Radiation Heat Transfer Between Fluidizing Particles and a Heat Transfer Surface in a Fluidized Bed

2001 ◽  
Vol 123 (3) ◽  
pp. 458-465 ◽  
Author(s):  
Jun Yamada ◽  
Yasuo Kurosaki ◽  
Takanori Nagai
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Radiation Heat Transfer ◽  
Particle Diameter ◽  
Heat Transfer Surface ◽  
Experimental Results ◽  
Optical Characteristics ◽  
Radiation Heat ◽  
Higher Temperature

We have investigated the radiation heat transfer occurring in a gas-solid fluidized bed between fluidizing particles and a cooled heat transfer surface. Experimental results reveal that cooled fluidizing particles exist near the surface and suppress the radiation heat transfer between the surface and the higher temperature particles in the depth of the bed. The results also clarify the effects of fluidizing velocity, optical characteristics of particles, and particle diameter on the radiation heat transfer. Based on these results, the authors propose a model for predicting the radiation heat transfer between fluidizing particles and a heat transfer surface.

Thermal radiation and conduction properties of materials ranging from sand to rock-fill

2011 ◽  
Vol 48 (4) ◽  
pp. 532-542 ◽  
Author(s):  
Marie-Hélène Fillion ◽  
Jean Côté ◽  
Jean-Marie Konrad
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Radiation ◽  
Effective Thermal Conductivity ◽  
Radiation Effects ◽  
Radiation Heat Transfer ◽  
Experimental Results ◽  
Radiation Heat ◽  
Rock Fill

This paper presents an experimental study on thermal radiation and the thermal conductivity of rock-fill materials using a 1 m × 1 m × 1 m heat transfer cell. Testing temperatures are applied by temperature-controlled fluid circulation at the top and bottom of the sample. Heat flux and temperature profiles are measured to establish the effective thermal conductivity λe, which includes contributions from both conduction and radiation heat transfer mechanisms. The materials studied had an equivalent particle size (d10) ranging from 90 to 100 mm and porosity (n) ranging from 0.37 to 0.41. The experimental results showed that thermal radiation greatly affects the effective thermal conductivity of materials with λe values ranging from 0.71 to 1.02 W·m−1·K−1, compared with a typical value of 0.36 W·m−1·K−1 for conduction alone. As expected, the effective thermal conductivity increased with particle size. An effective thermal conductivity model has been proposed, and predictions have been successfully compared with the experimental results. Radiation heat transfer becomes significant for d10 higher than 10 mm and predominant at values higher than 90 mm. The results of the study also suggest that the cooling potential of convection embankments used to preserve permafrost conditions may not be as efficient as expected because of ignored radiation effects.

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