Multi-component ion exchange kinetics with PAN-KCoFC composite ion exchanger

An ion exchange kinetic study was performed using PAN-KCoFC for removal of cesium ion from mixed solution of Cs, Sr, Ni and Ba ions. Uptake curves were obtained for a multi-component ion exchange system as well as binary system. A PAN-KCoFC composite ion exchanger showed higher selectivity for Cs ion over the Sr, Ba, Ni ions. A homogeneous model could predict accurately the uptake curve for both the binary and multi-component systems. Solid phase effective pore diffusivities obtained by modeling ranged between 10⁻⁵ cm₂/min and 10⁻⁶ cm₂/min.     

Formation and thermal properties of fluorite-pyrochlore composite structure in La2(ZrxCe1 − x)2O7 oxide system

Rare-earth oxides of La₂(Zr_xCe_1 ? x)₂O₇ for thermal barrier coatings (TBCs) are fabricated via a solid-state reaction at 1600 °C. As the phase formation, microstructure, and thermal properties of these oxides are examined, a fluorite–pyrochlore composite structure is found in the La₂(Zr_xCe_1 ? x)₂O₇ system. This composite structure is composed of coarse Ce-rich fluorite and fine Zr-rich pyrochlore grains. From XRD and microstructural analysis, the lattice parameter and volume fraction of each phase are evaluated in order to obtain the intrinsic thermal conductivity value of composite-structured oxide with porosity calibration. The thermal conductivity of the composite structure is similar to that of pyrochlore La₂Zr₂O₇, which is attributed to phonon scattering by phase boundaries.     

Thermo-hydraulic design verification of the neutral beam liner for the ITER vacuum vessel

The ITER vacuum vessel has upper, equatorial and lower port structures used for equipment installation, utility feedthroughs, vacuum pumping and access inside the vessel for maintenance. A neutral beam (NB) port of equatorial ports provides a path of neutral beam for plasma heating and current drive. An internal duct liner is built in the NB ports, and copper alloy panels are placed in the top and bottom of the liner to protect duct surface from high-power heat loads. Global NB liner models for the upper panel and the lower panel have been developed, and flow field and conjugate heat transfer analyses have been performed to find out pressure drop and heat transfer characteristics of the liner. Heat loads such as NB power, volumetric heating and surface heat flux are applied in the analyses for beam steering and misalignment conditions. For the upper panel, it is found that unbalanced flow distribution occurs in each flow path, and this causes poor heat transfer performance as well. In order to improve flow distribution and to reduce pressure losses, hydraulic analyses for modified cooling path schemes have been carried out, and design recommendations are made based on the analysis results. For the lower panel, local flow distributions and pressure drop values at each header and branch of the tube are obtained by applying design coolant flow rate. Together with the coolant flow field, temperature and heat transfer coefficient distributions are also acquired from the analyses. Based on the analysis results, it is concluded that the lower panel for the NB liner is relatively well designed even though the given heat loads are very severe.     

A New Emitter Switched Thyristor (EST) employing Trench Segmented p-base

A new emitter switched thyristor (EST) employing trench segmented p-base, which successfully improves the forward I-V and switching characteristics with decreasing the device active area, is proposed and verified experimentally with using shallow trench process of novel junction termination extension (JTE) method. The latching current of EST is determined by the p-base resistance of upper npn transistor. Floating n+emitter of conventional EST is enlarged to obtain large base resistance. However, the proposed EST increases the p-base resistance with shorter floating n+ emitter than that of conventional one. Shallow trench in floating emitter region forms the highly resistive p-base region under the bottom of trench. The experimental results show that the shortened floating n+ emitter and lowered latching current of proposed EST decrease experimentally the forward voltage drop by 17.7% and snap-back phenomenon with small active area. The breakdown voltage of series lateral MOSFET of proposed EST is increased from 7 to 14 V due to the trench filled with oxide which results in vertical redistribution of electric field, therefore current saturation capability and forward biased safe operating area (FBSOA) of proposed EST are enhanced. The simulation results show that the switching operation is performed successfully at the blocking voltage of 600 V and Eoff of the proposed one is reduced by 3.7%. The measured inductive load switching characteristics also shows that Eoff of proposed one is improved by 7.2%.     

Solvent power dependence of phase behavior of biodegradable polymers in high-pressure hydrofluorocarbons

Phase behavior data at temperatures from 30 °C to 100 °C and at pressures from 30 bar to 850 bar are presented for poly(D,L-lactide) in hydrofluorocarbon solvents: difluoromethane (HFC-32), trifluoromethane (HFC-23), and 1,1,1,2-tetrafluoroethane (HFC-134a). The cloud point pressures were measured by using a high-pressure equilibrium apparatus equipped with a variable-volume view cell, and were investigated as functions of temperature, polymer concentration, and polymer molecular weight. The solvent power of hydrofluorocarbon solvents of dissolving the poly(D,L-lactide) increased in the order HFC-23, HFC-32, and HFC-134a, in proportion to their dipole moments. Dedicated to Dr. Youn Yong Lee on the occasion of his retirement from Korea Institute of Science and Technology.     

