Experimental Investigation of Heat Transfer and Flow Mixing in Pebble Beds

Characteristics of convective heat transport in a packed pebble-bed reactor

“…In the open literature, the heat transfer data were obtained by direct measurements (in which the component particles are heated separately) and indirect means (by involving the transient heating of fluid or mass transfer experiments). On the other hand, the measurement techniques applied for packed pebble-bed heat transfer are as follows: (1) the electrically heated single sphere buried in the unheated packing (Achenbach, 1982(Achenbach, , 1995Schroder et al, 2006;Rimkevicius et al, 2006;Rimkevicius and Uspuras, 2008;Rousseau and van Staden, 2008); (2) mass transfer analogy and simultaneous heat and mass transfer (Achenbach, 1982(Achenbach, , 1995; and (3) the regenerative heating technique, which is based on the concept of unsteady heat transfer of a heated sphere in a packed pebble bed through which a cooling fluid flows (Hoogenboezem, 2007). In addition, semi-empirical methods (Gnielinski, 1978; and recently computational and theoretical models Laurien, 2001, 2003;Yesilyurt and Hassan, 2003;Lee et al, 2007;Stainsby et al, 2008Stainsby et al, , 2010aKim et al, 2010;du Toit and Rousseau, 2012) were used to predict the heat transfer rate and coefficients in pebble-bed reactors.…”

“…The surface temperature was taken to be the arithmetic average of the readings of three or four thermocouples, where their tips were flushed with the sphere surface (Rimkevicius et al, 2006;Hoogenboezem, 2007). In addition, the mass transfer analogy experiments are difficult and not an accurate as direct heat transfer measurements.…”

Experimental and Pore-Scale Analysis of Flow and Thermal Fields in a Packed Bed Channel

“…They reported with the same inlet velocity, the pressure drop and heat transfer in the packed bed with dimple particles would be lower than those in the packed bed with smooth particles. Heat transfer and fluid flow behaviors in pebble beds [3] and packed beds with spherical spheres [4] and packed beds of shredded materials [5] were studied experimentally to understand the effect of different arrangements of particles in the media. One of the key practical applications of this problem is packed bed thermal energy storage system in which the efficiency of the system is directly affected by the convective heat transfer between these two phases [6].…”