scholarly journals Analysis of the Radiation Dose in UV-Disinfection Flow Reactors

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 231 ◽  
Author(s):  
Artichowicz ◽  
Luczkiewicz ◽  
Sawicki
Keyword(s):  
Turbulent Flows ◽  
Fluid Velocity ◽  
Uv Disinfection ◽  
Radiation Doses ◽  
Flow Reactors ◽  
Direct Radiation ◽  
Radiation Zone ◽  
Uv Lamp ◽  
Pass Through ◽  
Time Required

UV-disinfection reactors may appear in a variety of forms, but it is useful for all types to identify the inflow and outflow zones (those in which the fluid approaches or, respectively, recedes from the radiation source) and the direct radiation zone (in which the flow occurs along the UV lamp). Due to the spatial variability of the velocity field and the radiation intensity, the radiation doses received in different zones of a reactor differ. In this work, theoretical considerations regarding functions describing the variability of UV radiation doses in flow reactors are presented. The most basic parameter of a UV-disinfection reactor is the minimal time required by the fluid to pass through the reactor. Such time depends on the maximum fluid velocity in the reactor. Based on the theoretical analysis of this phenomenon, the doses in different zones of the reactor have been compared for laminar and turbulent flows. The result of the analysis states that UV-disinfection reactors should be designed in such a way to deliver the required amount of radiation to the point at which the fluid velocity is the highest. The other main conclusion resulting from this comparison yields that the most effective in terms of disinfection is the direct radiation zone, whereas the influence of the inflow and outflow zones is negligible.

scholarly journals A Longitudinal Qualitative Analysis of the Way Peer Support Specialist Roles Change Over Time in a Psychiatric Hospital Setting in Asia

2021 ◽  
Author(s):  
Daniel Poremski ◽  
Jonathan Kuek ◽  
Yuan Qi ◽  
Ziqiang Li ◽  
Kah Lai Yow ◽  
...  
Keyword(s):  
Lived Experience ◽  
Peer Support ◽  
Service Use ◽  
Hospital Setting ◽  
Service Users ◽  
Role Clarity ◽  
Job Descriptions ◽  
Spheres Of Influence ◽  
Pass Through ◽  
Time Required

AbstractThe current study seeks to determine how peer support roles change as peer support specialists’ positions within organizations and departments mature. We followed ten peer support specialists over the course of a year, interviewing them at three points, starting approximately three months after they began working as peer support specialists. We used an inductive process to analyze our data and followed guidelines on the structuring of longitudinal qualitative trajectories to divide the data into watershed moments. Our participants worked in a variety of departments in the hospital, and their service use experiences generally echo those of their service users. Participants appear to pass through four phases over the course of their employment as peers: early beginnings, establishing the role, role narrowing, and role sustainability. Services wishing to integrate new peers must be aware of the time required for integration. Having general job descriptions limited to specifying that peers are expected to use their lived experience to support current service users may lead to uncertainty amongst new and existing staff. Without role clarity, peers may struggle to find their place. Pairing new staff with mentors may limit this burden. As roles consolidate, boundaries may emerge. If these boundaries narrow the role of the PSS, they may no longer find the role appealing. They may then choose other caregiver roles with wider or different spheres of influence. Organizations may benefit by clearly indicating if they expect peer support positions to be static or transitionary.

scholarly journals Flow topologies in bubble-induced turbulence: a direct numerical simulation analysis

2018 ◽  
Vol 857 ◽  
pp. 270-290 ◽  
Author(s):  
Josef Hasslberger ◽  
Markus Klein ◽  
Nilanjan Chakraborty
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Volume Fraction ◽  
Fluid Velocity ◽  
Small Scale ◽  
Flow Topology ◽  
Two Phase ◽  
Local Flow ◽  
Interface Curvature

