• Title/Summary/Keyword: duct design

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Numerical Study for Flow Uniformity in Selective Catalytic Reduction(SCR) Process (SCR 공정에서 반응기 내부의 유동 균일화를 위한 수치적 연구)

  • Jung, Yu-Jin;Hong, Sung-Gil;Kim, Min-Choul;Lee, Jae-Jeong;Lee, Gang-Woo;Shon, Byung-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.10
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    • pp.4666-4672
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    • 2011
  • Performance of NOx removal in SCR(Selective Catalytic Reduction) process depends on such various factors as catalyst factors (catalyst composition, catalyst form, space velocity, etc.), temperature of exhaust gas, and velocity distribution of exhaust gas. Especially the flow uniformity of gas stream flowing into the catalyst layer is believed to be the most important factor to influence the performance. In this research, the flow characteristics of a SCR process at design stage was simulated, using 3-dimensional numerical analysis method, to confirm the uniformity of the gas stream. In addition, the effects of guide vanes, baffles, and perforated plates on the flow uniformity for the inside and catalyst layer of the reactor were studied in order to optimize the flow uniformity inside the SCR reactor. It was found that the installation of a guide vane at the inlet duct L-tube part and the installation of a baffle at the upper part is very effective in avoiding chaneling inside the reactor. It was also found that additional installation of a perforated plate at the lower part of the potential catalyst layer buffers once more the flow for very uniform distribution of the gas stream.

A Study on the Operational Variables of the UV-TiO$_2$ Based Photocatalytic Air Cleaning System (UV-TiO$_2$ 광촉매 기반의 공기 정화 시스템의 운전조건에 대한 연구)

  • Han, Chang-Seok;Chang, Hyuk-Sang
    • Journal of Korean Society of Environmental Engineers
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    • v.30 no.3
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    • pp.293-301
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    • 2008
  • A study on the operational variables of the UV-TiO$_2$ based photocatalytic air cleaning system was tried. In this study, to examine effects as various air cleaning system conditions, a duct-type reactor was made, and TiO$_2$ was immobilized on a stainless mesh. Benzene was chosen as a target compound. Removal experiments for benzene were done under different initial benzene concentration, air velocity, TiO$_2$ loading, area coated TiO$_2$ as the same TiO$_2$ loading, and UV light intensity conditions. During the experiments, relative humidity was 55%, and reactor temperature was 45$^{\circ}C$. As a result, the photocatalytic degradation of benzene decreased as the inlet concentration increased. But the photocatalytic degradation increased as the concentration boundary layer thickness, amount of TiO$_2$, area coated TiO$_2$ as the same amount of TiO$_2$, and UV light intensity increased. Based on results of current study, they can be applied to the design of air cleaning system over low level VOCs in the indoor air.

Optimization of the Unducted Auxiliary Ventilation for Large-Opening Underground Limestone Mines (대단면 지하 석회석 광산내 무풍관 국부통기 최적화 연구)

  • Nguyen, Van Duc;Lee, Chang Woo
    • Tunnel and Underground Space
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    • v.29 no.6
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    • pp.480-507
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    • 2019
  • This paper aims at optimizing the auxiliary ventilation system in large-opening limestone mines with unducted fans. An extensive CFD and also site study were carried out for optimization at the blind entries. The fan location, operating mode, and layout are the parameters for optimization. Since the jet stream discharged from the auxiliary fan is flowing faster than 15 m/s in most of the cases, the stream collides with floor, sides or roof and even with the jet stream generated from the other fan placed upstream. Then, it is likely to lose a large portion of its inertial force and then its ventilation efficiency drops considerably. Therefore, the optimal fan installation interval is defined in this study as an interval that maximizes the uninterrupted flowing distance of the jet stream, while the cross-sectional installation location can be optimized to minimize the energy loss due to possible collision with the entry sides. Consequently, the optimization of the fan location will improve ventilation efficiency and subsequently the energy cost. A number of different three-dimensional computational domains representing a full-scale underground space were developed for the CFD study. The velocity profiles and the CO concentrations were studied to design and optimize the auxiliary ventilation system without duct and at the same time mine site experiments were carried out for comparison purposes. The ultimate goal is to optimize the auxiliary ventilation system without tubing to provide a reliable, low-cost and efficient solution to maintain the clean and safe work environment in local large-opening underground limestone mines.

