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Radiation Heat Transfer (radiation + heat_transfer)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

MONTE CARLO SIMULATION OF FAR INFRARED RADIATION HEAT TRANSFER: THEORETICAL APPROACH

JOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2006
F. TANAKA
ABSTRACT We developed radiation heat transfer models with the combination of the Monte Carlo (MC) method and computational fluid dynamic approach and two-dimensional heat transfer models based on the fundamental quantum physics of radiation and fluid dynamics. We investigated far infrared radiation (FIR) heating in laminar and buoyancy airflow. A simple prediction model in laminar airflow was tested with an analytical solution and commercial software (CFX 4). The adequate number of photon tracks for MC simulation was established. As for the complex designs model, the predicted results agreed well with the experimental data with root mean square error of 3.8 K. Because food safety public concerns are increasing, we applied this model to the prediction of the thermal inactivation level by coupling with the microbial kinetics model. Under buoyancy airflow condition, uniformity of FIR heating was improved by selecting adequate wall temperature and emissivity. [source]

Fundamental heat transfer mechanism between bed-to-membrane water-walls in circulating fluidized bed combustors

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2003
B.V. Reddy
Abstract In the present work, the fundamental mechanism between bed-to-membrane water-walls in the riser column of a circulating fluidized bed (CFB) combustor is presented. The bed-to-membrane water-wall heat transfer depends on the contributions of particle heat transfer, dispersed phase heat transfer and radiation heat transfer. The fundamental mechanism of particle heat transfer and the effect of fraction of wall exposed to clusters and gas gap thickness between cluster and wall on particle heat transfer coefficient and bed-to-wall heat transfer coefficient are investigated. The influence of operating parameters like cross-sectional average volumetric solids concentration and bed temperature on particle and bed-to-wall heat transfer are also reported. The present work contributes some fundamental information on particle heat transfer mechanism, which is responsible for increasing the bed-to-wall heat transfer coefficient (apart from dispersed phase convection and radiation heat transfer). The details on particle heat transfer mechanism will enable to understand the basic heat transfer phenomena between bed-to-membrane water-walls in circulating fluidized bed combustors in a detailed way, which in turn will aid for better design of CFB combustor units. The particle heat transfer mechanism is significantly influenced by the fraction of wall exposed to clusters and gas gap thickness between clusters and wall. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Ablative heat transfer in a shrinking packed-bed of ZnO undergoing solar thermal dissociation

AICHE JOURNAL, Issue 7 2009
L. O. Schunk
Abstract A transient heat transfer model is formulated for a shrinking packed-bed of reacting ZnO particles exposed to concentrated solar irradiation. The model combines conduction, convection, and radiation heat transfer with simultaneous sintering and reaction kinetics. Validation is accomplished in terms of temperatures and dissociation rates experimentally measured using a solar-driven thermogravimeter with ZnO packed-bed samples subjected to solar flux concentration ratios in the range 1225,2133 suns and surface temperatures in the range 1834,2109 K. Operating conditions are typical of an ablation regime controlled by the rate of radiative heat transfer to the first layers of ZnO undergoing endothermic dissociation. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Hydrogen generation in a reverse-flow microreactor: 1.

AICHE JOURNAL, Issue 8 2005
Model formulation, scaling
Abstract A 1-D model for methane partial oxidation in a tubular microreactor is considered. This work is motivated by a recent report by Kikas et al. that experimentally demonstrated the possibility of autothermal generation of hydrogen by partial oxidation of methane in a tubular microreactor. The reactor consists of four cylindrical channels, each 500 microns in diameter, containing Pt/13%,Rh catalyst. Autothermal generation of hydrogen was possible in both unidirectional (UD) and reverse-flow (RF) operations of the reactor, with the RF operation providing better hydrogen yield and lower temperatures than those of the UD operation. Critical comparison of methane oxidation and reforming kinetics from the literature is performed. An analysis of the timescales of individual processes within the reactor is presented to gain fundamental insight into the reactor operation. Finally, the effect of radiation heat transfer is also considered, and it is found to play an important role for a shorter-size reactor. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]