• Title/Summary/Keyword: Direct cooling

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Analysis of Diesel Combustion Flames with Highly Oxygenated Fuels

  • Kim Bong-Seock;Ogawa Hideyuki
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.6
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    • pp.662-670
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    • 2005
  • With highly oxygenated fuels the smoke emissions decreased sharply and linearly with increases in the fuel oxygen content and entirely disappeared at an oxygen content of $38wt-\%$ even at stoichiometric mixture conditions The NOx also decreased monotonically with increases in oxygen content. and thermal efficiency slightly improved because of a reduction in cooling loss and improvement in the degree of constant volume combustion. The mechanisms of the significant reductions in emissions and improvement in engine performance were analyzed with a bottom view type DI diesel engine. Together with direct flame images, flame images were taken through an optical fetter passing only two wavelengths for use in 2-D two-color analysis. The results showed that luminous flame decreased significantly with increases in oxygen content and was not detected for neat dimethoxy methane(DMM). The decrease in flame luminosity with highly oxygenated fuels corresponds with decreases in soot and cooling losses, including those due to heat radiation. The 2-D two-color flame analysis indicated that the high temperature flame and high KL factor areas apparently decreased with increasing fuel oxygen content. These results correspond strongly with decreases in NOx. smoke. and cooling loss with increases in oxygen content.

APPLICATION OF UNCERTAINTY ANALYSIS TO MAAP4 ANALYSES FOR LEVEL 2 PRA PARAMETER IMPORTANCE DETERMINATION

  • Roberts, Kevin;Sanders, Robert
    • Nuclear Engineering and Technology
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    • v.45 no.6
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    • pp.767-790
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    • 2013
  • MAAP4 is a computer code that can simulate the response of a light water reactor power plant during severe accident sequences, including actions taken as part of accident management. The code quantitatively predicts the evolution of a severe accident starting from full power conditions given a set of system faults and initiating events through events such as core melt, reactor vessel failure, and containment failure. Furthermore, models are included in the code to represent the actions that could mitigate the accident by in-vessel cooling, external cooling of the reactor pressure vessel, or cooling the debris in containment. A key element tied to using a code like MAAP4 is an uncertainty analysis. The purpose of this paper is to present a MAAP4 based analysis to examine the sensitivity of a key parameter, in this case hydrogen production, to a set of model parameters that are related to a Level 2 PRA analysis. The Level 2 analysis examines those sequences that result in core melting and subsequent reactor pressure vessel failure and its impact on the containment. This paper identifies individual contributors and MAAP4 model parameters that statistically influence hydrogen production. Hydrogen generation was chosen because of its direct relationship to oxidation. With greater oxidation, more heat is added to the core region and relocation (core slump) should occur faster. This, in theory, would lead to shorter failure times and subsequent "hotter" debris pool on the containment floor.

Blow Characteristics in Extrusion Blow Molding for Operational Conditions (압출 블로우 성형에서 성형조건에 따른 성형특성)

  • Jun Jae Hoo;Pae Youlee;Lyu Min-Young
    • Transactions of Materials Processing
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    • v.14 no.3 s.75
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    • pp.233-238
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    • 2005
  • Blow molding is divided into three categories, injection stretch blow molding, injection blow molding, and extrusion or direct blow molding. Extrusion blow molding has been studied experimentally to characterize the blowing behavior of parison. Blow conditions such as blowing temperature and cooling time were the experimental variables in this blowing experiment. Wall thickness of the lower part of blow molded sample was thicker than that of the upper part because of the sagging of parison during extrusion process. As temperature increases the wall thickness and the weight of blow molded sample decreased. No thickness variations in the blowing sample were observed according to the cooling time. The lower part of the sample showed high degree of crystallinity compare with the upper part of the sample. Thus the lower part of the sample was strong mechanically and structurally. It was recognized that the uniform wall thickness could not be obtained by only controlling the operational conditions. Parison variator should be introduced to get uniform wall thickness of parison and subsequently produce uniform wall thickness of blow molded product.

Assessment of the ATC Effect for Paddy Field and Forest Using Landsat Images and In-situ Measurement (Landsat영상과 현지조사에 의한 여름철 논과 산림의 기온저감효과 평가)

  • Park, Jong-Hwa;Na, Sang-Il;Kim, Jin-Soo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2007.05a
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    • pp.1943-1947
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    • 2007
  • The objective of this research was to find a direct and indirect method to estimate land surface temperature (LST) efficiently, using Landsat images and in-situ measurement. Agricultural fields including paddy fields have long been known to have multi-functions beneficial to the environment and ecology of the urban surrounding areas. Among these functions, the ambient temperature cooling (ATC) effect are widely acknowledged. However, quantitative and regional assessment of such effect has not had many investigations. Thermal remote sensing has been used over urban areas to assess ATC effect, to perform land cover classifications and as input for models of urban surface atmosphere exchange. Here, we review the use of thermal remote sensing in the study of paddy fields and urban climates, focusing primarily on the ATC effect. Landsat satellite images were used to determine the surface temperatures of different land cover types of a $441km^2$ study area in Cheongju, Korea. The results show that the ATC are a function of paddy area percentage in Landsat pixels. Pixels with higher paddy area percentage have more significant cooling effect.

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Experimental Investigation on Forced Convective Heat Transfer Characteristic Generated to Heated Tube (가열된 튜브에서 발생하는 강제 대류열전달 특성에 관한 실험적 연구)

  • Park, Hee-Ho;Lee, Yang-Suk;Kim, Sun-Jin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.10 no.3
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    • pp.90-98
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    • 2006
  • The Heated Tube Facility(HIF) was fabricated to identify the forced convective heat transfer and the cooling characteristic for the hydrocarbon fuel(Jet A-1), which is used for the coolant of the regenerative cooling system. The forced convective heat transfer coefficient was calculated from the measured coolant and tube surface temperature. In case of using the Jet A-1, the maximum heat flux which the coolant can absorb was identified by determining the critical wall temperature generating the burnout on the fixed flow condition. The inlet bulk-temperature of the coolant has a direct influence on the forced convective heat transfer characteristic.

