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Characteristics of heat transfer on the horizontal tube bundles of 90 MM diameter in a fluidized bed
Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics 167 a single spherical capsule and its packed bed. Heat storage and release experiments of single encapsulated (phase change materials) (PCMs) were conducted in the temperature range from 500 to 1100 K. Six kinds of materials were selected as PCM, two were inorganic materials and four were metallic materials, representing higher energy density, chemical stability, nontoxicity, and cost performance. Encapsulated PCMs were heated for heat storage and then cooled for heat release by nitrogen gas as heat transportating material under the condition of predominant convective heat transfer. Temperature distribution within PCM was measured and discussed theoretically. To design the packed bed for heat storage, which consisted of spherical capsule with PCM, gas flow, and heat transfer, simulation was conducted under various operating conditions. The packed bed for heat storage of waste gas in the high temperature range was optimized from four viewpoints: PCM property, ratio of PCM diameter to bed diameter, blowing direction, and blowing rate.
Packed Bed Performance: Effect of Packing Size and Shape E. A. Foumeny S. Bhatti
Department of Chemical Engineering University of Leeds Leeds, United Kingdom Transport properties of packed bed reactors are generally expressed in terms of Reynolds number. Recent advances in computational and measurement techniques have revealed the significance of particle properties on the structural characteristics of packed beds. An experimental setup was designed to provide temperature profiles within given beds of desired particles. This approach enables the effects of gas flow rate as well as particle size and shape on the thermal behavior of packed beds to be examined. This contribut~ia demonstrates the sensitivity of the thermal performance of packed beds to their structural parameters.
Characteristics of Heat Transfer on the Horizontal Tube Bundles of 90 MM Diameter in a Fluidized Bed Y. Katoh M. Miyamoto
Department of Mechanical Engineering Yamaguchi University Tokiwadai, Ube, Japan Y. Idei
Research and Development Division UBE Industry Co. Ltd. Okinoyama, Ube, Japan This report presents the characteristics of the time averaged heat transfer coefficients and the local heat transfer coefficients on the four rows of the horizontal tube bundles in a fluidized bed. We have especially dealt with the relatively large tube diameter of 90 mm for two kinds of fluidized particles such as alumina of 0.55 mm diameter and silica sand of 0.4 mm diameter. A rectangular test chamber consists of a 400 X 400 mm cross sectional area, height 1020 mm. This study was carried out on the two locations of the first row tubes (X1 = 110, 250 mm) from the distributor with various superficial gas velocities (Uo)
and static bed heights (Lc). We found that when X1 was in a higher location the values of the average heat transfer coefficient (Hx) increased. After the Hx has taken the maximum value, it will remain at the same value or will start to decrease. For the case of the different particle, there was qualitatively a similar shape of distribution but some differences quantitatively in values. In the comparison between the results of the 34 mm and 90 mm tubes' diameter, there are many differences in the distribution of local heat transfer and of the average Hx and these take some different values at similar conditions.
Experimental Heat-Transfer Coefficient Between an Immersed Body and a Gas Fluidized Bed at High Temperature: Effect of Particle Size Distribution and Body Shape Leonardo Goldstein Jr. R. Galvani F. L. Fassani UNICAMP-FEM-DETF
Campinas, SP, Brazil G. Lombardi J. D. Pagliuso USP-EESC-DHS
S~o Carlos, SP, Brazil Existing data on heat transfer between an immersed body and a gas fluidized bed are usually related to immersed tubes, tube bundles, or to water-cooled probes, and generally are not extended to temperatures on the order of 850°C. This work presents results for the total heat-transfer coefficient between spheres and cylinders and a gas fluidized bubbling bed at 850-900°C, heated by burning propane inside the bed. The effects of particle-size distribution and body shape are analyzed.
Analysis of the Heat-Transfer Coefficients by Pseudohomogeneous Modeling in Fixed Beds J. C. Thom~o
Departamento de Engenharia e Tecnologia de Alimentos Universidade Estadual Paulista S. J. Rio Preto, SP, Brazil J. T. Freire A. M. Silveira
Departamento de Engenharia Qulmica Universidade Federal de S~o Carlos, Sdo Carlos, SP, BR Studies were carried out on heat transfer in packed beds percolated by air and by a concurrent ascending air-water mixture at moderate fluid flows. The temperatures at the boundaries of the bed were measured and their influence on the heat parameters calculated by means of the pseudohomogeneous model. Data analysis was carried out using three formulations of the model, two being traditional ones, which impose flat temperature and fluid rate profiles at the inlet of the bed and the other which admits a radial variation of the fluid rates and of To. Results for one-phase flow indicate that the latter formulation gives constant effective radial heat conductivity (Kr) values at any height of the bed, which does not occur with the other formulations, indicating that the entrance effects are a combination of poorly represented heat boundary and wall effects.
