• Title, Summary, Keyword: Condensation

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An Experimental Investigation of Direct Condensation of Steam Jet in Subcooled Water

  • Kim, Yeon-Sik;Chung, Moon-Ki;Park, Jee-Won;Chun, Moon-Hyun
    • Nuclear Engineering and Technology
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    • v.29 no.1
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    • pp.45-57
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    • 1997
  • The direct contact condensation phenomenon, which occurs when steam is injected into the subcooled water, has been experimentally investigated. Two plume shapes in the stable condensation regime are found to be conical and ellipsoidal shapes depending on the steam mass flux and the liquid subcooling. Divergent plumes, however, are found when the subcooling is relatively small. The measured expansion ratio of the maximum plume diameter to the injector inner diameter ranges from 1.0 to 2.3. By means of fitting a large amount of measured data, an empirical correlation is obtained to predict the steam plume length as a function of a dimensionless steam mass flux and a driving potential for the condensation process. The average heat transfer coefficient of direct contact condensation has been found to be in the range 1.0~3.5 ㎿/$m^2$.$^{\circ}C$. Present results show that the magnitude of the average condensation heat transfer coefficient depends mainly on the steam mass fin By using dynamic pressure measurements and visual observations, six regimes of direct contact condensation have been identified on a condensation regime map, which are chugging, transition region from chugging to condensation oscillation, condensation oscillation, bubbling condensation oscillation, stable condensation, and interfacial oscillation condensation. The regime boundaries are quite clearly distinguishable except the boundaries of bubbling condensation oscillation and interfacial oscillation condensation.

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A Study on the Effect of the Heat Transfer Surface Position to the Condensation heat Transfer (전열면 자세가 응축 열전달에 미치는 영향에 관한 연구)

  • 조시기
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.1
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    • pp.25-29
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    • 2001
  • A study has been conducted to investigate the effect of the heat transfer surface position in the range of dropwise condensation, filmwise condensation, and glacial condensation. For dropwise condensation promoter, the heat transfer surface was evaporated by gold. As a result, heat transfer rate is almost same where the position of heat transfer surface is between 45 and 135 degree. It is found that heat transfer rate was reduced as subcooled degree was increased. And it is also found that if the subcooled degree becomes lower, the position of heat transfer surface is more effective. Adversely, if the subcooled degree becomes higher, the effectiveness of surface position is getting relatively lower. Regardless of the position, the transition temperatures from dropwise condensation to filmwise condensation is in the vicinity of 80K.

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A Passive Control of Interaction of Condensation Shock Wave anc Boundary Layer(I) (응축충격파와 경계층 간섭의 피동제어(I))

  • Choe, Yeong-Sang;Jeong, Yeong-Jun;Gwon, Sun-Beom
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.2
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    • pp.316-328
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    • 1997
  • There were appreciable progresses on the study of shock wave / boundary layer interaction control in the transonic flow without nonequilibrium condensation. But in general, the actual flows associated with those of the airfoil of high speed flight body, the cascade of steam turbine and so on accompany the nonequilibrium condensation, and under a certain circumstance condensation shock wave occurs. Condensation shock wave / boundary layer interaction control is quite different from that of case without condensation, because the droplets generated by the result of nonequilibrium condensation may clog the holes of the porous wall for passive control and the flow interaction mechanism between the droplets and the porous system is concerned in the flow with nonequilibrium condensation. In these connections, it is necessary to study the condensation shock wave / boundary layer interaction control by passive cavity in the flow accompanying nonequilibrium condensation with condensation shock wave. In the present study, experiments were made on a roof mounted half circular arc in an indraft type supersonic wind tunnel to evaluate the effects of the porosity, the porous wall area and the depth of cavity on the pressure distribution around condensation shock wave. It was found that the porosity of 12% which was larger than the case of without nonequilibrium condensation produced the largest reduction of pressure fluctuations in the vicinity of condensation shock wave. The results also showed that wider porous area, deeper cavity for the same porosity of 12% are more favourable "passive" effect than the cases of its opposite. opposite.

Development of Automatic Code Generation of Condensation Algorithm using MATLAB (MATLAB을 이용한 Condensation 알고리즘의 자동 코드 구현)

  • Lee, Yang-Weon
    • The Journal of Advanced Navigation Technology
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    • v.14 no.5
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    • pp.618-624
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    • 2010
  • This paper address the problem of tracking multiple objects encountered in many situations in developing condensation algorithms. The difficulty lies on the fact that the implementation of condensation algorithm is not easy for the general users. We propose an automatic code generation program for condensation algorithm using MATLAB tool. It will help for general user who is not familiar with condensation algorithm to apply easily for real system. The merit of this program is that a that a general industrial engineer can easily simulate the designed system and confirm the its performance on the fly.

