Wall-to-Suspension Heat Transfer in a CFB Downcomer

Table 1

Literature review of downcomer operation and heat transfer.

Van de Velden et al., 2008 and 2010 [21, 22]	The downcomer of a CFB is used to supply the endothermic heat of pyrolysis of biomass (450–550°C), through wall-to-sand preheating
Brems et al., 2013 [14]	The downcomer of a CFB pyrolysis reaction of solid (wall-to-bed) plastic waste can be used to supply the endothermic heat of pyrolysis by heating the sand carrier to appropriate temperatures
Baumann et al., 2012 and 2014 [26, 27]	The effect of powder properties on their use as heat transfer media in a moving bed heat exchanger (with embedded tubes) was investigated in view of concentrated solar power applications
Baird et al., 2008 [28]	Empirical and model fittings of experimental data from the wall to a moving bed of nickel pellets were investigated
Zhang et al., 1999 [29]	Characterization of local and overall gas-solid flow structure by measuring the distribution of local solids holdups and pressure gradients along the downcomer
Zhang and Zhu, 2000 [30]	Local solids fluxes were also calculated from the local particle velocities and solids holdups
Ball and Zhu, 2001 [31]	The effect of gas velocity, solids circulation rate, and axial and radial positions on the local solids flux in a gas-solids downcomer of a fluidized bed
Chen and Li, 2004 [32]	Probability density distribution was studied through low and high density downcomer operations and confirmed that solids flux is affecting the solids holdup
Lehner and Wirth, 1999 [33]	Experimental investigations concerning the local and cross-sectional solids distribution were conducted under different operating conditions and with different solids
Kim et al., 2001 [34]	The effects of operative conditions of subbituminous coal gasification in a downcomer reactor were experimentally determined
Ma and Zhu, 1999 [35]	Local heat transfer was investigated in a gas-solid concurrent downflow downcomer of a fluidized bed with FCC particles. HTC is closely related to the hydrodynamics, with bed suspension density being the most influential factor
Tamarin and Gorbachev, 1968 [36]	Heat transfer coefficient between a bed of moving slag particles and a vertical surface was experimentally determined in several gas atmospheres
Kim et al., 1999 [37]	Bed-to-wall heat transfer coefficient was determined in a downcomer reactor and results showed suspension density, gas convection, and particle size as influential factors. A model was proposed to predict the bed-to-wall HTC
Lehner and Wirth, 1999 [38]	The effect on the local and overall solids circulation in a downcomer was studied for various gas/solids distributors
Obuskovic, 1988 [39]	HTC was measured for a single vertical tube immersed in a moving packed bed of glass beads, sand, or copper in air at atmospheric pressure in order to obtain a general predictive equation
Peters and Dziugys, 2012 [40]	Heat transfer prediction in a fixed and moving packed bed by extended discrete element method
Basu et al., 2013 [41]	Investigation of heat transfer to cross and vertical tubes in a standpipe of a circulating fluidized bed boiler. A model provides a fair agreement with experimental results
Niegsch et al., 1994 [42]	The heat transfer of a steam heated tube bundle in a moving bed was investigated. Detailed heat transfer phenomena were described and a modelling approach was proposed
Meier et al., 2009 [43]	An alternative solution to heat and mass transfer problems was presented, by casting the system of equations into a matrix of the Sturm-Liouville type