scholarly journals Turbulence Enhancement and Mixing Analysis for Multi-Inlet Vortex Photoreactor for CO2 Reduction

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2237
Author(s):  
Jesús Valdés ◽  
Jorge Luis Domínguez-Juárez ◽  
Rufino Nava ◽  
Ángeles Cuán ◽  
Carlos M. Cortés-Romero
Keyword(s):  
Residence Time ◽  
Turbulence Intensity ◽  
Mass Fraction ◽  
Fluid Dynamic ◽  
Co2 Reduction ◽  
Point Of View ◽  
Molar Ratio ◽  
Cylindrical Shape ◽  
Turbulent Regime ◽  
Computational Fluid Dynamics Cfd

In this article, we describe a prototype photoreactor of which the geometrical configuration was obtained by Genetic Algorithms to maximize the residence time of the reactant gases. A gas reaction mixture of CO2:H2O (1:2 molar ratio) was studied from the fluid dynamic point of view. The two main features of this prototype reactor are the conical shape, which enhances the residence time as compared to a cylindrical shape reference reactor, and the inlet heights and position around the main chamber that enables turbulence and mass transfer control. Turbulence intensity, mixing capability, and residence time attributes for the optimized prototype reactor were calculated with Computational Fluid Dynamics (CFD) software and compared with those from a reference reactor. Turbulence intensity near the envisioned catalytic bed was one percentage point higher in the reference than in the optimized prototype reactor. Finally, the homogeneity of the mixture was guaranteed since both types of reactors had a turbulent regime, but for the prototype the CO2 mass fraction was found to be better distributed.

Analysis of Volumetric Residence Time of Blood Elements in Stenosed Arteries

2003 ◽  
Author(s):  
M. C. Kim ◽  
C. S. Lee ◽  
C. J. Kim
Keyword(s):  
Residence Time ◽  
Transient Flow ◽  
Fluid Dynamic ◽  
Viscous Drag ◽  
Shear Stresses ◽  
Drag Forces ◽  
Area Reduction ◽  
Dynamic Factors ◽  
Recirculation Zones ◽  
Computational Fluid Dynamics Cfd

Blood flow in arteries is known to be closely related to atherosclerosis. Presence of recirculation zones, and low, high, and oscillatory wall shear stresses have been suggested to be important fluid dynamic factors causing development and progress of atherosclerosis. Our study was motivated to develop fluid mechanical indices between residence time of blood particles in arteries and atherosclerosis. In rigid models of stenosed arteries with 75% area reduction, trajectories of blood particles were numerically computed and used to determine local volumetric residence time (VRT) of platelets. The motion of particles in the model artery was computed by considering viscous drag forces between blood particles and presolved transient flow field from computational fluid dynamics (CFD). Many cardiac cycles were considered in the computation to reflect temporally accumulative characteristics of VRT in the recirculation zones. Our results showed that VRT in the recirculation zone was relatively low in the first cardiac cycle. However it increased in the subsequent cycles as more particles were trapped in the same zone. The results suggested that VRT contour calculated in the present study would be an effective indicator of the presence of atherosclerosis.

Computational fluid dynamic prediction of the residence time of a vortex separator applied to disinfection

2005 ◽  
Vol 52 (3) ◽  
pp. 29-36 ◽  
Author(s):  
D. Egarr ◽  
M.G. Faram ◽  
T. O'Doherty ◽  
D. Phipps ◽  
N. Syred
Keyword(s):  
Fluid Dynamics ◽  
Residence Time ◽  
Air Conditioning ◽  
Fluid Dynamic ◽  
Dynamic Prediction ◽  
Disinfection Process ◽  
Computational Fluid Dynamics Cfd ◽  
Vortex Separator ◽  
The Mean ◽  
Computational Fluid Dynamic Prediction

A Hydrodynamic Vortex Separator (HDVS) has been modelled using Computational Fluid Dynamics (CFD) in order to predict the residence time of the fluid at the overflow and underflow outlets. A technique which was developed for use in Heating, Ventilation and Air Conditioning (HVAC) was used to determine the residence time and the results have been compared with those determined experimentally. It is shown that in using CFD, it is possible to predict the mean residence time of the fluid and to study the response to a pulse injection of tracer. It is also shown that it is possible to apply these techniques to predict the mean survival rate of bacteria in a combined separation and disinfection process.