An Experimental and Simulation Analysis of Condensation in the Walk-in Closet Attached to Apartment Bathroom (욕실과 인접한 아파트 드레스룸의 결로 원인 분석)

  • Choi, Young-Woo;Kim, Sean Hay
    • KIEAE Journal
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    • v.17 no.4
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    • pp.89-94
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    • 2017
  • Purpose: Condensation in walk-in closets attached to apartment bathroom has been known as an emerging issue that may threat occupants' comfort and health. Despite a number of design guidelines and enforcements to prevent condensation, condensation issues may still occur depending on various cases and scenarios. We aim to identify what condensation scenarios may lead to walk-in closet condensation and/or worse the existing condensation issues. Method: First we choose an actual walk-in closet of an apartment that suffers from sporadic condensation and resulting mold and mildew. Then we observe its relative humidity and temperature after the bathroom is used, in which excessive vapor is thought to be transported to the walk-in closet. We analyze Temperature Difference Ratio - a domestic indicator of condensation occurrence, and dew point temperature to compare it with surface temperature using 2D heat transfer simulation upon various condensation scenarios. Result: TDR of the test walk-in closet turns out be OK despite mold and mildew actually occurring. Hot water pipe installed in the floor would greatly reduce condensation. If hot water pipe in the upper floor, however, is not used, or hot water pipe of the closet is turned off during swing seasons, it is expected that condensations may still occur.

COMPARISON OF WARM GUTTA-PERCHA CONDENSATION TECHNIQUES IN RIBBON SHAPED CANAL : WEIGHT OF FILLED GUTTA-PERCHA (리본형태의 근관에서의 열연화 근관 충전법의 비교 : 근관 충전된 gutta-percha의 무게)

  • Kim, Hyun-Hee;Cho, Kyung-Mo;Kim, Jin-Woo
    • Restorative Dentistry and Endodontics
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    • v.27 no.3
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    • pp.277-283
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    • 2002
  • The purpose of this study is to evaluate the two warm gutta-percha filling techniques by measuring the weight changes of resin blocks before and after canal filling in ribbon shaped canal. Simulated ribbon shaped root canals in 30 transparent resin blocks were instrumented to #40 using .06 taper Profile. 15 resin blocks were obturated with gutta-percha using cold lateral condensation. Warm lateral condensation using the Endotec II was then accomplished on the same 15 blocks. Another 15 resin blocks were obturated using the System B. All canals were obturated without sealer. The resin blocks were weighed after canal preparation and after each subsequent obturation, and then weight changes of the resin blocks were calculated The results were as follows. 1. Warm lateral condensation using Endotec II and continuous wave of condensation using System B produced a denser obturation of gutta-percha compared with conventional cold lateral condensation (p<0.01). 2. There was no significant difference between warm lateral condensation and continuous wave condensation. In conclusion, the warm gutta-percha condensation techniques like warm lateral condensation and continuous wave condensation can be expected to bring favorable canal obturation results in ribbon shaped canals.

Modeling of Liquid-Vapor Interfaces of Condensation Flows Based on Molecular Dynamics Simulations

  • Kannan, Hiroki;Teramoto, Susumu;Nagashima, Toshio
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.418-425
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    • 2004
  • Characteristics of a liquid-vapor interface where a nonequilibrium condensation flow exists are considered based on molecular dynamics simulations, The condensation coefficient, the velocity distributions of the reflected and evaporated molecules and the number flux of the evaporated molecules are compared with those under the liquid-vapor equilibrium. The comparison shows that the condensation coefficient under the nonequilibrium condensation is slightly larger and the number flux of the evaporated molecules is considerably smaller than those under the liquid-vapor equilibrium. The net condensation flux under the nonequilibrium condensation is underestimated if it is evaluated from the condensation coefficient and the number flux of the evaporated molecules under the liquid-vapor equilibrium. However the underestimation is relatively small.

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The Effects of HVAC Management on Condensation Cause and Prevention in Indoor Swimming Pools (실내수영장 공조관리 요인이 시설물 결로원인과 예방에 미치는 영향)

