• 수산해양교육연구
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• 제28권5호
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• pp.1273-1279
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• 2016

Flow boiling pressure drop in multi channels was experimently investigated. The multi channel has a width and depth of 0.45 and 0.2mm respectively, and comprises 15 parallel channels. The measured total pressure drop is expressed by the sum of the frictional pressure drop and acceleration pressure drop. In order to predict the total pressure drop, it is required to obtain the correct frictional pressure drop. The existing correlations to predict the frictional pressure were compared with measured frictional pressure drop. The new correlation was developed in the form of the Chisholm correlation. It was related to Chisholm Constant B as a function of Martinelli parameter. The new correlation predicted the experimental data within a mean absolute error of 5.5%.

• 한국유체기계학회 논문집
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• 제16권1호
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• pp.32-39
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• 2013

The multi-stage control valve is one of the devices which controls cavitation and high pressure drop. To attain the high pressure drop, the conventional control valves adopted the multi-stage trim to avoid the occurrence of local cavitation in valves. This work studied the effect of divergence angle on the characteristics of multi-stage trim. Pressure drop and flow characteristics was calculated for the 1 passage of multi-staged trim by using the FLUENT 6.3.26. The result showed that the pressure drop is significantly influenced by the divergence angle of multi-stage trim. In addition, the pressure drop increased consistently as the Reynolds number and divergence angle increases.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.324-328
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• 2019

스포츠를 위해 제공되고 사용되는 몇 가지 전용 챔버가 공급되어 사용되고 있지만 스포츠 멀티 환경을 동시에 제공할 수 있는 다기능 올인원 챔버는 개발되지 않았다. 본 연구에서는 스포츠 다중 인공 환경 시스템에 사용할 수 있는 다중압력 (양 / 대기 / 음압) 일체형 챔버를 설계하였다. 키가 큰 사용자를 위해 공간을 넓힌 새로운 챔버 디자인을 제시 한 다음 최대 응력과 구조적 안전성검토를 통하여 챔버의 구조해석을 수행하였다. 목표로 하는 허용 압력 조건하에서 쉘과 출입구의 접합부에서 최대 응력이 발생했으며, 챔버 재료의 허용응력을 기준으로 하여 구조안전성 평가를 수행하였다. 다중 압력 일체형 챔버에 대하여 구조해석을 수행한 결과 양압과 음압 조건에 대한 최대 응력이 챔버 재료의 허용응력 보다 훨씬 작은 값이 발생되었으며, 구조안전성 평가 결과 안전율 2 이상을 만족하여 챔버의 최종 시제품의 설계가 구조적으로 안전하다는 것을 확인하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권4호
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• pp.439-449
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• 2018

In this paper, multi-objective optimization of a multi-bubble pressure cabin in the underwater glider with Blended-Wing-Body (BWB) is carried out using Kriging and the Non-dominated Sorting Genetic Algorithm (NSGA-II). Two objective functions are considered: buoyancy-weight ratio and internal volume. Multi-bubble pressure cabin has a strong compressive capacity, and makes full use of the fuselage space. Parametric modeling of the multi-bubble pressure cabin structure is automatic generated using UG secondary development. Finite Element Analysis (FEA) is employed to study the structural performance using the commercial software ANSYS. The weight of the primary structure is determined from the volume of the Finite Element Structure (FES). The stress limit is taken into account as the constraint condition. Finally, Technique for Ordering Preferences by Similarity to Ideal Solution (TOPSIS) method is used to find some trade-off optimum design points from all non-dominated optimum design points represented by the Pareto fronts. The best solution is compared with the initial design results to prove the efficiency and applicability of this optimization method.

• 센서학회지
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• 제27권3호
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• pp.186-191
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• 2018

Smart textile industries have been precipitously developed and extended to electronic textiles and wearable devices in recent years. In particular, owing to an increasingly aging society, the elderly healthcare field has been highlighted in the smart device industries, and pressure sensors can be utilized in various elderly healthcare products such as flooring, mattress, and vital-sign measuring devices. Furthermore, elderly healthcare products need to be more lightweight and flexible. To fulfill those needs, textile-based pressure sensors is considered to be an attractive solution. In this research, to apply a textile to the second layer using a pressure sensing device, a novel type of conductive textile was fabricated using vapor phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). Vapor phase polymerization is suitable for preparing the conductive textile because the reaction can be controlled simply under various conditions and does not need high-temperature processing. The morphology of the obtained PEDOT-conductive textile was observed through the Field Emission Scanning Electron Microscope (FESEM). Moreover, the resistance was measured using an ohmmeter and was confirmed to be adjustable to various resistance ranges depending on the concentration of the oxidant solution and polymerization conditions. A 3-layer 81-point multi-pressure sensor was fabricated using the PEDOT-conductive textile prepared herein. A 3D-viewer program was developed to evaluate the sensitivity and multi-pressure recognition of the textile-based multi-pressure sensor. Finally, we confirmed the possibility that PEDOT-conductive textiles could be utilized by pressure sensors.