This paper presents a detailed investigation of flow topologies in bubble-induced two-phase turbulence. Two freely moving and deforming air bubbles that have been suspended in liquid water under counterflow conditions have been considered for this analysis. The direct numerical simulation data considered here are based on the one-fluid formulation of the two-phase flow governing equations. To study the development of coherent structures, a local flow topology analysis is performed. Using the invariants of the velocity gradient tensor, all possible small-scale flow structures can be categorized into two nodal and two focal topologies for incompressible turbulent flows. The volume fraction of focal topologies in the gaseous phase is consistently higher than in the surrounding liquid phase. This observation has been argued to be linked to a strong vorticity production at the regions of simultaneous high fluid velocity and high interface curvature. Depending on the regime (steady/laminar or unsteady/turbulent), additional effects related to the density and viscosity jump at the interface influence the behaviour. The analysis also points to a specific term of the vorticity transport equation as being responsible for the induction of vortical motion at the interface. Besides the known mechanisms, this term, related to surface tension and gradients of interface curvature, represents another potential source of turbulence production that lends itself to further investigation.

scholarly journals E. coli Inactivation Kinetics Modeling in a Taylor-Couette UV Disinfection Reactor

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
M. L. Palacios-Contreras ◽  
F. Z. Sierra-Espinosa ◽  
K. Juárez ◽  
S. Silva-Martínez ◽  
A. Alvarez-Gallegos ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Polynomial Equation ◽  
Microbial Inactivation ◽  
Uv Disinfection ◽  
Order Kinetic ◽  
E Coli ◽  
Toroidal Vortices ◽  
Angular Velocities ◽  
Uv Lamp ◽  
Kinetics Of

A simple model was developed to predict the survival behavior of E. coli subjected to UV disinfection in a Taylor-Couette reactor. The model includes the CFD evaluation of the counterrotating toroidal vortices developed within the annular space of two coaxial cylinders. The UV lamp was located within the diameter of the internal rotating cylinder. The residence time of the bacteria near the UV lamp is, therefore, a function of both the size of the vortex and its angular velocity. The effect of angular velocity on the formation of counterrotating toroidal vortices and their impact on the kinetics of UV microbial inactivation was experimentally evaluated. The kinetics of microbial inactivation follow an apparent first-order kinetic equation between 300 and 2000 revolutions per minute. Therefore, in this range of angular velocities, a set of k values (indirectly taking into account the hydrodynamic pattern and UV irradiance) was obtained for a given concentration of bacteria. Then, the set of k values was correlated with the range of angular velocities applied using the polynomial equation. A k value can be obtained for an unknown angular velocity through the polynomial equation. Therefore, a simulation curve of microbial inactivation can be obtained from the first-order kinetic equation. The efficiency of bacteria removal improves depending on the angular velocity applied. A good agreement is observed between the simulation of the survival behavior of the microorganisms subjected to UV disinfection with the experimental data.

Intermittent Flow Modeling: Part 2—Time-Varying Flows and Flows in Variable Area Ducts

2010 ◽  
Author(s):  
J. P. Abraham ◽  
E. M. Sparrow ◽  
J. C. K. Tong ◽  
W. J. Minkowycz
Keyword(s):  
Reynolds Number ◽  
Flow Regime ◽  
Turbulent Flows ◽  
Intermittent Flow ◽  
Steady Regime ◽  
Cross Sectional ◽  
Friction Factors ◽  
Pass Through ◽  
Different Diameters ◽  
Reynolds Number Flows

The all-flow-regime model of fluid flow, previously applied in [1] to flows with axially and temporally uniform Reynolds numbers, has been implemented here for flows in which the Reynolds number may either vary with time or along the length of a pipe. In the former situation, the timewise variations were driven by a harmonically oscillating inlet flow. These oscillations created a succession of flow-regime transitions encompassing purely laminar and purely turbulent flows as well as laminarizing and turbulentizing flows where intermittency prevailed. The period of the oscillations was increased parametrically until the quasi-steady regime was attained. The predicted quasi-steady friction factors were found to be in excellent agreement with those from a simple model under which the flow is assumed to pass through a sequence of instantaneous steady states. In the second category of non-constant-Reynolds-number flows, axial variations of a steady flow were created by means of a finite-length conical enlargement which connected a pair of pipes of constant but different diameters. The presence of the cross-sectional enlargement gives rise to a reduction of the Reynolds number that is proportional to the ratio of the diameters of the upstream and the downstream pipes. Depending on the magnitude of the upstream inlet Reynolds number, the downstream fully developed flow could variously be laminar, intermittent, or turbulent. The presence or absence of flow separation in the conical enlargement had a direct effect on the laminarization process. For both categories of non-constant-Reynolds-number flows, laminarization and turbulentization were quantified by the ratio of the rate of turbulence production to the rate of turbulence destruction.

