Methanol Steam Reforming in a Spiral-Shaped Microchannel Reactor over Cu/ZnO/Al2O3 Catalyst: A Computational Fluid Dynamics Simulation Study

2017 ◽  
Vol 15 (4) ◽  
Author(s):  
Meisam heidarzadeh ◽  
Majid Taghizadeh
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Carbon Monoxide ◽  
Steam Reforming ◽  
Cfd Simulation ◽  
Dynamics Simulation ◽  
Methanol Steam Reforming ◽  
Microchannel Reactor ◽  
Flow Rates ◽  
Shift Reaction

Abstract Hydrogen production in microchannel reactor by reforming reaction is applied for fuel cells in order to effectively avoid the problem of hydrogen storage. In this study, the Computational Fluid Dynamics (CFD) simulation of methanol steam reforming process was studied for the purpose of producing hydrogen in an annular microchannel coated with Cu/ZnO/Al2O3 catalyst. The modeling mechanism included methanol reforming reaction, methanol decomposition, and water-gas shift reaction. Furthermore, the effects of temperature variations were investigated and the conducted surveys were compared with the experimental results. The simulation results were in good agreement with the experimental data in that the temperature increases at various feed flow rates would lead to enhanced amounts of carbon monoxide and dioxide, while at a constant temperature, the amounts of hydrogen and carbon monoxide and dioxide reduce with increasing feed flow rates.

Design Approach for the Development of the Flow Field of Bipolar Plates for a PEMFC Stack Prototype

2014 ◽  
Vol 11 (6) ◽  
Author(s):  
Paolo Sala ◽  
Paola Gallo Stampino ◽  
Giovanni Dotelli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fuel Cell ◽  
Cfd Simulation ◽  
Bipolar Plates ◽  
Flow Rates ◽  
Gas Leakage ◽  
Auxiliary Power ◽  
Computational Fluid Dynamics Cfd ◽  
Enhance Mass

This work is part of a project whose final aim is the realization of an auxiliary power fuel cell generator. It was necessary to design and develop bipolar plates that would be suitable for this application. Bipolar plates have a relevant influence on the final performances of the entire device. A gas leakage or a bad management of the water produced during the reaction could be determinant during operations and would cause the failure of the stack. The development of the bipolar plates was performed in different steps. First, the necessity to make an esteem of the dynamics that happen inside the feeding channels led to perform analytical calculations. The values found were cross-checked performing a computational fluid dynamics (CFD) simulation; finally, it was defined the best pattern for the feeding channels, so that to enhance mass transport and achieve the best velocity profile. The bipolar plates designed were machined and assembled in a laboratory scale two cells prototype stack. Influences of the temperature and of the humidity were evaluated performing experiments at 60 deg and 70 deg and between 60% and 100% of humidity of the reactant gasses. The best operating point achieved in one of these conditions was improved by modifying the flow rates of the reactant, in order to obtain the highest output power, and it evaluated the reliability of the plates in experiments performed for longer times, at fixed voltages.

Particle Image Velocimetry Experiment and Computational Fluid Dynamics Simulation of Flow Around Rigid Cylinder

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Guangyao Wang ◽  
Ye Tian ◽  
Spyros A. Kinnas
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Image Velocimetry ◽  
Vector Fields ◽  
Particle Image ◽  
Cfd Simulation ◽  
Dynamics Simulation ◽  
Reynolds Stresses ◽  
Rigid Cylinder ◽  
Image Velocimetry

This work focuses on the study of the flow around a rigid cylinder with both particle image velocimetry (PIV) experiment and computational fluid dynamics (CFD) simulation. PIV measurements of the flow field downstream of the cylinder are first presented. The boundary conditions for CFD simulations are measured in the PIV experiment. Then the PIV flow is compared with both Reynolds-averaged Navier–Stokes (RANS) two-dimensional (2D) and large eddy simulation (LES) three-dimensional (3D) simulations performed with ANSYS fluent. The velocity vector fields and time histories of velocity are analyzed. In addition, the time-averaged velocity profiles and Reynolds stresses are analyzed. It is found that, in general, LES (3D) gives a better prediction of flow characteristics than RANS (2D).

Computational Fluid Dynamics Simulation of the Right Coronary Artery Moving With the Cardiac Wall

2002 ◽  
Author(s):  
H. Hayashi ◽  
T. Yamaguchi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Coronary Artery ◽  
Right Coronary Artery ◽  
Cfd Simulation ◽  
Dynamics Simulation ◽  
Cardiac Wall ◽  
Computational Fluid Dynamics Cfd ◽  
The Right ◽  
Heart Wall

The beating motion of the heart wall, to which the major coronary arteries are fixed, is interesting, due to its possible mechanical influence on the flow inside the artery, and hence its effect on atherogenesis [1–2]. In this study, we conducted a computational fluid dynamics (CFD) simulation using a simplified model of the right coronary artery, which deforms with heart contractions. The results are discussed with respect to the local hemodynamics characteristics, particularly the streamline pattern and the wall shear stress distribution.