Analysis on Ventilation Efficiency of Standard Duck House using Computational Fluid Dynamics (전산유체역학을 이용한 표준 오리사 설계안에 대한 환기효율성 분석)

  • Yeo, Uk-Hyeon;Jo, Ye-Seul;Kwon, Kyeong-Seok;Ha, Tae-Hwan;Park, Se-Jun;Kim, Rack-Woo;Lee, Sang-Yeon;Lee, Seung-No;Lee, In-Bok;Seo, Il-Hwan
    • Journal of The Korean Society of Agricultural Engineers
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    • v.57 no.5
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    • pp.51-60
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    • 2015
  • In Korea, 69.4 % of duck farms had utilized conventional plastic greenhouses. In this facilities, there are difficulties in controlling indoor environments for raising duck. High rearing density in duct farms also made the environmental control difficult resulting in getting more stressed making their immune system weaker. Therefore, a facility is needed to having structurally enough solidity and high efficiency on the environmental control. So, new design plans of duck house have recently been conducted by National Institute of Animal Science in Korea. As a study in advance to establish standard, computational fluid dynamics (CFD) was used to estimate the aerodynamic problems according to the designs by means of overall and regional ventilation efficiencies quantitatively and qualitatively. Tracer gas decay (TGD) method was used to calculate ventilation rate according to the structural characteristics of duck houses including installation of indoor circulation fan. The results showed that natural ventilation rate was averagely 164 % higher than typically designed ventilation rate, 1 AER ($min^{-1}$). Meanwhile, mechanically ventilated duck houses made 81.2 % of summer ventilation rate requirement. Therefore, it is urgent to develop a new duck house considering more structural safety as well as higher efficiency of environmental control.

System Development for Analysis and Compensation of Column Shortening of Reinforced Concrete Tell Buildings (철근콘크리트 고층건물 기둥의 부등축소량 해석 및 보정을 위한 시스템 개발)

  • 김선영;김진근;김원중
    • Journal of the Korea Concrete Institute
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    • v.14 no.3
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    • pp.291-298
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    • 2002
  • Recently, construction of reinforced concrete tall buildings is widely increased according to the improvement of material quality and design technology. Therefore, differential shortenings of columns due to elastic, creep, and shrinkage have been an important issue. But it has been neglected to predict the Inelastic behavior of RC structures even though those deformations make a serious problem on the partition wall, external cladding, duct, etc. In this paper, analysis system for prediction and compensation of the differential column shortenings considering time-dependent deformations and construction sequence is developed using the objected-oriented technique. Developed analysis system considers the construction sequence, especially time-dependent deformation in early days, and is composed of input module, database module, database store module, analysis module, and analysis result generation module. Graphic user interface(GUI) is supported for user's convenience. After performing the analysis, the output results like deflections and member forces according to the time can be observed in the generation module using the graphic diagram, table, and chart supported by the integrated environment.

Effects of Product Value of Outlet Stores on Customer Satisfaction and Loyalty (아울렛의 제품 가치가 고객 만족도와 충성도에 미치는 영향)

