Correlation for Calculating Heat Transfer Coefficient in Conical Spouted Beds

Abstract

A correlation has been proposed for predicting local bed-to-surface heat transfer coefficients in conical spouted beds based on an experimental study conducted using beds made up of sand, sawdust, and their mixtures under various operating conditions, namely, different static bed heights and gas velocities over minimum spouting. A comparison of the results with those obtained using the correlations in the literature proved that they provide very poor predictions and, furthermore, they are not able to predict local coefficients in the bed. Based on a statistical analysis, the significant moduli have been identified in the relevant literature correlations and two new moduli related to the radial and longitudinal positions have been contemplated. The analysis identified two groups of heat transfer coefficients: those within the bed and those on its surface. The correlation proposed is specifically suitable for ascertaining the best location of heat transfer devices within the annulus of the spouted beds.

Physicochemical Analysis and Essential Oils Extraction of the Gorse (Ulex europaeus) and French Broom (Genista monspessulana), Two Highly Invasive Species in the Colombian Andes

“…Our results coincided with previous findings; for example, Saldarriaga et al [34] found an HHV of 19.43 MJ/kg for U. europaeus. We found high HHVs for all functional parts, very similar to those of pine sawdust, which is one of the most commonly used biomasses for thermal processes worldwide [39,[41][42][43]. In general, the volatile matter of both species was very high while the ash content was very low, which, according to Vassilev et al [41], is important because where there is a higher volatile content in a thermal process, the yield of biomass includes light hydrocarbons, CO, CO 2 , H 2 , moisture and tars.…”

Modelling of Spouted and Spout-Fluid Beds: Key for Their Successful Scale Up

“…Following the unsatisfactory agreement between the correlations available in literature to describe the local heat transfer coefficients in SB reactors (mandatory for the correct design of drying processes), a new expression was obtained by Saldarriaga et al [252] using a bed of sand and sawdust inside a conical SB reactor. The model was found valid for the definition of the most adequate position of heat transfer devices within the annulus of the reactor.…”

Empirical Correlation for Calculating the Pressure Drop in Microhydrocyclones

“…This procedure continues until all of the significant regressors are inserted into the correlation. Figure 7 shows the flow diagram of the algorithm written in Scilab, which has been adapted from that by Saldarriaga et al 50,51 The methodology described for regression analysis has been applied to eqs 1−6. Overall, this strategy improved the fit quality of the correlations for predicting the capacity curves of the microhydrocyclones studied in this paper, but acceptable fit levels were not attained.…”

“…Given that the fit quality of the correlations in the literature is not suitable, modifications in their proportionality and/or exponential coefficients should be tried to improve their predictions. To that end, a methodology has been used based on that established by Saldarriaga et al , for proposing correlations for the minimum operational velocity and heat-transfer coefficients in conical spouted beds. This methodology is based on the combination of multivariate regression and optimization techniques for the stepwise minimization of the residual error according to significance tests applied to the coefficients.…”