Application of Computational Fluid Dynamics Simulation to Squeeze Film Damper Analysis

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Gil Jun Lee ◽  
Jay Kim ◽  
Tod Steen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Cfd Simulation ◽  
Design Guidelines ◽  
Dynamics Simulation ◽  
Squeeze Film ◽  
Computational Time ◽  
Small Clearance ◽  
Computational Fluid Dynamics Cfd

Squeeze film dampers (SFDs) are used in high-speed turbomachinery to provide external damping to the system. Computational fluid dynamics (CFD) simulation is a highly effective tool to predict the performance of SFDs and obtain design guidance. It is shown that a moving reference frame (MRF) can be adopted for CFD simulation, which saves computational time significantly. MRF-based CFD analysis is validated, then utilized to design oil plenums of SFDs. Effects of the piston ring clearances, the oil groove, and oil supply ports are studied based on CFD and theoretical solutions. It is shown that oil plenum geometries can significantly affect the performance of the SFD especially when the SFD has a small clearance. The equivalent clearance is proposed as a new concept that enables quick estimation of the effect of oil plenum geometries on the SFD performance. Some design practices that have been adopted in industry are revisited to check their validity. Based on simulation results, a set of general design guidelines is proposed.

Validation of the free area method for modelling fabric air dispersion system without orifices in computational fluid dynamics simulation

2017 ◽  
Vol 27 (7) ◽  
pp. 969-982 ◽  
Author(s):  
Fu-Jiang Chen ◽  
Qin-Yu Wu ◽  
Dan-Dan Huang ◽  
Yun Zhang ◽  
Wang Lu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cfd Simulation ◽  
Ventilation System ◽  
Dynamics Simulation ◽  
Complex Flow ◽  
Air Velocity ◽  
Dispersion System ◽  
Air Dispersion ◽  
Free Area

The fabric air dispersion system (FADS) is a ventilation terminal made of special polymer fabric. The porous structure of the fabric causes complex flow motion. Due to its advantages over the conventional ventilation system, i.e. ducts and diffusers, the FADS has been widely favoured by architects and researchers. In computational fluid dynamics (CFD) simulation the FADS is usually simplified into a free opening with an area equal to all pores and perforations, called the free area (FA) method in this present work. However, the effectiveness of this simplified method has not been validated. The present work took a half cylindrical FADS without orifices as an example and employed the FA method to simulate the airflow properties inside a chamber under isothermal and non-isothermal conditions. The simulated distributions of air velocity and temperature were compared with those by the direct description (DD) method. Meanwhile, the uniformity of air velocity distribution close to the FADS was validated against test data and the flow visualization using the dry ice as a smoking material. Results demonstrate that the FA method is effective and easy to implement, and performs as well as the DD method in predicting the distribution of airflow generated by the FADS without orifices.

scholarly journals Computational Fluid Dynamics Simulation of Airflow and Air Pattern in the Living Room for Reducing Coronavirus Exposure

2021 ◽  
Author(s):  
Majid Bayatian ◽  
Khosro Ashrafi ◽  
Zahra Amiri ◽  
Elahe Jafari
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Indoor Air ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Dynamics Simulation ◽  
Living Room ◽  
Air Velocity ◽  
Cfd Validation ◽  
Airflow Pattern

Abstract Viruses can be transmitted in indoor environments. Important factors in Indoor Air Quality (IAQ) are air velocity, relative humidity, temperature, and airflow pattern and Computational fluid dynamics (CFD) can use for IAQ assessment. The objective of this study is to CFD simulation in the living room to the prediction of the air pattern and air velocity. A computational fluid dynamic model was applied for airflow pattern and air velocity simulation. For simulation, GAMBIT, FLUENT, and CFD post software were used as preprocessing, processing, and post-processing, respectively. CFD validation was carried out by comparing the computed data with the experimental measurements. The final mesh number was set to 1,416,884 elementary cells and SIMPLEC algorithm was used for pressure-velocity coupling. PERSTO, and QUIK schemes have been used for the pressure terms, and the other variables, respectively. Simulations were carried out in ACH equals 3, 6 and 8 in four lateral walls. The maximum error and root mean square error from the air velocity were 14% and 0.10, respectively. Terminal settling velocity and relaxation time were equal to 0.302 ×10− 2 m/s and 0.0308 ×10− 2 s for 10 µm diameter particles, respectively. The stopping distance was 0.0089m and 0.011m for breathing and talking, respectively. The maximum of mean air velocity is in scenario 4 with ACH = 8 that mean air velocity is equal to 0.31 in 1.1m height, respectively. The results of this study showed that avoiding family gatherings is necessary for exposure control and suitable airflow and pattern can be improving indoor air conditions.