Phase Behavior of Three PBX Elastomers in High-Pressure Chlorodifluoromethane

The phase equilibrium behavior data are presented for three kinds of commercial polymer-bonded explosive (PBX) elastomers in chlorodifluoromethane (HCFC22). \(\hbox {Levapren}^{{\textregistered }}\) ethylene-co-vinyl acetate (LP-EVA), \(\hbox {HyTemp}^{{\textregistered }}\) alkyl acrylate copolymer (HT-ACM), and \(\hbox {Viton}^{{\textregistered }}\) fluoroelastomer (VT-FE) were used as the PBX elastomers. For each elastomer + HCFC22 system, the cloud point (CP) and/or bubble point (BP) pressures were measured while varying the temperature and elastomer composition using a phase equilibrium apparatus fitted with a variable-volume view cell. The elastomers examined in this study indicated a lower critical solution temperature phase behavior in the HCFC22 solvent. LP-EVA showed the CPs at temperatures of 323 K to 343 K and at pressures of 3 MPa to 10 MPa, whereas HT-ACM showed the CPs at conditions between 338 K and 363 K and between 4 MPa and 12 MPa. For the LP-EVA and HT-ACM elastomers, the BP behavior was observed at temperatures below about 323 K. For the VT-FE + HCFC22 system, only the CP behavior was observed at temperatures between 323 K and 353 K and at pressures between 6 MPa and 21 MPa. As the elastomer composition increased, the CP pressure increased, reached a maximum value at a specific elastomer composition, and then remained almost constant.     

Characteristics of phosphate adsorption on ferric hydroxide synthesized from a Fe<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript> aqueous solution discharged from a hydrometallurgical process

Ferric hydroxide adsorbent was prepared by a chemical treatment process with H₂O₂, NaOH, and aeration from a Fe₂(SO₄)₃ aqueous solution as a side product discharged from the hydrometallurgical process used to extract neodymium. The ferric hydroxide was used as an adsorbent to prevent eutrophication in water. At the time of synthesis, the most important process variable is the pH condition, which, in this experiment, was changed from pH 3 to 13. The cost of synthesizing ferric hydroxide was sharply reduced by using ferric sulfate, which is considered a side product of the aforementioned hydrometallurgical process, as a starting material, and an adsorbent with high adsorption ability was prepared by controlling the pH level. Microstructural characterization of the synthesized ferric hydroxide revealed particles with a specific surface area of 194.2 m²/g and an average pore diameter of 2.66 nm at pH 6 and 298 K. A column-type packed-bed adsorption experiment was conducted under the following conditions: a flow rate of 0.567 BV/min (3.2 mL/min), 298 K, and atmospheric pressure. The results of the adsorption performance test indicated that the adsorption efficiency of phosphate at concentrations of 10 ppm was 100% at a flow rate of 0.567 BV/min within a contact time of 2 min, and the maximum adsorption capacity for phosphate ions was 65 mg/g.     

Prediction of PVT behavior of polymer melts by the group-contribution lattice-fluid equation of state

The group-contribution lattice-fluid equation of state (GCLF-EOS), which is capable of predicting equilibrium behavior in polymer systems, was developed by establishing group contributions of the lattice-fluid EOS using the PVT properties of low molecular weight compounds only. This model was used to predict the PVT behavior of common polymers over a wide temperature range in the melt region and over a wide range of pressures up to about 2,000 bar. The GCLF-EOS predicted accurately the effect of pressure and temperature on the specific volumes of the polymer melts. Prediction results by the GCLF-EOS were compared with those by the group-contribution volume (GCVOL) method. The GCLF-EOS requires only the structure of the polymer repeat unit in terms of their functional groups as input information. No other polymer properties are needed. The GCLF-EOS is the only model that is capable of predicting the specific volumes of polymer melts as a function of temperature and pressure.     

Heat transfer property of refrigerant-oil mixture in a flooded evaporator: The role of bubble formation and oil retention

We examined the effect of oil retention on the heat transfer performance of a shell-and-tube-type evaporator which had 26 inner tubes and was filled with the refrigerant R-134a. The refrigerant was boiled on the surface of the inner tubes in the evaporator, while chilled water circulated through these tubes. An experimental apparatus was designed to measure both the pressure and temperature profiles at the inlet and outlet of the flooded evaporator. Four windows were installed for observing the operation of the flooded evaporator. A series of experiments were carried out under the following conditions: the refrigerant saturation temperature, 5 °C; refrigerant inlet quality, 0.1; heat fluxes from water to the refrigerant, 5–7 kW/m². The concentration of the oil retained in the refrigerant was then varied up to approximately 10% to observe the effect on the heat transfer performance of the flooded evaporator. Increasing the oil content (i.e., increasing the concentration up to a maximum of approximately 10%) in the refrigerant R134a did not lead to any appreciable reduction in the overall heat transfer coefficient of a flooded evaporator with multiple-innertubes. When the oil concentration in the refrigerant was approximately 10%, the heat transfer degradation in the case of the flooded evaporator with multiple-inner-tubes was approximately 11%, which was found to be much smaller than the heat transfer degradation in the case of a flooded evaporator with a single-tube (26–49%). This observation suggested that the oil retained in the refrigerant did not significantly deteriorate the heat transfer performance of the flooded evaporator, presumably because the presence of tube bundles promoted forced convection by agitating bubbles.