Integration of coliform decay within a CFD (computational fluid dynamic) model of a waste stabilisation pond

2003 ◽  
Vol 48 (2) ◽  
pp. 205-210 ◽  
Author(s):  
A. Shilton ◽  
J. Harrison
Keyword(s):  
Flow Reactor ◽  
Fluid Dynamic ◽  
Reaction Model ◽  
Cfd Model ◽  
Treatment Efficiency ◽  
Cfd Modelling ◽  
Ideal Flow ◽  
Standard Design ◽  
Order Of Magnitude ◽  
Predicted Values

CFD mathematical modelling offers the potential to predict the actual flow pattern in a pond rather than generalising its mixing and mass transport as either an ideal flow reactor or, in the case of the non-ideal flow reactor, as a single dispersion number. However, perhaps the greatest benefit that CFD offers over the previous approaches is its ability to directly account for physical influences on the pond hydraulics such as the addition of baffles for example. In addition to solving the equations of fluid flow, CFD modelling also allows incorporation of other equations. The next logical development is, therefore, the integration of a reaction model within its solution domain. This potential has been recognised by several researchers, but to date no such work has been published. The primary aim of this paper was to present a CFD model of a field pond that incorporates the first order decay equation for coliforms. Experimental monitoring of the field pond gave an average effluent concentration of 3,710 f.c./100 mL, while the CFD model predicted 4,600 f.c./100 mL. Considering the pond provides an order of magnitude decrease in faecal coliform concentration, the integrated CFD model has clearly predicted the treatment efficiency very well. The secondary aim of this paper was to demonstrate the potential application of this technique. A typical pond was designed and modelled along with two variations incorporating two baffles and six baffles respectively. As is typically found in pond systems, the standard design suffered from severe short-circuiting with the model predicting a value of 6.2 × 106 f.c./100 mL at the outlet. The simulations of the baffled designs illustrate how treatment efficiency was improved by reducing the short-circuiting through the pond. The model predicted values of 6.0 × 103 f.c./100 mL for the 2-baffle design and 5.7 × 102 f.c./100 mL for the 6-baffle design.

scholarly journals Measurement of flow velocity profiles in tank structures using the prototype device OCM Pro LR

2011 ◽  
Vol 64 (1) ◽  
pp. 263-270 ◽  
Author(s):  
K. Klepiszewski ◽  
M. Teufel ◽  
S. Seiffert ◽  
E. Henry
Keyword(s):  
Flow Velocity ◽  
Large Scale ◽  
Fluid Dynamic ◽  
Waste Water Treatment ◽  
Transport Processes ◽  
Treatment Efficiency ◽  
Cleaning Efficiency ◽  
Cfd Modelling ◽  
Ultrasonic Signals ◽  
Cfd Models

Generally, studies investigating the treatment efficiency of tank structures for storm water or waste water treatment observe pollutant flows in connection with conditions of hydraulic loading. Further investigations evaluate internal processes in tank structures using computational fluid dynamic (CFD) modelling or lab scale tests. As flow paths inside of tank structures have a considerable influence on the treatment efficiency, flow velocity profile (FVP) measurements can provide a possibility to calibrate CFD models and contribute to a better understanding of pollutant transport processes in these structures. This study focuses on tests carried out with the prototype FVP measurement device OCM Pro LR by NIVUS in a sedimentation tank with combined sewer overflow (CSO) situated in Petange, Luxembourg. The OCM Pro LR measurement system analyses the echo of ultrasonic signals of different flow depths to get a detailed FVP. A comparison of flow velocity measured by OCM Pro LR with a vane measurement showed good conformity. The FVPs measured by OCM Pro LR point out shortcut flows within the tank structure during CSO events, which could cause a reduction of the cleaning efficiency of the structure. The results prove the applicability of FVP measurements in large-scale structures.

scholarly journals Decomposition of Additive-Free Formic Acid Using a Pd/C Catalyst in Flow: Experimental and CFD Modelling Studies

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 341
Author(s):  
Sanaa Hafeez ◽  
Felipe Sanchez ◽  
Sultan M. Al-Salem ◽  
Alberto Villa ◽  
George Manos ◽  
...  
Keyword(s):  
Experimental Data ◽  
Formic Acid ◽  
Catalyst Deactivation ◽  
Fluid Dynamic ◽  
Fixed Bed ◽  
Reaction System ◽  
Cfd Model ◽  
Cfd Modelling ◽  
Fresh Sample ◽  
Modelling Studies

