A New Method for Flow Regime Identification in a Fluidized Bed Based on Gamma-Ray Densitometry and Information Entropy

Abstract

The accurate identi cation of the boundaries of the main ow regimes in uidized beds is very important since the degrees of mixing and mass and heat transfer depend on the prevailing ow regime. Both the minimum uidization velocity U mf (0.103 m•s 1 ) and the transition velocity U trans (0.12 m•s 1 ) to bubbling uidization regime have been successfully identi ed based on a newly developed maximum information entropy (IE max ) algorithm applied to gamma photon time series. The latter are recorded by means of gamma-ray densitometry scans performed in an air-polyethylene uidized bed (0.438 m in ID) operated at ambient conditions. A comparison with the Kolmogorov entropy (KE) algorithm has found that the new approach yielded more accurate transition velocities. The value of U mf is also validated by means of the pro les of both bed pressure drop and bed height, respectively. It has been found, however, that these parameters are not capable of identifying the second transition velocity U trans . It is demonstrated that the U mf value identi ed on the basis of IE max is theoretically predictable. In the bubbling uidization regime, a simple correlation between both the KE and IE max values is developed.

New methods for flow regime identification in bubble columns and fluidized beds

“…An electric steam humidifier was used to control the relative humidity of the inlet gas in order to eliminate the electrostatic charges caused by the flowing particles. More details about the experimental setup are available in Nedeltchev et al (2012).…”

“…Beyond that U G value the bed height increased monotonously up to 1.21 m (at U G ¼ 0.275 m/s). The results for both the pressure drop and bubble bed height were presented in Nedeltchev et al (2012). The fully developed bubbling fluidization regime begins at U G ¼0.172 m/s and is characterized with the monotonous decrease of the IE values.…”

Flow Regimes in Gas‐Solid Fluidized Beds via Micro‐Foil Heat Flux Sensor

“…The five repetitions are also allowed to determine the error bars shown in the following results figures. and Van Ommen et al [29], while for the KE analysis, a local minimum of the heat flux oscillation indicates a transition velocity [32,34]. In other words, the KE increase when raising the superficial gas inlet velocity implies that the system disorder or the chaotic behavior of the system is incrementing.…”

“…KE was calculated based on the maximum likelihood estimation of entropy, as described by Schouten et al [31] and Nedeltchev et al [32,33]:…”

Detecting stability of conical spouted beds based on information entropy theory

“…The approach followed in this work was based on a new applicable definition of the information entropy and it was employed to quantify the stability of the bed. The employed information entropy algorithm is extensively described by Nedeltchev et al [32][33][34][35][36][37]. In this algorithm, minimum and maximum of each pressure fluctuations time series were determined.…”