A MODEL OF RADIATIVE HEAT TRANSFER IN HIGH TEMPERATURE FLUIDIZED BEDS

1990 ◽  
Author(s):  
Yunsheng Xu ◽  
Renzhang Qian
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Radiative Heat Transfer ◽  
Fluidized Beds ◽  
Radiative Heat

Analysis of the Heat Transfer Mechanism in High-Temperature Circulating Fluidized Beds by a Numerical Model

2002 ◽  
Vol 124 (1) ◽  
pp. 34-39 ◽  
Author(s):  
Qiao He ◽  
Franz Winter ◽  
Ji-Dong Lu
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Radiative Heat Transfer ◽  
Fluidized Beds ◽  
Radiative Heat ◽  
Total Heat ◽  
Circulating Fluidized Beds ◽  
Total Heat Transfer

A general numerical model is presented here to describe the complex fluid dynamics and the heat transfer process in high-temperature circulating fluidized beds (CFBs). The core-wall concept is used to describe the gas-solid flow in the dilute phase section of CFBs. The variation of the thickness of the wall layer along the height direction is considered in the fluid dynamic model in order to approach the practical conditions. Three components of heat transfer, i.e., the particle-convective heat transfer, the gas-convective heat transfer, and the radiative heat transfer, and their contributions to the total heat transfer coefficient are investigated. The influences of some operating parameters on the total heat transfer and its components are predicted. Detailed information about the mechanism of heat transfer is discussed. The radiative heat transfer accounts for about 30∼60% of the total heat transfer in high temperature CFBs. It gradually increases along the height direction of the furnace. When the contribution of particle convection increases, the contribution of gas convection decreases, and vice versa. Particle size shows a significant effect on the radiative heat transfer and the convective heat transfer. High bed and wall temperatures will primarily increase the radiative heat transfer.

scholarly journals The Treatment of Nongray Properties in Radiative Heat Transfer: From Past to Present

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Michael F. Modest
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Radiative Heat Transfer ◽  
Historical Development ◽  
Radiative Heat ◽  
State Of The Art ◽  
Participating Media ◽  
Box Models ◽  
Property Data ◽  
Gradual Development

Radiative heat transfer in high-temperature participating media displays very strong spectral, or “nongray,” behavior, which is both very difficult to characterize and to evaluate. This has led to very gradual development of nongray models, starting with primitive semigray and box models based on old experimental property data, to today's state-of-the-art k-distribution approaches with properties obtained from high-resolution spectroscopic databases. In this paper a brief review of the historical development of nongray models and property databases is given, culminating with a more detailed description of the most modern spectral tools.

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