Heat Transfer in a Fluidized Bed with Immersed Tubes Using Moist Coal Particles

The moisture content of coal (MCC) has an important effect on the thermophysical properties and the granular flowability. However, it brings both active and negative influence to the heat transfer between the fluidizing moist coal and the immersed tubes in the fluidized bed. Four groups of bituminous coal with same size distribution (0.25–2.8 mm) but different MCC (7.86–15.18%) have been examined to study the variation of the heat transfer in an experimental setup. The average heat transfer coefficients (havg)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(h_{\mathrm{avg}})$$\end{document} for the four groups of test samples have the same changing trend by increasing the superficial velocity (Ug)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(U_{\mathrm{g}})$$\end{document}. However, the maximum heat transfer coefficients (hmax)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(h_{\mathrm{max}})$$\end{document} display different peak values. With the increase in MCC, the hmax\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$h_{\mathrm{max}}$$\end{document} rises at first and begins to fall when reaching a critical value. To predict the havg\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$h_{\mathrm{avg}}$$\end{document} accurately with different MCC, the angle of repose has been imported to measure the variation of the granular flowability. A novel semiempirical correlation has been thereupon proposed by the dimensional analysis, and it accords well to the experimental data from this study and the previous research.