scholarly journals Minimizing the exposure of airborne pathogens by upper-room ultraviolet germicidal irradiation: an experimental and numerical study

2012 ◽  
Vol 9 (77) ◽  
pp. 3184-3195 ◽  
Author(s):  
Y. Yang ◽  
W. Y. Chan ◽  
C. L. Wu ◽  
R. Y. C. Kong ◽  
A. C. K. Lai
Keyword(s):  
Numerical Study ◽  
Local Variation ◽  
Airborne Bacteria ◽  
Experimental Measurements ◽  
Ultraviolet Germicidal Irradiation ◽  
Drift Flux ◽  
Inactivation Mechanism ◽  
Overall Performance ◽  
Bacteria Removal ◽  
Upper Room

There has been increasing interest in the use of upper-room ultraviolet germicidal irradiation (UVGI) because of its proven effectiveness in disinfecting airborne pathogens. An improved drift flux mathematical model is developed for optimizing the design of indoor upper-room UVGI systems by predicting the distribution and inactivation of bioaerosols in a ventilation room equipped with a UVGI system. The model takes into account several bacteria removal mechanisms such as convection, turbulent diffusion, deposition and UV inactivation. Before applying the model, the natural die-off rate and susceptibility constants of bioaerosols were measured experimentally. Two bacteria aerosols, Escherichia coli and Serratia marcescens , were tested for this purpose. It was found out that the general decay trend of the bioaerosol concentration predicted by the numerical model agrees well with the experimental measurements. The modelling results agree better with experimental observations for the case when the UVGI inactivation mechanism dominates at the upper-room region than for the case without UVGI. The numerical results also illustrate that the spatial distribution of airborne bacteria was influenced by both air-flow pattern and irradiance distribution. In addition to predicting the local variation of concentration, the model assesses the overall performance of an upper-room UVGI system. This model has great potential for optimizing the design of indoor an upper-room UVGI systems.

UV Air Cleaners and Upper-Room Air Ultraviolet Germicidal Irradiation for Controlling Airborne Bacteria and Fungal Spores

2006 ◽  
Vol 3 (10) ◽  
pp. 536-546 ◽  
Author(s):  
Elmira Kujundzic ◽  
Fatimah Matalkah ◽  
Cody J. Howard ◽  
Mark Hernandez ◽  
Shelly L. Miller
Keyword(s):  
Fungal Spores ◽  
Airborne Bacteria ◽  
Ultraviolet Germicidal Irradiation ◽  
Air Cleaners ◽  
Upper Room

The use of ultraviolet germicidal irradiation (UVGI) in disinfection of airborne bacteria and rhinoviruses

1998 ◽  
Vol 29 ◽  
pp. S777-S778 ◽  
Author(s):  
P.V. Scarpino ◽  
N.J. Jensen ◽  
P.A. Jensen ◽  
R. Ward
Keyword(s):  
Airborne Bacteria ◽  
Ultraviolet Germicidal Irradiation

Bejan’s Constructal Theory Analysis of Gas-Liquid Cooled Finned Modules

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Giulio Lorenzini ◽  
Simone Moretti
Keyword(s):  
Thermal Behavior ◽  
Heat Exchangers ◽  
High Performance ◽  
Numerical Study ◽  
Constructal Theory ◽  
Electronic Components ◽  
Theory Analysis ◽  
Pressure Losses ◽  
Different Types ◽  
Overall Performance

High performance heat exchangers represent nowadays the key of success to go on with the trend of miniaturizing electronic components as requested by the industry. This numerical study, based on Bejan’s Constructal theory, analyzes the thermal behavior of heat removing fin modules, comparing their performances when operating with different types of fluids. In particular, the simulations involve air and water (as representative of gases and liquids), to understand the actual benefits of employing a less heat conductive fluid involving smaller pressure losses or vice versa. The analysis parameters typical of a Constructal description (such as conductance or Overall Performance Coefficient) show that significantly improved performances may be achieved when using water, even if an unavoidable increase in pressure losses affects the liquid-refrigerated case. Considering the overall performance: if the parameter called Relevance tends to 0, air prevails; if it tends to 1, water prevails; if its value is about 0.5, water prevails in most of the case studies.

scholarly journals Numerical study of flow patterns and heat transfer in mini twisted oval tubes

2015 ◽  
Vol 26 (12) ◽  
pp. 1550140 ◽  
Author(s):  
Amin Ebrahimi ◽  
Ehsan Roohi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Critical Role ◽  
Reynolds Numbers ◽  
Flow Patterns ◽  
Working Fluid ◽  
Transfer Performance ◽  
Temperature Dependent ◽  
Overall Performance

Flow patterns and heat transfer inside mini twisted oval tubes (TOTs) heated by constant-temperature walls are numerically investigated. Different configurations of tubes are simulated using water as the working fluid with temperature-dependent thermo-physical properties at Reynolds numbers ranging between 500 and 1100. After validating the numerical method with the published correlations and available experimental results, the performance of TOTs is compared to a smooth circular tube. The overall performance of TOTs is evaluated by investigating the thermal-hydraulic performance and the results are analyzed in terms of the field synergy principle and entropy generation. Enhanced heat transfer performance for TOTs is observed at the expense of a higher pressure drop. Additionally, the secondary flow generated by the tube-wall twist is concluded to play a critical role in the augmentation of convective heat transfer, and consequently, better heat transfer performance. It is also observed that the improvement of synergy between velocity and temperature gradient and lower irreversibility cause heat transfer enhancement for TOTs.