  • Choi, Soon-Hwa;Jung, Yeon-Sung;Kim, Moon-Seop
    • Journal of Distribution Science
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    • v.14 no.4
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    • pp.93-101
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    • 2016
  • Purpose - As more consumers pursue high quality products at reasonable prices, Korean retail companies are increasing investment in expanding their outlet stores. Despite the growing importance of the outlet business, there has been very little empirical research on consumers' outlet shopping behaviors. This study aimed to investigate the relationships between consumers' perceived product value (performance quality, value for money, and social value) of outlet stores and overall shopping satisfaction and the effect of shopping satisfaction on outlet store loyalty. Research design, data and methodology - The authors developed a structural model in which performance quality, value for money, and social value of products are proposed to affect overall outlet shopping satisfaction, thus increasing customer loyalty. To analyze the research model, data were collected from 88 shoppers at suburban outlets. SPSS 21.0 and AMOS 21.0 were utilized to test the hypotheses. The unidimensionality of each construct was supported from the results of the reliability test with Cronbach's α and confirmatory factor analyses. Correlation analysis was performed and the results warranted the nomological validity of the measures. The fit statistics of the overall model analysis demonstrated an acceptable fit(X2(161)=171.651, p=.000; X2/df=1.546; GFI=.821, NFI=.879, TLI=.942, CFI=.953, RMR=.035, RMSEA=.079). Results - The findings are as follows. First, consumers' perceived value of product performance quality had a significant positive effect on overall outlet shopping satisfaction. Consumers, who evaluate performance quality of the product more positively, tend to express stronger satisfaction and happiness about outlet shopping experience. Second, consumers' perceived social value of outlet products influenced their overall satisfaction significantly. Consumers who believe that products of outlet stores enhance self-concepts are more likely to satisfy with outlet shopping experience. However, consumers' perception of outlet products on value for money was not found to significantly influence overall shopping satisfaction. Finally, overall shopping satisfaction had a significant and positive influence on loyalty. Conclusions - While outlet retailers have traditionally focused on promoting competitively priced merchandise, the results of this study suggest that customers' overall satisfaction with outlet shopping is influenced more by the non-price-related product values. In the context of an outlet shopping environment, performance quality and social value of the products were found to be more critical predictors of customer overall satisfaction. Therefore, it would not be efficient for outlet retailers to highlight economic value of their merchandise. Instead, they need to investigate the performance quality of the products regularly and try to deliver quality guaranteed goods to enhance customer satisfaction. Also, outlet retailers should differentiate their businesses by carrying more unique and prestigious brands and emphasize higher social value and symbolic meanings of their products. As competition among outlet retailers are getting fierce, retail companies need to focus on strengthening customer loyalty with a long-term perspective. With a deeper understanding of the relationship between consumers' perceived product values and shopping satisfaction, outlet retailers will be able to develop customer loyalty strategies effectively and to achieve competitive advantage.

Enhancement of combustion efficiency of a air-cooled combustor system with single F.D. Fan Using CFD (전산유체역학을 이용한 단일 송풍기가 적용된 공냉식 연소설비의 효율개선)

  • Kim, Min-Choul;Shon, Byung-Hyun;Lee, Jae-Jeong;Park, Hung-Suck
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.6
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    • pp.460-468
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    • 2021
  • This study investigated the enhanced combustion efficiency of an "air-cooled combustion system" with single F.D. fan, and performed a numerical analysis for the operation and design conditions to increase the combustion efficiency. The combustion efficiency in an actual combustor was compared before and after the structure modification. Numerical analysis for application of a single fan revealed the difficulty of forming a turbulence for circular combustion conditions. This is because the supply ratio of combustion air supplied into 2 flow paths becomes irregular in the combustion furnace due to a change in friction force and pressure in each flow path. Subsequently, two methods of supplying air into the combustion furnace were analyzed numerically to obtain the optimal combustion conditions of an air-cooled combustion system. The first method involved injecting the preheated combustion air after a 180~360 degree rotation from the outer wall, whereas in the second method, the combustion air was injected into the combustion furnace in a tangential direction after primary heat exchange outside the combustion furnace, by applying a rotatable vane structure in the combustion furnace. Results reveal that application of a single F.D. fan to the air injection into a rotatable combustion furnace is desirable for optimization of the combustion conditions for applying a duct structure having a dual cooling wall for the cooling of the outer wall of the combustion furnace, and for maintaining perfect mixing in the combustion furnace. We therefore confirmed enhanced combustion efficiency by comparing the actual combustion efficiency before and after structure modification.

