scholarly journals Bacteriological evaluation of a laminar cross-flow tunnel for surgery under operational conditions

1974 ◽  
Vol 72 (2) ◽  
pp. 145-153 ◽  
Author(s):  
D. van der Waaij ◽  
P. J. Heidt ◽  
W. D. H. Hendriks
Keyword(s):  
Flow Pattern ◽  
Cross Flow ◽  
Surgical Team ◽  
Front Side ◽  
Air Velocity ◽  
Operational Conditions ◽  
Disappearance Time ◽  
Detectable Concentration ◽  
Bacteriological Evaluation ◽  
Stable Flow

SUMMARYA transportable surgery cross-flow unit has been tested under ‘operational conditions’. By the use of artificial aerosols and a volunteer surgical team, or dummies, it was found that, at an air velocity of 0·45 m./sec., a detectable transfer to above the table occurred only when quite highly concentrated aerosols (of more than 103·6 bacteria/m.3 of air or more) existed underneath the table. The short disappearance time under these conditions and the quite stable flow pattern above the table found when a surgical team was working, standing along both sides of the table, make it unlikely that an aerosol of detectable concentration can develop during surgery, at this site. The chance that particles, liberated from the heads of the surgical team, settle on the table, was found to be strongly reduced when a cross-flow tunnel operated at an air velocity of 0·45 m./sec. The transfer from outside the unit to the inside was prevented by closing the upper part of the open front side.

Suppression of the Surging Phenomenon by Modifying Tongue Shape of Air Conditioner Mounted With Cross-Flow Fan

2019 ◽  
Author(s):  
Haruki Nukaga ◽  
Hiroshi Maita ◽  
Hisashi Daisaka
Keyword(s):  
Flow Pattern ◽  
Environmental Concern ◽  
Cross Flow ◽  
Low Flow ◽  
Air Conditioner ◽  
Test Results ◽  
Air Velocity ◽  
High Static Pressure ◽  
Cross Flow Fan ◽  
Center Area

Abstract Energy saving of room air-conditioner (RAC) is strongly required due to growing environmental concern. It is difficult to work a cross flow fan (CFF) at the most efficient operating point (OP) because a surging phenomenon occurs near this efficient OP. The conventional method for suppressing the surging phenomenon by increasing a rotation speed is unfavorable because a fluidic noise and a fan power consumption increase. Therefore, we investigated the new method for suppressing the surging phenomenon focusing on a structure of a fan casing. It is known that the surging phenomenon is likely to occur from both right and left ends of the CFF. However, an area where surging occurs and a flow pattern in this area have not been revealed in detail. In this study, we experimentally investigated the area where surging occurs by measuring the outlet air velocity distribution across the CFF. In addition, the flow pattern in this area was compared with that of the center area using simulation. Simulation results showed that an area ratio of a vortex flow inside the CFF is high at both ends of the CFF, and a part of the mainstream flows back to the upstream side through a gap between the tongue and the CFF. Therefore, we thought that the function of the tongue, which divide inflow and outflow, is not sufficient. The influence of modifying the tongue shape was experimentally evaluated. The test results showed that the surging limit shifted to the low flow rate and high static pressure side, and the noise at the condition of the surging limit decreased. The surging phenomenon was suppressed by modifying the tongue shape at both ends of the CFF compared to the center area. This technique makes it possible to work the CFF in a more efficient OP.

Karakteristik aliran dua fase pada saluran ekspansi tiba-tiba

2018 ◽  
Vol 11 (1) ◽  
pp. 7
Author(s):  
Latif Ngudi Wibawanto ◽  
Budi Santoso ◽  
Wibawa Endra Juwana
Keyword(s):  
Standard Deviation ◽  
Flow Pattern ◽  
Flow Characteristic ◽  
Homogeneous Model ◽  
Flow Equation ◽  
Pressure Recovery ◽  
Sudden Expansion ◽  
Air Velocity ◽  
Model Flow ◽  
Two Phases

This research was conducted to find out the flow characteristic of two phases through the channel with sudden expansion in the form of change of flow pattern and pressure recovery. The test was carried out with variation of superficial velocity of water 0.2-1.3 m / s and superficial air velocity of 0.2-1.9 m / s resulting in pattern of three flow patterns ie bubble, plug, and slug. The expansion channel resulted in some changes to the flow pattern that originally plugs in the upstream channel into bubble in the downstream channel and the slug becomes plug. Pressure recovery experimental results compared with the homogeneous model flow equation and Wadle correlation, both correlations have predictions with standard deviation values of 0.32 and 0.43.

