Joo Hyun Moon

Gyeongju University, Gyeongju, Gyeongsangbuk-do, South Korea

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Publications (49)45.86 Total impact

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    ABSTRACT: We did a numerical examination of the heat transfer and chemical reaction characteristics in methane-steam reforming, which is widely used in the petrochemical industry. In fact, the prediction of temperature variation along the reformer tube is essential for methanesteam reforming, as it also causes material failures, such as thermal stress concentration. Thus, the influence of the Reynolds number and the porosity variation of catalysts inside the reformer tube on methane-steam reforming was examined. The commercial code of Fluent (V. 13.0) was used for the current simulation. An axisymmetric reformer tube with porous catalytic medium was modeled and two kinds of porosity, which ranged from 0.35 to 0.50, were adopted. The temperature of the fuel gas and the external heat source were 780.15 K and 1291.55 K, respectively. The standard k-ε model and the eddy-dissipation-concept model were employed. In addition, conjugated heat transfer was considered for estimation of the heat transfer from the external heat sources to the reformer tube. The Discrete ordinate (DO) model for radiation effects was also used. It was found that the radial temperature distribution of the high Reynolds number is lower than that of the low Reynolds number. The axial temperature distribution varied because of the heat transfer from the external heat source and the dominant endothermic chemical reactions. The mole fraction of products increased as the Reynolds number decreased. Both radial and axial temperature increased inside the reformer tube as the porosity was denser. However, the effect of porosity variation on the methane-steam reforming could not be distinctively observed in this study.
    No preview · Article · Jan 2016 · Journal of Mechanical Science and Technology
  • Joo Hyun Moon · Sangmin Lee · Jung-Yeul Jung · Seong Hyuk Lee

