• Title/Summary/Keyword: Heat-exchanger

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A Study on the Estimation of Soil Formation Thermal Conductivities and Borehole Resistances with One-Dimensional Numerical Model and In-Situ Field Tests (1차원 수치모델과 현지측정에 의한 지중열전도율 및 보어홀 전열저항 해석에 관한 연구)

  • Lee Se-Kyoun;Woo Joung-Son;Ro Jeong-Geun;Kim Dae-Ki
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.10
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    • pp.783-790
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    • 2006
  • A one-dimensional numerical model coupled with parameter estimation is used to predict the effective thermal conductivities of soil formations and borehole resistances from in situ field test data. In this application a new method of using initial ignoring time (IIT) obtained from error estimation is tried and turned out to be successful in determining soil thermal conductivities. This method is used for single-U and double-U borehole system. The results of this method are compared and agreed well with those of existing software (GPM) in the analysis of single-U borehole data. In the analysis of double-U borehole data this method seems to be better in predicting soil and borehole properties.

Characteristics of T-phase flow distribution and pressure drop in a horizontal T-type evaporator tube (수평 T형 증발관내 2상류의 유량분배 및 압력강하 특성)

  • 박종훈;조금남;조홍기
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.5
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    • pp.658-668
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    • 1999
  • The objective of the present study is to investigate the effect of experimental parameters on the hydrodynamic characteristics in a horizontal tee-type evaporator using R-22. The experimental apparatus consisted of an unheated tee-type test section, a liquid-vapor separator, a preheated, mass flow meters, a plate heat exchanger, pump, and other measurement devices. The experimental parameters were mass flux(500 and 600kg/$m^2$s), inlet quality(0.1~0.3) and separation ratio(0.3~0.7). Absolute pressure at the inlet of the test section was 0.652 MPa. The branch-to-inlet inner diameter ratio was 0.61. Pressure gradient at the branch section was larger than that at the run section at the same separation ratio. Pressure drop per unit length increased at the run section and decreased at the branch section as the separation ratio increased. Pressure drop predicted by the separated flow model agreed with experimental data within -35 to +16%. Generally, predicted values showed similar trend with the data. Mass flow ratio of vapor refrigerant was affected by the inlet quality more than the mass flux.

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A Study on Thermal Conductivity Characteristics of Nanofluids (나노유체 열전도도 특성 연구)

  • Hwang, Yu-Jin;Park, Jae-Hong;Kim, Hong-Suk;Lee, Jae-Keun
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.162-167
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    • 2006
  • Nanofluid is a kind of new engineering material consisting of nanoparticles dispersed in base fluid. Nanofluids could have various applications such as magnetic fluids, heat exchanger working fluids, lubricants, drug delivery and so on in present study, various nanoparticles, such as MWCNT (Multi-walled Carbon Nanotube), fullerene, copper oxide, and silicon dioxide are used to produce nanofluids. As base fluids, DI-water, ethylene glycol, oil, and silicon oil are used. To investigate the thermo-physical properties of nanofluids, thermal conductivity and kinematic viscosity are measured. Stability estimation of nanofluid is conducted with UV-vis spectrophoto-meter. In this study, the high pressure homogenizer is the most effective method to produce nanofluid with the prepared nanoparticle and base fluid. Excellently stable nanofluids are produced with the magnetron sputtering system. Thermal conductivity of nanofluid increases with increasing particle volume fraction except water-based fullerene nanofluid which has lower thermal conductivity than base fluid due to its lower thermal conductivity, 0.4 W/mK. The experimental results can't be predicted by Jang and Choi model.