  • Sung, Ha-Dong
    • Journal of the Korea Safety Management and Science
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    • v.20 no.2
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    • pp.9-20
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    • 2018
  • This study is empirically intended to look into the effects of HVAC management on condensation cause and prevention in indoor swimming pools. The findings are summarized as follows. First, the experience of condensation in indoor swimming pools showed that 132 out of 142 people in total experienced the condensation in indoor swimming pools, which they had a high experience rate of 92.3%. For the location of condensation, the wall joints were 46.8% and the windows were 34.5%, which a total of 72.3% occurred in the wall joints and windows. Second, the effect of construction design, HVAC management and building construction on the cause of condensation in indoor swimming pools showed that building construction had an effect on the cause and location of condensation depending on the seasonal time, partially adopting hypothesis 1. Third, the effect of condensation-causing factors on condensation-preventing factors in indoor swimming pools showed that condensation had a close relationship with air and temperature conditions depending on the time and location of condensation, adopting hypothesis 2. As for the above-stated findings, the HVAC management in indoor swimming pools is an important concern factor that continues to cause condensation despite the development of advanced construction materials. Especially, building construction is a main factor that has a direct effect on condensation in the HVAC management of facilities. This implies that the window management is important in maintaining the wall joints - which can suppress the selective use and defect occurrence of construction materials - or confined spaces for a long time.

A COMPARISON OF THE APICAL SEALING ABILITY OF OBTURATION TECHNIQUES BY THERMALLY SOFTENED GUTTA PERCHA (열연화시킨 근관충전방법에 따른 근단폐쇄성에 관한 연구)

  • Baek, Seung-Ho
    • Restorative Dentistry and Endodontics
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    • v.23 no.2
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    • pp.607-617
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    • 1998
  • The purpose of this study was to evaluate the apical sealing ability of lateral condensation method, vertical condensation method, and MicroSeal obturation system. Sixty-four extracted anterior teeth were instrumented to #40 using Profile. Three groups of 20 teeth were obturated by lateral condensation technique, vertical condensation technique, and and MicroSeal obturation system. Control group were not obturated. Teeth were immersed in resorcinol-formaldehyde resin for 5 days at $4^{\circ}C$, and the resin was allowed to polymerize completely for 4 days at room temperature. Teeth were ground horizontally at 1,5mm(level 1), 2.5mm(level 2), and 3.5mm(level 3) from the anatomic apex and examined with a stereomicroscope at X40 magnification. The photographs were taken a at X40 magnification of the filling in each level and scanned. The leakage area, which was filled with the resin, was measured at each of the three levels. Each ratio of leakage was evaluated by calculating the ratio of thearea of the resin to the total area of the canal and was analyzed statistically. The results were as followed: 1. Vertical condensation group had significantly higher percentage of the area which was obturated by gutta percha than other two technique at each level. 2. At the level 1, there was the greatest leakage in the lateral condensation group, but there was no statistically significant(P>0.05) 3. At the level 2, there was the least leakage in the MicroSeal group, and the most leakage in the lateral condensation group. There was statistically significant difference between the MicroSeal group and the lateral condensation group(P<0.05). 4. At the level 3, there was least leakage in the vertical condensation group, and the most leakage in the lateral condensation group. There was statistically significant difference between the vertical condensation group and the lateral condensation group(P<0.05).

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Comparison of Total Moisture Content by Internal Condensation Evaluation Method (내부결로 평가방법에 따른 총 함습량 비교)

  • Kim, Kyung-Soo;Jang, Hyang-In;Park, Chang-Young;Yoo, Dong-Chul;Choi, Chang-Ho
    • 한국건축친환경설비학회 논문집
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    • v.11 no.6
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    • pp.558-571
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    • 2017
  • Although the domestic condensation standards are set forth in the "Standards for Preventing Condensation in Multi-Residential Houses" stipulated by the Ministry of Land, Infrastructure and Transport, they are interpretation on surface condensation acquired by using the method evaluating the dew point temperature, and cannot be applied to the interpretation of interstitial condensation. As such, this study aims to contemplate foreign interstitial condensation evaluation methods and conducts comparative analysis according to the interstitial condensation evaluation factors. After the interpretation model is set, the comparison through the performance evaluation following the evaluation standards are conducted based on the interpretation factors contemplated in the previous stage. Thus, this study intends to contribute to the improvement of the standards for the domestic interstitial condensation evaluation. The study results are as follows. (1) Even though ISO 13788 and EN 15026 predict the condensation based on the humidity transfer, ISO 13788 cannot respond to complex external environments. Hence, EN 15026 of the condensation calculation method is more precise than the ISO 13788. (2) Results of the performance evaluation suggested that in the case (Interstitial Surface 1) of Solid Brick Masonry and Interior Plaster, the risk of condensation of ISO 13788 and EN 15026 are 40.2% and 24.0%, respectively, and it is analyzed that complex climate factors and water transfer (capillary phenomenon) are reasons for such difference. (3) Results of the performance evaluation indicated that in the case (Interstitial Surface 2) of EPS and Interior Plaster, the risk of condensation of ISO 13788 and EN 15026 are 20.8% and 0%. Accordingly, it is viewed that the evaluation method considering water transfer (capillary phenomenon) and complex climate factors should be added to the domestic condensation standards.