SIGNIFICANCE OF THE RADIAL POROSITY PROFILE FOR THE DESCRIPTION OF HEAT-TRANSPORT IN WALL-COOLED PACKED-BEDS

被引:28
作者
BORKINK, JGH [1 ]
WESTERTERP, KR [1 ]
机构
[1] TWENTE UNIV TECHNOL,DEPT CHEM ENGN,CHEM REACT ENGN LABS,POB 217,7500 AE ENSCHEDE,NETHERLANDS
关键词
D O I
10.1016/0009-2509(94)80023-5
中图分类号
TQ [化学工业];
学科分类号
0817 ;
摘要
The influence of a radial porosity and velocity profile on the predicted temperature and concentration profiles in wall-cooled packed beds is studied, with and without an exothermic first-order chemical reaction, on the basis of literature correlations for the effective transport coefficients. Furthermore, values for the effective heat transport coefficients are obtained from ''cold-flow'' experiments by means of model fitting, with and without taking the radial velocity profile into account. The radial porosity and velocity profiles are approximated by a step-function, which is referred to as the ''two-region model''. It is shown that the effective radial heat conductivity can be taken constant over the radius, despite the wall effect. Nevertheless, the influence of a radial superficial velocity profile can be significant through the convective term in the heat balance, especially for low tube-to-particle diameter ratios. The predicted NTU can increase the order of 20% for high values of the Reynolds number and up to 100% for low values. This is confirmed by the results obtained from the model fitting. In case of a first-order exothermic reaction, significantly higher values for the hot-spot temperatures are predicted, if a radial porosity and velocity profile is incorporated in the heat and mass balances. This is found to be mainly caused by the non-uniform distribution of active catalyst over the radius, due to the porosity profile.
引用
收藏
页码:863 / 876
页数:14
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共 43 条
  • [1] Agnew J.B, 1970, TRANS INST CHEM ENG, V48, pT15
  • [2] [Anonymous], 2013, HDB MATH FUNCTIONS F
  • [3] INFLUENCE OF TUBE AND PARTICLE DIAMETER ON HEAT-TRANSPORT IN PACKED-BEDS
    BORKINK, JGH
    WESTERTERP, KR
    [J]. AICHE JOURNAL, 1992, 38 (05) : 703 - 715
  • [4] MODELING OF RADIAL HEAT-TRANSPORT IN WALL-COOLED PACKED-BEDS - CONFIDENCE-INTERVALS OF ESTIMATED PARAMETERS AND CHOICE OF BOUNDARY-CONDITIONS
    BORKINK, JGH
    BORMAN, PC
    WESTERTERP, KR
    [J]. CHEMICAL ENGINEERING COMMUNICATIONS, 1993, 121 : 135 - 155
  • [5] BORKINK JGH, 1991, THESIS TWENTE U TECH
  • [6] THE MASS BALANCE FOR GAS-PHASE REACTIONS IN TUBULAR REACTORS
    BOS, ANR
    WESTERTERP, KR
    [J]. CHEMICAL ENGINEERING COMMUNICATIONS, 1991, 99 : 139 - 153
  • [7] THEORETICAL-MODEL OF HEAT-TRANSFER TO A PACKED OR QUIESCENT FLUIDIZED-BED
    BOTTERILL, JSM
    DENLOYE, AOO
    [J]. CHEMICAL ENGINEERING SCIENCE, 1978, 33 (04) : 509 - 515
  • [8] TRUE MEAN VELOCITIES IN THE WALL AND BULK REGIONS OF FIXED-BEDS
    CAYCIK, M
    GUNN, DJ
    [J]. CHEMICAL ENGINEERING SCIENCE, 1988, 43 (07) : 1637 - 1646
  • [9] TRANSVERSE THERMAL DISPERSION AND WALL CHANNELING IN A PACKED-BED WITH FORCED CONVECTIVE FLOW
    CHENG, P
    VORTMEYER, D
    [J]. CHEMICAL ENGINEERING SCIENCE, 1988, 43 (09) : 2523 - 2532
  • [10] DASKOWSKI T, 1992, CHEM ENG SCI, V47, P2245