• Title/Summary/Keyword: Nonuniform Cooling

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A Study on the Heat-treatment Technique for Deformation Control of SM45C steel (SM45C 강의 변형제어를 위한 열처리기술에 관한 연구)

  • Ryu, Seong-Gi;Nam, Tae-Hyeon;Park, Jun-Cheol
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.4
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    • pp.78-84
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    • 2001
  • This study deals with the heat-treatment technique of SM45C steel with respect to less of deformation in control. The whole process for the production of landing gear must go through with uniformally controlled heat treatment, where as most deformation usually occur in nonuniform cooling environment. When a heated metal is submerged into a certain quenchant, the rate of cooling rapidity can be measured rather slow during the early stage of the procedure due to an Occurrence of a vapor blanked. As the additional course of cooling action is applied and the vapor from a vapor blanked is destroyed simultaneously, the speed of cooling promptness can be considered rather swift. The object of this study is to control the certain deformations as in the procedure of a heat treatment for landing gear by analyzing and improving the conditions of different substance of quenching liquids. Several noticeable curves indicating the temperature variation on the ap-plied metals during the cooling procedures, along with detectable rates of water verses oil and that of different polymer solutions are illustrated.

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Performance Prediction of Liquid Rocket Thrust Chambers with Nonuniform Propellant Mixing (추진제의 비균일 혼합분포를 고려한 액체로켓 추력실의 성능 예측기법 개발)

  • 김성구;최환석;한영민;이광진
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.9
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    • pp.82-88
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    • 2006
  • In order to effectively reduce thermal loads on regenerative cooled walls, fuel cooling injectors and film cooling devices have often been employed. The present study has established a numerical methodology for prediction of performance and near-wall temperature distribution taking into account the nonuniform mixing due to these additional cooling devices. A correction procedure for main propulsive parameters has also been proposed based on comparison between prediction and experimental data. Under the computational framework of this study, the predicted results were in good agreement with hot-firing test data for a 30 tonf-class full-scale combustor at the design and off-design conditions. As a consequence, the present numerical method is expected to be useful for design and evaluation of regenerative cooled liquid rocket thrust chambers.

Characteristic of Refrigerant for Heat-treatment Deformation Control of SCM415 Steel (SCM415강의 열처리 변형제어를 위한 냉각 매질의 특성)

  • Ahn, Min-ju;Lyu, Sung-ki
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.9 no.6
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    • pp.59-65
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    • 2010
  • This study deals with the characteristic of refrigerant for heat-treatment deformation control of SCM415 steel. The control of heat-treatment deformation must need the progress of production parts for an industry machine. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for the part of the industry machine by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on the thermal deformation and fatigue strength are also investigated.

An Analysis of Engine Cooling using a Three-dimensional Radiator Model (3차원 방열기 모델을 이용한 엔진냉각 해석)

  • 이영림
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.4
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    • pp.10-17
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    • 2001
  • The performance of a radiator is generally determined using a wind tunnel, in which the air velocity is uniform. However, when it is installed in a car, the distribution of the air velocity becomes nonuniform due to front-end openings, cross members, and horns etc., resulting in lower performance. In this study, several underhood flow simulations have been first performed to get flow rates and velocity distributions over the radiator. Secondly heat release rates are calculated by both a performance curve and a radiator model. Finally, using an engine cooling system simulator, radiator-top-tank temperature is predicted and the variations of heat release rate and radiator-top-tank temperature with nonuniformity of air velocity distributions are analyzed. The results show that the current engine cooling model successfully accounts for the nonuniformity effects that should be considered for higher accuracy in predicting engine cooling performance.

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Design of automotive engine cooling fan and study on noise reduction through modification of system (자동차용 냉각팬의 설계와 시스템 개선을 통한 저소음화 연구)

  • 김병주;강상규;김규영;이덕주;이재영;이덕호;신동수
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.196-201
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    • 2003
  • Axial fans are widely used for automotive engine cooling device due to their ability to produce high flow rate to keep engine cool. At the same time, the noise generated by these fans causes one of the most serious problems. Especially, engine cooling fan noise in idle condition of a car is noticeable. Therefore, the high efficient and low-noise fan is seriously needed. When a new fan system is designed, system resistance and non-uniform inflow are the key factors to get the high performance and low noise fan system. In this study, experimental study on the fan and system was carried out and brought a successful result of performance and noise from a designed fan. And through the modification of the fan system, the fan produced more flow rate and became less noisy.