scholarly journals Hemodynamic analysis for stenosis microfluidic model of thrombosis with refined computational fluid dynamics simulation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yunduo Charles Zhao ◽  
Parham Vatankhah ◽  
Tiffany Goh ◽  
Rhys Michelis ◽  
Kiarash Kyanian ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Shear Rate ◽  
Cfd Simulation ◽  
Critical Role ◽  
Three Dimensions ◽  
Dynamics Simulation ◽  
Water Medium ◽  
Cfd Method

AbstractDisturbed blood flow has been increasingly recognized for its critical role in platelet aggregation and thrombosis. Microfluidics with hump shaped contractions have been developed to mimic microvascular stenosis and recapitulate the prothrombotic effect of flow disturbance. However the physical determinants of microfluidic hemodynamics are not completely defined. Here, we report a refined computational fluid dynamics (CFD) simulation approach to map the shear rate (γ) and wall shear stress (τ) distribution in the stenotic region at high accuracy. Using ultra-fine meshing with sensitivity verification, our CFD results show that the stenosis level (S) is dominant over the bulk shear rate (γ0) and contraction angle (α) in determining γ and τ distribution at stenosis. In contrast, α plays a significant role in governing the shear rate gradient (γ′) distribution while it exhibits subtle effects on the peak γ. To investigate the viscosity effect, we employ a Generalized Power-Law model to simulate blood flow as a non-Newtonian fluid, showing negligible difference in the γ distribution when compared with Newtonian simulation with water medium. Together, our refined CFD method represents a comprehensive approach to examine microfluidic hemodynamics in three dimensions and guide microfabrication designs. Combining this with hematological experiments promises to advance understandings of the rheological effect in thrombosis and platelet mechanobiology.

Validation of computational fluid dynamics simulation methods for venous pulsatile tinnitus

2021 ◽  
Author(s):  
Yue-Lin Hsieh ◽  
Dan Wang ◽  
Xiaobing Xu ◽  
Dengtao Yu ◽  
Yongzhen Wu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Doppler Ultrasound ◽  
Cfd Simulation ◽  
Computational Simulation ◽  
Case Series ◽  
Temporal Analysis ◽  
Dynamics Simulation ◽  
Pulsatile Tinnitus ◽  
Cfd Method

There has been a growing interest in the investigation of hydroacoustic characteristics of pulsatile tinnitus (PT). However, a proper technique for computational fluid dynamics (CFD) simulation has yet to be discussed. The primary goal of this paper was to investigate the intrasinus hydroacoustic characteristics of PT at the transverse-sigmoid junction (TSJ) using Doppler ultrasound and examine the validity of CFD techniques in simultaneity. The preoperative and intraoperative Doppler ultrasound were performed on a patient with PT at upper jugular vein and TSJ, respectively. Canonical CFD techniques were applied to solve the computational transverse-sigmoid sinus flow domain and compared with the Doppler’s measurements. In addition, the spectro-temporal analysis was performed for the sonification of PT. PT was associated with the recirculating flows at the TSJ according to ultrasonographic detection. This pathogenic region was characterized by a sudden deceleration of flow velocity and inverse increase of flow static pressure, which large eddy simulation (LES) resulted in the smallest 6% velocity difference compared to the measured Doppler data, albeit with little differences compared to other solvers. Therefore, based on this case study, the transient LES approach is an optimal CFD method for the computational simulation of the complex hemodynamics at the TSJ. Further numerical studies with large case series are warrranted.

Evaluating effective volume and hydrodynamic behavior in a full-scale ozone contactor with computational fluid dynamics simulation

2004 ◽  
Vol 4 (5-6) ◽  
pp. 277-288
Author(s):  
T. Mizuno ◽  
N.-S. Park ◽  
H. Tsuno ◽  
T. Hidaka
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mass Balance ◽  
Ozone Concentration ◽  
Cfd Simulation ◽  
Reaction Model ◽  
Dynamics Simulation ◽  
Effective Volume ◽  
Hydrodynamic Behavior ◽  
Ozone Contactor

An ozone reaction model combined with CFD (Computational Fluid Dynamics) technique was developed in this research. In the simulation of ozonation, hydrodynamic behavior caused by bubbling of ozone contacting-gas is important as well as reaction kinetics. CFD technique elucidated hydrodynamic behavior in the selected ozone contactor, which consisted of three main chambers. Back-mixing zone was found in each chamber. The higher velocities of water were observed in the second and third chambers than that in the first one. The flow of the opposite direction to the main flow was observed near the water surface. Based on the results of CFD simulation, each chamber was divided into small compartments, and hydrodynamic behavior and effective volume were discussed. Mass balance equations were also established in each compartment with reaction terms associated with DOC, odor compounds, bacteria, bromide ion and bromate ion. This reaction model was intended to predict dissolved ozone concentration, especially. We concluded that the model could predict favourably the mass balance of ozone, namely absorption efficiency of gaseous ozone, dissolved ozone concentration and ozone consumption. After establishing the model, we discussed the effects of hydrodynamic behavior on dissolved ozone concentration.

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