scholarly journals Molecular Indications of Protein Damage in Adenoviruses after UV Disinfection

2010 ◽  
Vol 77 (3) ◽  
pp. 1145-1147 ◽  
Author(s):  
Anne C. Eischeid ◽  
Karl G. Linden
Keyword(s):  
Cell Culture ◽  
Viral Proteins ◽  
Low Pressure ◽  
Protein Damage ◽  
Uv Disinfection ◽  
Medium Pressure ◽  
The Difference ◽  
Uv Lamp ◽  
Detailed Work

ABSTRACTAdenoviruses are resistant to monochromatic, low-pressure (LP) UV disinfection—but have been shown to be susceptible to inactivation by polychromatic, medium-pressure (MP) UV—when assayed using cell culture infectivity. One possible explanation for the difference between UV lamp types is that the additional UV wavelengths emitted by MP UV enable it to cause greater damage to viral proteins than LP UV. The objective of this study was to examine protein damage in adenoviruses treated with LP and MP UV. Results show that MP UV is more effective at damaging viral proteins at high UV doses, though LP UV caused some damage as well. To our knowledge, this study is the first to investigate protein damage in UV-treated adenovirus, and the overview presented here is expected to provide a basis for further, more detailed work.

scholarly journals Spin-up in a tank induced by a rotating bluff body

1999 ◽  
Vol 388 ◽  
pp. 49-68 ◽  
Author(s):  
D. MAYNES ◽  
J. KLEWICKI ◽  
P. McMURTRY
Keyword(s):  
Steady State ◽  
Turbulent Diffusion ◽  
Bluff Body ◽  
Fluid Velocity ◽  
Tangential Velocity ◽  
The Body ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
Acceleration Rate ◽  
Time Required

Spin-up of a turbulent flow in a cylindrical tank caused by a rotating bluff body has been investigated using flow visualization, fluid velocity measurements, and hydrodynamic torque measurements. During the spin-up process three distinct temporal regimes exist. These regimes are: (i) a build-up regime where the torque and the tangential velocity fluctuations in the close proximity of the body remain constant; (ii) a decay regime where these quantities decay with power-law relations; and (iii) a mean flow steady state where these values remain relatively constant. Experiments were conducted in two tanks differing in volume by a factor of 80 and with a large range of bluff body sizes. A non-dimensional time scale, τ, based upon turbulent diffusion is determined and the tangential velocity fluctuations and torque coefficient start to decay at a fixed value of τ. Likewise, steady state is attained at a larger fixed value of τ. This time scaling is physically based upon the time required for momentum to be transferred over the entire tank volume due to turbulent diffusion, and is general for any body size, tank size, rotation rate, and acceleration rate.

scholarly journals High-beta turbulence in two-dimensional magnetohydrodynamics

1976 ◽  
Vol 16 (2) ◽  
pp. 181-191 ◽  
Author(s):  
David Fyfe ◽  
David Montgomery
Keyword(s):  
Magnetic Fields ◽  
Turbulent Flows ◽  
Fluid Dynamic ◽  
Fluid Velocity ◽  
Navier Stokes ◽  
Magnetic Islands ◽  
Dissipation Energy ◽  
Energy Cascades ◽  
Wide Range ◽  
Current Filaments

Incompressible turbulent flows are investigated in the framework of ideal magnetohydrodynamics. All the field quantities vary with only two spatial dimensions. Equilibrium canonical distributions are determined in a phase space whose co-ordinates are the real and imaginary parts of the Fourier coefficients for the field variables. In the geometry considered, the magnetic field and fluid velocity have variable x and y components, and all field quantities are independent of z. Three constants of the motion are found (one of them new) which survive the truncation in Fourier space and permit the construction of canonical distributions with three independent temperatures. Spectral densities are calculated. One of the more novel physical effects is the appearance of macroscopic structures involving long wavelength, self-generated, magnetic fields (‘magnetic islands’) for a wide range of initial parameters. Current filaments show a tendency toward consolidation in much the same way that vorticity filaments do in the guiding-centre plasma case. In the presence of finite dissipation, energy cascades to higher wavenumbers can be accompanied by vector potential cascades to lower wavenumbers, in much the same way as, in the fluid dynamic (Navier-Stokes) case, energy cascades to lower wavenumbers accompany enstrophy cascades to higher wavenumbers. It is suggested that the techniques may be relevant to theories of the magnetic dynamo problem and to the generation of megagauss magnetic fields when pellets are irradiated by lasers.