Influence of Circuitry Arrangement on the Pressure Drops of Two-Row Finned Tube Evaporators

2000 ◽  
Vol 123 (1) ◽  
pp. 100-103 ◽  
Author(s):  
Chi-Chuan Wang ◽  
Min-Sheng Liu ◽  
Jin-Sheng Leu
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Cross Flow ◽  
Finned Tube ◽  
Parallel Flow ◽  
Pressure Drops ◽  
Heat Addition ◽  
Side Pressure ◽  
Flow Pattern Transition ◽  
Flow Circuit

This study experimentally investigates the effect of circuitry on the refrigerant-side pressure drops of plate finned tube evaporators. Experiments were performed with countercross, parallel-cross, and z-shape arrangements. The results showed that the parallel-cross-flow circuit gives a lower pressure drop than other arrangements. Generally, the refrigerant-side pressure drops increase with air frontal velocities. However, for G=200 kg/m2s˙s and parallel flow, the pressure drops decrease with increase of air frontal velocity. This unusual characteristic is most likely related to the flow pattern transition when subjected to heat addition.

scholarly journals A bacteriological evaluation of laminar-flow systems for orthopaedic surgery

1973 ◽  
Vol 71 (3) ◽  
pp. 559-564 ◽  
Author(s):  
W. Whyte ◽  
B. H. Shaw ◽  
R. Barnes
Keyword(s):  
Laminar Flow ◽  
Operating Room ◽  
Orthopaedic Surgery ◽  
Flow System ◽  
Air Flow ◽  
Cross Flow ◽  
Operating Rooms ◽  
Airborne Bacteria ◽  
Flow Systems ◽  
Bacteriological Evaluation

SUMMARYAn evaluation has been undertaken of the efficiency of laminar-flow ventilation in operating-rooms in which conventional operating-room clothing was used. It has been demonstrated that velocities in the region of 0·3–0·4 m/sec. will give maximum returns for effort in both down-flow and cross-flow systems. At this velocity the laminar-flow system, in terms of airborne bacteria measured at the would site, was about 11 times more effients using horizontal air-flow and 35–90 times more efficient using vertical air-flow than a plenum-ventilated operating room.

scholarly journals Two-Phase Flow Characteristics on The Extensive Expansion Channel

2017 ◽  
Vol 16 (2) ◽  
Author(s):  
Latif Ngudi Wibawanto ◽  
Budi Santoso ◽  
Wibawa Endra Juwana
Keyword(s):  
Flow Pattern ◽  
Homogeneous Model ◽  
Flow Characteristics ◽  
Flow Equation ◽  
Pressure Recovery ◽  
Sudden Expansion ◽  
Air Velocity ◽  
Two Phase ◽  
Model Flow ◽  
Two Phases

This research was conducted to find out the flow characteristic of two phases through channel with sudden expansion in the form of change of flow pattern and pressure recovery. The test was conducted with variation of superficial velocity of water 0.2-1.3 m / s and superficial air velocity of 0.2-1.9 m / s resulting in pattern of three flow patterns ie bubble, plug, and slug. The expansion channel resulted in some changes to the flow pattern that originally plugs in the upstream channel into bubble in the downstream channel and the slug becomes plug. Pressure recovery experimental results were compared with the homogeneous model flow equation and Wadle correlation, the two correlations had predictions with standard deviation values of 0.32 and 0.43.