scholarly journals Computational fluid dynamic prediction of the residence time distribution of a prototype hydrodynamic vortex separator operating with a base flow component

2005 ◽  
Vol 219 (1) ◽  
pp. 53-67 ◽  
Author(s):  
D. A. Egarr ◽  
M. G. Faram ◽  
T O'Doherty ◽  
D. A. Phipps ◽  
N Syred
Keyword(s):  
Residence Time ◽  
Air Conditioning ◽  
Fluid Dynamic ◽  
Base Flow ◽  
Hydraulic Systems ◽  
Dynamic Prediction ◽  
Computational Fluid Dynamics Cfd ◽  
Vortex Separator ◽  
The Mean ◽  
Computational Fluid Dynamic Prediction

A hydrodynamic vortex separator (HDVS) has been modelled using computational fluid dynamics (CFD) in order to accurately determine the residence time of the fluid at the two outlets of the HDVS using a technique that was developed for use in heating, ventilation, and air conditioning (HVAC). The results have been compared with experimental data [1]. It is shown that, in using CFD, it is possible to study the response to a variety of inputs, and also to determine the mean residence time of the fluid within the separator. Although the technique used for determining the residence time was developed for use in HVAC, it is shown here to be applicable for the analysis of hydraulic systems, specifically, wastewater treatment systems.

Performance of lamella clarifiers for juice and syrup clarification

2017 ◽  
pp. 144-150
Author(s):  
Peter W. Rein ◽  
M. Getaz ◽  
A. Raghunandan ◽  
N. du Pleissis ◽  
H. Saleh ◽  
...  
Keyword(s):  
Residence Time ◽  
Flow Characteristics ◽  
Preliminary Test ◽  
Practical Experience ◽  
Operating Costs ◽  
Capital Costs ◽  
Computational Fluid Dynamics Cfd ◽  
Improved Performance ◽  
Work Done ◽  
Good Flow

A new design for syrup and juice clarifiers is presented. The design takes advantage of the considerably improved performance of clarifiers incorporating lamella plates, and the reasons for the improvement are outlined. Computational fluid dynamics (CFD) work done to simulate the performance is summarised. This design enables the residence time to be dramatically reduced and the simplified design leads to cheaper and better clarifiers. Practical experience with factory scale units is described, confirming the good flow characteristics. The results of preliminary test work on a factory syrup clarifier are presented, which is also shown to operate efficiently as a phosphatation clarifier. In addition the performance of a full-scale juice clarifier has been evaluated and compared with the performance of a Rapidorr clarifier. This work confirms the considerable advantages which this type of design provides, in realising substantial reductions in residence time, capital costs and operating costs.

scholarly journals Risk Analysis of Road Tunnels: A Computational Fluid Dynamic Model for Assessing the Effects of Natural Ventilation

2020 ◽  
Vol 11 (1) ◽  
pp. 32
Author(s):  
Ciro Caliendo ◽  
Gianluca Genovese ◽  
Isidoro Russo
Keyword(s):  
Natural Ventilation ◽  
Fluid Dynamic ◽  
Movement Time ◽  
Radiant Heat ◽  
Heat Fluxes ◽  
Maximum Heat ◽  
Road Tunnels ◽  
Maximum Heat Release ◽  
Computational Fluid Dynamics Cfd ◽  
Time Required

We have developed an appropriate Computational Fluid Dynamics (CFD) model for assessing the exposure to risk of tunnel users during their evacuation process in the event of fire. The effects on escaping users, which can be caused by fire from different types of vehicles located in various longitudinal positions within a one-way tunnel with natural ventilation only and length less than 1 km are shown. Simulated fires, in terms of maximum Heat Release Rate (HRR) are: 8, 30, 50, and 100 MW for two cars, a bus, and two types of Heavy Goods Vehicles (HGVs), respectively. With reference to environmental conditions (i.e., temperatures, radiant heat fluxes, visibility distances, and CO and CO2 concentrations) along the evacuation path, the results prove that these are always within the limits acceptable for user safety. The exposure to toxic gases and heat also confirms that the tunnel users can safely evacuate. The evacuation time was found to be higher when fire was related to the bus, which is due to a major pre-movement time required for leaving the vehicle. The findings show that mechanical ventilation is not necessary in the case of the tunnel investigated. It is to be emphasized that our modeling might represent a reference in investigating the effects of natural ventilation in tunnels.