Development of UV Distribution Model for the Non-Contact Type UV Disinfection System

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Sung Hong Kim ◽  
Young Gyun Choi ◽  
Dooil Kim
Keyword(s):  
Mathematical Model ◽  
Exposure Time ◽  
Uv Light ◽  
Treatment Plant ◽  
Water Layer ◽  
Distribution Model ◽  
Uv Disinfection ◽  
Contact Type ◽  
Irradiation System ◽  
Uv Lamp

Fouling on the quartz sleeve reduces the transmittance of UV light through the sleeve into the water in submerged UV disinfection system. The concept of a non-contact type of UV disinfection system was introduced in this study. UV lamps and their quartz sleeves hang over the water surface and there is no interface between the sleeve and water. Indeed, there is no fouling. Based on optical laws and UV distribution model, a detailed mathematical model for a non-contact type UV disinfection system was developed and simulated in this study. UV light passes through 4 media of air-quartz-air and water in case of non-contact type irradiation system. By the simulation of the mathematical model of the system, it is known that the non-contact type of UV system requires 2.5 times more powerful UV lamp or a lamp with longer exposure time than that of the submerged type of UV system. In a non-contact type of UV system, high-reflective ceiling material can increase the UV intensity of the water layer as much as 28 percent more than the case of non-reflective ceiling material. The non-contact type UV irradiation system requires more powerful lamp or one that have longer exposure time. Nevertheless, considering the fouling attenuation and maintenance problem associated with the fouling, non-contact type of UV disinfection system deserves to be practically considered, especially in a small to middle scale water or wastewater treatment plant.

Influence of lamp intensity and water transmittance on the UV disinfection of water

1997 ◽  
Vol 35 (11-12) ◽  
pp. 113-118 ◽  
Author(s):  
R. Sommer ◽  
A. Cabaj ◽  
W. Pribil ◽  
T. Haider
Keyword(s):  
Supply Voltage ◽  
Uv Disinfection ◽  
Uv Detector ◽  
Uv Irradiance ◽  
Flow Through ◽  
Uv Lamp ◽  
Uv Transmittance ◽  
Two Parameters ◽  
Uv Lamps ◽  
Irradiation Chamber

The efficiency of UV disinfection devices depends on flow, lamp intensity and water transmittance. In practice the flow is controlled by suitable methods, whereas the other two parameters, to date, have not been taken into consideration sufficiently. The surveillance of the function of UV disinfection plants is routinely based on a sensor placed on the irradiation chamber wall. This measures changes of UV irradiance without differentiating if the effect is caused by transmittance or lamp intensity so that two different conditions of disinfection may occur at the same sensor readings. We investigated the influence of transmittance vs intensity on disinfection at the same sensor readings in a specially designed laboratory flow through UV irradiation system with one single UV lamp as well as in commercially available UV disinfection plants with multiple UV lamps. All devices were equipped with a calibrated selective UV detector connected to a UV radiometer. Lamp intensity was decreased by diminishing the supply voltage. UV transmittance was reduced by pumping aqueous sodium thiosulphate solution into the water inflow. The disinfection capacity was determined by measuring the reduction equivalent doses (RED) using a standardised biodosimetric method. We showed that equal sensor readings, either achieved by reducing the lamp intensity or by lowering the UV transmittance of the water, resulted in different REDs in one-lamp systems. The diminishing of UV intensity caused a greater decrease of REDs than reducing the water transmittance. However, in the multiple-lamp systems tested, equal sensor readings yielded equal REDs.

Sign in / Sign up

Export Citation Format

Share Document