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Effect analysis of ISLOCA pathways on fission product release at Westinghouse 2-loop PWR using MELCOR

  • Kim, Seungwoo;Park, Yerim;Jin, Youngho;Kim, Dong Ha;Jae, Moosung
    • Nuclear Engineering and Technology
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    • v.53 no.9
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    • pp.2878-2887
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    • 2021
  • As the amount of fission product released from ISLOCA was overestimated because of conservative assumptions in the past, several studies have been recently conducted to evaluate the actual release amount. Among several pathways for the ISLOCA, most studies were focused on the pathway with the highest possibility. However, different ISLOCA pathways may have different fission product release characteristics. In this study, fission product behavior was analyzed for various pathways at the Westinghouse two-loop plant using MELCOR. Four pathways are considered: the pipes from a cold leg, from a downcomer, from a hot leg to the outlet of RHR heat exchanger, and the pipe from the hot leg to the inlet of RHR pump (Pathway 1-4). According to the analysis results, cladding fails at around 2.5 h in Pathways 1 and 2, and on the other hand, about 3.3 h in Pathways 3 and 4 because the ISLOCA pathways affect the safety injection flow path. While the release amount of cesium and iodine ranges between 20 and 26% in Pathways 1 to 3, Pathway 4 allows only 5% to the environment because the break location is submerged. Also, as more than 90% of cesium released to the environment passes through the personnel door, reinforcing the pressure capacity of the doors would be a significant factor in the accident management of the ISLOCA.

High Temperature Oxidation Behavior of Nickel and Iron Based Superalloys in Helium Containing Trace Impurities

  • Tsai, C.J.;Yeh, T.K.;Wang, M.Y.
    • Corrosion Science and Technology
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    • v.18 no.1
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    • pp.8-15
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    • 2019
  • A high-temperature gas-cooled reactor (HTGR) is recognized as the best candidate reactor for next generation nuclear reactors. Helium is used to be the coolant in the core of the HTGR with temperature expected to exceed $900^{\circ}C$ at the core outlet. Several iron- and nickel-based superalloys, including Alloy 800H, Hastelloy X, and Alloy 617, are potential structural materials for intermediate heat exchanger (IHX) in an HTGR. Oxidation behaviors of three selected alloys (Hastelloy X, Alloy 800H, and Alloy 617) were investigated at four different temperatures from $650^{\circ}C$ to $950^{\circ}C$ under helium environments with various concentrations of $O_2$ and $H_2O$. Preliminary results showed that chromium oxide as the primary protective layer was observed on surfaces of the three tested alloys. Based on results of mass gain and SEM analyses, Hastelloy X alloy exhibited the best corrosion resistance in all corrosion tests. Further details on the oxidation mechanism of these alloys are presented in this study.

Low-frequency modes in the fluid-structure interaction of a U-tube model for the steam generator in a PWR

  • Zhang, Hao;Chang, Se-Myong;Kang, Soong-Hyun
    • Nuclear Engineering and Technology
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    • v.51 no.4
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    • pp.1008-1016
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    • 2019
  • In the SG (steam generator) of PWR (pressurized water reactor) for a nuclear plant, hundreds of U-shaped tubes are used for the heat exchanger system. They interact with primary pressurized cooling water flow, generating flow-induced vibration in the secondary flow region. A simplified U-tube model is proposed in this study to apply for experiment and its counterpart computation. Using the commercial code, ANSYS-CFX, we first verified the Moody chart, comparing the straight pipe theory with the results derived from CFD (computational fluid dynamics) analysis. Considering the virtual mass of fluid, we computed the major modes with the low natural frequencies through the comparison with impact hammer test, and then investigated the effect of pump flow in the frequency domain using FFT (fast Fourier transform) analysis of the experimental data. Using two-way fluid-structure interaction module in the CFD code, we studied the influence on mean flow rate to generate the displacement data. A feasible CFD method has been setup in this research that could be applied potentially in the field of nuclear thermal-hydraulics.