    No preview · Article · Sep 2015

  • No preview · Article · Aug 2015 · Journal of Heat Transfer

  • No preview · Article · Aug 2015 · Journal of Heat Transfer
  • Rinah Kim · Chan Hee Park · Joo Hyun Moon
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    ABSTRACT: A fiber-optic temperature sensor (FOTS) using an infrared optical fiber was developed and applied to remote and real-time measurements of the temperature of the water in a spent nuclear fuel pool (SNFP) at a nuclear power plant (NPP). In this study, metal caps were employed as the sensing probe of the FOTS owing to their high thermal conductivity. An infrared optical fiber, PIR AgCl:AgBr polycrystalline fiber, was used to transmit the infrared light emitted from the water at a certain temperature. The FOTS was used to measure the temperature of the water in oil bath by changing the temperature in 5 °C increments over the range from 30 to 70 °C. The temperatures measured by using the FOTS with a metal cap varied almost linearly over that range, which means that the FOTS with a metal cap can be used as an auxiliary monitoring system for measuring the temperature of the water in a SNFP water temperature.
    No preview · Article · May 2015 · Journal- Korean Physical Society
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    Rinah Kim · Chan Hee Park · Arim Lee · Joo Hyun Moon
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    ABSTRACT: This study developed a noncontact fiber-optic temperature sensor that can be installed in a spent nuclear fuel pool. This fiber-optic temperature sensor was fabricated using an infrared optical fiber to transmit the infrared light emitted from water at a certain temperature. To minimize the decrease in the detection efficiency of the fiber-optic temperature sensor due to vapor generation, its surface was coated by spraying an antifog solution and drying several times. The measurement data of the fiber-optic temperature sensor was almost linear in the range of 30~70°C. This sensor could be used as an auxiliary temperature monitoring system in a spent nuclear fuel pool.
    Preview · Article · Feb 2015 · Science and Technology of Nuclear Installations
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    ABSTRACT: This study numerically investigated the influence of spanwise pressure gradient on heat transfer of a 3D turbulent boundary layer with longitudinal vortices. A 30° bend in the passage provided the spanwise pressure gradient. The longitudinal pair vortices were generated using a pair of delta winglets. The Reynolds-averaged Navier-Stokes and energy equations based on the conventional Reynolds stress model were used. The predictions agreed well with the experimental data for the straight plate. The turbulent boundary layer was significantly perturbed with the longitudinal vortices. The spanwise pressure gradient contributed to faster degradation of the longitudinal vortices and widened the perturbed flow region. The local Stanton number distributions were asymmetric because of the difference in the evolution of the longitudinal vortices in the curved region. Moreover, comparison showed that the local Stanton number in the downstream of the straight channel increased near the surface because of the secondary re-circulating vortex. The thickness of the thermal boundary layers increased in the streamwise direction because of the significant flow mixing and heat transfer.
    No preview · Article · Feb 2015 · Journal of Mechanical Science and Technology
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    ABSTRACT: A fiber-optic radiation sensor (FORS) was fabricated using a cerium-doped silicate-yttriumlutetium (LYSO:Ce) scintillator crystal and a silica optical fiber (SOF) to measure gamma-rays accurately in elevated temperature conditions. Throughout this study, a LYSO:Ce crystal was employed as a sensing material of the FORS due to its high light yield (32,000 photons/MeV), fast decay time (≤ 47 ns) and high detection efficiency. Although the LYSO:Ce crystal has many desirable qualities, the thermoluminescence (TL) should be eliminated by using a heat annealing process because the light yield of the LYSO:Ce crystal varies with its TL. In this study, therefore, we obtained the TL curve of the LYSO:Ce crystal by increasing the temperature up to 280 ℃, and we demonstrated that almost all of the TL of the LYSO:Ce crystal was eliminated by the heat annealing process.
    No preview · Article · Jan 2015 · Journal- Korean Physical Society
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    ABSTRACT: In this study, a Cerenkov radiation sensor for detecting low-energy beta-particles was fabricated using various Cerenkov radiators such as an aerogel and CaF2-, SiO2-, and Al2O3-based optical glasses. Because the Cerenkov threshold energy (CTE) is determined by the refractive index of the Cerenkov radiator, the intensity of Cerenkov radiation varies according to the refractive indices of the Cerenkov radiators. Therefore, we measured the intensities of Cerenkov radiation induced by beta-particles generated from a radioactive isotope as a function of the refractive indices of the Cerenkov radiators. Also, the electron fluxes were calculated for various Cerenkov radiators by using a Monte Carlo N-Particle extended transport code (MCNPX) to determine the relationship between the intensities of the Cerenkov radiation and the electron fluxes.
    No preview · Article · Jan 2015 · Journal- Korean Physical Society
