• 제목/요약/키워드: Comparison of reducing characteristics

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EnergyPlus를 이용한 바닥공조시스템의 모델링 방법에 따른 에너지 성능 비교 (Comparison on the Energy Performance of Underfloor Air Distribution System According to Modeling Method Using EnergyPlus)

  • 장향인;윤성훈;이현수;서승직
    • 설비공학논문집
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    • 제24권10호
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    • pp.718-723
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    • 2012
  • The purpose of this study is to propose modeling method of Underfloor Air Distribution System with reliability and validity by comparing characteristics of modeling methods. For this, the modeling methods of UFAD were selected by investigating various modeling methods of previous researches. Then, simulations were conducted by using EnergyPlus which is dynamic analysis program of building energy. Annual energy consumption for each method was compared with a wide range of indoor thermal loads. As a result, the methodology of reducing internal gains can cause under sizing of the system. It suggests modeling methods to reflect occupied zone air-conditioning, temperature stratification and supply plenum which are the main characteristics of UFAD.

메탈로센 선형 저밀도 폴티에틸렌의 결정화 거동 (Crystallization Characteristics of Metallocene Low Density Polyethylene)

  • 김경룡;한정우;조봉규;강호종
    • 폴리머
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    • 제25권6호
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    • pp.833-839
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    • 2001
  • 광산란 장치를 이용하여 메탈로센 촉매 하에 제조된 메탈로센 선형 저밀도 폴리에틸렌의 결정화거동을 Ziegler-Natta 촉매에 의하여 제조된 선형 저밀도 폴리에틸렌과 비교하여 보았다. 특히 branching수와 길이 그리고 공단량체의 함량이 결정화 거동에 미치는 영향을 중점적으로 살펴보았다. 같은 수의 branching 수를 가지고 있는 메탈로센 선형 저밀도 폴리에틸렌은 기존의 선형 저밀도 폴리에틸렌에 비하여 결정화를 시작하기 위한 induction time이 길어짐을 알 수 있으나 구정의 성장속도는 두 경우가 유사함을 확인하였다. 메탈로센 선형 저밀도 폴리에틸렌의 branching 수를 감소시킬 경우 induction time과 구정성장속도가 모두 빨라짐을 알 수 있었다. 또한 일반적으로 최대 구정의 크기는 branching 수에 관계없이 메탈로센 선형 저밀도 폴리에틸렌이 기존의 선형 저밀도 폴리에틸렌에 비하여 커짐을 알 수 있었다.

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전자식 조향 장치용 매입형 영구자석 동기전동기의 Skew를 고려한 파라미터 산정 (Calculation of Parameters Considering Skew in EPS Interior Permanent Magnet Synchronous Motor)

  • 이수진;홍정표
    • 전기학회논문지
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    • 제62권10호
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    • pp.1403-1407
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    • 2013
  • This paper presents the method to calculate the motor parameters considering skew in EPS Interior Permanent Magnet Synchronous Motor (IPMSM). The skew is applied to stator or rotor by general technology used for design of reducing noise and vibration in motor. The characteristics analysis of motor including the skew is mostly used by 3D Finite Element Analysis (FEA), though, this analysis is a very time-consuming to perform. Besides, The reliability lacks due to the considerable change of motor characteristics according to the number of elements in 3D FEA. However, analysis time and effort can be saved by characteristic analysis considering skew using 2D FEA. Therefore, in this paper, a quick and accurate method for the calculations of motor parameters considering skew is suggested. The proposed method is verified by the comparison of calculated and experimental results.

기존 및 개량 고속분기기의 소음특성 평가에 대한 사례연구 (A Case Study on the Evaluation of Noise Characteristics Around the Conventional, Improved and High-speed Turnout System)

  • 엄기영;엄주환;이진형
    • 환경영향평가
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    • 제15권6호
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    • pp.453-458
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    • 2006
  • A turnout system which permits trains to pass from one track to another consists of the switch, the crossing, lead rails which are necessary to connect the switch and the crossing, two guard rails and a switch machine for operating the switch. A turnout is the sole moving part among the railway components and has complex configuration, so the safety has always been raised an issue. In Korea, it is planned to adopt the high speed tilting train, which operates at the maximum speed of 180km/h, at conventional lines by the year of 2010. However, for the application of the tilting train to conventional lines, it is prerequisite to establish a stable turnout system allowing the tilting train to pass through it without reducing speed. Therefore, the improved turnout system for the speed-up of conventional lines has been developed and the prototype of the turnout system has been constructed. In this study, evaluation of noise characteristics around the improved turnout system was performed through the field measurements. Field measurements of noise around the conventional and the high-speed turnout system were also carried out for the comparison.

