• Title/Summary/Keyword: cooling curve

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Pressure-temperature limit curve for reactor vessel evaluated by ASME code

  • Jhung, Myung Jo;Kim, Seok Hun;Jung, Sung Gyu
    • Structural Engineering and Mechanics
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    • v.14 no.2
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    • pp.191-208
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    • 2002
  • A comparative assessment study for a generation of the pressure-temperature (P-T) limit curve of a reactor vessel is performed in accordance with ASME code. Using cooling or heating rate and vessel material properties, stress distribution is obtained to calculate stress intensity factors, which are compared with the material fracture toughness to determine the relations between operating pressure and temperature during reactor cool-down and heat-up. P-T limit curves are analyzed with respect to defect orientation, clad thickness, toughness curve, cooling or heating rate and neutron fluence. The resulting P-T curves are compared each other.

Calculation of Jominy Hardenability Curve of Low Alloy Steels from TTT/CCT data (TTT/CCT 데이터를 이용한 저합금강의 죠미니 경화능 곡선 계산)

  • Jung, Minsu;Son, YoonHo
    • Journal of the Korean Society for Heat Treatment
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    • v.32 no.1
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    • pp.17-28
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    • 2019
  • Jominy hardenability curves of low alloy steel containing less than 5 wt.% of alloying elements in total were calculated by applying Scheil's rule of additivity to pre-calculated isothermal transformation curve. Isothermal transformation curve for each phase in steel was approximated as a simple mathematical equation by using Kirkaldy's approach and all coefficients in the equation were estimated from experimental temperature-time-transformation (TTT) and/or continuous cooling transformation (CCT) data in the literature. Then jominy test with simple boundary conditions was performed in computer by applying the finite difference scheme. The resultant cooling curves at each location along a longitudinal direction of Jominy bar were applied to calculate phase fractions as well as mechanical properties such as micro Vickers hardness. The simulated results were compared with experimental CCT data and Jominy curves in the literature.

Mist Cooling of High-Temperature Cylinder Surface (고온 실린더의 미스트 냉각)

  • Kim, Mu-Hwan;Lee, Su-Gwan;Park, Ji-Man;Lee, Pil-Jong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.3
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    • pp.448-457
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    • 2002
  • Heat treatment such as quenching of a high-temperature cylinder is being used on steel to produce high strength levels. Especially, the mist cooling with the high and uniform surface heat flux rate s expected to contribute for better products. The experimental mist cooling curve is produced for better understanding, and two distinct heat transfer regions are recognized from the cooling curve produced. It is shown that the liquid film evaporation dominated region follows the film boiling-dominated region as decreasing the temperature of test cylinder by mist flow. Based on the intuitive view from some previous investigations, a simplified model with some assumptions is introduced to explain the mist cooling curve, and it is shown that the estimation agrees well with our experimental data. In the meanwhile, it is known that the wetting temperature, at which surface heat flux rate is a maximum, increases with mass flow rate ratio of water to air ($\varkappa$ < 10). However, based on our experimental data, it is explained that there exists a critical mass flow rate ratio, at which the wetting temperature is maximum, in the range of 3 < $\varkappa$ < 130. Also, it is described that despite of the same value of $\varkappa$, the wetting temperature may increase with mist velocity.

A Study on the Spray Cooling Characteristics of hot Flat Plates (고온평판의 분무냉각특성에 관한 연구)

  • 윤석훈
    • Journal of Advanced Marine Engineering and Technology
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    • v.22 no.6
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    • pp.880-887
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    • 1998
  • In order to study heat transfer characteristics of spray cooling for the purpose of uniform and soft cooling of high temperature surface a series of experiments for a hot horizontal copper flat plate was performed by downflow spray water using flat spray nozzle. Cooling curves were mea-sured under the various experimental conditions of flow rates and temperatures of cooling water Surface temperature surface heat fluxes and heat transfer coefficients of horizontal upward-facing flat surface were calculated with cooling curves measured at each radial positions near the cooling surface by TDMA method. Generally heat transfer characteristics for spray cooling is simi-lar to boiling phenomenon of pool boiling. The minimum heat flux(MHF) appear at the surface temperature of about ${\Delta}Tsat=250^{\circ}C$ and the critical heat flux(CHF) appear at about ${\Delta}Tsat=250^{\circ}C$.

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A Study on The Counter-Flow Cooling Tower Performance Anaysis and Experiments

  • Seo, Moo-Gyo;Kim, Young-Soo;Kim, Eun-Pil;Yoon, Jung-In
    • International Journal of Air-Conditioning and Refrigeration
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    • v.9 no.1
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    • pp.50-57
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    • 2001
  • The thermal performance of cooling towers is affected by the temperature of inlet water, wet bulb temperature of entering air and water-air flow rate. In this stud${\gamma}$, the effects of these variables are simulated using NTU-method and experimentally investigated for the counter-flow cooling towers. The simulation program to evaluate these variables which affect the performance of cooling tower was developed. The maximum errors between the results of simulations and experiments were 3.8% under the standard design conditions and 5.4% under the other conditions. The performance was increased up to 46~50% as the water loading was increased from 6.8$m^3/hr{\cdot}m^2$ to 159$m^3/hr{\cdot}m^2$. The range was reduced up to 56~42% when the wet bulb temperature of the entering air was increased from 22${\circ}C$ to 29${\circ}C$.

