Preliminary Study of the Effect of Secondary Airflow on Fiber Attenuation During Melt Blowing

Huawei Xu,Zhijun Zhou,Jie Liu,Lie Zhao,Sheng Xie,Junfeng Zhang 한국섬유공학회 2022 Fibers and polymers Vol.23 No.11

In order to enhance the fiber attenuation during the melt-blown process, a pair of air nozzle, which could eruptairflow as secondary airflow, below the spinning die was arranged and used. Firstly, the effect of applying secondary airflowon the whole airflow was explored by Computational Fluid Dynamics (CFD) simulation. The simulation results demonstratethe interactive relationship between the primary airflow from the spinning die and the secondary airflow. Then, the airvelocity of the whole airflow at conditions of with and without secondary airflow was experimental verified. Finally, theeffect of secondary airflow on the fiber diameter and the fiber evenness was investigated by a spinning experiment. Thespinning results reveals that the application of secondary airflow does not certainly enhance the fiber attenuation. The fiberdiameter decreases only when the inlet velocity of secondary airflow is higher than a critical value. In addition, the spinningexperiment indicates that the application of secondary airflow improves the evenness of fiber.

만성 부비동염 환자에서 비기류에 대한 민감도의 변화

나기상,이석호,임동우,김병국,박찬일 충남대학교 의과대학 지역사회의학연구소 1999 충남의대잡지 Vol.26 No.2

Nasal patency may be considered to have two aspects: the resistance to airflow and the sensation of airflow. Although the sensation of nasal airflow has received little attention from clinicians, it is likely that it is of great importance in clinical practice. However, there are no study that assess the sensation of nasal airflow in patients complaining of nasal obstruction. The aim of this study is to assess the airflow sensitivity of the nose in patients with chronic paranasal sinusitis. To assess the airflow sensitivity, we designed an apparatus delivering a pulsing jet of air at varying velocities. We measured threshold velocities at six different sites of each nasal cavity in fifteen patients and compared with the values in normal subjects. All patients had bilateral chronic sinusitis with polyp. The threshold velocities at all but site 5 were higher in sinusitis patients than in normal subjects. The difference at site 1, 3, 4 and 6 was statistically significant. Since a high threshold velocity indicates low sensitivity, our results suggest that airflow sensitivity is lowered in patients with chronic sinusitis. Disturbance of airflow sensation may contribute to the sensation of nasal obstruction in patients with chronic paranasal sinusitis.

Investigation of Parameters for Preparing Nanofiber Yarn via a Stepped Airflow-assisted Electrospinning

Yuman Zhou,Hongbo Wang,Jianxin He,Kun Qi,Bin Ding,Shizhong Cui 한국섬유공학회 2018 Fibers and polymers Vol.19 No.10

Electrospinning is a simple and cost-effective method to prepare fiber with nanometer scale. More importantly, 3D flexible nanofiber yarns that fabricated by electrospinning have shown excellent application prospects in smart textiles, wearable sensors, energy storage devices, tissue engineering, and so on. However, current methods for preparing electrospinning nanofiber yarns had some limitations, including low yarn yield and poor yarn structure. In this paper, a stepped airflow-assisted electrospinning method was designed to prepare continuously twisted nanofiber yarn through introducing stepped airflow into traditional electrospinning system. The stepped airflow could not only help to improve nanofiber yield, but also good for controlling the formed nanofibers to be deposited in a small area. In addition, the experimental methods of single factor variables were used to study the effects of stepped airflow pressure, applied voltage, spinning distance, solution flow rate, air pumping volume and friction roller speed on nanofiber yarn yield, nanofiber diameter, yarn twist and mechanical property. The results showed that prepared nanofiber yarns exhibited perfect morphologies and the yield of nanofiber yarn could reach to a maximum of 4.207 g/h. The breaking strength and elongation at break of the prepared yarn could reach to 23.52 MPa and 30.61 %, respectively.

Investigation on Airflows in Abnormal Nasal Cavity with Adenoid Vegetation by Particle Image Velocimetry

Kim, Sung Kyun,Son, Young Rak The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.10

Knowledge of airflow characteristics in nasal cavity is essential to understand the physiological and pathological aspects of nasal breathing. Several studies have utilized physical models of the healthy nasal cavity to investigate the relationship between nasal anatomy and airflow. Since the final goal of these works is their contribution to the diagnosisand treatment of nasal diseases, the next step on this topic is naturally studies for disordered nasal cavities. In this paper, as the first application, airflows in the normal and abnormal nasal cavities with adenoid vegetation are investigated experimentally by PIV, and comparisons of both cases are appreciated. Dense CT data and careful treatment of model surface under the ENT doctor's advice provide more sophisticatedcavity model. The CBC PIV algorithm with window offset is used for PIV flow analysis. Average and RMS distributions are obtained for inspirational and expirational nasal airflows. Airflow characteristics that are related with the abnormalities in nasal cavity are presented.

