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한종훈(Jong Hun Han),조길원(Kil Won Cho),이건홍(Kun Hong Lee),김화용(Hwa Yong Kim) 한국화학공학회 1997 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.35 No.5
Accurate thermal conductivity measurements are important in order to analyze the thermal transport phenomena inside the reaction beds. In this study, the transient one-dimensional heat flow technique was used as a direct method of thermal conductivity measurement for reaction beds. The experimental apparatus was built based on this method and measurements on the standard sample from NIST confirmed that this technique is accurate to within 2 %. Measurements of thermal conductivities were also carried out with graphite matrices used as heat conductive medium in reaction beds. For graphite matrices with bulk densities of 0.1-0.4g/㎤, the thermal conductivities in the axial direction were in the range of 4.1-20.0W/mK, while the thermal conductivities in the radial direction were in the range of 4.6-42.3 W/mK.
한종훈,조길원,이건홍 ( Jong Hun Han,Kil Won Cho,Kun Hong Lee ) 한국화학공학회 1996 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.34 No.6
Expanded graphite powders were prepared by heating natural flake graphites intercalated with sulfuric acid. Graphite matrices were fabricated by pressing expanded graphite powders. Impregnation of salts into the graphite matrices were done using vacuum filtration with 20 wt% CaCl₂ solution followed by vacuum drying at 200℃ and 20 ㎪. Techniques used to examine the properties of blocks include EDAX and EPMA for amount and distribution of salts in the block, Hepycnometer for porosity, permporometer for gas permeability and transient 1-dimensional heat flow technique for thermal conductivity measurement. Basic chemical heat pump system is used to examine the dimensional stability and temperature distribution for blocks in the reactor. Results showed that Darcy`s permeability constants of graphite matrices were in 0.01-l.0 Darcy at △P=0.8 bar. For graphite matrices with p_b=100-400 ㎏/㎥, thermal conductivities were in the range of 4-22 W/mK. CaCl₂ was uniformly dispersed on the surface of expanded graphites in the block. The porosities of blocks were in the range of 0.4-0.83. The dimension of blocks was found to be more stabilized as bulk density increases. Temperature profile was governed by the reaction kinetics at the initial stage and by the external heat transfer in the long run.