Abstract
Data in the literature on the influence of water temperature on the terminal velocity of a single rising bubble are highly contradictory. Different variations in bubble velocity with temperature are reported even for potentially pure systems. This paper presents a systematic study on the influence of temperature between 5 °C and 45 °C on the motion of a single bubble of practically constant size (equivalent radius 0.74 ± 0.01 mm) rising in a clean water and n-pentanol solution of different concentrations. The bubble velocity was measured by a camera, an ultrasonic sensor reproduced in numerical simulations. Results obtained by image analysis (camera) were compared to the data measured by an ultrasonic sensor to reveal the similar scientific potential of the latter. It is shown that temperature has a significant effect on the velocity of the rising bubble. In pure liquid, this effect is caused only by modifying the physicochemical properties of the water phase, not by changing the hydrodynamic boundary conditions at the bubble surface. In the case of the solutions with surface-active substances, the temperature-change kinetics of the dynamic adsorption layer formation facilitate the immobilization of the liquid/gas interface.
Highlights
The hydrodynamics of a single bubble are a crucial matter for such engineering and environmental applications as froth flotation, foam fractionation, waste treatment, oil recovery, pulp and paper, distillation, the aeration of water reservoirs and pipe flow [1,2,3,4]
The description of bubble motion in solutions of surface-active substances (SAS) is used to determine the evolution and development of the dynamic adsorption layer (DAL) [6], the properties of which are essential for predicting real foam stability [7]
This proved that the bubble was generated under conditions that allowed the establishment of an equilibrium between Fb and Fc, so the bubble Rb could be considered at equilibrium
Summary
The hydrodynamics of a single bubble are a crucial matter for such engineering and environmental applications as froth flotation, foam fractionation, waste treatment, oil recovery, pulp and paper, distillation, the aeration of water reservoirs and pipe flow (cavitation) [1,2,3,4]. Reports on the influence of temperature on the velocity of rising bubbles, even in pure liquids, are quite scarce, despite the fact that this effect has significance for engineering and industrial applications. They show considerable contradictory data and trends. The bubble characteristics in a bubble column between 30 and 60 ◦C was studied by Issaoui and Ben Mansour [21] They found that an increase in liquid temperature caused only a slight increase in the bubble rise velocity. Liu et al [22] reported no temperature influence on the terminal velocity in distilled water for 0–100 ◦C for bubble of 3.3–6.1 mm
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