Annals of the Assembly for International Heat Transfer Conference 13
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ARTICLE:
K. Murata K. Araga ABSTRACT It is known that small quantities of surfactant additives can greatly reduce the friction factors during the flow of a heat transfer medium. This is because the generation of turbulent vortexes is suppressed by the formation of rod-like micelles, and the flow remains laminar in the larger Reynolds number range. However, the values of the heat transfer coefficients decrease during flow laminarization; this would result in a requirement for heat exchangers with a larger heat transfer area. This paper presents an experimental investigation on the heat transfer characteristics in an air-surfactant solution two-phase flow through tubes. The research objective is to examine heat transfer enhancement effects by air injection. The experimental results may be summarized as follows: 1) Heat transfer coefficients were enhanced drastically with the injection of air into a drag-reducing surfactant solution flow. The enhancement rates were much larger for the surfactant solution than for water. 2) Heat transfer coefficients were smaller for an air-surfactant solution flow than for an air-water flow due to the drag-reducing effects. However, as the gas quality increased, the heat transfer coefficients for air-surfactant solution flow approached those for air-water flow. It is inferred from these experimental results that the injected air can not only cause flow mixing but also break the rod-like micelles in the surfactant solution; furthermore, the amount of micelles in the liquid phase decreases since some surfactant additives accumulate at the gas-liquid interface. MPH-07 pages |
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