Design of Retarder Control Logic for Cooling System of Commercial Vehicle (상용차의 냉각 시스템을 고려한 리타더 제어로직 설계)

  • Lee, Chang-Kyu;Jeong, Jong-Kyu;Kim, Gwan-Hyung
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2016.10a
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    • pp.668-669
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    • 2016
  • The retarder as a hydraulic brake system in order to assist a service brakes in commercial vehicle is operated by automatic and manual mode due to driver. Braking energy by retarder operation is transmitted to the engine radiator of vehicle cooling system, passing through the retarder oil heat exchanger. At this moment, the retarder ECU performs the function that is controlled a braking torque with consideration for automatic and manual mode, temperature of retarder oil/water, engine coolant temperature, vehicle speed, and etc. In this paper, it deals with the design of retarder control logic and the results of retarder braking performance test regarding a cooling system of retarder and vehicle.

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Study on Cooling of Hydrogen Gas for the Pre-Cooler in the Hydrogen Refueling Station (수소충전소용 프리쿨러를 위한 수소가스 냉각에 관한 연구)

  • LEE, KYUNG-HAN;KOO, KYUNG-MO;RYU, CHEOL-HWI;HWANG, GAB-JIN
    • Transactions of the Korean hydrogen and new energy society
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    • v.30 no.3
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    • pp.237-242
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    • 2019
  • In the hydrogen refueling station (HRS), it is need the pre-cooling system (PCS) to limit the inside temperature ($85^{\circ}C$) of the onboard thank (700 bar) and to charge the hydrogen at short time (within 3 minutes) to fuel cell electric vehicle (FCEV). From those safety reasons, the temperature of hydrogen gas must be controled $-33^{\circ}C$ to $-40^{\circ}C$ in PCS. The cooling test of the gaseous ($N_2$, He, $H_2$) was carried out using heat exchanger (pre-cooler) by indirect cooling and direct cooling method. It was confirmed that the temperature of hydrogen gas had below $-40^{\circ}C$ at below $-75^{\circ}C$ of chiller temperature in direct cooling.

A Study of Development of Regrigerated Truck Small Scale Cooling System and Key-Part using Natural Refrigerants. (자연냉매인 CO2를 이용한 냉동탑차 냉장시스템과 핵심부품개발에 관한 연구)

  • Jeong, Se Jin;Park, Seong Sin;Min, Ho Ki;Jo, Ga Yeong
    • Journal of the Korean Institute of Gas
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    • v.23 no.1
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    • pp.19-26
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    • 2019
  • In this study, we developed a cooling system for 1 ton size refrigeration vehicle using carbon dioxide natural refrigerant among hydrocarbon type refrigerant which is attracting attention as environment friendly refrigerant, and designed a heat exchanger and a unit cooler to raise COP. In addition, existing CNG 5 ton refrigerated trucks were converted into LNG vehicles to increase the efficiency of the cooling system and ensure safety against CNG. As a result, environmentally friendly refrigerated trucks using natural refrigerants of 1 ton and 5 ton sizes were developed.

PILLAR: Integral test facility for LBE-cooled passive small modular reactor research and computational code benchmark

  • Shin, Yong-Hoon;Park, Jaeyeong;Hur, Jungho;Jeong, Seongjin;Hwang, Il Soon
    • Nuclear Engineering and Technology
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    • v.53 no.11
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    • pp.3580-3596
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    • 2021
  • An integral test facility, PILLAR, was commissioned, aiming to provide valuable experimental results which can be referenced by system and component designers and used for the performance demonstration of liquid-metal-cooled, passive small modular reactors (SMRs) toward their licensing. The setup was conceptualized by a scaling analysis which allows the vertical arrangements to be conserved from its prototypic reactor, scaled uniformly in the radial direction achieving a flow area reduction of 1/200. Its final design includes several heater rods which simulate the reactor core, and a single heat exchanger representing the steam generators in the prototype. The system behaviors were characterized by its data acquisition system implementing various instruments. In this paper, we present not only a detailed description of the facility components, but also selected experimental results of both steady-state and transient cases. The obtained steady-state test results were utilized for the benchmark of a system code, achieving a capability of accurate simulations with ±3% of maximum deviations. It was followed by qualitative comparisons on the transient test results which indicate that the integral system behaviors in passive LBE-cooled systems are able to be predicted by the code.