Hwayong Kim

Effective Thermal Conductivity of Graphite -Metallic Salt Complex for Chemical Heat Pumps

An experimental procedure was developed for measuring the effective thermal conductivities of graphite-CaCl 2 -nNH 3 (n = 8, 4, 2), MnCl 2 -nNH 3 (n = 6, 2), and BaCl 2 -8NH 3 complex for chemical heat pumps. Graphite-metallic salt complex was manufactured tbrougb the impregnation of metallic salt Into a porous graphite matrix. Experimental conditions of pressure and temperature were directly established by the thermodynamic equilibrium lines of salt-ammonia systems obtained by the calorimetric method. Afterward, effective thermal conductivities were measured using a transient one-dimensional heat flow technique at a fixed pressure and temperature under an ammonia atmosphere. Effective thermal conductivities of the graphite-metallic salt complex were in the range of 10-49 W/mK, which are significant higher values than powder beds of 0.1-0.5 W/mK. Results showed that the effective thermal conductivity of a graphite-metallic salt complex has a strong dependency on the bulk density, the weight fraction of graphite, and the ammoniated state of salt

Beam emittance measurements of transformer coupled plasma ion source for focused ion beam

A transformer coupled plasma (TCP) ion source has been tested in order to test its feasibility as a high brightness ion source for focused ion beam. When operating the TCP ion source with filter magnets in front of plasma electrode for a negative ion source, lower emittances are expected. Extracted beam emittances are measured with an Allison-type scanning device for various plasma parameters and extraction conditions. The normalized emittance has been measured to be around 0.2 (π mm mrad) with beam currents of up to 0.55 mA. In particular, noting that multicusp magnets have a role in decreasing the emittance as well as increasing plasma discharge efficiency, transverse magnetic field has been confirmed to be a useful tool for decreasing emittance via electron energy control.

Transient one-dimensional heat flow technique applied to porous reactive medium

A transient one-dimensional heat flow technique was presented to measure the effective thermal conductivity of porous reactive media. The porous reactive medium was in contact with a flat thermistor in a cell, and vacuum was applied to remove the air and the moisture. Afterwards, ammonia atmosphere was maintained in the cell under a fixed temperature and pressure. A varistor with max. 100 Ω was used to equate with the resistance of the thermistor corresponding to the fixed temperature. The temperature increase of thermistor was 2–3 °C, which was sufficient to avoid the enthalpy effect due to chemical reaction. A graphite-CaCl2⋅nNH3 complex was given as a test specimen for the porous reactive medium. Measurements showed that the thermal conductivity of graphite-CaCl2⋅8NH3 complex has distinctively higher values than the graphite-CaCl2⋅4NH3 and CaCl2⋅2NH3 complex. The accuracy of measured conductivity was estimated to be within 10%.

3-메틸펜테인과 에틸렌 글리콜 모노프로필 에테르 및 에틸렌 글리콜 아이소프로필 에테르 혼합물에 대한 2성분계 등온 기-액 상 평형

− Isothermal vapor liquid equilibria for the binary system of 3-methylpentane with ethylene glycol monopropyl ether (C 3 E 1 ) and ethylene glycol isopropyl ether (iC 3 E 1 ) were measured at 303.15, 318.15, and 333.15K. In our previous work, phase equilibria for the binary system of C 3 E 1 mixtures were investigated according to the chain length of alkane, alcohol or those isomer. But in this study, we discussed the different effect of C 3 E 1 and its isomer, iC 3 E 1 , on the phase equilibria. The measured systems were correlated with a Peng-Robinson equation of state (PR EOS) combined with Wong-Sandler mixing rule for the vapor phase, and NRTL, UNIQUAC, and Wilson activity coefficient models for the liquid phase. All the measured systems showed good agreement with the correlation results. And it was found that the phase equilibria showed very little difference between the iC 3 E 1 mixture system and the C 3 E 1 mixture system.

Prediction of temperature profile in MCFC stack

A simple three dimensional model was developed to simulate the temperature distribution and the performance of various flow types of the MCFC stack. The objective of this study was to understand the complicated phenomena occurring in the MCFC stack and to supply the basic data for optimizing the operating condition of the MCFC stack. Assuming that the stack consists of a number of differential elements which have uniform temperature and gas composition, the model was solved by finite difference method. The performance of this model was demonstrated by comparing the calculated value with experimental data of the 1.5kW class co-flow type MCFC stack operated in KIST. This model can be utilized as a simple diagnostic tool in case of the operational abnormality such as the hot spot which often occurs inside the stack.