• Title/Summary/Keyword: part-load

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The Characteristics of a Bypass Air Conditioning System for Load Variation (부하변동에 대한 바이패스 공조시스템의 특성)

  • 김보철;신현준;김정엽
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.3
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    • pp.240-246
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    • 2002
  • Bypass air conditioning systems are divided into three types; an outdoor air bypass, a mixed air bypass and a return air bypass system. What makes the return air by pass system more effective is that it directs all of moist outdoor air through the cooling coil. The bypass air conditioning system can maintain indoor R.H (Relative Humidity) less than a conventional CAV (Constant Air Volume) air conditioning system by adjusting face and bypass dampers at part load. When a design sensible load (the ratio of sensible load to total sensible load) is 70 percent (at this time, RSHF (Room Sensible Heat Factor) . 0.7), indoor R.H was maintained 59 percent by the return air bypass system, but 65 percent by the conventional CAV air conditioning system (valve control system). The bypass air conditioning system can also improve IAQ (Indoor Air Quality) in many buildings where the number of air change is high.

Crack Closure and Growth Behavior of Short Fatigue Cracks under Random Loading (Part I : Details of crack Closure Behavior) (짧은 피로균열의 랜덤하중하의 균열닫힘 및 진전거동 (Part I: 균열닫힘 거동 상세))

  • Lee, Shin-Young;Song, Ji-Ho
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.79-84
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    • 2000
  • Crack closure and growth behavior of physically short fatigue cracks under random loading are Investigated by performing narrow- and wide-band random loading tests for various stress ratios. Artificially prepared two-dimensional, short through-thickness cracks are used. The closure behavior of short cracks under random loading is discussed, comparing with that of short cracks under constant-amplitude loading and also that of long cracks under random loading. Irrespective of random loading spectrum or block length, the crack opening load of short cracks is much lower under random loading than under constant-amplitude loading corresponding to the largest load cycle in a random load history, contrary to the behavior of long cracks that the crack opening load under random loading is nearly the same as or slightly higher than constant-amplitude results. This result indicates that the largest load cycle in a random load history has an effect to enhance crack opening of short cracks.

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Forming Analysis and Experiment of Hard to Forming T Shape Aluminum Part (난성형 T형상 알루미늄 부품의 성형공정 해석 및 실험)

  • Jin, Chul-Kyu
    • Journal of the Korean Society of Industry Convergence
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    • v.20 no.2
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    • pp.141-148
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    • 2017
  • A process comprising a hot extrusion process and a warm forging process was designed to form a T-shaped aluminum structural component with a high degree of difficulty by the plastic forming method. A circular cylindrical part was extruded with a hot extrusion process, and then an embossing part was formed with a warm forging process. The formability and the maximum load required for forming were then determined using a forming analysis program. The hot extrusion process was executed at $450^{\circ}C$ under the extrusion speed at 6 mm/s, while the warm forging process was executed at $260^{\circ}C$ under the forging speed at 150 mm/s. For both the processes, a condition by which friction would not be generated between the mold and the material was implemented. The analysis results showed that the load required for hot extrusion was 1,019 tons, while the load required for the warm forging was 534 tons. The T-shaped part was manufactured by using a 1,600 tons capacity press. The graphite lubricant was coated on the mold as well as the material. A forming experiment was performed under the same condition with the analysis condition. The measured values from the load cell were 1,210 tons in the hot extrusion process and 600 tons in the warm forging process.