The use of hydrogen as a renewable fuel has gained increasing attention in recent years due to its abundance and efficiency. The decomposition of formic acid for hydrogen production under mild conditions of 30 °C has been investigated using a 5 wt.% Pd/C catalyst and a fixed bed microreactor. Furthermore, a comprehensive heterogeneous computational fluid dynamic (CFD) model has been developed to validate the experimental data. The results showed a very good agreement between the CFD studies and experimental work. Catalyst reusability studies have shown that after 10 reactivation processes, the activity of the catalyst can be restored to offer the same level of activity as the fresh sample of the catalyst. The CFD model was able to simulate the catalyst deactivation based on the production of the poisoning species CO, and a sound validation was obtained with the experimental data. Further studies demonstrated that the conversion of formic acid enhances with increasing temperature and decreasing liquid flow rate. Moreover, the CFD model established that the reaction system was devoid of any internal and external mass transfer limitations. The model developed can be used to successfully predict the decomposition of formic acid in microreactors for potential fuel cell applications.

CFD (computational fluid dynamics) modelling of baffles for optimizing tropical waste stabilization pond systems

2005 ◽  
Vol 51 (12) ◽  
pp. 103-106 ◽  
Author(s):  
A.N. Shilton ◽  
D.D. Mara
Keyword(s):  
Longitudinal Axis ◽  
Field Studies ◽  
Cfd Model ◽  
Cfd Modelling ◽  
E Coli ◽  
Waste Stabilization Pond ◽  
Waste Stabilization ◽  
Order Of Magnitude ◽  
Dynamics Modelling ◽  
Potential Improvement

CFD modelling of the incorporation of two baffles equally spaced along the longitudinal axis of the pond and with a length equal to 70% of the pond breadth, indicated a potential improvement in the removal of E. coli in a 4-day secondary facultative pond at 25°C from 5 × 106 per 100 ml in the effluent from a 1-day anaerobic pond to 4 × 104 per 100 ml; the reduction in an un-baffled pond was an order of magnitude less effective. The addition of a similarly baffled 4-day primary maturation pond reduced the effluent E. coli count to 340 per 100 ml; the reduction in an un-baffled series was two orders of magnitude less effective. Well designed baffles thus have considerable potential for reducing pond area requirements and hence costs in the hot tropics. These very promising results highlight the need for field studies on baffled pond systems to validate (or allow calibration) of the CFD model used in this study.

scholarly journals Mass and Heat Transfer Coefficients in Automotive Exhaust Catalytic Converter Channels

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 507
Author(s):  
Chrysovalantis C. Templis ◽  
Nikos G. Papayannakos
Keyword(s):  
Heat Transfer ◽  
Flow Reactor ◽  
Catalytic Converter ◽  
Reaction Rates ◽  
Cfd Model ◽  
Automotive Exhaust ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Wide Range ◽  
Mass And Heat Transfer

Mass and heat transfer coefficients (MTC and HTC) in automotive exhaust catalytic monolith channels are estimated and correlated for a wide range of gas velocities and prevailing conditions of small up to real size converters. The coefficient estimation is based on a two dimensional computational fluid dynamic (2-D CFD) model developed in Comsol Multiphysics, taking into account catalytic rates of a real catalytic converter. The effect of channel size and reaction rates on mass and heat transfer coefficients and the applicability of the proposed correlations at different conditions are discussed. The correlations proposed predict very satisfactorily the mass and heat transfer coefficients calculated from the 2-D CFD model along the channel length. The use of a one dimensional (1-D) simplified model that couples a plug flow reactor (PFR) with mass transport and heat transport effects using the mass and heat transfer correlations of this study is proved to be appropriate for the simulation of the monolith channel operation.

CFD Analysis of the Coolant Mixing within the Upper Plenum of a Pressurized Water Reactor (PWR)

2013 ◽  
Vol 444-445 ◽  
pp. 411-415 ◽  
Author(s):  
Fu Cheng Zhang ◽  
Shen Gen Tan ◽  
Xun Hao Zheng ◽  
Jun Chen
Keyword(s):  
Temperature Distribution ◽  
Fluid Dynamic ◽  
Characteristic Temperature ◽  
Reactor Core ◽  
Flow Distribution ◽  
Sensitivity Study ◽  
Cfd Model ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor

