Generalized Prediction of Maximum Heat Transfer to Single Cylinders and Spheres in Gas-Fluidized Bed
TL;DR: In this paper, a simple dimensionless correlation is presented and compared with data from 35 experimental studies, including spheres, horizontal and vertical cylinders, cylinder diameters from 0.13 to 220 mm, particle diameters ranging from 104 to 15,000 m, bed temperatures up to 900/sup 0/C, and bed pressures up to 9.25 bars.
Abstract: A simple dimensionless correlation is presented and compared with data from 35 experimental studies. Data include spheres, horizontal and vertical cylinders, cylinder diameters from 0.13 to 220 mm, particle diameters from 104 to 15,000 ..mu..m, bed temperatures up to 900/sup 0/C, and bed pressures up to 9.25 bars. Fluidizing gases include air, helium, CO/sub 2/, H/sub 2/, and R-12. Particle densities range from 1986 to 11,340 kg/m/sup 3/ and p /SUB s/ C /SUB s/ from 1474 to 4173 kJ/m/sup 30/C. A total of 142 data points are correlated with a mean deviation of 17%. Complete tabulations are provided for all data analyzed. Application to tube bundles is discussed briefly.
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TL;DR: In this article, the transfer of heat and mass between a large sublimable object and a sand fluidized bed is studied in terms of both particle size and object diameter, and dimensional correlations are proposed to predict them.
13 citations
TL;DR: In this article, the authors investigated heat and mass transfer to or from single active particles surrounded by inert (passive) particles in a fluidized bed based on published correlations and found a suitable relationship, describing the size ratio of inert to active particles on heat transfer to/from particles in fluidized beds.
9 citations
TL;DR: In this article, a 26 mm i.d. smooth tube, horizontally immersed in a gas fluidized bed, is studied using particulate solids in the size range 70-161 μm and multiorifice distributors of different free area.
6 citations
TL;DR: In this article, a general correlation is presented for predicting maximum heat transfer coefficient for surfaces submerged in gas-fluidized beds, which has been verified with data for horizontal and vertical cylinders and spheres in beds of a wide variety of particles and gases.
6 citations
01 Jan 2007
TL;DR: In this paper, the effect of different bed material on the characteristics of fluidization and heat transfer between bed and immersed body was studied, and the evaluated parameters included: (1) different particle materials; (2) particle size; and (3) weight fraction of different particles.
Abstract: The heat transfer coefficient between sand bed and an immersed body is an important parameter in a fluidized bed incinerator. The characteristics of fluidization will be changed when ash accumulates during incineration. When the ash accumulates in the sand bed, the distribution of particle size and density will be changed to form different distributions. The distribution of particle size influences many operating parameters including mixing, minimum fluidization velocity, heat transfer coefficient and hydrodynamic behavior during incineration. Therefore, the accumulation of ash will influence the combustion efficiency or increase the generation of secondary pollutants. However, the effect of ash on fluidized behavior, such as heat transfer coefficient has rarely been investigated. In this study, the effect of different bed material on the characteristics of fluidization and heat transfer between bed and immersed body was studied. The evaluated parameters included: (1) different particle materials; (2) particle size; and (3) weight fraction of different particles. The results indicated that the fluidized behavior of a binary bed material was affected by weight fraction, particle size and density of the added material. Among these parameters, the weight fraction of added particle played an important role in influencing the fluidized behavior of the binary system. The sand bed to surface heat transfer coefficients at minimum fluidization velocity in the binary system was similar, when either Al2O3 or SiO2 was added. Since particle and gas convection was small, the effect of heat characteristics on heat transfer coefficient was insignificant. The addition of particles exhibited a higher density and larger size as well as increased concentration of bed materials, because the high density or large size increased the bed particle packing concentration at the same superficial gas velocity. The contact frequency between heat transfer surface and bed materials will increase significantly in enhancing heat transfer coefficient.
2 citations
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TL;DR: The behavior of solids fluidized by gases falls into four clearly recognizable groups, characterized by density difference (ϱs −ϱf) and mean particle size as discussed by the authors, and a numerical criterion which distinguishes between groups A and B has been devised and agrees well with published data.
3,007 citations
TL;DR: In this paper, a dimensionless correlation for predicting heat transfer coefficients during film condensation inside pipes is presented, which has been verified by comparison with a wide variety of experimental data.
1,304 citations
TL;DR: In this article, a modified packet model for heat transfer between a gas-fluidized bed and an immersed surface is presented, and the model readily explains the effect of particle moisture content, shape of the immersed body and other factors on bed to immersed body heat transfer.
196 citations