Computational modeling of UV photocatalytic reactors: model development, evaluation, and application

2014 ◽  
Vol 50 (1) ◽  
pp. 21-33 ◽  
Author(s):  
J. Esteban Duran ◽  
Madjid Mohseni ◽  
Fariborz Taghipour
Keyword(s):  
Design Optimization ◽  
Reactor Design ◽  
Base Case ◽  
Emission Model ◽  
Hydrodynamic Conditions ◽  
Efficient Design ◽  
Chemical Reaction Kinetics ◽  
Taguchi Design Of Experiments ◽  
Wide Range ◽  
Uv Lamp

A computational model for simulating the performance of immobilized photocatalytic ultraviolet (UV) reactors used for water treatment was developed, experimentally evaluated, and applied to reactor design optimization. This model integrated hydrodynamics, species mass transport, chemical reaction kinetics, and irradiance distribution within the reactor. Among different hydrodynamic models evaluated against experimental data, the laminar, Abe–Kondoh–Nagano, and Reynolds stress turbulence models showed better performance (errors <5%, 12%, and 20%, respectively) in terms of external mass transfer and surface reaction prediction capabilities at different hydrodynamic conditions. A developed finite-volume-based UV lamp emission model was able to predict, with errors of less than 5%, near- and far-field irradiance measurements. Combining all these models, the integrated computational fluid dynamics (CFD)-based model was able to successfully predict the photocatalytic degradation rate of model pollutants (benzoic acid and 2,4-D) in various configurations of annular reactors and UV lamp sizes, over a wide range of hydrodynamic conditions (350 < Re < 11,000). In addition, the integrated model was used in combination with a Taguchi design of experiments method to perform reactor design optimization. Following this approach, a base case annular reactor design was modified to obtain a 50% more efficient design.

scholarly journals Photocatalysis of Ethylene in Air: Reactor Design and Performance Evaluations

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 636b-636 ◽  
Author(s):  
K.C. Cushman ◽  
T.W. Tibbitts ◽  
M. Anderson ◽  
X. Fu ◽  
W. Zeltner
Keyword(s):  
Reactor Design ◽  
Dew Point ◽  
Performance Evaluations ◽  
Ethylene Concentration ◽  
Dewpoint Temperature ◽  
Air Stream ◽  
Wide Range ◽  
Reactor Temperature ◽  
Uv Lamp ◽  
And Performance

The performance of a reactor designed to convert volatile hydrocarbons to carbon dioxide and water by a combination of surface chemistry and UV radiation was tested under conditions relevant to horticulture. Air containing 65 to 1100 nL·L–1 ethylene gas passed through a bed of catalyst crystals at a rate of 0.1 to 2.0 L·min–1. The catalyst bed consisted of 14 g of zirconia-titania particles, 0.50 to 0.75 mm in size, that occupied the space between a 4-W UV lamp and a stainless-steel housing. Dew-point temperatures of the air passing through the reactor ranged from 5 to 22°C and internal reactor temperatures ranged from 20 to 80°C. Increasing internal reactor temperature, ethylene concentration, or air flow resulted in increasing ethylene photocatalysis by the reactor. Increasing dewpoint temperature of the air stream resulted in decreasing ethylene photocatalysis by the reactor. Operation of the reactor over a 120-day period showed that reactor design and catalyst performance were stable and robust during continuous duty. Our results demonstrate that the reactor performed well over a wide range of conditions and may be useful for applications in horticulture. This research was, in part, NASA sponsored, and a reactor similar in design to that used in our studies has been used for plant growth in space.

Integrated Design and Multi-Objective Optimization of a Single Stage Heat-Pump Turbocompressor

2013 ◽  
Author(s):  
J. Schiffmann
Keyword(s):  
Design Optimization ◽  
High Efficiency ◽  
Integrated Design ◽  
Heat Pumps ◽  
Small Scale ◽  
Multi Objective Optimization ◽  
Design Constraints ◽  
Multi Objective ◽  
Wide Range ◽  
Standard Design

Small scale turbomachines in domestic heat pumps reach high efficiency and provide oil-free solutions which improve heat-exchanger performance and offer major advantages in the design of advanced thermodynamic cycles. An appropriate turbocompressor for domestic air based heat pumps requires the ability to operate on a wide range of inlet pressure, pressure ratios and mass flows, confronting the designer with the necessity to compromise between range and efficiency. Further the design of small-scale direct driven turbomachines is a complex and interdisciplinary task. Textbook design procedures propose to split such systems into subcomponents and to design and optimize each element individually. This common procedure, however, tends to neglect the interactions between the different components leading to suboptimal solutions. The authors propose an approach based on the integrated philosophy for designing and optimizing gas bearing supported, direct driven turbocompressors for applications with challenging requirements with regards to operation range and efficiency. Using previously validated reduced order models for the different components an integrated model of the compressor is implemented and the optimum system found via multi-objective optimization. It is shown that compared to standard design procedure the integrated approach yields an increase of the seasonal compressor efficiency of more than 12 points. Further a design optimization based sensitivity analysis allows to investigate the influence of design constraints determined prior to optimization such as impeller surface roughness, rotor material and impeller force. A relaxation of these constrains yields additional room for improvement. Reduced impeller force improves efficiency due to a smaller thrust bearing mainly, whereas a lighter rotor material improves rotordynamic performance. A hydraulically smoother impeller surface improves the overall efficiency considerably by reducing aerodynamic losses. A combination of the relaxation of the 3 design constraints yields an additional improvement of 6 points compared to the original optimization process. The integrated design and optimization procedure implemented in the case of a complex design problem thus clearly shows its advantages compared to traditional design methods by allowing a truly exhaustive search for optimum solutions throughout the complete design space. It can be used for both design optimization and for design analysis.