In this study, a Computational Fluid Dynamic (CFD) model is established to obtain the 3-D flow characteristic, temperature distribution of the pressurized water reactor (PWR) upper plenum and hot-legs. In the CFD model, the flow domain includes the upper plenum, the 61 control rod guide tubes, the 40 support columns, the three hot-legs. The inlet boundary located at the exit of the reactor core and the outlet boundary is set at the hot-leg pipes several meters away from upper plenum. The temperature and flow distribution at the inlet boundary are given by sub-channel codes. The computational mesh used in the present work is polyhedron element and a mesh sensitivity study is performed. The RANS equations for incompressible flow is solved with a Realizable k-ε turbulence model using the commercial CFD code STAR-CCM+. The analysis results show that the flow field of the upper plenum is very complex and the temperature distribution at inlet boundary have significant impact to the coolant mixing in the upper plenum as well as the hot-legs. The detailed coolant mixing patterns are important references to design the reactor core fuel management and the internal structure in upper plenum.

Application of CFD Model for Inlet Flow Region of 17×17 Fuel Assembly

2006 ◽  
Author(s):  
Milorad B. Dzodzo ◽  
Bin Liu ◽  
Pablo R. Rubiolo ◽  
Zeses E. Karoutas ◽  
Michael Y. Young
Keyword(s):  
Fuel Assembly ◽  
Fluid Dynamic ◽  
Flow Distribution ◽  
Flow Region ◽  
Fretting Wear ◽  
Jet Flows ◽  
Cfd Model ◽  
Lateral Velocity ◽  
Fuel Assemblies ◽  
Inlet Conditions

A numerical investigation was performed to study the variation in axial and lateral velocity profiles occurring downstream of the inlet nozzle of a typical Westinghouse 17×17 PWR fuel assembly. A Computational Fluid Dynamic (CFD) model was developed with commercial CFD software. The model comprised the lower region of the fuel assembly, including: the Debris Filter Bottom Nozzle (DFBN), P-grid, Bottom Inconel grid, one and half grid span, as well as the lower core plate hole. The purpose of the study was to obtain insight into the flow redistribution resulting from the interaction of the jet arising from the lower core plate hole and the fuel assembly structure. In particular the axial and lateral velocities before and after the nozzle were studied. The results, axial and lateral velocity contours, streamlines and maximum axial and lateral velocity distributions at various elevations are presented and discussed in relation to the potential risk of high turbulent excitation over the rod and the resulting rod-to-grid fretting-wear damage. The CFD model results indicated that the large jet flows from the lower core plate are effectively dissipated by DFBN nozzle and the grids components of the fuel assembly. The breakup of the large jets in the DFBN and the lower grids helps to reduce the steep velocity gradients and thus the rod vibration and fretting-wear risk in the lower part of the fuel assembly. The presented CFD model is one step towards developing advanced tools that can be used to confirm and evaluate the effect of complex PWR structures on flow distribution. In the future the presented model could be integrated in a larger CFD model involving several fuel assemblies for evaluating the lateral velocities generated due to the non-uniform inlet conditions into the various fuel assemblies.

scholarly journals CO Preferential Oxidation in a Microchannel Reactor Using a Ru-Cs/Al2O3 Catalyst: Experimentation and CFD Modelling

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 867
Author(s):  
Kyatsinge Cedric Musavuli ◽  
Nicolaas Engelbrecht ◽  
Raymond Cecil Everson ◽  
Gerrit Lodewicus Grobler ◽  
Dmitri Bessarabov
Keyword(s):  
Goodness Of Fit ◽  
Fossil Fuels ◽  
Fluid Dynamic ◽  
Hydrogen Fuel Cell ◽  
Preferential Oxidation ◽  
Microchannel Reactor ◽  
Cfd Modelling ◽  
Preferential Oxidation Of Co ◽  
Reactor Technology ◽  
Al2o3 Catalyst

This work presents an experimental and modelling evaluation of the preferential oxidation of CO (CO PROX) from a H2-rich gas stream typically produced from fossil fuels and ultimately intended for hydrogen fuel cell applications. A microchannel reactor containing a washcoated 8.5 wt.% Ru/Al2O3 catalyst was used to preferentially oxidise CO to form CO2 in a gas stream containing (by vol.%): 1.4% CO, 10% CO2, 18% N2, 68.6% H2, and 2% added O2. CO concentrations in the product gas were as low as 42 ppm (99.7% CO conversion) at reaction temperatures in the range 120–140 °C and space velocities in the range 65.2–97.8 NL gcat−1 h−1. For these conditions, less than 4% of the H2 feed was consumed via its oxidation and reverse water-gas shift. Furthermore, a computational fluid dynamic (CFD) model describing the microchannel reactor for CO PROX was developed. With kinetic parameter estimation and goodness of fit calculations, it was determined that the model described the reactor with a confidence interval far greater than 95%. In the temperature range 100–200 °C, the model yielded CO PROX reaction rate profiles, with associated mass transport properties, within the axial dimension of the microchannels––not quantifiable during the experimental investigation. This work demonstrates that microchannel reactor technology, supporting an active catalyst for CO PROX, is well suited for CO abatement in a H2-rich gas stream at moderate reaction temperatures and high space velocities.