An Experimental Study on Heat Transfer of a Falling Liquid Film in Air Channel Flow (채널내 공기유동이 있는 유하액막의 열전달특성에 관한 실험적 연구)

  • Oh, Dong-Eun;Kang, Byung-Ha;Kim, Suk-Hyun;Lee, Dae-Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.5
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    • pp.335-341
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    • 2008
  • Thermal transport from vertical heated surface to falling liquid film in a channel has been investigated experimentally. Air-flow is introduced into channel to make a counter flow against falling liquid film. This problem is of particular interest in the design of direct contact heat exchange system, such as cooling tower, evaporative cooling system, absorption cooling system, and distillation system. The effects of channel width and air flow rate on the heat transfer to falling liquid film are studied in detail. The results obtained indicate that heat transfer rate is gradually decreased with an increase in the channel width without air flow as well as with air flow in a channel. It is also found that heat transfer rate of air-flow is increased while heat transfer rate of falling liquid film is decreased with an increase in the air flow rate at a given channel width. However, total heat transfer rate from the heated surface is increased as the air flow rate is increased.

Numerical Modeling of Heat Transfer for Squeeze Casting of MMCs (용탕주조법을 이용한 금속복합재료 제조공정의 열전달 해석)

  • Jung, Chang-Kyu;Jung, Sung-Wook;Nam, Hyun-Wook;Han, Kyung-Seop
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.10
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    • pp.2104-2113
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    • 2002
  • A finite element model is developed for the process of squeeze casting of metal matrix composites (MMCs) in cylindrical molds. The fluid flow and the heat transit. are fundamental phenomena in squeeze casting. To describe heat transfer in the solidification of molten aluminum, the energy equation is written in terms of temperature and enthalpy are applied in an axisymmetric model which is similar to the experimental system. A one dimensional flow model simulates the transient metal flow. A direct iteration technique was used to solve the resulting nonlinear algebraic equations, using a computer program to calculate the enthalpy, temperature and fluid velocity. The cooling curves and temperature distribution during infiltration and solidification were calculated fer pure aluminum. Experimentally, the temperature was measured and recorded using thermocouple wire. The measured time-temperature data were compared with the calculated cooling curves. The resulting agreement shows that the finite element model can accurately estimate the solidification time and predict the cooling process.

Analysis of the Molten Metal Direct Rolling for Magnesium Considering Thermal Flow Phenomena (열 유동 현상을 고려한 마그네슘 용탕 직접 압연공정 해석)

  • Bae J.W.;Kang C.G.;Kang S.B.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.10a
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    • pp.786-789
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    • 2005
  • The proper parameters in a twin roll strip casting are important to obtain the stabilization of the Mg sheet. What is examined in this paper is the quantitative relationships of the important control parameters such as the roll speed, height of pool region, outlet size of nozzle, solidification profile and the final point of solidification in a twin roll strip casting Unsteady conservation equations were used for transport phenomena in the pool region of a twin roll strip casting in order to predict a velocity, temperature distributions of fields and a solidification process of molten magnesium. The energy equation of cooling roll Is solved simultaneously with the conservation equations of molten magnesium In order to consider the heat transfer through the cooling roil. The finite difference method (2-D) and the finite element method (2-D) are used in the analysis of pool region and cooling roil to reduce computing time and to improve the accuracy of calculation respectively.

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Experimental investigation of two-phase natural circulation loop as passive containment cooling system

  • Lim, Sun Taek;Kim, Koung Moon;Kim, Haeseong;Jerng, Dong-Wook;Ahn, Ho Seon
    • Nuclear Engineering and Technology
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    • v.53 no.12
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    • pp.3918-3929
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    • 2021
  • In this study, we experimentally investigate of a two-phase natural circulation loop that functions as a passive containment cooling system (PCCS). The experimental apparatus comprises two loops: a hot loop, for simulating containment under severe accidents, and a natural circulation loop, for simulating the PCCS. The experiment is conducted by controlling the pressure and inlet temperature of the hot loop in the range of 0.59-0.69 MPa (abs) and 119.6-158.8 ℃, respectively. The heat balance of the hot loop is established and compared with a natural circulation loop to assess the thermal reliability of the experimental apparatus, and an additional system is installed to measure the vapor mass flow rate. Furthermore, the thermal-hydraulic characteristics are considered in terms of a temperature, mass flow rate, heat transfer coefficient (HTC), etc. The flow rate of the natural circulation loop is induced primarily by flashing, and a distortion is observed in the local HTC because of the fully develop as well as subcooled boiling. As a result, we present the amount of heat capacity that the PCCS can passively remove according to the experimental conditions and compared the heat transfer performance using Chen's and Dittus-Boelter correlation.

Simi-solid 재료의 직접압연 공정해석

  • 김영도;강충길
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1993.10a
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    • pp.518-523
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    • 1993
  • A computer program has been developed for analyzing the two-dimensional unsteady conservation equations for transport phenomena in the ool region of direct rolling with semi-solid metal in order to describe the velocity and temperature, and the solidification process of the semi-solid metal. The energy equations of cooling roll is solved simultaneously with semi-solid metal in order consider heat transfer through the cooling roll. The FDM(finite difference method) and FEM(finite element method) are used in region of pool and roll, respsctively, to reduce computing time and to improve accuracy of calculation. In the present study, influence of solid fraction and casting speed are investigated in a point of view of strip formability with semi-solid metal.

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