Recent Progress in Air Conditioning and Refrigeration Research -A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2000 and 2001- (공기조화, 냉동 분야의 최근 연구 동향 -2000년 및 2001년 학회지 논문에 대한 종합적 고찰 -)

  • 강신형;한화택;조금남;이승복;조형희;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.12
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    • pp.1102-1139
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    • 2002
  • A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2000 and 2001 has been done. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environment. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation of facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat, humidity was also interesting for comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing topics. Well developed CFD technologies were widely applied for developing facilities and their systems. (2) Most of papers related with heat transfer analysis and heat exchanger shows dealt with convection, evaporation, and channel flow for the design application of heat exchanger. The numerical heat transfer simulation studies have been peformed and reported to show heat transfer characteristics. Experimental as well as numerical studies on heat exchanger were reported, while not many papers are available for the system analysis including heat exchanger. (3) A review of the recent studies on heat pump system shows that performance analysis and control of heat pump have been peformed by various simulations and experiments. The research papers on multi-type heat pump system increased significantly. The studies on heat pipe have been examined experimently for change of working characteristics and strut lure. Research on the phase change has been carried out steadily and operation strategies of encapsulated ice storage tank are reported experimentally in several papers. (4) A review of recent studies on refrigeration/air conditioning system have focused on the system performance and efficiency for new alternative refrigerants. Evaporation and condensation heat transfer characteristics are investigated for tube shapes and new alternative refrigerants. Studies on components of refrigeration/air conditioning system are carried to examine efficiency for various compressors and performance of new expansion devices. In addition to thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out, however research works on two-phase flow seemed to be insufficient. (5) A review of the recent studies on absorption cooling system indicates that heat and mass transfer phenomena have been investigated to improve absorber performance. Various experimental data have been presented and several simulation models have been proposed. A review of the recent studies on duct and ventilation shows that ventilation indices have been proposed to quantify the ventilation performance in buildings and tunnels. Main efforts have been focused on the applications of ventilation effectiveness in practice, either numerically using computational fluid dynamics or experimentally using tracer gas techniques. (6) Based on a review of recent studies on indoor thermal environment and building service systems, research issues have mainly focused on many innovative ideas such as underfloor air-conditioning system, personal environmental modules, radiant floor cooling and etc. Also, the new approaches for minimizing energy consumption as well as improving indoor environmental conditions through predictive control of HVAC systems, various activities of building energy management and cost-benefit analysis for economic evaluation were highlighted.

A study on the effect of air velocity through a damper on smoke extraction performance in case of fire in road tunnels (도로터널 화재 시 집중배기방식의 배기포트 통과풍속이 배연성능에 미치는 영향에 관한 연구)

  • Ryu, Ji-Oh;Na, Kwang-Hoon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.22 no.4
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    • pp.347-365
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    • 2020
  • In order to resolve traffic problems in urban areas and to increase the area of green spaces, tunnels in downtown areas are being increased. Additionally, the application of large port smoke extraction ventilation systems is increasing as a countermeasure to smoke extraction ventilation for tunnels with high potential for traffic congestion. It is known that the smoke extraction performance of the large port smoke extraction system is influenced not only by the amount of the extraction flow rate, but also by various factors such as the shape of the extraction port (damper) and the extraction air velocity through a damper. Therefore, in this study, the design standards and installation status of each country were investigated. When the extraction air flow rate was the same, the smoke extraction performance according to the size of the damper was numerically simulated in terms of smoke propagation distance, compared and evaluated, and the following results were obtained. As the cross-sectional area of the smoke damper increases, the extraction flow rate is concentrated in the damper close to the extraction fan, and the smoke extraction rate of the damper in downstream decreases, thereby increasing the smoke propagation distance on the downstream side. In order to prevent such a phenomenon, it is necessary to reduce the cross-sectional area of the smoke damper and increase the velocity of passing air through the damper so that the pressure loss passing through the damper increases, thereby reducing the non-uniformity of smoke extraction flow rate in the extraction section. In this analysis, it was found that when the interval distance of the extraction damper was 50 m, the air velocity passing through damper was 4.4 m/s or more, and when the interval distance of the extraction dampers was 100 m, the air velocity passing through damper was greater than 4.84 m/s, it was found to be advantageous to ensure smoke extraction performance.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.12
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.