• 설비공학논문집
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• 제9권3호
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• pp.376-388
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• 1997

In this study, an experiment was performed to investigate the characteristics of pressure drop and heat transfer of multi-channel tubes for automotive condenser using HFC-134a as an alternative refrigerant. The mass flux and inlet saturation pressure of the refrigerant were controlled, respectively, in the range of 200 to $500kg/m^2s$ and 1.0 to 1.6MPa. Pressure drop and heat transfer coefficient were compared with the previously proposed correlations and new correlations based on Traviss' correlation were suggested. Prediction of pressure drop and heat transfer coefficient based on the new correlations agrees with experimental results within ${\pm}9%$ and -18~+11%, respectively.

• 동력기계공학회지
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• 제17권6호
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• pp.63-72
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• 2013

The main purpose of this study is to analyze the collection characteristics of multi-layer multi-stage porous plate system with ionizer and dielectric-substance experimentally. The experiment is carried out to analyze the characteristics of pressure drop and collection efficiency for the present system with experimental parameters such as applied voltage, inlet velocity, stage number and inlet particle concentration, etc. In results, for multi-layer multi-stage porous plate system of inflow type, at 5 stage and $v_{in}$=2.58 m/s, the pressure drop becomes lower 15 $mmH_2O$ as 95 $mmH_2O$ than that of non-inflow type system. It is estimated that for the present system with ionizer and dielectric-substance, the collection efficiency represents 98.5% showing higher 5.2% comparing to that of multi-layer multi-stage porous plate system without ionizer and dielectric-substance at 5 stage, $v_{in}$=2.58 m/s and inlet concentration $3g/m^3$(fly ash).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.289-290
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• 2010

• Wind and Structures
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• 제35권5호
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• pp.297-307
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• 2022

Over the past few decades, the use of wind tunnels has been increasing as a result of the rapid growth of cities and the urge to build taller and non-typical structures. While the accuracy of a wind tunnel study on a tall building requires several aspects, the precise extraction of wind pressure plays a significant role in a successful pressure test. In this research study, a low-cost expandable synchronous multi-pressure sensing system (SMPSS) was developed and validated at Ryerson University's wind tunnel (RU-WT) using electronically scanning pressure sensors for wind tunnel tests. The pressure system consists of an expandable 128 pressure sensors connected to a compact data acquisition and a host workstation. The developed system was examined and validated to be used for tall buildings by comparing mean, root mean square (RMS), and power spectral density (PSD) for the base moments coefficients with the available data from the literature. In addition, the system was examined for evaluating the mean and RMS pressure distribution on a standard low-rise building and were found to be in good agreement with the validation data.

• 한국전산구조공학회논문집
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• 제34권1호
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• pp.1-8
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• 2021

플랜트 증기운 폭발은 TNT 폭발물에 의한 폭발과는 다른 특징이 있으며 압력파 양상과 비슷하다. 대표적인 유형의 폭압 산정법은 TNT 등가량 환산법과 멀티에너지법이 있다. TNT 등가량 환산법은 폭굉과 같은 충격파를 전제로 하며, 멀티에너지법은 폭연과 같은 압력파를 전제로 한다. 본 연구는 세 가지 플랜트 폭발 사례를 적용하여 플랜트 증기운 폭발의 적절한 폭압을 도출하기 위한 연구를 수행하였다. 폭발 사례에 대하여 피해를 입은 부재를 선정한 후, 단자유도 해석과 비선형 동적 해석을 수행하여 변형과 손상 정도를 비교분석하였다. 구조물의 피해 정도는 TNT 등가량 환산법보다는 멀티에너지법에 의한 폭압을 사용한 경우가 실제 상황에 더욱 근접한 것으로 나타났다. 또한, 멀티에너지법의 폭발강도계수를 7 또는 8로 가정할 경우 증기운 폭발의 폭압 모델을 비교적 정확하게 산정할 수 있을 것으로 판단된다.