Flow Excited Acoustic Resonance of Two Side-by-Side Cylinders in Cross Flow

2006 ◽  
Author(s):  
Ronald Hanson ◽  
Atef Mohany ◽  
Samir Ziada
Keyword(s):  
Flow Regime ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Resonance Mechanism ◽  
Flow Phenomenon ◽  
Stable Flow ◽  
Center Distance

The aeroacoustic response of two side-by-side cylinders in cross-flow is investigated experimentally. In order to investigate the effect of the gap between the cylinders on the acoustic resonance mechanism, six spacing ratios between the cylinders have been investigated. These spacing ratios are in the range of T/D = 1.25 to 3, where D is the diameter of the cylinders and T is the center-to-center distance between them. Special attention is given to the bi-stable flow regime, which is reported in the literature for intermediate spacing ratios. During the tests, the acoustic cross-modes of the duct housing the cylinders are self-excited. For the intermediate spacing ratios, T/D = 1.25, 1.35, 1.46 and 1.75, two distinct vortex shedding frequencies at the off-resonance conditions are observed. These are associated with the wider and narrower wakes of the cylinders, as described in the literature. In this case, acoustic resonance occurs at a Strouhal number that is between those observed before the onset of resonance. In addition, the acoustic resonance synchronizes vortex shedding in the two wakes and thereby eliminates the bi-stable flow phenomenon. For large spacing ratios, T/D = 2.5 and 3, vortex shedding occurs at a single Strouhal number at which the acoustic resonance is initiated.

Computer Modelling Of Multicomponent Gas Separation By Membranes

1998 ◽  
pp. 23-33
Author(s):  
Thomas S.Y Choong ◽  
Ramlan Abdul Aziz ◽  
Hamdani Saidi
Keyword(s):  
Flow Pattern ◽  
Gas Separation ◽  
Computer Modelling ◽  
Cross Flow ◽  
Cocurrent Flow ◽  
Countercurrent Flow ◽  
Feed System ◽  
Membrane Area ◽  
Chemical Process Industry ◽  
Multicomponent Gas

Gas separation using membrane is now an established unit operation in the chemical process industry. The performance of a single stage membrane permeator depends, among other things, on the feed and permeate flow pattern. In this paper, models for five different idealized flow patterns namely cocurrent flow, countercurrent flow, cross flow, perfect mixing and on-side mixing have been presented. A computer program written in Power Basic has also been developed. The models developed can be used for a binary mixture or multi-component gas feed system. A simple bisection method is used instead of the Newton iterative method originally suggested by Shindo et.al.[6] to solve the root finding-problem in order to ensure convergence. In this study countercurrent flow is found to be the most efficient flow pattern, giving the highest degree of separation and requiring the least membrane area.

scholarly journals Hydrodynamic Analysis of the Flow inside the Submerged Entry Nozzle

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Jesus Gonzalez-Trejo ◽  
Cesar Augusto Real-Ramirez ◽  
Ignacio Carvajal-Mariscal ◽  
Florencio Sanchez-Silva ◽  
Francisco Cervantes-De-La-Torre ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Flow Pattern ◽  
Liquid Steel ◽  
Similarity Criterion ◽  
Submerged Entry Nozzle ◽  
The Other ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Operational Conditions ◽  
Physical Experiments

The quality of steel produced by continuous casting depends mainly on the characteristics of the liquid steel flow pattern within the mold. This pattern depends on the flow dynamics of the nozzle that is immersed in liquid steel. This work characterizes the fluid dynamics within two separate submerged entry nozzle models with a square cross section bore. The Froude similarity criterion and water as working fluid have been used. The models consist of a square-shaped tube with one inlet and two lateral squared exits at the bottom. To enhance the flow visualization, the models do not have exit ports. Moreover, one of the models has a “pool,” a volume at the bottom, and the other prescinds of it. The geometrical parameters and operational conditions of physical experiments were reproduced in the numerical simulations. The turbulence model used in this work is large eddy simulation (LES) with dynamic k-equation filtering. It was found that transient numerical simulations reproduce the dynamic nature of the internal flow pattern seen in physical experiments. The results show that the flow pattern within the pool nozzle is defined by only one large vortex; on the other hand, in the nozzle, without the pool, the flow pattern achieves a complex behavior characterized by two small vortexes. This study will allow to build nozzles that produce a symmetric, regular fluid flow pattern inside the mold, which leads to improvements on the process such as low energy consumption and finally in cost reductions.

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