• Title/Summary/Keyword: Heat Transfer Capability

Search Result 114, Processing Time 0.025 seconds

High Reliability Design for New Concept Machining Center (신개념 머시닝센터의 신뢰성 향상 설계기술)

  • Lee, Chan-Hong;Kim, Yang-Jin
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.28 no.8
    • /
    • pp.894-903
    • /
    • 2011
  • In this paper, the capability index is introduced in order to improve the reliability of new concept machine tools and the method to improve the machine accuracy from the analysis of cutting process, statistical methodology and influence factors are proposed. In addition, the rib structure of bed and column in machine tools is analyzed by using the thermal impact method in order to analogize the rib pattern which has the small thermal deformation under thermal boundary condition. In the analysis of column rib structure, thermal boundary condition is separated to heat conduction and heat transfer to appropriate real boundary condition. Finally, performance chart of bed and column rib structure is provided for designer to estimate each rib pattern and select rib structure appropriating to thermal condition.

Experiment of Natural Circulation Loop Using a Cryocooler (극저온냉동기를 이용한 자연순환 루프의 실험)

  • Kim, M.J.;Chang, H.M.
    • Proceedings of the KSME Conference
    • /
    • 2007.05b
    • /
    • pp.2194-2199
    • /
    • 2007
  • An experimental study is performed to investigate the thermal and flow characteristics of subcooled liquid nitrogen in a natural circulation loop. Experimental apparatus is designed and constructed such that a closed loop is cooled at the top by a cryocooler and heated nearly at the bottom by cartridge heaters. Steady state is obtained by controlling the heating power to the cartridge heaters and a thin-film heater to reduce the cooling power of the cryocooler. Temperature is measured at several locations of the loop and the mass flow rate through the loop is estimated from the energy balance in terms of the measured temperatures. Experiment is repeated for various values of the vertical height between the cooling and heating parts. The results show that the heat transfer capability of the loop has a maximum at a certain value of height. The optimal height to maximize the heat transfer is in a good agreement with analytical prediction to take into account the buoyancy and viscous forces in the loop.

  • PDF

MARS Code Applicability Assessments for the HTGR RCCS (고온가스로 원자로공동냉각계통(RCCS)에 대한 MARS Code 적용성 평가)

  • Kang Doo-Hyuk;Kim Hyung-Seok;Chung Bum-Jin
    • Journal of Energy Engineering
    • /
    • v.14 no.4 s.44
    • /
    • pp.232-240
    • /
    • 2005
  • In this study, the IAEA Benchmark problems far HTR-10 and HTTR RCCS were assessed in order to assess the applicability of MARS code, a thermal-hydraulic safety analysis code developed for water reactors. The calculated results were compared with those or THERMIX, THANPACST2 code, and available experimental data. The calculated results showed generally good agreements with those obtained by the THERMIX code and THANPACST2 code. Deviations were analyzed to be originated from the simplification of complicated geometry and from the modeling capability of heat transfer characteristics in the HTGR components such as water cooler and air tooler. Especially, it was found that the radiation heat transfer in the reactor cavity played an important role in the after heat removal in the RCCS. Thus, it is concluded that MARS code can be successfully applied to the calculation of the RCCS cooling capability of the HTGR in this study.

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
    • /
    • v.26 no.12
    • /
    • pp.605-619
    • /
    • 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.

Steam generator performance improvements for integral small modular reactors

  • Ilyas, Muhammad;Aydogan, Fatih
    • Nuclear Engineering and Technology
    • /
    • v.49 no.8
    • /
    • pp.1669-1679
    • /
    • 2017
  • Background: Steam generator (SG) is one of the significant components in the nuclear steam supply system. A variety of SGs have been designed and used in nuclear reactor systems. Every SG has advantages and disadvantages. A brief account of some of the existing SG designs is presented in this study. A high surface to volume ratio of a SG is required in small modular reactors to occupy the least space. In this paper, performance improvement for SGs of integral small modular reactor is proposed. Aims/Methods: For this purpose, cross-grooved microfins have been incorporated on the inner surface of the helical tube to enhance heat transfer. The primary objective of this work is to investigate thermal-hydraulic behavior of the proposed improvements through modeling in RELAP5-3D. Results and Conclusions: The results are compared with helical-coiled SGs being used in IRIS (International Reactor Innovative and Secure). The results show that the tube length reduces up to 11.56% keeping thermal and hydraulic conditions fixed. In the case of fixed size, the steam outlet temperature increases from 590.1 K to 597.0 K and the capability of power transfer from primary to secondary also increases. However, these advantages are associated with some extra pressure drop, which has to be compensated.