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    ABSTRACT: A fiber-optic sensor system using a multiplexed array of sensing probes based on an aqueous solution of sodium chloride (NaCl solution) and an optical time-domain reflectometer (OTDR) for simultaneous measurement of temperature and water level is proposed. By changing the temperature, the refractive index of the NaCl solution is varied and Fresnel reflection arising at the interface between the distal end of optical fiber and the NaCl solution is then also changed. We measured the modified optical power of the light reflected from the sensing probe using a portable OTDR device and also obtained the relationship between the temperature of water and the optical power. In this study, the water level was simply determined by measuring the signal difference of the optical power due to the temperature difference of individual sensing probes placed inside and outside of the water. In conclusion, we demonstrate that the temperature and water level can be obtained simultaneously by measuring optical powers of light reflected from sensing probes based on the NaCl solution. It is anticipated that the proposed fiber-optic sensor system makes it possible to remotely monitor the real-time change of temperature and water level of the spent fuel pool during a loss of power accident.
    Full-text · Article · Oct 2014 · Sensors
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    ABSTRACT: A fiber-optic sensor system using a multiplexed array of sensing probes based on an aqueous solution of sodium chloride (NaCl solution) and an optical time-domain reflectometer (OTDR) for simultaneous measurement of temperature and water level is proposed. By changing the temperature, the refractive index of the NaCl solution is varied and Fresnel reflection arising at the interface between the distal end of optical fiber and the NaCl solution is then also changed. We measured the modified optical power of the light reflected from the sensing probe using a portable OTDR device and also obtained the relationship between the temperature of water and the optical power. In this study, the water level was simply determined by measuring the signal difference of the optical power due to the temperature difference of individual sensing probes placed inside and outside of the water. In conclusion, we demonstrate that the temperature and water level can be obtained simultaneously by measuring optical powers of light reflected from sensing probes based on the NaCl solution. It is anticipated that the proposed fiber-optic sensor system makes it possible to remotely monitor the real-time change of temperature and water level of the spent fuel pool during a loss of power accident.
    Full-text · Article · Oct 2014 · Sensors
  • Joo Hyun Moon · Dae Yun Kim · Seong Hyuk Lee
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    ABSTRACT: The present study aims to investigate the influence of the Weber number and surface temperature on the spreading and receding characteristics of Newtonian (DI-water) and non-Newtonian (xanthan gum solution) droplets impinging on heated surfaces. The surface temperature was in the range from 25°C to 85 °C, which is below the Leidenfrost temperature (∼ 300 °C). Using high-speed camera images, this study measured the dynamic contact angle as well as spreading and receding diameters. It also used a modified model to predict the maximum spreading diameter by using the effective viscosity. From the results, the modified model using the effective viscosity was in good agreement with the experimental data in predicting the maximum spreading diameter. In addition, the maximum spreading diameter for a DI-water droplet was larger than that of a non-Newtonian droplet because of the difference in liquid viscosity. In particular, for the Newtonian and non-Newtonian droplets, the dynamic contact angle was almost similar in the spreading regime, but in the receding regime, it substantially changes with temperature owing to the variation of viscosity with temperature. Moreover, the spreading diameter rapidly decreased with the increase in surface temperature in the receding regime in which the change in viscous dissipation energy would be important for the receding motion. Finally, the retraction rates of the Newtonian droplet remained constant with temperature, whereas those of the non-Newtonian droplet increased with temperature, thereby supporting the assertion that the viscosity effect is dominant in the receding characteristics after impact.
    No preview · Article · Sep 2014 · Experimental Thermal and Fluid Science
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    ABSTRACT: In this study, two fiber-optic sensors were fabricated to measure water level and temperature using optical fibers, a coupler, a Lophine and an OTDR (optical time-domain reflectometer). First, using Fresnel's reflection generated at the distal-ends of each optical fiber, which was installed at different depth, we measured the water level according to the variation of water level. Next, we also measured the temperature of water tising a temperature sensing probe based on the Lophine, whose absorbance changes with the temperature. The measurable temperature range of the fiber-optic sensor is from 5°C to 65°C because the maximum operation temperature of the optical fiber without a physical deterioration is up to 80°C.
    No preview · Article · Sep 2014 · Transactions of the Korean Institute of Electrical Engineers
  • Joo Hyun Moon · Seong Hyuk Lee · Kee Bong Yoon · Ji Yoon Kim

