transfer Predictions Using Statistically Modeled Data From a Cooled 1-1/2 Stage High-Pressure Transonic Turbine

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Harika S. Kahveci ◽  
Kevin R. Kirtley
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
High Pressure ◽  
Wall Temperature ◽  
Temperature Measurements ◽  
Navier Stokes ◽  
Inlet Temperature ◽  
Statistical Representation ◽  
Computational Fluid Dynamics Analysis ◽  
Transonic Turbine

This paper compares predictions from a 3D Reynolds-averaged Navier–Stokes code and a statistical representation of measurements from a cooled 1-1/2 stage high-pressure transonic turbine to quantify predictive process sensitivity. A multivariable regression technique was applied to both the inlet temperature measurements obtained at the inlet rake, the wall temperature, and heat transfer measurements obtained via heat-flux gauges on the blade airfoil surfaces. By using the statistically modeled temperature profiles to generate the inlet boundary conditions for the computational fluid dynamics analysis, the sensitivity of blade heat transfer predictions due to the variation in the inlet temperature profile and uncertainty in wall temperature measurements and surface roughness is calculated. All predictions are performed with and without cooling. Heat transfer predictions match reasonably well with the statistical representation of the data, both with and without cooling. Predictive precision for this study is driven primarily by inlet profile uncertainty followed by surface roughness and gauge position uncertainty.

Numerical Simulation and Experimental Analysis of Laser Surface Remelting of AISI 304 Stainless Steel Samples

2010 ◽  
Vol 636-637 ◽  
pp. 1119-1124
Author(s):  
Noé Cheung ◽  
M.A. Larosa ◽  
Wislei R.R. Osório ◽  
M.S.F Lima ◽  
Maria Clara F. Lerardi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Stainless Steel ◽  
Laser Surface ◽  
Temperature Fields ◽  
304 Stainless Steel ◽  
Operating Parameters ◽  
Aisi 304 ◽  
Laser Surface Remelting ◽  
304 Austenitic Stainless Steel

The aim of this work is to develop a heat transfer mathematical model based on the finite difference method in order to simulate temperature fields in the laser surface remelting process. Convective heat transfer in the remelted pool is taken into account by using the effective thermal conductivity approach. Experiments of laser surface remelting of AISI 304 austenitic stainless steel samples were carried out in the present investigation, and numerical simulations were applied for the CO2 laser machine operating parameters. The work also encompasses the analysis of microstructural and microhardness variations throughout the resulting treated and unmolten zones. This study permits to conclude that numerical simulation is a useful tool in setting the laser operating parameters, enabling pre-programming of the extent of the treated area.

scholarly journals Numerical Investigation on Supercritical Heat Transfer of RP3 Kerosene Flowing inside a Cooling Channel of Scramjet

2014 ◽  
Vol 6 ◽  
pp. 213438 ◽  
Author(s):  
Ning Wang ◽  
Yu Pan ◽  
Heng Bao ◽  
Jin Zhou
Keyword(s):  
Heat Transfer ◽  
Specific Heat ◽  
Wall Temperature ◽  
Numerical Study ◽  
Hydrocarbon Fuel ◽  
Inlet Temperature ◽  
Good Prediction ◽  
Cooling Channels ◽  
Commercial Code ◽  
Cooling Technology

Supercritical convective heat transfer characteristics of hydrocarbon fuel play a fundamental role in the active cooling technology of scramjet. In this paper, a 2D-axisymmetric numerical study of supercritical heat transfer of RP3 flowing inside the cooling channels of scramjet has been conducted. The main thermophysical properties of RP3, including density, specific heat, and thermal conductivity, are obtained from experimental data, while viscosity is evaluated from a commercial code with a ten-species surrogate. Effects of heat flux, mass flow rate, and inlet temperature on supercritical heat transfer processes have been investigated. Results indicate that when the wall temperature rises above the pseudocritical temperature of RP3, heat transfer coefficient decreases as a result of drastic decrease of the specific heat. The conventional heat transfer correlations, that is, Gnielinski formula, are no longer proper for the supercritical heat transfer of RP3. The modified Jackson and Hall formula, which was proposed for supercritical CO2 and water, gives good prediction except when the wall temperature is near or higher than the pseudocritical temperature.

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