자탈형(自脫型) 콤바인 환원장치(還元裝置)의 환원물(還元物) 유동현상(流動現象)과 환원성능(還元性能) 개선(改善)에 관한 연구(硏究)(II) -환원물(還元物) 유동(流動)의 이론해석(理論解析)과 실험분석(實驗分析)- (Tailings Behavior and Performance of the Tailings Return Unit of the Head-feed Combine(II) -Theoretical and Experimental Analysis of Tailing Behavior-)

  • 조영길;정창주;최규홍;박판규
    • Journal of Biosystems Engineering
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    • 제16권2호
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    • pp.133-141
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    • 1991
  • This study was undertaken to investigate the structural and configurational characteristics of the tailings return-unit in the commercially available head-feed combines and to study the aero-dynamical behavior of the tailings in the units. The mathematical model of the motion of tailings in the thrower casing was developed and the simulated trajectories for different type of units was analyzed to compare with the measured ones. The air-stream velocity profile in various locations along the tailings returning duct was measured to find the effect of configurational characteristics and blade tip speed. The results of the study are summerized as follows. 1. The ejecting angle, which is the angle between the direction of the particle velocity ejecting from the blade and the horizontal axis, was found to be about $66^{\circ}$ in both the simulation and experiment. The angle was much greater than the setting angle of actual duct of the combines studied, which were $48{\sim}56^{\circ}$. By comparison of these results, it was suggested to change duct setting angle so as to reduce the frictional force, between the duct wall and tailings, by reducing the difference between the ejecting and setting angles. 2. The velocity of the air stream in the duct was in general higher in the upper bound of the duct compared to the lower and decreased as the stream went toward the end of duct. The comparison of the tailings units among the combines studied showed a superior performance with the tapered duct having small diameter in the outlet and with greater number of thrower blade.

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Performance of a Modified Multicarrier Direct Sequence CDMA System

  • Lee, Dong-Wook;Lee, Hun;Kim, Jin-Su
    • ETRI Journal
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    • 제19권1호
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    • pp.1-12
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    • 1997
  • In this paper, we present an improved multicarrier direct sequence (DS) code division multiple access (CDMA) scheme by modifying the system originally proposed by Kondo and Milstein [13]. In this modified system, different spreading sequences multiplied by a data sequence modulate different carriers. This is to prevent the multiple access capability from reducing when the fading characteristics of different carrier frequencies are highly correlated. We have derived a formula which determines the mean values of the relative received signal strength in a single carrier DS CDMA rake system and in a multicarrier DS-CDMA system. We present results on the comparison of the bit error rate (BER) performance of the two systems including the effect of correlation between fading characteristics of different frequencies under various multipath fading conditions. The results indicate that with 50 users the modified multicarrier DS CDMA system can achieve an uncoded irreducible BER of $1.7{\times}10^{-3}$ with an average received signal-to-noise ratio per bit of 10dB, which is better that $3.0{\times}10^{-3}$ achieved by the single carrier DS CDMA rake system, and also show that if multicarrier CDMA system is used with respect to single carrier CDMA system, the SNR gain is up to 4.5 dB for the uncode BER of $10^{-3}$ being achieved.

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A Study on the Flow Field Characteristics of Air Induction System for Reducing the Signal-to-Noise in the MAFS Output

  • 유성출
    • 한국분무공학회지
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    • 제5권1호
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    • pp.49-57
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    • 2000
  • This study presents the flow visualization results, velocity and turbulence intensity measurements made within an air filter cover and entry region of a mass air flow sensor (MAFS) which is used in an induction system of 3.8L engine. Flow structure in two air filter cover assemblies were examined. The first was a clear plastic replica of the production cover while the second was a modified clear plastic cover with a geometry configured to reduce fluctuations. High speed flow visualization and laser doppler velocimetry (LDV) systems were used to reveal and analyze the flow field characteristics encountered in the sensor design process under steady flow conditions. A 40-watt copper vapor laser was used as a light source. Its beam is focused down to a sheet of light approximately 1.5mm thick. The light scattered off the particles was recorded by a 16mm high speed rotating prism camera at 5000 frames per second. A comparison of the flow patterns and LDV measurements in the original and modified air filter covers is presented to illustrate the controlling effect of the cover design on the turbulence structure formation near the bypass and on the sensor output signal. In both axial and radial planes of the main passage it was found that the turbulence flow pattern is remarkably influenced by the air filter cover and main passage configuration.