A Electrical Characteristics of Disk-type Piezotransformer with Electrode Ratio of Driving and Generating Part (디스크형 압전변압기의 전극비에 따른 전기적 특성)

  • 이종필;채홍인;정수현;홍진웅
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.52 no.10
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    • pp.458-463
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    • 2003
  • In order to develope piezoelectric transformer for the ballast of fluorescent lamp, a new shape and electrode pattern of piezoelectric transformer has been investigated in this work. The composition of piezoelectric ceramics was 0.95Pb(Zr$_{0.51}$Ti$_{0.49}$)O$_3$+0.03Pb(Mn$_{1}$3/Nb$_{2}$3/)O$_3$+0.02Pb(Sb$_{1}$2/Nb$_{1}$2/)O$_3$. The sample prepared by this composition system showed the characteristics which has about 1200 of relative dielecric constant, 1100 of the mechanical quality factor, 0.53 of the electromechanical coupling coefficient, 320 pC/N of the piezoelectric constant d$_{33}$, 0.3 % of the dissipation factor. Diameter and thickness of disk-type piezoelectric transformer was 45 mm and 4 mm, respectively. The driving and generating electrode with their gap of 1mm were fabricated on the top surface. But the common electrode was fabricated on the whole bottom surface. The electrode surface ratio of driving and generating part on the top surface ranges from 1.4:1 to 3:1. We investigated the electrical characteristics with the variation of the electrode surface ratio of driving and generating part in the range of load resistance of 100 $\Omega$~70 k$\Omega$. The set-up voltage ratio of this piezoelectric transformer increases with increasing both the electrode surface of driving part and the load resistance. The set-up voltage ratio at no load resistance was more than 60 times. On the other hand, the efficiency decreases with increasing the electrode surface of driving part. In the case of the electrode surface of both 1.4:1 and 2:1, maximum efficiency showed above 97 % at load resistance of 2 k$\Omega$. However, in the case of the electrode surface of 3:1, maximum efficiency showed about 94 % at load resistance of 3 k$\Omega$.>.>.>.

Development of Structure Analysis Program for Jointed Concrete Pavement Applying Load Discretization Algorithm (하중변환 알고리듬을 적용한 줄눈 콘크리트 포장해석 프로그램 개발)

  • Yun, Tae-Young;Kim, Ji-Won;Cho, Yoon-Ho
    • International Journal of Highway Engineering
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    • v.5 no.4 s.18
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    • pp.1-11
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    • 2003
  • Recently, the new pavement design method considering Korean environment and the specification for improving performance of pavement are being developed in Korea. The Jointed Concrete Pavement Program Applying Load Discretization Algorithm (called HEART-JCP) is one of the results of Korea Pavement Research Project in Korea. HEART-JCP program is developed to analyze various loading condition using the load discretization algorithm without mesh refinement. In addition, it can be modified easily into multi-purpose concrete pavement nidyses program because of the modularized structure characteristic of HEART-JCP. The program consists of basic program part and load discretization part. In basic program part, the displacement and stress are computed in the concrete slab, sub-layer, and dowel bar, which are modeled with plate/shell element, spring element and beam element. In load discretization program part, load discretization algorithm that was used for the continuum solid element is modified to analyze the model with plate and shell element. The program can analyze the distributed load, concentrated load, thermal load and body load using load discretization algorithm. From the result of verification and sensitivity study, it was known that the loading position, the magnitude of load, and the thickness of slab were the major factors of concrete pavement behavior as expected. Since the result of the model developed is similar to the results of Westergaard solution and ILLISLAB, the program can be used to estimate the behavior of jointed concrete pavement reasonably.

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A Study on the Non-Axisymmetric Closed-Die Ring Forging (비축대칭 형상의 밀폐형 링 단조에 관한 연구)

  • 배원병;김영호;이종헌;이원희
    • Transactions of Materials Processing
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    • v.3 no.2
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    • pp.202-214
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    • 1994
  • An upper bound elemental technique(UBET) is applied to predict the forging load and die-cavity filling for non-axisymmetric ring forging. In order to analyze the process easily, it is suggested that the finial product is divided into three different deformation regions. That is axisymmetric part in corner, lateral plane-strain part and shear deformation on boundaries between them. the place-strain and axisymmetric part are combinded by building block method. Also the total energy is computered through combination of three deformation part. Experiments have been carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.