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A Study on the Heat Transfer of the High Temperature Metals in Quenching 1st Reprot; Subcooled Transient Boiling Heat Transfer and Colling Curves (고온 강재의 담금질 열전달에 관한 연구 제1보 : 과냉과도 비등열전달과 냉각곡선)

  • 윤석훈;홍영표;김경근;김용모
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.6
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    • pp.1529-1540
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    • 1993
  • The quenching of steels by water is one of the imprtant problems in the applications of heat treatment, but the fundamental researches by way of theoretical approaches have not been satisfactorily improbed yet. This study aimed at measuring the exact subcooled transient boiling curve for cylindrical specimens and at conducting the analytical researches into the prediction of cooling curves, including the latent heat of phase transformation of steel. Experiments of quenching were made with cylindrical specimens of carbon steel S45C of diameters from 12 to 30 mm and with Cu specimens of 12 mm diameter respectively. The internal temperature of specimens during the quenching process was measured by C-A sheathed thermocouple. The heat fluxes were numerically calculated by the numerical method of inverse heat conduction problem, using the measured inner temperature of specimen as a boundary condition. In case of ${\Delta}T_{sub}=80K$, $q_{s}$ is as follows $q_{s}=2.02{\times}10^{5}{\Delta}T_{set}^{0.05}:{\Delta}T_{set}\le500K.$ And the numerical analysis of unsteady heat conduction during the quenching process was made and the cooling curves were calculated by TDMA method.

Evaluation of Material Properties for Yonggwang Nuclear Piping System(I)-Shutdown Cooling System- (영광원자력 배관소재의 재료물성치 평가 (1)-정지냉각계통-)

  • 석창성;최용식;장윤석;김종욱
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.5
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    • pp.1106-1116
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    • 1994
  • Leak Before Break(LBB) design concept is applied to piping systems of newly-built Yonggwang 3, 4 nuclear generating stations as a design alternative to the provision of pipe whip restraints, in recognition of the questionable benefits of providing such restraints. The objective of this paper is to evaluate the material properties (tensile and fracture toughness) of SA312 TP316 stainless steel and their associated welds manufactured for shutdown cooling system of Yonggwang 3, 4 nuclear generating stations. Effect of various parameters such as specimen orientation, test temperature, welding on material properties were examined.

Observation of Water Level and Temperature Properties by using a Giant Magnetoresistance-Spin Valve Film

  • Choi, Jong-Gu;Park, Kwang-Jun;Lee, Sang-Suk
    • Journal of Magnetics
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    • v.17 no.3
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    • pp.214-218
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    • 2012
  • The water level and temperature properties for the cooling system of potassium titanyl phosphate laser systems were observed. The middle point of the GMR-SV magnetoresistance curve is set in the neighborhood of high magnetic sensitivity (2.8 %/Oe). The experimental results for resistance dependence on water height and temperature showed linear regions with rates of 0.4 ${\Omega}/mm$ and 0.1 ${\Omega}/^{\circ}C$, respectively. The proposed results were found to be for adjusting the water level and temperature in the laser cooling system.

Thermoluminescent Properties by the Cooling Temperature and Grain Size in the LiYSiO4 : La Phosphors (LiYSiO4: La 열형광체의 온도에 따른 열발광 특성)

  • Kim, Young-Kook
    • Korean Journal of Materials Research
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    • v.19 no.9
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    • pp.494-498
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    • 2009
  • The thermoluminescent phosphors of LiYSi$O_4$ containing rare earth metal(La) dopants of 1 wt.%5 wt.% were prepared, and their TL characteristics have been investigated as a function of parameters such as the doping level and the heating rate. The grain size and cooling temperature of the highly sensitive LiYSi$O_4$: La phosphors have been investigated. The glow curve of LiYSi$O_4$: La has two peaks ($P_1,\;P_2$), and the peak height ratio of the two peaks is called $P_2/P_1$; here, the main peak is $P_2$. Experimental results indicate that the peak height ratios of the glow curve for LiYSi$O_4$: La are clearly correlated with the grain size and cooling temperature. The maximum $P_2/P_1$ ratio 3.25, the maximum sensitivity was observed for a grain size between 100-150 ${\mu}m$. The intensity of the TL peak of the phosphors was linearly proportion to the dose of X-rays.

Analysis of Eutectic Reaction as a Function of Cooling Rate in High Manganese Flake Graphite Cast Irons (고 망간 편상흑연주철에서 냉각속도별 공정반응 분석)

  • Lee, Sang-Hwan;Lee, Hyun-Woo;Lee, Sang-Mok
    • Journal of Korea Foundry Society
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    • v.33 no.4
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    • pp.162-170
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    • 2013
  • The effects of Mn content and cooling rate on the eutectic reaction of flake graphite cast irons were studied by a combined analysis of macro/micro-structure and cooling curve data. The correlation between the eutectic reaction parameter and macro/microstructure was systematically investigated. Two sets of chemical compositions with different Mn contents were designed to cast. Three types of molds for cylindrical specimens with different diameters were prepared to analyze the cooling rate effect. The difference between undercooling temperature and cementite eutectic temperature (${\Delta}T_1=T_U-T_{E,C}$), which is decreased by increasing the Mn content or increasing the cooling rate, is considered to be a suitable eutectic reaction parameter for predicting graphite morphology. According to the criterion, A-type graphite is mainly suggested to form for ${\Delta}T_1$ over $20^{\circ}C$, and D-type graphite is mainly suggested to form for ${\Delta}T_1$ below $0^{\circ}C$. Eutectic reaction time (${\Delta}T$), which is increased by increasing the Mn content and decreased by increasing the cooling rate, is regarded as a suitable eutectic reaction parameter for predicting eutectic cell size. Eutectic cell size is found to decrease in proportion to the decrease of ${\Delta}T$.