• 제목/요약/키워드: Heat Input

검색결과 1,095건 처리시간 0.025초

상부가 개방된 수직 캐비티내의 한쪽면에 배열된 다양한 발열조건을 갖는 발열체의 최적배열 (The optimal array of various heat-generating heaters located on one wall of a vertical open top cavity)

  • 유갑종;추홍록;최병철
    • 대한기계학회논문집B
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    • 제21권1호
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    • pp.15-23
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    • 1997
  • An experimental investigation of two-dimensional steady natural convection cooling in a vertical open top cavity with conducting side walls of finite thickness is presented. The various heat-generating discrete heaters are located on one vertical wall of the cavity. When each heater dissipates different amount of power, the purpose of the work is to obtain the optimal array condition of the heaters. The four cases of non-uniform heating conditions are considered. The temperature fields in the cavity were visualized by the interferometer and local temperatures of the vertical wall were measured by thermocouples. The heaters were arranged in two configurations: flush-mounted on a vertical wall or protruding from the wall about 4.5 mm. The vertical wall was constructed out of copper or epoxy-resin sheet. Experiments have been conducted for air with constant Prandtl number(Pr=0.7), the aspect ratio of 4.6, 7.5, 9.5, power input in the range of 0.9 W ~ 4.2 W. For the enhancement of the cooling effectiveness, the upper and lower of vertical wall would give the better position for the heaters of higher heat flux.

원전 배관용 SA 106 Gr.C의 협개자동용접 적용에 관한 연구 (The Application of Narrow-Gap Welding Process for SA 106 Gr.C in Nuclear Power Plant)

  • 우승환;권재도;이춘열;강석철;신호상
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.96-101
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    • 2004
  • Conventionally, SMAW process was applied to join pipes of RCL, which caused lot of loss in time and cost due to excessive heat input and defects in joining section. Recently, narrow-gap welding(NGW) process was introduced to overcome the disadvantages of SMAW. However, the application of NGW to nuclear power plant is not yet common because safety of NGW process is not proven. In present paper, the welded coupons are made of carbon steel. They are manufactured under different processes; general welding(GW), post-weld heat treatment(PWHT) after GW, repair welding after GW and PWHT with repair welding after GW in carbon steel. Performed are various mechanical tests investigation of microstructure, hardness test, tensile test at room and high temperature, bending test, impact test and J-R test. It is verified that the mechanical properties of carbon steel are greatly changed after repair welding process due to applied heat flux, and that the effect of PWHT is beneficial.

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EPS foam의 선형 열선 절단시 절단 경사각의 영향에 관한 연구 (Investigation into effect of cutting angle on the thermal characteristics in the linear heat cutting of EPS foam)

  • 안동규;이상호;양동열;윤석환
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2002년도 춘계학술대회 논문집
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    • pp.947-951
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    • 2002
  • During the hotwire cutting of EPS foam sheet, the dimensional accuracy and part quality of the cut par are highly dependent upon the thermal field in the EPS. The thermal field is determined by operating parameters such as heat input, cutting speed and cutting angle. The objective of this study is to investigate into the influence of cutting angle on the kerfwidth and part quality of the cut part in hotwire cutting of EPS foam using the experiments and the numerical analysis in the case of a single sloped cutting. In order to estimate an accurate temperature field, the transient thermal analysis using a moving coordinate system and the sloped heat flux model is carried out. From the results of the experiments and the analysis, it has been found that the effect of cutting angle on the kerfwidth and the melted area at the edge are 0.1 mm and 0.11 m$m^2$ respectively. The results of the experiments show that the surface roughness is not appreciably influenced by the cutting angle.

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Nd:YAG 레이저를 이용한 하스텔로이 박판의 겹치기 이음 용접 특성 (Welding Characteristics of Lap-Joint Hastelloy C-276 Sheet Metal Using Nd:YAG Laser)

  • 김찬규;정윤교;조영태
    • 한국정밀공학회지
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    • 제32권8호
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    • pp.681-685
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    • 2015
  • Hastelloy C-276 composed of Cr, Mo, and Ni is a versatile, corrosion-resistant alloy with numerous industrial applications including its use in nuclear reactors, general chemical plants, and as a superconducting base material. Of especial significance, it can be used as a thin-sheet type whereby lap-joint welding is occasionally necessary. The main welding problems for thin-sheet metals are deformation and burn-through from an excessive heat input. Laser welding can minimize these problems because it has a high energy density and low heat effect on the base material. In this study, the laser-welding characteristics of lap-joint Hastelloy C-276 sheet metal were determined. The criteria of the laser-welding variables were chosen using a heat-conduction analysis, and the optimal welding parameters were selected by experimenting with an Nd:YAG laser.

마찰용접을 이용한 대형선박 터보챠저용 이종 로타샤프트 개발 (Development of Large Rotor Shaft for Marine Turbo Charger Using Friction Welding with Dissimilar Materials)

  • 문광일;전종원;정호승;조종래;최성규
    • 한국정밀공학회지
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    • 제33권4호
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    • pp.257-264
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    • 2016
  • Solid state joining techniques are increasingly applied in a wide range of industrial applications. Friction welding is a solid state welding technique that is used to join similar or dissimilar materials. In this study, friction welding was applied to rotor shaft composed of a disk and a shaft. The disk and shaft were manufactured by hot forging and rolling, respectively. The aim of the study was to predict the structural characteristics during hot forging and friction welding process for rotor shaft of turbo charger. The structural characteristics were determined by heat input and heat affected zone (HAZ) during a short cycle time. Thus, transient FE analysis for hot forging and friction welding was based on heat transfer. The results were used to predict structural characteristics during hot forging and friction welding processes. The prototype of rotor shaft was manufactured by the result-based process parameters.