    No preview · Article · Aug 2014
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    Chan Hee Park · Arim Lee · Rinah Kim · Joo Hyun Moon
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    ABSTRACT: The aim of this study was to develop and evaluate fiber-optic sensors for the remote detection of gamma rays in areas that are difficult to access, such as a spent fuel pool. The fiber-optic sensor consists of a light-generating probe, such as scintillators for radiation detection, plastic optical fibers, and light-measuring devices, such as PMT. The (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator was chosen as the light-generating probe. The (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator has higher scintillation efficiency than the others and transmits light well through an optical fiber because its refraction index is similar to the refractive index of the optical fiber. The fiber-optic radiation sensor using the (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator was evaluated in terms of the detection efficiency and reproducibility for examining its applicability as a radiation sensor.
    Preview · Article · Apr 2014 · Science and Technology of Nuclear Installations
  • Joo Hyun Moon · Byung Gi Park
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    ABSTRACT: The time-dependent radiation release characteristics of nuclear fuel assemblies need to be understood to manage operation safely and protect workers from the radiation released over the operation period of a nuclear reactor, including its overhaul period. This study examines the time-dependent radiation release characteristics of 2 types of PWR nuclear fuel assemblies in Korea according to their burn-up. Two types of nuclear fuel assemblies considered were: a 16 x 16 fuel assembly of Ulchin units 5&6 (KSNP type) and a 17x17 fuel assembly of Kori units 3&4 (Westinghouse type). The 5 different burn-ups (MWD/MTU) were considered: 100, 10,000, 20,000, 30,000, and 40,000. The calculations showed that the increase rate of neutron dose distribution was relatively higher than that of the gamma dose distribution according to burn-up, while the gamma dose distributions were much higher than the neutron dose distributions.
    No preview · Article · Feb 2014 · Kernkraftwerke in Deutschland: Betriebsergebnisse ..
  • Joo Hyun Moon · Jeongmin Lee · Jooheon Kim · Seong Hyuk Lee
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    ABSTRACT: The present study aims to investigate numerically the effective thermal conductivity for different radial nanowire heterostructures (RNWHSs), such as core–shell, tubular–shell, and core–shell–shell types, which are used for resolving thermal dissipation problem. The influence of core radius and shell thickness on the effective thermal conductivity was examined by using the boundary/interfacial scattering (BS) method derived from the Casimir theory. It was found that the effective thermal conductivity of the RNWHSs was smaller than the bulk thermal conductivity of multi-walled carbon nanotubes (MWCNTs) because of the diffusive interfacial scattering effect. When the shell thickness was much thinner than the core radius, the thermal conductivity of the core MWCNT was relatively higher than that of the shell material. Comparing MWCNT/Al2O3 and MWCNT/SiO2 core–shell RNWHSs, the effective thermal conductivities were similar when the core radius was greater than 100 nm or the core porosity was above 0.4, owing to the effect of MWCNT bulk thermal conductivity. Besides, the effective thermal conductivity of the tubular–shell RNWHS with the same cross-sectional area was always lower than that of the core–shell RWNHSs because of additional interfacial scattering at the pores inside the tubular-shell RNWHSs. When the Al2O3 thickness in the core–shell–shell RNWHS of MWCNT/Al2O3/W was less than 135 nm at a fixed MWCNT radius of 100 nm, the effective thermal conductivity increased with core porosity. When the Al2O3 thickness was 1.0 nm, the effective thermal conductivity rapidly decreased with the increase in porosity.
    No preview · Article · Jan 2014 · MATERIALS TRANSACTIONS
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    Full-text · Dataset · Dec 2013
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    ABSTRACT: Aluminum-hydroxide-covered multi-walled carbon nanotubes (A-MWCNT) were fabricated as a thermally conductive material. The thermal conductivity of A-MWCNT was estimated based on Casimir theory. The effective thermal conductivity of A-MWCNT was estimated at about similar to 26 W/mK. The thermal conductivity of A-MWCNT/epoxy-terminated polydimethylsiloxane (ETDS) composite was examined as a function of A-MWCNT loading, and the results showed the maximum value at 1.5 wt% of A-MWCNT loading, above which it decreased slightly. The effective medium approximation (EMA) developed by Maxwell-Garnett (M-G) was used to analyze the thermal conducting behavior of the composite. The experimental results showed negative deviation from the expected thermal conductivity, k(e), beyond 1.5 wt% of A-MWCNT loading, because the composites containing A-MWCNT were strongly affected by interfacial resistance. The interfacial resistance value calculated from M-G approximation increased when filler loading was higher than 1.5 wt% because of the folded and partially agglomerated A-MWCNT along with insufficient interfacial interactions.
    No preview · Article · Nov 2013 · Composites Part A Applied Science and Manufacturing
  • Chan Hee Park · Joo Hyun Moon · Bum Kyoung Seo
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    ABSTRACT: In this study, we developed and characterized an integrated fiber-optic sensor for the remote detection of alpha radiation emitted from radioactive contamination in areas relatively inaccessible by radiation workers. The fiber-optic sensor consisted of an epoxy-resin supporter and a sensing probe attached to it. The epoxy-resin supporter to hold the optical fiber tightly was fabricated by using epoxy-resin and a small amount of hardener. The sensing probe was fabricated by mixing epoxy-resin with inorganic scintillator ZnS(Ag) powder and solidifying the mixture. Then, the sensing probe was attached to the epoxy-resin supporter. As a light guide, an optical fiber, which was also compatible with the epoxy-resin, was used. The optical fiber was submerged in the epoxyresin supporter before solidification to make it in an integral form to minimize the loss of scintillation light due to incomplete connections between them. The four assembled fiber-optic sensors with sensing probes whose density thicknesses of ZnS(Ag) were 10, 15, 20 and 25 mg/cm2, respectively, were evaluated in terms of the total counts of alpha radiation to determine the optimum density thickness of ZnS(Ag). From the evaluation, a density thickness of 15 mg/cm2 was found to be the best for detecting alpha radiation.
    No preview · Article · Nov 2013 · Journal- Korean Physical Society

Publication Stats

198 Citations
45.86 Total Impact Points

Institutions

  • 2013-2015
    • Gyeongju University
      Gyeongju, Gyeongsangbuk-do, South Korea
  • 2012-2015
    • Chung-Ang University
      • School of Mechanical Engineering
      Sŏul, Seoul, South Korea
  • 2007-2015
    • Dongguk University
      • • Department of Civil and Environmental System Engineering
      • • College of Science and Technology
      Sŏul, Seoul, South Korea
  • 2010
    • Konkuk University
      • Department of Biological Engineering
      Seoul, Seoul, South Korea
  • 2002-2006
    • Seoul National University
      • Department of Nuclear Engineering
      Sŏul, Seoul, South Korea
  • 2004-2005
    • Korea Institute of Nuclear Safety
      Sŏul, Seoul, South Korea
  • 1999
    • Korea Hydro and Nuclear Power - Central Research Institute
      Sŏul, Seoul, South Korea