Heat transfer coefficients in a high-pressure bubble column

Estimation of heat transfer coefficient in bubble column reactors using support vector regression

“…The values of h measured at the centre of the column, are relatively higher than those measured at the column wall. The reason for this difference lies with the predominant existence of the large size, high rise velocity bubbles at the centre (relatively high turbulence zone) of the column, and small size, having low rise velocity bubbles (relatively low turbulence zone) at the column wall [11,25]. This has been explained by a direct connection of the local heat transfer coefficient to the bubble size: it increases with an increase in bubbles size, because large bubbles can create strong vortices and intense mixing in the wake region [21].…”

Bioreactors: Airlift Reactors

“…In general, and as expected from the radial distribution of bubbles and of liquid velocities, the values of the heat transfer coefficient at the center are of the order of 10% higher than that at the walls. High pressure produces a decrease in these coefficients (281).…”

Heat transfer study in a pilot-plant scale bubble column

“…The knowledge and understanding of heat transfer phenomena in bubble columns and quantifying the heat transfer rates and coefficients are important since they are required for proper, safe and efficient design and operation of these reactors. Significant studies on heat transfer in bubble columns have been conducted and reported in the literatures (Wu et al, 2007;Wu, 2008). In general, these studies can be divided into: (i) estimation of wall-to-bed heat transfer and (ii) estimation of inserted objects-to-bed heat transfer.…”

“…Most of these studies measured the time-averaged local heat transfer coefficients (i.e. a certain point location inside the column) Prakash, 2001, 2002;Kantarci et al, 2005;Wu et al, 2007). It is noteworthy that the local time-averaged heat transfer coefficients and their radial profiles or cross-sectional distribution provide valuable insight into the mechanisms of heat transfer …”

“…In addition, the bubble dynamics and liquid circulation intensity in bubble column can be qualitatively assessed using such measurements. Heat transfer coefficients in bubble columns have been measured based on the measurement of energy input using slow response assembly probe (Saxena and Chen, 1994) and based on the measurement of the direct heat flux using fast response sensor (Wu et al, 2007). In general, most of these studies were performed using up to 0.16 m column diameter and hence, heat transfer rate and coefficient are still not well characterized in larger scale bubble columns where wall effects are further diminished.…”