scholarly journals Computational fluid dynamics (CFD) simulation analysis on retinal gas cover rates using computational eye models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Makoto Gozawa ◽  
Yoshihiro Takamura ◽  
Tomoe Aoki ◽  
Kentaro Iwasaki ◽  
Masaru Inatani
Keyword(s):  
Cfd Simulation ◽  
Simulation Analysis ◽  
Fluid Dynamic ◽  
Fluid Analysis ◽  
Intraocular Gas ◽  
Pars Plana ◽  
Computational Fluid Dynamics Cfd ◽  
Multiple Breaks ◽  
Gas Volume ◽  
Wall Wettability

AbstractWe investigated the change in the retinal gas cover rates due to intraocular gas volume and positions using computational eye models and demonstrated the appropriate position after pars plana vitrectomy (PPV) with gas tamponade for rhegmatogenous retinal detachments (RRDs). Computational fluid dynamic (CFD) software was used to calculate the retinal wall wettability of a computational pseudophakic eye models using fluid analysis. The model utilized different gas volumes from 10 to 90%, in increments of 10% to the vitreous cavity in the supine, sitting, lateral, prone with closed eyes, and prone positions. Then, the gas cover rates of the retina were measured in each quadrant. When breaks are limited to the inferior retina anterior to the equator or multiple breaks are observed in two or more quadrants anterior to the equator, supine position maintained 100% gas cover rates in all breaks for the longest duration compared with other positions. When breaks are limited to either superior, nasal, or temporal retina, sitting, lower temporal, and lower nasal position were maintained at 100% gas cover rates for the longest duration, respectively. Our results may contribute to better surgical outcomes of RRDs and a reduction in the duration of the postoperative prone position.

Computational Fluid Dynamic Using Parallel Loop of Multi-Cores Processor

2014 ◽  
Vol 493 ◽  
pp. 80-85 ◽  
Author(s):  
C.L Siow ◽  
Jaswar ◽  
Efi Afrizal
Keyword(s):  
Fluid Flow ◽  
Early Stage ◽  
Fluid Dynamic ◽  
Visual Basic ◽  
Computer Hardware ◽  
Navier Stokes ◽  
Computer Memory ◽  
Large Size ◽  
Computational Fluid Dynamics Cfd ◽  
Reynolds Average

Computational Fluid Dynamics (CFD) software is often used to study fluid flow and structures motion in fluids. The CFD normally requires large size of arrays and computer memory and then caused long execution time. However, Innovation of computer hardware such as multi-cores processor provides an alternative solution to improve this programming performance. This paper discussed loop parallelize multi-cores processor for optimization of sequential looping CFD code. This loop parallelize CFD was achieved by applying multi-tasking or multi-threading code into the original CFD code which was developed by one of the authors. The CFD code was developed based on Reynolds Average Navier-Stokes (RANS) method. The new CFD code program was developed using Microsoft Visual Basic (VB) programming language. In the early stage, the whole CFD code was constructed in a sequential flow before it is modified to parallel flow by using VBs multi-threading library. In the comparison, fluid flow around the hull of round-shaped FPSO was selected to compare the performance of both the programming codes. Besides, executed results of this self-developed code such as pressure distribution around the hull were also presented in this paper.