Packed Bed Performance: Effect of Packing Size and Shape E. A. Foumeny S. Bhatti
Department of Chemical Engineering University of Leeds Leeds, United Kingdom Transport properties of packed bed reactors are generally expressed in terms of Reynolds number. Recent advances in computational and measurement techniques have revealed the significance of particle properties on the structural characteristics of packed beds. An experimental setup was designed to provide temperature profiles within given beds of desired particles. This approach enables the effects of gas flow rate as well as particle size and shape on the thermal behavior of packed beds to be examined. This contribut~ia demonstrates the sensitivity of the thermal performance of packed beds to their structural parameters.
Characteristics of Heat Transfer on the Horizontal Tube Bundles of 90 MM Diameter in a Fluidized Bed Y. Katoh M. Miyamoto
Department of Mechanical Engineering Yamaguchi University Tokiwadai, Ube, Japan Y. Idei
Research and Development Division UBE Industry Co. Ltd. Okinoyama, Ube, Japan This report presents the characteristics of the time averaged heat transfer coefficients and the local heat transfer coefficients on the four rows of the horizontal tube bundles in a fluidized bed. We have especially dealt with the relatively large tube diameter of 90 mm for two kinds of fluidized particles such as alumina of 0.55 mm diameter and silica sand of 0.4 mm diameter. A rectangular test chamber consists of a 400 X 400 mm cross sectional area, height 1020 mm. This study was carried out on the two locations of the first row tubes (X1 = 110, 250 mm) from the distributor with various superficial gas velocities (Uo)
and static bed heights (Lc). We found that when X1 was in a higher location the values of the average heat transfer coefficient (Hx) increased. After the Hx has taken the maximum value, it will remain at the same value or will start to decrease. For the case of the different particle, there was qualitatively a similar shape of distribution but some differences quantitatively in values. In the comparison between the results of the 34 mm and 90 mm tubes' diameter, there are many differences in the distribution of local heat transfer and of the average Hx and these take some different values at similar conditions.
Experimental Heat-Transfer Coefficient Between an Immersed Body and a Gas Fluidized Bed at High Temperature: Effect of Particle Size Distribution and Body Shape Leonardo Goldstein Jr. R. Galvani F. L. Fassani UNICAMP-FEM-DETF
Campinas, SP, Brazil G. Lombardi J. D. Pagliuso USP-EESC-DHS
S~o Carlos, SP, Brazil Existing data on heat transfer between an immersed body and a gas fluidized bed are usually related to immersed tubes, tube bundles, or to water-cooled probes, and generally are not extended to temperatures on the order of 850°C. This work presents results for the total heat-transfer coefficient between spheres and cylinders and a gas fluidized bubbling bed at 850-900°C, heated by burning propane inside the bed. The effects of particle-size distribution and body shape are analyzed.
Analysis of the Heat-Transfer Coefficients by Pseudohomogeneous Modeling in Fixed Beds J. C. Thom~o
Departamento de Engenharia e Tecnologia de Alimentos Universidade Estadual Paulista S. J. Rio Preto, SP, Brazil J. T. Freire A. M. Silveira
Departamento de Engenharia Qulmica Universidade Federal de S~o Carlos, Sdo Carlos, SP, BR Studies were carried out on heat transfer in packed beds percolated by air and by a concurrent ascending air-water mixture at moderate fluid flows. The temperatures at the boundaries of the bed were measured and their influence on the heat parameters calculated by means of the pseudohomogeneous model. Data analysis was carried out using three formulations of the model, two being traditional ones, which impose flat temperature and fluid rate profiles at the inlet of the bed and the other which admits a radial variation of the fluid rates and of To. Results for one-phase flow indicate that the latter formulation gives constant effective radial heat conductivity (Kr) values at any height of the bed, which does not occur with the other formulations, indicating that the entrance effects are a combination of poorly represented heat boundary and wall effects.