Effective thermal conductivity and internal thermal radiation in burning black liquor particles

2003 ◽  
Vol 175 (5) ◽  
pp. 873-900 ◽  
Author(s):  
M. P. Järvinen* ◽  
R. Zevenhoven ◽  
E. K. Vakkilainen ◽  
M. Forssén
Keyword(s):  
Thermal Conductivity ◽  
Thermal Radiation ◽  
Effective Thermal Conductivity ◽  
Black Liquor

Modeling Effective Thermal Conductivity of Thermal Radiation for Nuclear Packed Pebble Beds

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Hao Wu ◽  
Nan Gui ◽  
Xingtuan Yang ◽  
Jiyuan Tu ◽  
Shengyao Jiang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Radiation ◽  
Effective Thermal Conductivity ◽  
Transfer Cells ◽  
Transfer Model ◽  
Radiation Model ◽  
Radial Temperature ◽  
Effective Heat ◽  
Good Agreement

In nuclear packed pebble beds, it is a fundamental task to model effective thermal conductivity (ETC) of thermal radiation. Based on the effective heat transfer cells of structured packing, a short-range radiation model (SRM) and a subcell radiation model (SCM) are applied to obtain analytical results of ETC. It is shown that the SRM of present effective heat transfer cells are in good agreement with the numerical simulations of random packing and it is only slightly higher than empirical correlations when temperature exceeds 1200 °C. In order to develop a generic theoretical approach of modeling ETC, the subcell radiation model is presented and in good agreement with Kunii–Smith correlation, especially at very high temperature ranges (over 1500 °C). Based on SCM, one-dimensional (1D) radial heat transfer model is applied in the analysis of the HTTU experiments. The results of ETC and radial temperature distribution are in good agreement with the experimental data.

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.

Sign in / Sign up

Export Citation Format

Share Document