Aerodynamic and aeroelastic flutters driven triboelectric nanogenerators for harvesting broadband airflow energy

Phan, Hai,Shin, Dong-Myeong,Heon Jeon, Sang,Young Kang, Tae,Han, Pyunghwa,Han Kim, Gyu,Kook Kim, Hyung,Kim, Kyujung,Hwang, Yoon-Hwae,Won Hong, Suck Elsevier 2017 Nano energy Vol.33 No.-

<P><B>Abstract</B></P> <P>Aerodynamic and aeroelastic flutter-driven triboelectric nanogenerators are successfully used to harvest broadband airflow energy. The unit component of the flutter membrane consists of thin, free-standing Al foil electrodes covered on both sides with electrospun poly(vinyl chloride) nanofiber-structured mats, which provide advantageous tribo-surfaces specifically to increase the friction area. The airflow-induced triboelectric power generation from a single unit of the flutter-membrane-based triboelectric nanogenerator (FM-TENG) was up to 0.33 μW under a mild airflow condition. The use of a multi-layered triboelectric nanogenerator, fabricated by simply stacking the single units, can improve the output performance of the device. In a separate configuration, we designed a novel FM-TENG structure by mounting an aeroelastic flutter-belt adapted for use with a flutter-membrane energy-harvester. A rubber belt, which was sandwiched between the flutter membranes, created a rapid periodic vibrational mode via aeroelastic fluttering, synergistically harvesting triboelectric energy with the application of a constant air stream through the closed channel of the FM-TENG. Thus, our flutter-membrane-based approach creates a sustainable and cost-efficient energy harvesting system for collecting broadband airflow energy. Furthermore, the aerodynamic and aeroelastic FM-TENG have great potential to be used in numerous areas of self-powered electronic systems and in-situ wireless sensor applications for automobiles or aircraft.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Aerodynamic and aeroelastic flutter-driven triboelectric nanogenerators. </LI> <LI> Multi-layered triboelectric nanogenerators. </LI> <LI> Adapting an aeroelastic flutter to synergistically combine aerodynamic and aeroelastic movement. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The harvest of broadband airflow energy is accomplished using aerodynamic and aeroelastic flutter-driven triboelectric nanogenerators. Multi-layered triboelectric nanogenerators are made by simply stacking single units and can improve the output performance of the device. Adapting an aeroelastic flutter to synergistically combine aerodynamic and aeroelastic movement enables dramatic improvements in the electrical output of the triboelectric nanogenerator.</P> <P>[DISPLAY OMISSION]</P>

Increase TFT LCD Yield by Improvement of Clean Room Airflow

元??(Young-Jae Won),李?(Li Li) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7

Optimum Airflow to Reduce Particle Contamination Inside Welding Automation Machine of Hard Disk Drive Production Line

Jatuporn Thongsri,Monsak Pimsarn 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Welding automation machine (WAM), used for welding minute components to the head gimbal assembly (HGA) of a hard disk drive(HDD), needs to operate in a strictly clean environment. In today’s HDD factories, to prevent airborne particle contamination to theWAM, Fan Filter Units (FFUs) are installed on top of it to supply clean air and blow away outside airborne micro particles, keepingthe microenvironment clean. Furthermore, the mass of the clean air should also carry away harmful particles generated inside themicroenvironment. In this research, numerical simulation of airflow inside a WAM was performed in order to verify these cleaningfunctions of the airflow. A transition shear stress transport turbulence model was employed to simulate airflow from the FFUs throughand out of the microenvironment. The simulation results showed that the airflow from the FFUs truly performs the two cleaningfunctions as intended. Moreover, they also revealed that the optimum air speed, the speed resulting in the lowest particle counts, isin the range of 0.35-0.55 m/s. Our findings can be useful for developers who may use FFUs to reduce particle counts in theenvironment of other types of industrial machinery

VAV 터미널 박스의 최소풍량 설정에 따른 실내 열환경 및 에너지 성능 분석

강수현(Kang, Su-hyun),조영흠(Cho, Young-hum) 한국건축친환경설비학회 2011 한국건축친환경설비학회 논문집 Vol.5 No.3

The minimum airflow of VAV terminal boxes is a key factor for comfort, indoor air quality(IAQ) and energy cost. If the minimum airflow is not resonable, it would waste energy and make IAQ problems. A building simulation was conducted to evaluate the energy consumption and the IAQ according to the minimum airflow of the VAV terminal boxes. It was found that the 4.5% energy savings when reducing the minimum airflow as CASE 2. And CASE 1 did not satisfy the IAQ during the Winter. And there are the two factors(indoor load and IAQ) to decide the minimum airflow.

