Han Seo

CRITICAL HEAT FLUX ENHANCEMENT IN FLOW BOILING OF Al₂O₃ AND SiC NANOFLUIDS UNDER LOW PRESSURE AND LOW FLOW CONDITIONS

Critical heat flux (CHF) is the thermal limit of a phenomenon in which a phase change occurs during heating (such as bubbles forming on a metal surface used to heat water), which suddenly decreases the heat transfer efficiency, thus causing localized overheating of the heating surface. The enhancement of CHF can increase the safety margins and allow operation at higher heat fluxes; thus, it can increase the economy. A very interesting characteristic of nanofluids is their ability to significantly enhance the CHF. Nanofluids are nanotechnology-based colloidal dispersions engineered through the stable suspension of nanoparticles. All experiments were performed in round tubes with an inner diameter of 0.01041 m and a length of 0.5 m under low pressure and low flow (LPLF) conditions at a fixed inlet temperature using water, 0.01 vol.% Al2O3/water nanofluid, and SiC/water nanofluid. It was found that the CHF of the nanofluids was enhanced and the CHF of the SiC/water nanofluid was more enhanced than that of the Al2O3/water nanofluid.

Hybrid Graphene and Single-Walled Carbon Nanotube Films for Enhanced Phase-Change Heat Transfer.

Nucleate boiling is an effective heat transfer method in power generation systems and cooling devices. In this letter, hybrid graphene/single-walled carbon nanotube (SWCNT), graphene, and SWCNT films deposited on indium tin oxide (ITO) surfaces were fabricated to investigate the enhancement of nucleate boiling phenomena described by the critical heat flux and heat transfer coefficient. The graphene films were grown on Cu foils and transferred to ITO surfaces. Furthermore, SWCNTs were deposited on the graphene layer to fabricate hybrid graphene/SWCNT films. We determined that the hybrid graphene/SWCNT film deposited on an ITO surface is the most effective heat transfer surface in pool boiling because of the interconnected network of carbon structures.

Measurement of Velocity and Temperature Profiles in the 1/40 Scaled-Down CANDU-6 Moderator Tank

In order to simulate the CANDU-6 moderator circulation phenomena during steady state operating and accident conditions, a scaled-down moderator test facility has been constructed at Korea Atomic Energy Institute (KAERI). In the present work an experiment using a 1/40 scaled-down moderator tank has been performed to identify the potential problems of the flow visualization and measurement in the scaled-down moderator test facility. With a transparent moderator tank model, a flow field is visualized with a particle image velocimetry (PIV) technique under an isothermal state, and the temperature field is measured using a laser induced fluorescence (LIF) technique. A preliminary CFD analysis is also performed to find out the flow, thermal, and heating boundary conditions with which the various flow patterns expected in the prototype CANDU-6 moderator tank can be reproduced in the experiment.

Measurement of Velocity and Temperature Profiles in the Scaled-Down CANDU-6 Moderator Tank

We are planning to construct a scaled-down moderator test facility to simulate the CANDU-6 moderator circulation phenomena during steady state operation and accident conditions at the Korea Atomic Energy Research Institute. In the present work a preliminary experiment using a 1/40 scaled-down moderator tank has been performed to identify the potential problems of the flow visualization and measurement in the scaled-down moderator test facility. With a transparent moderator tank model, a flow field is visualized with a Particle Image Velocimetry (PIV) technique under an isothermal state, and the temperature field is measured using a Laser Induced Fluorescence (LIF) technique. A preliminary CFD analysis is also performed to find out the flow, thermal, and heating boundary conditions with which the various flow patterns expected in the prototype CANDU-6 moderator tank can be reproduced in the experiment.Copyright

MOESM1 of STAMPS: development and verification of swallowing kinematic analysis software

Additional file 1: Figure S1. Fluoroscopic images of different lengths and angles for validation. The lengths (A) and angles (B) were measured by swallowing kinematic analysis and compared with predetermined reference values.

PIV Measurement of Velocity Profile in the 1/8 Scale CANDU6 Moderator Circulation Test

The Korea Atomic Energy Research Institute (KAERI) has a scaled-down moderator test program to simulate the CANDU6 moderator circulation phenomena during steady state operation and accident conditions. In the present work a preliminary experiment using a 1/8 scaled-down moderator tank has been performed to identify the potential problems of the flow visualization and measurement in the scaled-down moderator test facility. With a transparent moderator tank model, a velocity field is measured with a Particle Image Velocimetry (PIV) technique under an isothermal state. The flow patterns from the inlet nozzles to the top region of the tank are investigated using PIV for a 1/8 scale moderator tank.

Experimental Study of Moderator Circulation in CANDU6 Calandria Tank

As a CANDU6 reactor has a high pressure primary cooling system and an independently cooled moderator system, the moderator in the calandria would act as a supplementary heat sink during a loss of coolant accident (LOCA) if the primary cooling and emergency coolant injection systems fail to remove the decay heat from the fuel. For the safety concern it is required to predict the 3-dimensional velocity and temperature distribution of moderator fluid to confirm the effectiveness of moderator heat sink.Korea Atomic Energy Research Institute (KAERI) is carrying out a scaled-down moderator test program to simulate the CANDU6 moderator circulation phenomena during steady state operation and accident conditions. This research program includes the construction of the Moderator Circulation Test (MCT) facility, production of the validation data for self-reliant CFD tools, and development of optical measurement system using the Particle Image Velocimetry (PIV). In the present work the PIV technique is used to measure the velocity distributions in the scaled moderator tank of MCT under iso-thermal test conditions. The preliminary PIV measurement data are obtained and compared with CFX code predictions.Copyright