Raised Floor Computer Data Center: Effect on Rack Inlet Temperatures When Adjacent Racks Are Removed

2003 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Center Effect ◽  
Air Temperatures ◽  
Baseline Case ◽  
Finite Control

This paper focuses on the effect on inlet rack air temperatures when adjacent racks are removed. Only the above floor (raised floor) flow and temperature distributions were analyzed for various air flowrates exhausting from the perforated tiles and the rack. A Computational Fluid Dynamic (CFD) model was generated for the room with electronic equipment installed on a raised floor with particular focus on the effects on rack inlet temperatures of these high powered racks. The baseline case was with forty racks of data processing (DP) equipment arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide × 13.4 m long. Since the arrangement of the racks in the data center was symmetric only one-half of the data center was modeled. To see the effect of missing racks adjacent to high powered racks various configurations were analyzed. The numerical modeling was performed using a commercially available finite control volume computer code called Flotherm (Trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Experimental and Numerical Characterization of an Orifice Type Cryogenic Pulse Tube Refrigerator

2011 ◽  
Author(s):  
Dion Savio Antao ◽  
Bakhtier Farouk
Keyword(s):  
Porous Media ◽  
Heat Exchanger ◽  
Fluid Dynamic ◽  
Travelling Wave ◽  
Cryogenic Cooling ◽  
Energy Separation ◽  
Pulse Tube ◽  
Cfd Model ◽  
Pulse Tube Refrigerator ◽  
Energy Equations

An orifice type pulse tube refrigerator (OPTR) was designed, built and operated to provide cryogenic cooling. The OTPR is a travelling wave thermoacoustic refrigerator that operates on a modified reverse Stirling cycle. We consider a system that is comprised of a pressure wave generator (a linear motor), an aftercooler heat-exchanger, a regenerator (comprising of a porous structure for energy separation), a pulse tube (in lieu of a displacer piston as found in Stirling refrigerators) with a cold and a warm heat-exchanger at its two ends, a needle-type orifice valve, an inertance tube and a buffer volume. The experimental characterization is done at various values of mean pressure of helium (∼ 0.35 MPa–2.2 MPa), amplitude of pressure oscillations, frequency of operation and size of orifice opening. A detailed time-dependent axisymmetric computational fluid dynamic (CFD) model of the OPTR is simulated to predict the performance of the OPTR. In the CFD model, the continuity, momentum and energy equations are solved for both the refrigerant gas (helium) and the porous media regions (the regenerator and the three heat-exchangers) in the OPTR. An accurate representation of heat transfer in the porous media is achieved by employing a thermal non-equilibrium model to couple the gas and solid (porous media) energy equations. In the future, a validated computational model can be used for system improvement and optimization.

Passive Alignment Method for the Bonding of Flat Surfaces Using a Squeeze Flow

2019 ◽  
Vol 86 (9) ◽  
Author(s):  
Willy Lecarpentier ◽  
Julien Sylvestre
Keyword(s):  
Integrated Circuits ◽  
Fluid Dynamic ◽  
Squeeze Flow ◽  
Cfd Model ◽  
Flat Surfaces ◽  
Shear Rates ◽  
High Shear Rates ◽  
Potential Applications ◽  
3D Integrated Circuits ◽  
Squeeze Flow Phenomenon

A method to passively align bonded components without direct mechanical contact has been developed. This method uses the pressure field generated by the squeeze flow between the parts during the bonding process to increase the parallelism of planar components. A computational fluid dynamic (CFD) model has been developed to study the squeeze flow phenomenon and to determine generated efforts. Based on these calculations, an assembly stage standing on a flexure pinned linkage has been developed. This assembly stage had two purposes. The first was to show the possibility of passive mechanical alignment using a squeeze flow. The second was to measure efforts to confirm the CFD model. These measurements have led to a refined CFD model taking into account the non-Newtonian behavior of the fluid at high shear rates. This technique was initially developed for the assembly of a fiber-optic-to-silicon-chip-interface. Other potential applications could be wafer bonding, bonding of multiple wafer stacks, or 3D integrated circuits.

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