Maximum heat-transfer coefficient for an immersed body in a bubbling fluidized bed

Abstract

The heat-transfer coefficient between the bed and an immersed body is an important parameter for determining the surface temperature of a body, which affects the rate of combustion, reaction, drying, or heat treatment. In this paper the following simple correlation for the maximum heattransfer coefficient, hap,, was obtained within the accuracy of +70% and -50% by a comprehensive data set covering a wide range of operating conditions (d = 0.08-3 mm, d, = 4-60 mm, temperature = 293-1323 K and pressure = 0.1-8.1 MPa): Nu,,,, p R,,,d,/k, = (d,/d,)O.*, where d,, d,, and k,are particle diameter, body diameter, and effective thermal conductivity of a bed. In this correlation, k, was used instead of gas thermal conductivity. The correlation was successfully validated. Eleven previous correlations were tested and evaluated by the same data set.

Drying characteristics of porous material immersed in a bed of hygroscopic porous particles fluidized under reduced pressure

“…The calculated results by the equation of Tsukada and Horio (1992) were in good agreement with the experimental data of the heat transfer coefficient. A mass transfer coefficient for the surface evaporation k H was determined from the experimental data of surface evaporation rate in the case of inert particles (glass beads), i.e., the value of k H was obtained from the drying rate at the earlier period of drying.…”

“…The heat transfer coefficient on the sample surface was calculated from the following equation (Tsukada and Horio, 1992):…”

Magnetic tracking of a fuel particle in a fluid-dynamically down-scaled fluidised bed

“…In indirect gasification units, this leads to a product gas of reduced quality and a thermal unbalance in the dual fluidized bed system, whereas in chemical looping combustion, this creates more stringent requirements for the performance of the carbon strippers to avoid CO 2 emissions. Further, for both combustion and gasification, axial segregation of fuel is relevant in that fuel particles that segregate to the bed surface experience a higher mass transfer with the surrounding bed [35] while the heat transfer is decreased [36]. Moreover, it has been shown experimentally that the reduced heat transfer experienced by segregated fuel decreases the char reactivity [37].…”

Experimental study of fixed and fluidized beds of PCM with an internal heat exchanger

“…In contrast, the heat transfer coefficient of the sand linearly increases to the maximum tested flow rate of 1000 l/min. The flow rate that obtains the maximum heat transfer coefficient can be estimated according to Todes' correlation [22][23][24]:…”