An experimental investigation of radiative and total heat transfer around a horizontal tube immersed in a high temperature gas-solid fluidized bed Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/ww72bh218

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  • This study is primarily concerned with the measurement of thelocal radiative component of total heat transfer around a horizontaltube immersed in a large particle fluidized bed at elevated temperatures.Total heat transfer was also measured in order to assess therelative radiation contribution.The radiation measurement probe employs a silicon window mountedflush with the tube wall to transmit the radiative heat flux. Athin-film thermopile-type heat flow detector placed behind the windowsensed the transmitted radiation. The thermal conductivity of siliconis sufficiently large to prevent the conduction error (less than3%) resulting from the convective component of heat transfer. Siliconalso has a wide spectral transmission wave band extending from1.3 um to 12.0 um. The total heat transfer probe uses a similar heatflow detector bonded to the tube wall and covered tightly with astainless steel foil to protect the detector against abrasion.The radiation probe was calibrated using a narrow-angle blackbodysource. The purpose of the calibration was to establish therelation between the heat flux detected by the radiation probe andthe incident radiative flux to the tube wall. This relation wasfound to be linear and insensitive to the tube wall temperaturevariations encountered in this study.The instrument has been used to measure local radiative andtotal heat transfer at 0
  • This study is primarily concerned with the measurement of thelocal radiative component of total heat transfer around a horizontaltube immersed in a large particle fluidized bed at elevated temperatures.Total heat transfer was also measured in order to assess therelative radiation contribution.The radiation measurement probe employs a silicon window mountedflush with the tube wall to transmit the radiative heat flux. Athin-film thermopile-type heat flow detector placed behind the windowsensed the transmitted radiation. The thermal conductivity of siliconis sufficiently large to prevent the conduction error (less than3%) resulting from the convective component of heat transfer. Siliconalso has a wide spectral transmission wave band extending from1.3 um to 12.0 um. The total heat transfer probe uses a similar heatflow detector bonded to the tube wall and covered tightly with astainless steel foil to protect the detector against abrasion.The radiation probe was calibrated using a narrow-angle blackbodysource. The purpose of the calibration was to establish therelation between the heat flux detected by the radiation probe andthe incident radiative flux to the tube wall. This relation wasfound to be linear and insensitive to the tube wall temperaturevariations encountered in this study.The instrument has been used to measure local radiative andtotal heat transfer at 0, 45, 90, 135, and 180 degree positionsaround a horizontal tube immersed in a fluidized bed. Measurementswere obtained at bed temperatures of 812 K and 1050 K with 2.14 mmand 3.23 mm mean diameter particles at gas velocities up to two timesthe minimum fluidization velocity.A sharp increase was noted for spatial average radiative, totaland convective heat transfer coefficients when the gas velocity exceededthe minimum fluidizing velocity. Generally, these coefficientsshowed little variation with further increase in gas flowrate.The radiative heat transfer coefficient was increased with anincrease in particle size and bed temperature, the latter having amuch more pronounced effect, as expected. The radiation contributionto overall heat transfer was found to increase from 9% to 15% for3.23 mm particles and from 8% to 13% for 2.14 mm particles when thebed temperature was elevated from 812 K to 1050 K at the optimum gasvelocity (maximum total heat transfer).Finally, fast sampling rate (25 samples sec) data were obtainedusing the radiation probe with a measured response time of about 120 msec. This data was treated as instantaneous and an attempt was madeto obtain hydrodynamic parameters such as emulsion residence time andbubble contact fraction. However, this analysis did not yield satisfactoryresults.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-06-26T16:26:59Z (GMT) No. of bitstreams: 1 AlavizadehSeyedN1986.pdf: 1206760 bytes, checksum: e580245645c0b43bcd1b63273b00e8f6 (MD5)
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  • 1986
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