비강내 주기유동장의 실험적 해석에 관한 연구

김성균(Sung Kyun Kim),손영락(Yong Rak Soon),신석재(Seok Jae Shin) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

CT 사진을 이용하여 살아있는 사람의 비강 형상을 얻고 RP 를 이용하여 모형을 만들고 이 모형으로 정교한 비강 유로 모형을 제작하였고, 호흡을 정확하게 모사하는 펌프를 만들었다. 사람의 호흡 데이터를 이용하여 캠을 제작하고 대형 피스톤 펌프를 만들어 사람의 호흡을 정확 하게 모사 하였다. 이를 이용하여 생리적 주기를 갖는 비강내 유동에 대한 결과를 획득하고 기존의 일정유량하의 실험결과와 비교 분석하였다. Airflow in the nasal cavity of a normal Korean adult is investigated experimentally by tomographic PIV measurement. Knowledge of airflow characteristics in nasal cavities is essential to understand the physiology and pathology aspects of nasal breathing. Several studies have utilized physical models of the healthy nasal cavity to investigate the relationship between nasal anatomy and airflow. All of these researches on nasal airflow are under the condition of constant flow-rate. In this study, nasal cavity flow with the physiological period is investigated by tomographic PIV, for the first time. A pumping system that can produce the periodic flow is created. Thanks to a new method for the model casting by a combination of the rapid prototyping and curing of clear silicone, a transparent rectangular box containing the complex nasal cavity can be made for PIV. The CBC PIV algorithm is used for analysis. Phase-averaged mean and RMS velocity distributions are obtained for inspirational and expiration nasal airflows. The comparison with the constant flow case is appreciated. There exist many flow patterns depending on each phase.

고령노인을 중심으로 한 실내 주거공간의 창문 환기 방식 연구

한연 ( Han Yan ),최경란 ( Choi Kyungran ) 한국공간디자인학회 2023 한국공간디자인학회논문집 Vol.18 No.8

(Background and Purpose) The increase in the number of elderly people is contributing to the aging of the population, and at the same time, the physiological functions of the elderly decline with age, which increases the time they spend in the living space and decreases their access to nature. Windows exist as a medium for communicating between indoors and outdoors, and have the property of introducing natural elements such as air, wind, and sunlight into the interior, which is not only a means for the occupants to contact nature, but also a way of ventilating the living space that is favored by the elderly. (Method) This paper explores the optimal window openings for natural ventilation in indoor spaces frequented by senior citizens. Using the principles of fluid dynamics (CFD), simulated experiments were conducted through Airpak computer technology and the zero-equation model in turbulence model. The four common window types studied include left/right sliding windows, casement windows, top-hung windows, and bottom-hung windows. The comparative study analyzed airflow and temperature in the indoor space under these four types of window openings. (Results) After simulation experiments, it was found that natural ventilation under the left and right sliding windows have the greatest impact on the airflow in the space, the strongest sense of indoor wind and the best ventilation effect, followed by casement windows. The airflow in the space under the influence of upper and lower hung windows is smooth, and the wind sense and ventilation effect are weak or no wind sense. In terms of temperature, the four forms of window openings in the range of temperature regulation is not obvious, but only under the lower-hung windows due to less interference from indoor objects so that the indoor temperature distribution is uniform, the human body around the temperature is also under the influence of the lower-hung windows show a significantly lower situation. (Conclusions) This study proposes a design strategy based on the physiological and psychological needs of elderly people for constant temperature, soft breeze and contact with nature in the living space, combined with the results of simulation experiments. It is believed that by combining the features of casement windows, which have the best natural ventilation effect, and downward-hung windows, which have a more uniform temperature distribution, and from the perspective of the combination of window openings, window opening methods, and the design of the transmission device, the window design will better meet the physical and mental needs of the elderly by reasonably utilizing the features of bottom-hung windows that block and direct airflow upward, and the features of casement windows that directly bring in airflow.