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A Study for the Use of Solar Energy for Agricultural Industry - Solar Drying System Using Evacuated Tubular Solar Collector and Auxiliary Heater -

  • Lee, Gwi Hyun
    • Journal of Biosystems Engineering
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    • 제38권1호
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    • pp.41-47
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    • 2013
  • Purpose: The objectives of this study were to construct the solar drying system with evacuated tubular solar collector and to investigate its performance in comparison with indoor and outdoor dryings. Methods: Solar drying system was constructed with using CPC (compound parabolic concentrator) evacuated tubular solar collector. Solar drying system is mainly composed of evacuated tubular solar collector with CPC reflector, storage tank, water-to-air heat exchanger, auxiliary heater, and drying chamber. Performance test of solar drying system was conducted with drying of agricultural products such as sliced radish, potato, carrot, and oyster mushroom. Drying characteristics of agricultural products in solar drying system were compared with those of indoor and outdoor ones. Results: Solar drying system showed considerable effect on reducing the half drying time for all drying samples. However, outdoor drying was more effective than indoor drying on shortening the half drying time for all of drying samples. Solar drying system and outdoor drying for oyster mushroom showed the same half drying time. Conclusions: Oyster mushroom could be dried easily under outdoor drying until MR (Moisture Ratio) was reached to about 0.2. However, solar drying system showed great effect on drying for most samples compared with indoor and outdoor dryings, when MR was less than 0.5.

기존선 분기기시스템 인근 소음측정 및 분석 (Evaluation of Noise Characteristics around the Conventional Turnout System through the Field Measurements)

  • 신한철;엄기영;박용걸
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2008년도 추계학술대회 논문집
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    • pp.985-992
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    • 2008
  • A turnout system which permits trains to pass from one track to another is a combination of the switch, the crossing, lead rails which are necessary to connect the switch and the crossing, two guard rails and a switch machine for operating the switch. A turnout is the sole moving part among the railway components and has complex configuration, so the safety has always been raised an issue. In Korea, it is planned to adopt the high speed tilting train, which operates at the maximum speed of 180km/h, at conventional lines by the year of 2010. However, for the application of the tilting train to conventional lines, it is prerequisite to establish a stable turnout system allowing the tilting train to pass through it without reducing speed. Therefore, the improved turnout system for the speed-up of conventional lines has been developed and the prototype of the turnout system has been constructed. In this study, evaluation of noise characteristics around the improved turnout system was performed through the field measurements. Field measurements of noise around the conventional and the high-speed turnout system were also carried out for the comparison.

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대형 디젤 엔진의 연료 분사 노즐 형상이 NOx 발생량 및 연료소비율에 미치는 영향 연구 (A Study on the Optimization of Fuel Injection Nozzle Geometry for Reducing NOx Emission in a Large Diesel Engine)

  • 김기두;하지수;윤욱현
    • Journal of Advanced Marine Engineering and Technology
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    • 제28권7호
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    • pp.1123-1130
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    • 2004
  • Numerical simulations have been carried out to investigate the effect of nozzle hole geometry on the combustion characteristics of the large diesel engine. 6S90MC-C. Spray and combustion phenomena were examined numerically using FIRE code. Wane breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation processes. Predictions on the cylinder peak pressure and NOx emission were first verified with the experimental data to confirm the reliability of numerical calculations. The comparison results showed good agreements within the range of 0.64% and 4.6% respectively. Finally, the effects of fuel spray angle and diameter on the engine performance were investigated numerically to find the optimum nozzle hole geometry considering fuel consumption, NOx emission and heat flux of the combustion chamber wall. It was concluded that the combustion gas recirculation in cylinder by changing fuel injection direction is an effective method to reduce NOx emission by about 10% with increasing fuel oil consumption, 1.4% in a large diesel engine.