Heat transfer to a large mobile particle in gas-fluidized beds of smaller particles

Linjewile, Temi M.; Hull, Ashley S.; Agarwal, Pradeep K.

doi:10.1016/0009-2509(93)81023-o

Cited by 12 publications

(11 citation statements)

References 3 publications

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“…In fact, h was constant for U U mf . This contrasts with previous work (Agarwal, 1991;Linjewile et al, 1993;Pal'chenok and Tamarin, 1983;Prins, 1987) done with d s > d b , i.e. relatively large heat transfer spheres.…”

Section: Discussioncontrasting

confidence: 75%

The heat transfer coefficient between a particle and a bed (packed or fluidised) of much larger particles

Collier

Hayhurst

Richardson

et al. 2004

Chemical Engineering Science

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Section: Discussioncontrasting

confidence: 75%

The heat transfer coefficient between a particle and a bed (packed or fluidised) of much larger particles

Collier

Hayhurst

Richardson

et al. 2004

Chemical Engineering Science

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“…[3][4][5] This approach has been most successful for large, mobile spheres in a fluidized bed of finer particles with 3 < d s /d p < 200. Others have correlated the Nusselt number with the Reynolds number, both being based on the properties of the fluidizing gas.…”

Section: Heat-transfer Mechanisms In a Fluidizedmentioning

confidence: 98%

“…However, assumptions had to be made about the location of the combustion reactions, specifically whether the carbon burns to give CO 2 directly at the surface of a particle or whether CO 2 is formed from CO burning away from the surface. Others have embedded a thin, flexible thermocouple in an inert particle which was then either heated or cooled by immersion in a fluidized bed. − The heat-transfer coefficient was then obtained from the dynamic temperature response of the mobile sphere. One concern with this type of experiment is whether the thermocouple lead impedes the motion of the sphere.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer to a Single Sphere Immersed in Beds of Particles Supplied by Gas at Rates above and below Minimum Fluidization

Scott

Davidson

Dennis

et al. 2004

Ind. Eng. Chem. Res.

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The coefficient of heat transfer to a mobile sphere in a fluidized bed of relatively large particles has been measured. Measurements were also made for U < U mf , where the solids are stationary. One feature of these experiments is that the heat-transfer sphere was of a size comparable to that of the bed particles. Two methods of measuring heat-transfer coefficients in the bed were employed: (i) The rate of cooling of a sphere, initially hot, was measured by means of a tiny inserted thermocouple with fine lead wires connected to a temperature recorder external to the bed, and (ii) a small number of spherical CO 2 particles (dry ice) were put into an air-fluidized bed of inert particles. The subsequent concentration of CO 2 in the off-gas from the bed provided a measure of the evaporation rate of the dry ice particles and, hence, of the heat-transfer rate to each dry ice particle. Good agreement between values of h from the two methods implies that the thermocouple lead wires of method (i) did not restrain the free motion of the heat-transfer sphere. The meaning of the heat-transfer coefficient is discussed with regard to its applicability to a transient experiment, and a criterion is suggested for determining when it is valid to derive a heat-transfer coefficientsa steady-state parametersfrom a transient experiment. At high Reynolds numbers (100 < Re mfs < 830) and with small spheres in a bed of large particles (0.2 < d s /d p < 2.75), the dominant mechanism of heat transfer is found to be to the flowing gas. In this case, Nu ) 2 + 1.0Re mfs 0.6 (d s /d p ) 0.26 .

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“…Many aspects of the heat transfer characteristics associated with fl uidized beds have been studied. Researchers have attempted to look at the particle/fl uid heat transfer characteristics associated with individual particles when immersed into a fl uidized bed (Linjewile et al, 1993;Turton et al, 1989). In addition, heat transfer from fl uidized particles to fi xed surfaces has also been addressed (Molerus et al, 1994;Sunderesan and Clark, 1995).…”

Section: Discussionmentioning

confidence: 99%

“…Many researchers have also attempted to study particle-bed heat transfer using the very direct approach of embedding small probes with fi ne thermocouples (Linjewile et al, 1993;Parmar and Hayhurst, 2002). This technique is limited to particles of a minimum size of 2-3 mm because the thermocouple must be inserted into the probe.…”

Section: Introductionmentioning

confidence: 99%

Thermal Blending Time Associated With a Charge of Hot Particles Added to a Fluidized Bed of Uniform Temperature

Brown¹,

Pinchuk²,

Pinchuk³

et al. 2006

Can J Chem Eng

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The process of heat transfer between particles in a fluidized bed is important for many industrial fluidized bed processes. The problem associated with studying this phenomenon is the confounding effect of particle mixing on heat transfer. The work described here was undertaken to describe the process in which heat is added to a fluid bed process by adding a hot charge of particles to a colder fluidized bed. The rate of heat transfer in this instance can have a significant impact on performance of the fluid bed process, depending upon its application. Both the method of analysis and the results of the work are applicable to other fluidized bed processes, particularly those associated with the thermal upgrading of heavy oil. The method of data analysis, based on binomial statistics, allowed useful data to be extracted from a complex system without the need for a large number of experiments. The analysis also allowed for some assessment of the relative importance of mixing and heat transfer, which has not been possible with other approaches. The results of the experiments were further explored using a bubbling bed model that incorporated both heat transfer and solids mixing. This allowed for the formation of a conceptual model, validated by the experimentation, that explains the relative functions of the two transfer processes in the dispersion of heat from a hot charge of particles to the bulk of a fluidized bed.

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Heat transfer to a large mobile particle in gas-fluidized beds of smaller particles

Cited by 12 publications

References 3 publications

The heat transfer coefficient between a particle and a bed (packed or fluidised) of much larger particles

The heat transfer coefficient between a particle and a bed (packed or fluidised) of much larger particles

Heat Transfer to a Single Sphere Immersed in Beds of Particles Supplied by Gas at Rates above and below Minimum Fluidization

Thermal Blending Time Associated With a Charge of Hot Particles Added to a Fluidized Bed of Uniform Temperature

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