STUDY ON THE EFFECT OF RESIDUAL STRESS ON THE EXTERNALLY LOADED WELDED STRUCTURE

  • ;방한서;주성민;김인식
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2004년도 추계학술발표대회 개요집
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    • pp.58-60
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    • 2004
  • In the field of welding the behavior of a welded structure under consideration may be predicted via heat transfer and residual stress analysis. In order to facilitate the industrial applications of welding, numerical modeling of heat transfer and residual stress in weldment has been carried out applying Finite Element Method (FEM) and the analysis with the external load including this residual stress due to welding has been done. The present work includes the specialized finite element codes for the calculation of nonlinear heat transfer details and residual stress redistributed along with the external load in the welded structures. A basic interface, which allows models, built in commercial preprocessing package access to the data necessary to build standard input decks for these specialized FEM codes, which are not supported by commercial package. The results from the FEM codes are imported back into commercial package for visualization. In addition the residual stress values are exported to commercial package (such as ANSYS, PATRAN etc.) for further analysis with the external loads, which make the FEM codes fully applicable to the industrial purpose.

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애주(艾炷)의 형태별(形態別) 연소(燃燒) 특성(特性)에 대한 연구(?究) - 연소온도(燃燒溫度)의 유형(類型)을 중심(中心)으로 - (An Experimental Study on the Characteristics of Moxa Combustion in the Moxa Cone size - On the Pattern of Combustion temperature -)

  • 박영배;강성길;김창환;고형균;오환섭;허웅
    • 대한한의학회지
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    • 제16권1호통권29호
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    • pp.370-378
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    • 1995
  • In order to consider the clinical efficacy of moxa combustion, understand the quality and quantity of heat stimulation and get the basic data for the development of electric moxibustion apparatus, the pattern of combustion temperature was measured by size of moxa(small, medium, large and maximum size). The results were as follows. 1. The pattern of combustion temperature by moxa burning was classified into input period, consisting of preheating and heating periods, and output period, consisting of heat retaining and cooling periods, in all experimental groups. But it was difficult to observe the preheating period in small sized moxa. 2. It was inclined that the more moxa size was large, the more the heating and heat retaining periods were long and the maximum temperature was high. The characteristics of moxa combustion is primarily by the rate of combustion temperature, gradient temperature and duration of combustion, and their correlation among these factors and their clinical effects in practice.

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다단계 최적화 수법을 이용한 열원 설비 설계법에 관한 연구 (A Study on the Multi-level Optimization Method for Heat Source System Design)

  • 유민경;남유진
    • 설비공학논문집
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    • 제28권7호
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    • pp.299-304
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    • 2016
  • In recent years, heat source systems which have a principal effect on the performance of buildings are difficult to design optimally as a great number of design factors and constraints in large and complicated buildings need to be considered. On the other hand, it is necessary to design an optimum system combination and operation planning for energy efficiency considering Life Cycle Cost (LCC). This study suggests a multi-level and multi-objective optimization method to minimize both LCC and investment cost using a genetic algorithm targeting an office building which requires a large cooling load. The optimum method uses a two stage process to derive the system combination and the operation schedule by utilizing the input data of cooling and heating load profile and system performance characteristics calculated by dynamic energy simulation. The results were assessed by Pareto analysis and a number of Pareto optimal solutions were determined. Moreover, it was confirmed that the derived operation schedule was useful for operating the heat source systems efficiently against the building energy requirements. Consequently, the proposed optimization method is determined by a valid way if the design process is difficult to optimize.

UM 자료를 이용한 노면온도예측모델(UM-Road)의 개발 (Development of Road Surface Temperature Prediction Model using the Unified Model output (UM-Road))

  • 박문수;주승진;손영태
    • 대기
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    • 제24권4호
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    • pp.471-479
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    • 2014
  • A road surface temperature prediction model (UM-Road) using input data of the Unified Model (UM) output and road physical properties is developed and verified with the use of the observed data at road weather information system. The UM outputs of air temperature, relative humidity, wind speed, downward shortwave radiation, net longwave radiation, precipitation and the road properties such as slope angles, albedo, thermal conductivity, heat capacity at maximum 7 depth are used. The net radiation is computed by a surface radiation energy balance, the ground heat flux at surface is estimated by a surface energy balance based on the Monin-Obukhov similarity, the ground heat transfer process is applied to predict the road surface temperature. If the observed road surface temperature exists, the simulated road surface temperature is corrected by mean bias during the last 24 hours. The developed UM-Road is verified using the observed data at road side for the period from 21 to 31 March 2013. It is found that the UM-Road simulates the diurnal trend and peak values of road surface temperature very well and the 50% (90%) of temperature difference lies within ${\pm}1.5^{\circ}C$ (${\pm}2.5^{\circ}C$) except for precipitation case.

CW Nd:YAG 레이저에 의한 열간금형 공구강의 표면경화특성 (The Surface Hardening Characteristics of Hot work Tool Steel by CW Nd:YAG Laser)

  • 신호준;유영태;안동규;신병헌
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2006년도 춘계학술대회 논문집
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    • pp.219-220
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    • 2006
  • Laser surface hardening technologies have been used to improve characteristics of wear and to enhance the fatigue resistance for mold parts. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser surface hardening for the case of SKD61 steel. CW Nd:YAG laser is selected as the heat source. The optical lens with the elliptical profile is designed to obtain a wide surface hardening area with a uniform hardness. From the results of the experiments, it has been shown that the maximum hardness is approximatly 740 Hv when the power, focal position and the travel of laser are 1,095 W, +1mm and 0.3 m/min, respectively. In addition, the hardening width using the elliptical lens was three time larger than that using the defocusing of laser beam.

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