Adaptive Complex Method for Efficient Design Optimization

2007 ◽  
Author(s):  
Marcus Pettersson ◽  
Johan O¨lvander
Keyword(s):  
Design Optimization ◽  
Optimization Problem ◽  
Global Optimum ◽  
Direct Search ◽  
Complex Method ◽  
Efficient Design ◽  
Direct Search Methods ◽  
Simulation Based ◽  
Set Of Points ◽  
Quasi Newton

Box’s Complex method for direct search has shown promise when applied to simulation based optimization. In direct search methods, like Box’s Complex method, the search starts with a set of points, where each point is a solution to the optimization problem. In the Complex method the number of points must be at least one plus the number of variables. However, in order to avoid premature termination and increase the likelihood of finding the global optimum more points are often used at the expense of the required number of evaluations. The idea in this paper is to gradually remove points during the optimization in order to achieve an adaptive Complex method for more efficient design optimization. The proposed method shows encouraging results when compared to the Complex method with fix number of points and a quasi-Newton method.

scholarly journals Fast in-situ X-ray scattering reveals stress sensitivity of gypsum dehydration kinetics

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Christoph Eckart Schrank ◽  
Oliver Gaede ◽  
Tomasz Blach ◽  
Katherine Carmen Michelle Gioseffi ◽  
Stephen Mudie ◽  
...  
Keyword(s):  
Stress Sensitivity ◽  
Water Vapour Pressure ◽  
Fast Time ◽  
Dehydration Kinetics ◽  
Efficient Design ◽  
X Ray ◽  
Triggered Earthquakes ◽  
X Ray Scattering ◽  
Wide Range ◽  
Ray Scattering

AbstractThe dehydration of gypsum to hemihydrate has been studied for decades because it is an important model reaction for understanding fluid-triggered earthquakes, and due to the global use of plaster of Paris in the construction industry. The dehydration kinetics of gypsum strongly depend on temperature and water vapour pressure. Here, we perform fast, time-resolved synchrotron X-ray scattering on natural alabaster samples, finding that a small elastic load accelerates the dehydration reaction significantly. The mechanical acceleration of the reaction consumes about 10,000 times less energy than that due to heating. We propose that this thermodynamically surprising finding is caused by geometry-energy interactions in the microstructure, which facilitate nucleation and growth of the new crystalline phase. Our results open research avenues on the fundamental thermo-mechanics of crystal hydrates and the interaction of stress and chemical reactions in crystalline solids with a wide range of implications, from understanding dehydration-triggered earthquakes to the energy-efficient design of calcination processes.

Design Optimization of RML Glove for Improved Grasp Performance

2018 ◽  
Author(s):  
Teja Vanteddu ◽  
Bijo Sebastian ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Design Optimization ◽  
Daily Living ◽  
Experimental Validation ◽  
Large Diameter ◽  
Future Research ◽  
Linkage Mechanism ◽  
Design Variables ◽  
Wide Range ◽  
Optimal Values ◽  
Optimal Set

This paper describes the design optimization of the RML Glove in order to improve its grasp performance. The existing design is limited to grasping objects of large diameter (> 110mm) due to its inability in attaining high bending angles. For an exoskeleton glove to be effective in its use as an assistive and rehabilitation device for Activities of Daily Living (ADL), it should be able to interact with objects over a wide range of sizes. Motivated by these limitations, the kinematics of the existing linkage mechanism was analyzed in detail and the design variables were identified. Two different cost functions were formulated and compared in their ability to yield optimal values for the design variables. The optimal set of design variables was chosen based on the grasp angles achieved and the resulting mechanism was simulated in CAD for feasibility testing. An exoskeleton mechanism corresponding to the index finger was manufactured with the chosen design variables and detailed experimental validation was performed to illustrate the improvement in grasp performance over the existing design. The paper ends with a summary of the experimental results and directions for future research.

Fluorescence correlation spectroscopy: The technique and its applications in soft matter

2018 ◽  
Vol 4 (4) ◽  
Author(s):  
Anjali Gupta ◽  
Jagadish Sankaran ◽  
Thorsten Wohland
Keyword(s):  
Single Molecule ◽  
Fluorescence Correlation Spectroscopy ◽  
Soft Matter ◽  
Photophysical Properties ◽  
Spatiotemporal Analysis ◽  
Correlation Spectroscopy ◽  
Basic Principles ◽  
Chemical Reaction Kinetics ◽  
Fluorescence Correlation ◽  
Wide Range

Abstract Fluorescence correlation spectroscopy (FCS) is a well-established single-molecule method used for the quantitative spatiotemporal analysis of dynamic processes in a wide range of samples. It possesses single-molecule sensitivity but provides ensemble averaged molecular parameters such as mobility, concentration, chemical reaction kinetics, photophysical properties and interaction properties. These parameters have been utilized to characterize a variety of soft matter systems. This review provides an overview of the basic principles of various FCS modalities, their instrumentation, data analysis, and the applications of FCS to soft matter systems.

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