A note on heat transfer between spherical particles and a fluid in a bed

Zabrodsky, S.S.

doi:10.1016/0017-9310(63)90055-3

Cited by 8 publications

(3 citation statements)

References 2 publications

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“…Prediction of steam explosions requires accounting for the multiphase heat transfer between the volcaniclastic particles and liquid water. Several multiphase heat transfer models have been advanced in the fields of chemical and nuclear engineering over the last 30 years [ Gunn , 1978; Zabrodsky , 1963]. These approaches commonly develop an empirical heat transfer coefficient for the mean heat transfer from the dispersed phase to the fluid.…”

Section: Introductionmentioning

confidence: 99%

Littoral blasts: Pumice‐water heat transfer and the conditions for steam explosions when pyroclastic flows enter the ocean

2007

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[1] Steam explosions, or littoral blasts, generated when pyroclastic flows interact with seawater may be a common, although rarely documented, phenomena. The development of steam explosions rather than passive steam production is related to the rate of thermal energy transfer from hot pyroclasts to water. We conduct a series of laboratory experiments to quantify the heat transfer and steam production rates when hot pyroclasts encounter water. Hot pumice (>200°C) rapidly ingests water while remaining at the surface, producing measurable amounts of steam during the process. Approximately 10% of the thermal energy of the pumice particles is partitioned into the production of steam, and smaller particles have greater steam production rates. The laboratory experiments are used to develop a subgrid model for steam production that can be incorporated into a multiphase numerical framework. We use this model to study the critical steam production rates required to initiate explosive events. For conditions typical of many pyroclastic flows, particles smaller than $1-5 mm are required to initiate a littoral blast. A second set of two-dimensional numerical simulations is conducted to simulate the 12-13 July Soufrière Hills dome collapse event that reached the sea. The simulations predict that the focus of the blast is likely generated several hundred meters offshore and although the landward directed base surge is primarily dry (<15% water vapor), the area immediately above the blast is steam-rich and may be a likely site for the production of accretionary lapilli.

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Section: Introductionmentioning

confidence: 99%

Littoral blasts: Pumice‐water heat transfer and the conditions for steam explosions when pyroclastic flows enter the ocean

2007

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“…For an assemblage of particles, such as a fixed bed, the lower limiting value for the Sherwood or Nusselt numbers has been calculated by theory to be 2 or somewhat above 2, depending on the bed voidage (Rowe, 1963;Rowe and Claxton, 1965;Zabrodsky, 1963). In direct opposition to these theoretical predictions, the measured Sherwood and Nusselt numbers of over a dozen investigators (Kunii and Suzuki, 1967) do not level off but keep falling continuously as the Reynolds number is lowered.…”

Section: Gas-solid Mass Transfermentioning

confidence: 99%

“…The theories which predict a leveling off of Sherwood or Nusselt numbers concern local coefficients; the coefficients reported by experiment are those measured in beds with their bypassing and channeling but which assume plug flow of gas through the bed. Zabrodsky (1963) recognized that the large extent of by- passing of solids by bubbling gas could be the reason for the lowered observed coefficients, and he proposed a model which viewed that the surplus gas beyond that needed for minimum fluidization bypassed one or more rows of solids, then mixed completely with the percolating gas. This process is repeated throughout the bed.…”

Section: Gas-solid Mass Transfermentioning

confidence: 99%