On Flowfield Periodicity in the NASA Transonic Flutter Cascade: Part II — Numerical Study

2000 ◽  
Author(s):  
R. V. Chima ◽  
E. R. McFarland ◽  
J. R. Wood ◽  
J. Lepicovsky
Keyword(s):  
Static Pressure ◽  
Numerical Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Wave Structure ◽  
Experimental Measurements ◽  
Flow Conditions ◽  
Pressure Sensitive ◽  
Transonic Flutter ◽  
Probe Measurements

The transonic flutter cascade facility at NASA Glenn Research Center was redesigned based on a combined program of experimental measurements and numerical analyses. The objectives of the redesign were to improve the periodicity of the cascade in steady operation, and to better quantify the inlet and exit flow conditions needed for CFD predictions. Part I of this paper describes the experimental measurements, which included static pressure measurements on the blade and endwalls made using both static taps and pressure sensitive paints, cobra probe measurements of the endwall boundary layers and blade wakes, and shadowgraphs of the wave structure. Part II of this paper describes three CFD codes used to analyze the facility, including a multibody panel code, a quasi-three-dimensional viscous code, and a fully three-dimensional viscous code. The measurements and analyses both showed that the operation of the cascade was heavily dependent on the configuration of the sidewalls. Four configurations of the sidewalls were studied and the results are described. For the final configuration, the quasi-three-dimensional viscous code was used to predict the location of mid-passage streamlines for a perfectly periodic cascade. By arranging the tunnel sidewalls to approximate these streamlines, side-wall interference was minimized and excellent periodicity was obtained.

Empirical Heat Transfer Correlations during Frost Deposition on a Triangular Tube Banks Arrangement

2016 ◽  
Vol 366 ◽  
pp. 88-96
Author(s):  
Raquel da Cunha Ribeiro da Silva ◽  
Carlos Salinas Sedano ◽  
Kamal A.R. Ismail ◽  
Paúl Adrian Delgado Maldonado
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Numerical Study ◽  
Experimental Measurements ◽  
Empirical Correlations ◽  
Frost Formation ◽  
Cylindrical System ◽  
Experimental Correlation ◽  
Tube Banks ◽  
Dimensionless Correlations

An experimental study was reported earlier on the development of frost formation by humid flow passing over the cylinder. In this study, dimensionless correlations used in previous experimental data, and reported empirical correlations of the Nusselt number, were used. This paper reports results of an experimental and numerical investigation where the emphasis was placed on obtaining empirical correlation for the Nusselt number. In this work some experimental results of the frost thickness around every cylinder in a triangular arrangement are presented, an estimated experimental correlation to find Nusselt number. This correlation is based on the experimental measurements in a wind tunnel situated in the Laboratory of Thermal storage and Fluids in the Mechanical Engineering Faculty at Unicamp. A numerical study is performed to study the frost formation in the cylindrical system.

Microwave signal emission in spin-torque vortex oscillators in metallic nanowires: Experimental measurements and micromagnetic numerical study

2012 ◽  
Vol 86 (6) ◽  
Author(s):  
F. Abreu Araujo ◽  
M. Darques ◽  
K. A. Zvezdin ◽  
A. V. Khvalkovskiy ◽  
N. Locatelli ◽  
...  
Keyword(s):  
Numerical Study ◽  
Microwave Signal ◽  
Spin Torque ◽  
Experimental Measurements ◽  
Metallic Nanowires

Ac Response of Heterogeneous Materials: A Numerical Study

1996 ◽  
Vol 463 ◽  
Author(s):  
A. A. Rodriguez ◽  
J. Valbuena
Keyword(s):  
Distribution Function ◽  
Electrical Properties ◽  
Numerical Study ◽  
Experimental Measurements ◽  
Power Law Distribution ◽  
Scaling Properties ◽  
Strong Disorder ◽  
Hierarchical Lattices ◽  
Ac Response ◽  
Dc Electrical Properties

ABSTRACTThe ac and dc electrical properties of composite materials are studied using hierarchical lattices. First we show that the hierarchical model can correctly account for the main scaling properties of critical percolative structures. Then we study the effect of potential disorder by assuming that the microscopic conductances are distributed according to a power law distribution function. We find that in the limit of strong disorder, the predictions are in qualitative agreement with reported experimental measurements.

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