Design and evaluation of the thermal capability to secure a working time of cryogenic explosion-proof camera in LNG carrier tank

  • Kang, Geun-Il;Kwak, Si-Young;Park, Chun-Seong
    • International Journal of Naval Architecture and Ocean Engineering
    • /
    • v.9 no.5
    • /
    • pp.568-576
    • /
    • 2017
  • With an increase in the usage of LNG, there is a heightened interest about its safety aspects regarding the explosion of LNG carrier tank. The need for a cryogenic explosion-proof camera has increased. The camera has to work in cryogenic environment (below $-160^{\circ}C$) in LNG carrier. This study conducted design and heat transfer analysis of cryogenic camera to secure working time in limitation of heat source. The design with gap width of double pane windows was conducted based on simple vertical cavity model to insulate from cryogenic environment. The optimal gap width was 12.5 mm. For effective analysis considering convection within the camera, equivalent thermal conductivity method was adopted with ABAQUS. The working time of the camera predicted was over 10 h at warm-start condition. In cold-start condition, it required about 5 h of pre-warming time to work. The results of analysis were compared with the ones of the actual cryogenic test.

Laminar Flamelet Modeling of Combustion Processes and NO Formation in Nonpremixed Turbulent Jet Flames (Laminar Flamelet Model을 이용한 비예혼합 난류제트화염의 연소과정 및 NO 생성 해석)

  • Kim, Seong-Ku;Kim, Hoo-Joong;Kim, Yong-Mo
    • Journal of the Korean Society of Combustion
    • /
    • v.4 no.2
    • /
    • pp.51-62
    • /
    • 1999
  • NOx formation in turbulent flames is strongly coupled with temperature, superequilibrium concentration of O radical, and residence time. This implies that in order to accurately predict NO level, it is necessary to develop sophisticated models able to account for the complex turbulent combustion processes including turbulence/chemistry interaction and radiative heat transfer. The present study numerically investigates the turbulent nonpremixed hydrogen jet flames using the laminar flamelet model. Flamelet library is constructed by solving the modified Peters equations and the turbulent combustion model is extended to nonadiabatic flame by introducing the enthalpy defect. The effects of turbulent fluctuation are taken into account by the presumed joint PDFs for mixture fraction, scalar dissipation rate, and enthalpy defect. The predictive capability of the present model has been validated against the detailed experimental data. Effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

  • PDF

Laminar Flamelet Modeling of Combustion Processes and NO Formation in Nonpremixed Turbulent Jet Flames (Laminar Flamelet Model을 이용한 비예혼합 난류제트화염의 연소과정 및 NO 생성 해석)

  • Kim, Seong-Ku;Kim, Hoo-Joong;Kim, Yong-Mo
    • 한국연소학회:학술대회논문집
    • /
    • 1999.10a
    • /
    • pp.93-104
    • /
    • 1999
  • NOx formation in turbulent flames is strongly coupled with temperature, superequilibrium concentration of O radical, and residence time. This implies that in order to accurately predict NO level, it is necessary to develop sophisticated models able to account for the complex turbulent combustion processes including turbulence/chemistry interaction and radiative heat transfer. The present study numerically investigates the turbulent nonpremixed hydrogen jet flames using the laminar flamelet model. Flamelet library is constructed by solving the modified Peters equations and the turbulent combustion model is extended to nonadiabatic flame by introducing the enthalpy defect. The effects of turbulent fluctuation are taken into account by the presumed joint PDFs for mixture fraction, scalar dissipation rate, and enthalpy defect. The predictive capability of the present model has been validated against the detailed experimental data. Effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

  • PDF

Application of The Boundary Element Analysis Software BEASY in Engineering Pratice (공학실무에서의 경계요소해석 소프트웨어 BEASY의 적용)

  • Huh, Young;Cho, Jun-Sang
    • Proceedings of the Computational Structural Engineering Institute Conference
    • /
    • 1994.10a
    • /
    • pp.31-37
    • /
    • 1994
  • BEASY is a soft-ware tool which may be used to solve problems in heat transfer(linear and non-linear, steady state and transient) and linear elastic stress analysis. It is based on the boundary element method. The central part is the analysis module, called BEASY. For pre- and post-processing the BEASY Interactive Modeling System BEASY-IMS can be used. Three examples are devoted to show the capability of BEASY.

  • PDF

Experimental Evaluation of Hydrophilic Membrane Humidifier with Isolation of Heat Transfer Effect (친수성 막을 통한 수분 전달 특성 연구)

  • Tak, Hyun Woo;Kim, Kyoung Teck;Han, Jae Young;Im, Seok Yeon;Yu, Sang Seok
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.37 no.9
    • /
    • pp.815-821
    • /
    • 2013
  • The efficiency and lifetime of a polymer electrolyte membrane fuel cell (PEMFC) system is critically affected by the humidity of the incoming gas, which should be maintained properly under normal operating conditions. Typically, the incoming gas of a fuel cell is humidified by an external humidifier, but few studies have reported on the device characteristics. In this study, a laboratory-scale planar membrane humidifier is designed to investigate the characteristics of water transport through a hydrophilic membrane. The planar membrane humidifier is immersed in a constant temperature bath to isolate the humidifier from the effect of temperature variations. The mass transfer capability of the hydrophilic membrane is first examined under isothermal conditions. Then, the mass transfer capability is investigated under various conditions. The results show that water transport in the hydrophilic membrane is significantly affected by the flow rate, operating temperature, operating pressure, and flow arrangement.