Numerical Study of Air-Flow Phenomena Through a Baffled Rectangular Micro-Channel

The aim of this study is to investigate the heat transfer characteristics of turbulent airflow phenomena in a rectangular micro-channel in presence of two plane shaped (type-1) and diamond shaped (type-2) baffles which will help to develop various heat exchanger models. Finite volume method has been used to solve the governing equations and the FLUENT software has been employed to visualize the simulation results. For both the baffles, the profile of flow structure, normalized velocity profile, normalized friction factor and average Nusselt number have been investigated with the variations of Reynolds number ranges between [10,000-50,000]. In terms of fluid flow and heat transfer phenomena, it has been found that in the presence of diamond shaped baffles (type-2) are more convenient than plane shaped baffles.

Experimental investigation of the effects of intermediate gravity waves on the water evaporation rate

This experiment was done to predict the evaporation rate from the wavy water surface under the different convection regimes ( free, forced, and mixed) at turbulent airflow conditions over a wide range of the ratio(Gr/Re2 ). Evaporation rate from wavy water surface is strongly affected by combinations between wave steepness and main airflow velocity above the wavy water surface. Experimental results show that no pattern can be followed for which combinations of evaporation rate will increase. Thus, only two facts can be noticed: the evaporation rate is larger than that measured under the same airflow velocity conditions with no waves existing on evaporated water surface because the airflow is smooth and attached along the still water surface and when increasing the wave steepness(H/L,H/T), Airflow will separate at the lee side of wave crest near to the bottom of the wave trough. Thus, vortex will generate in the airflow separation region. These vortexes are unstable and cause an increase in turbulence, reducing the water surface's resistance to vertical transport water vapor and increasing the evaporation rate. Also, experimental results show that the evaporation rates are somewhat less than that measured under the same airflow velocity with smaller wave steepness due to air trapped region observed at the leeside of the wave crest near the bottom of the wave trough. Evaporation rate is increasing with increase airflow velocity under the same convection regime.

Modeling the airflow field of vortex spinning

Vortex spinning technology adopts a high-speed swirling airflow to rotate the fibers with open-ends to form yarn with real twists. The airflow behavior within the nozzle has a great effect on the yarn-formation process. In this study, a three-dimensional calculation nozzle model and corresponding three-dimensional airflow region model were established to enable the numerical calculation; airflow behavior—pressure, velocity, and the turbulent airflow field, and the streamline of airflow—was investigated in the presence of fiber bundles within the vortex spinning nozzle. Hybrid hexahedral/tetrahedral control volumes were utilized to mesh the grids in the calculation region. To consider airflow diffusion and convection in the nozzle, the Realizable k- ε turbulence model with wall function was adopted to conduct the calculation. Dynamic and static pressure values were obtained by numerical analysis to predict the action of the inner surface of nozzle and the wall resistance on the high-speed swirling airflow. The numerical simulation of dynamic airflow behavior can generate great insight into the details of airflow behavior and its distribution characteristics, and is helpful for understanding the spinning mechanism and promoting optimization of the spinning process.

Microbial Air Monitoring in Turbulent Airflow Operating Theatres: Is It Possible to Calculate and Hypothesize New Benchmarks for Microbial Air Load?

Multiple studies have demonstrated the presence of microorganisms commonly associated with surgical site infections (SSIs), in the air within the operating theatre (OT). In some countries such Italy, the limit of microbial concentration in the air for OT with turbulent airflows is 35 CFU/m3 for an empty OT and 180 CFU/m3 during activity. This study aims to hypothesize new benchmarks for the airborne microbial load in turbulent airflow operating theatres in operational and at rest conditions using the percentile distribution of data through a 17-year environmental monitoring campaign in various Italian hospitals that implemented a continuous quality improvement policy. The quartile distribution analysis has shown how in operational and at rest conditions, 75% of the values were below 110 CFU/m3 and 18 CFU/m3, respectively, which can be considered a new benchmark for the monitored OTs. During the initial stages of the monitoring campaign, 28.14% of the concentration values in operational conditions and 29.29% of the values in at rest conditions did not conform to the Italian guidelines’ reference values. In contrast, during the last 5 years, all values in both conditions conformed to the reference values and 98.94% of these values were below the new benchmarks. Continuous improvement has allowed contamination to be reduced to levels well below the current reference values.

Numerical Simulations of Heat Transfer Phenomena through a Baffled Rectangular Channel

In presence of baffle, the turbulent airflow phenomena as well as forced convective heat exchange characteristics in two-dimensional rectangular channel have been analyzed in this work. For variations in Reynolds number (Re), we have studied the variations in characteristics of thermal behavior due to the change in the shape of baffle. Computations have been done using finite volume method (FVM) and FLUENT software and the SIMPLE algorithm has been employed for solving the governing equations. Finally, the flow and thermal exchange characteristics viz., streamline flow, turbulence intensity (TE), axial velocity, turbulence kinetic energy (TKE), normalized friction factor (F), normalized average Nusselt number (Nuavg) and thermal enhancement factor (TEF) have been studied in details from numerical standpoint. It has been found that the triangular shaped baffle provides highest value of F at Re = 30,000 and at Re = 46, 000, the maximum value of the TEF is found for the same baffle implying that triangular shaped baffle is more suitable for overall purposes.

Wind Noise Management in Hearing Aids

Many hearing aid users are negatively impacted by wind noise when spending time outdoors. Turbulent airflow around hearing aid microphones caused by the obstruction of wind can result in noise that is not only perceived as annoying but may also mask desirable sounds in the listening environment, such as speech. To mitigate the adverse effects of wind noise, hearing aid developers have introduced several technological solutions to reduce the amount of wind noise at the hearing aid output. Some solutions are based on mechanical modifications; more recently, sophisticated signal processing algorithms have also been introduced. By offering solutions to the wind noise problem, these signal processing algorithms can promote more optimal use of hearing aids during outdoor activities. This article reviews how wind noise is generated in hearing aids, outlines the technological challenges in wind noise management, and summarizes the technological solutions that have been proposed and/or implemented in modern hearing aids.

Bronchoscopic evaluation of children less than 5 years old with stridor

Background: Stridor is a harsh, vibratory sound with variable pitch which is caused by partial obstruction of airway that results in turbulent airflow. It is mainly due to anatomic deformities in the infantile age group. However, various acquired conditions affecting upper airway may also cause stridor. Here, we evaluated 87 cases of stridor using Flexible bronchoscope in order to determine the cause of stridor. Objective: To determine the clinical characteristics, Flexible bronchoscopy findings and clinical correlation in children admitted in our hospital with complains of stridor. Design: Retrospective observational study. Setting: Single center study conducted in Amrut medical foundation. 87 children aged less than 5 years with a clinical complains of stridor were included in the study and Flexible bronchoscopy was performed. The findings were analyzed and results were reported. Results: A total of 87 children with stridor were enrolled in the study and Flexible Bronchoscopy was performed in them. Of these, 68 children had an abnormal bronchoscopy finding. Laryngomalacia was the commonest cause of stridor observed followed by subglottic stenosis and tracheomalacia. Cough was the commonest presenting symptom associated with stridor and tachypnea was the commonest clinical sign observed in these children. Conclusion: Flexible bronchoscopy plays an important role in diagnosing the exact cause of stridor in pediatric age group. Key words: Stridor, Flexible Bronchoscopy, Laryngomalacia.