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Flow and Heat Transfer Characteristics of Ammonium Alum Hydrate Slurries with Surfactants as Drag-Reducers and with Polyvinyl Alcohol as Stabilizers

DOI: 10.1615/IHTC15.fcv.009469
pages 3017-3030

Ruri Hidema
Kobe University

Hiroshi Suzuki
Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan

Takuya Tano
Kobe University

Yoshiyuki Komoda
Department of Chemical Science and Engineering, Kobe University, Kobe, Japan

KEY WORDS: Convection, Energy conversion and storage, Phase change materials, Drag reduction, Sedimentation


A slurry containing aluminum ammonium sulfate disodium dodecahydrate (ammonium alum hydrate) at the concentration of 35 wt% is recently proposed as a promising material for latent heat transportation systems at higher temperature than 50oC. However, there exist two big problems to the ammonium alum hydrate slurry, that is, the sedimentation of the hydrate particles and low fluidity due to increase of the viscosity. In order to solve these problems, effects of drag-reducing surfactants and poly(vinyl alcohol) (PVA) on the hydrate slurry were analysed. Viscosities of the hydrate solution and slurry with and without the surfactant and PVA were measured to know the formation of rod-like micelles of the surfactants. Sedimentation and particle growth of the hydrate particles in solution with and without the surfactant and PVA were also observed. From the results, it was found that PVA does not disturb the formation of rod-like micelles. On the contrary, PVA enhances the effect of surfactants on the sedimentation and on preventing the particle growth. Friction and heat transfer coefficients of the hydrate solution and the slurry were measured. Drag-reducing surfactant effectively reduces the friction coefficient, which was not disturbed by PVA. While the heat transfer coefficient was decreased by adding the surfactant and PVA, the value of the Colburn’s j-factor divided by the friction coefficient was higher than that of the hydrate solution or the slurry without the surfactant and PVA. Thus, the fluidity and heat transfer of the hydrate slurry can be improved by adding the surfactant and PVA at an appropriate concentration.

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