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Design of Automotive Engine Cooling Fan and Study on Noise Reduction through Modification of System (자동차용 냉각홴의 설계와 시스템 개선을 통한 저소음화 연구)

  • 김병주;강상규;김규영;이재영;이덕호;신동수
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.11
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    • pp.1107-1114
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    • 2004
  • Axial fans are widely used for automotive engine cooling device due to their ability to produce high flow rate to keep engine cool. At the same time, the noise generated by these fans causes one of the most serious problems. Especially, engine cooling fan noise in idle condition of a car is noticeable. Therefore. the high efficient and low-noise fan is seriously needed. When a new fan system is designed, system resistance and non-uniform inflow are the key factors to get the high performance and low noise fan system. In this study, aerodynamic and acoustic calculations are carried out on the automotive cooling fan and system. Effects of various design parameters are studied through the free wake analysis and experiments. Better performance and noise characteristic are obtained for the new design fan using the methodology. Furthermore through the modification of the fan system geometry parameters, the fan system produce more flow rate and become less noisy.

Experimental and Numerical Studies on the Flow Characteristics of a Fan-Sink (팬싱크의 유동 특성에 관한 실험 및 수치해석적 연구)

  • Lee Kyoung-Yong;Choi Young-Seok;Yun Jae-Ho
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.3
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    • pp.225-230
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    • 2006
  • The overall performance and local flow fields of the fan, heat sink, and fan-sink were experimentally and numerically studied to investigate the flow characteristics of a fan-sink. The flow resistance of the heat sink was measured by small fan tester based on AMCA standards and compared with the CFD results to select available cooling fan for the fan-sink. The nonuniform velocity profile behind the fan outlet was shown by the flow visualization. The effects of nonuniform velocities on the performance of heat sink were discussed. To validate the commercial CFD code CFX-5.6, the predicted performance curve was compared with that of fan testing. The local flow fields of the fan-sink were analyzed by CFD results. MFR (multiple frame of reference) was used as a computational model combining rotating fan and stationary heat sink. Through the CFD results of the fan-sink, the flow patterns behind the fan outlet influenced the flow resistance and overall performance of the heat sink.

Numerical Study of Hydrogen Absorption in a Metal Hydride Hydrogen Storage Vessel (금속수소화물 수소 저장 용기 내부의 수소흡장에 대한 수치해석적 연구)

  • Nam, Jin-Moo;Kang, Kyung-Mun;Ju, Hyun-Chul
    • Transactions of the Korean hydrogen and new energy society
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    • v.21 no.4
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    • pp.249-257
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    • 2010
  • In this paper, a three-dimensional hydrogen absorption model is developed to precisely study hydrogen absorption reaction and resultant heat and mass transport phenomena in metal hydride hydrogen storage vessels. The 3D model is first experimentally validated against the temperature evolution data available in the literature. In addition to model validation, the detailed simulation results shows that at the initial absorption stage, the vessel temperature and H/M ratio distributions are uniform throughout the entire vessel, indicating that the hydrogen absorption is so efficient during the early hydriding process and thus local cooling effect is not influential. On the other hand, nonuniform distributions are predicted at the latter absorption stage, which is mainly due to different degrees of cooling between the vessel wall and core regions. This numerical study provides the fundamental understanding of detailed heat and mass transfer phenomena during hydrogen absorption process and further indicates that efficient design of storage vessel and cooling system is critical to achieve fast hydrogen charging and high hydrogen storage efficiency.

Application of Commercial FEM Code to Coupled Analysis of Casting Deformation (범용 구조해석 프로그램의 주물 열변형 해석에의 적용성)

  • Kim, Ki-Young;Kim, Jung-Tae;Choi, Jung-Gil
    • Journal of Korea Foundry Society
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    • v.22 no.4
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    • pp.192-199
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    • 2002
  • Dimensional defects of castings are mainly due to the stresses and strains caused by a nonuniform temperature distribution and phase transformation during solidification and cooling, and by mechanical constraint between the mold and casting. It is, however, nearly impossible to trace movements of the casting and mold during solidification and cooling by experimental measurements for castings with complex shape. Two and three dimensional deformation analyses of the casting and the mold were performed using commercial finite element code, MARC. It was possible to calculate deformation and temperature distribution in the casting and mold simultaneously. Cooling curves of the casting obtained by calculation were close to that measured in the field since it was possible to treat latent heat evolution of the casting which could be divided into two parts, primary and eutectic parts. Mold bent inward just after pouring due to the temperature gradient across the mold thickness, and mold returned to its previous position with time. Plastic deformation occurred at the part of the casting where solidification was slow.

Effects of Air Flow Nonuniformity on the Thermal Performance of a Compact Evaporator for Natural Working Fluids (밀집형 자연냉매 증발기의 열성능에 미치는 불균일 공기유동분포의 영향)

  • 박병규;김근오;김무근
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.11
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    • pp.1114-1124
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    • 2001
  • The application of carbon dioxide as an attractive natural working fluid in air cooling and heating system is increasingly important in view of the CFC substitution problem. The thermal performance of compact evaporator was analyzed using section-by-section method. The effects of the two-dimensional nonuniformity of air flow through the evaporator is presented. The detrimental effect of the aid flaw nonuniformity on the thermal performance of the evaporator is found to be significant for many typical applications. It is shown that total heat transfer rate of evaporator using $CO_2$ is higher than that using R134a at the simulation conditions.

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