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대구경 소켓경사반력말뚝의 인발거동에 관한 연구

  • 최용규;김상옥;정창규;정성기;김상일
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.11a
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    • pp.277-284
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    • 2000
  • Using the large diameter (D = 2,500mm, L = 40m) batter steel pipe piles, designed as compression piles but used as reaction piles during the static compression load test of socketed test piles (D = 1,000mm, L = 40m), static pile load tests for large diameter instrumented rock-socketed piles were performed. The reaction steel pipe piles were driven 20m into the marine deposit and weathered rock layer and then l0m socketed with reinforced concrete through the weathered rock layer and into hard rock layer. Steel pipe and concrete in the steel pile part, and concrete and rebars in the socketed parts were instrumented to measure strains in each part. The pullout amounts of reaction pile heads were also measured with LVDT. During the static pile load test, total compressional load of about 20MN was loaded on the head of test piles, but load above 20MN was not loaded due to lack of loading capacity of loading system. Over the course of the study, maximum pullout amount up to 7mm was measured in the heads of reaction piles when loaded op to 10MN and 1mm of pullout amount was measured. More than 85% of pullout load was transfered in the residual weathered rock layer and about 10% in the soft rock layer, which was somewhat different transfer mechanism in the static compressional load tests.

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Study on Analysis of Driving Torque and Reduction for Naval Surveillance Radar Antenna (함정용 탐색레이더 안테나의 구동 토크 분석 및 감쇄에 대한 연구)

  • Kim, Seung-Woo;Yang, Yun-Suk
    • Journal of the Korea Institute of Military Science and Technology
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    • v.12 no.3
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    • pp.388-395
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    • 2009
  • Surveillance Radar System for naval vessels is a primary core sensor for command and fire control, and provides CFCS(Command and Fire Control System) information for 3-D surveillance and fire control. It's composed of Antenna, Transmitter/Receiver, Signal Processor, and Air drier, which are installed on and under deck. They should be designed and produced in order to endure at any operating circumstances. This paper analyzes load of a driving part for driving the antenna considering factors under external operating circumstances, and proposes a condition of load for maintaining fixed RPM through analyzing internal load of the driving part, and how to reduce the load to meet the condition. This paper is verified through experimental studies.

Thermo-Mechanica1 Stress Analyses of Part with Coated Layer under Contact Load Using Partial Model (부분 모델을 이용한 접촉하중을 받는 코팅층이 있는 부재의 열적/기계적 응력해석)

  • 권영두;김석삼;신세현;추상우
    • Tribology and Lubricants
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    • v.18 no.3
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    • pp.228-234
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    • 2002
  • Generally, space structures are subjected to severe situations, such as, sublimation, strong evaporation of lubricants, thermal stresses, high temperature gradients, irradiation, impacts by microscopic meteorites, and other factors. Recent]y, various kinds of coatings are applied to the parts under heavy contact stresses, in order to insure long wear-free lives and/or reduce friction coefficients. In space structures, molybdenum disulfide is using frequently. Moreover TiN, Al$_2$O$_3$, PTFE(Poly Tetra Fluor Ethylene) are introduced recently for space structure. In this part we are going to apply the partial model method, developed in reference[11] to analyze part with coated layer. In referencer[l1], we compute the reasonable size of partial model and aspect ratio. Using these data, we analyze the structures coated with TiN, Al$_2$O$_3$, PTFE under contact load, temperature and crack model . Beside, we consider the stress analysis under time dependent load and transient thermal effect.

Influence on heat transfer due to uneven flow (유동 불균일이 전열관 튜브에 미치는 영향)

  • Chong, Chae-Hon;Song, Jung-Il
    • 한국태양에너지학회:학술대회논문집
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    • 2008.11a
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    • pp.273-279
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    • 2008
  • The purpose of this study is not only to evaluate thermal performance but also to find the stress behavior of heat transfer tubes under the part load operation in Heat Recovery Steam Generator. Flow analysis was performed to know the behavior of exhaust gas from gas turbine and thermal performance was calculated using distribution of hot exhaust velocity. In addition, tubes temperature during operation were gathered from actual plant to verify the uneven flow distribution under part load operation. Stress analysis was performed using tubes temperature data gathered from actual plant under both part and full load operations to know the stress behavior of tubes.

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