New Promising Generation of Twin-Gondola LNG Carriers Optimized with the Aid of CFD Calculations

2005 ◽  
Author(s):  
Henk V. Valkhof ◽  
Eduardo Minguito ◽  
Klaas Kooiker
Keyword(s):  
Viscous Flow ◽  
Far East ◽  
Point Of View ◽  
Maximum Efficiency ◽  
Hull Form ◽  
Overall Design ◽  
Computational Fluid Dynamics Cfd ◽  
New Generation ◽  
Hydrodynamic Optimization ◽  
Adequate Design

As natural gas is becoming an important energy source, a large fleet is needed to transport it in liquefied form across the oceans in specially designed LNG carriers from mainly the Middle East towards the Far East. During the overall design process of such a vessel the shape of the hull form and its propulsors play an important role from a hydrodynamic point of view. This paper describes the design of a twin-gondola LNG carrier for Navantia. The twingondola aft body has proven to be an adequate design concept, but due to the complexity of the flow around the aft body the design should be carried out with great care. Computational Fluid Dynamics (CFD) tools are extremely valuable in the hydrodynamic optimization process of the hull. In this design both potential flow codes and viscous flow codes have been used to obtain the optimum hull form. With the results of the PARNASSOS viscous flow calculations it was possible to make decisions with regard to the horizontal angle and the inclination of the gondolas, and the slope of the buttocks in the area between the gondolas. Special attention has been paid to avoid flow separation around the aft body. The gondolas have been oriented in such a way that maximum efficiency is achieved. The performance of the resulting design has been verified by model tests in MARIN’s Deep Water Towing Tank. Given the very promising results of this new generation of LNG carriers, achieving besides the excellent propulsive properties also a higher payload target, the yard became more competitive and is expecting quite some orders for this particular ship type.

scholarly journals Performance Analyses of Temporary Membrane Structures: Energy Saving and CO2 Reduction through Dynamic Simulations of Textile Envelopes

2018 ◽  
Vol 10 (7) ◽  
pp. 2548 ◽  
Author(s):  
Mariangela De Vita ◽  
Paolo Beccarelli ◽  
Eleonora Laurini ◽  
Pierluigi De Berardinis
Keyword(s):  
Energy Saving ◽  
Environmental Sustainability ◽  
Co2 Reduction ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Point Of View ◽  
Thermal Mass ◽  
Membrane Structures ◽  
Dynamic Simulations ◽  
Carbon Reduction

The aim of this research, carried out in collaboration with Maco Technology Inc., was to analyse the energy performance of temporary textile structures that are often used to host itinerant events. This paper illustrates the dynamic simulations carried on the Ducati Pavilion, designed by Maco Technology, which hosted Ducati staff during the different stages of the Superbike World Championship. Specific aspects relating to the structural/constructive system of the project were also analysed. The theme of energy saving and carbon reduction is of great importance in temporary and itinerant structures and environmental sustainability in relation to the materials used, storage, re-use, mode of transport and ability to respond efficiently to the climatic conditions of the installation sites is an important aspect. The Ducati Pavilion was modelled and analysed from an energy point of view using Design Builder software. Ways of improving performance were analysed under summer conditions. The paper focuses on the importance of optimizing the performance of textile envelopes: the methodology proposed allows visible savings in terms of energy consumption and achieves good levels of environmental comfort in temporary buildings with low thermal mass structure.

Thermal-Mechanical Effects and Near-Critical Fluid Dynamic Behaviors in Micro-Scale

2021 ◽  
pp. 55-111
Author(s):  
Lin Chen
Keyword(s):  
Fluid Dynamic ◽  
Spatial Scales ◽  
Small Time ◽  
Point Of View ◽  
Dynamic Responses ◽  
Chemical Extraction ◽  
Scaling Effects ◽  
Mechanical Process ◽  
Micro Scale ◽  
Leading Role

Supercritical CO2 fluid has been widely used in chemical extraction, chemical synthesis, micro-manufacturing, and heat transfer apparatus, and so forth. The current chapter deals with near-critical CO2 micro-scale thermal convective flow and the effects of thermal-mechanical process. When the scale becomes smaller, new, and detailed figures of near-critical thermal effects emerges. To explore this new area, theoretical developments and numerical investigations are discussed and explained in this chapter. From a theoretical point of view, the thermal-mechanical nature of near-critical fluid would play a leading role in small time and spatial scales. This effect is found dominant to the thermal dynamic responses and convective structures of micro-scale fluid behaviors. The scaling effects, boundary thermal-mechanical process, instability evolutions, mixing flows and characteristics, possible extensions, and applications are also discussed in this chapter.

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