Abstract
This paper presents the results of analyses of the impact of heat transfer conditions on the hydrodynamics of downward co-current annular flow in vertical tubes of very viscous liquid and gas. The research was conducted within the range of gas velocities of 0–30.0 m/s and liquid velocities of 0.001–0.254 m/s, while the viscosity was in the unprecedented range of 0.046–3.5 Pas. The research demonstrates that the volume and nature of the liquid waves with various amplitudes and frequencies arising on the surface of the film are relative to the flow rate and viscosity of the gas phase. At the same time, we found that, under the condition of liquid cooling, an increase in viscosity resulted in the formation of a smooth interface whereas, under the conditions where the liquid is heated at the end of the channel section, a greater number of capillary waves were formed. This research resulted in the development of new dependencies which take into account the influence of selected thermal and flow parameters (including mass fraction) on the values of volumes specific to very viscous liquid film flows. These dependencies improve the accuracy of calculation by 8–10% and are fully applicable to the description of the performance of an apparatus with a hydraulically generated liquid film.
Highlights
The two-phase flow of a gas and a highly viscous liquid includes a wide range of phenomena, which have attracted interest in both industrial and academic circles
This research resulted in the development of new dependencies which take into account the influence of selected thermal and flow parameters on the values of volumes specific to very viscous liquid film flows
Liquid film thickness, as the value identified both for local and averaged states; characteristics of waves formed on the interfacial surface, which are possible to represent by means of such liquid film parameters as: frequency and amplitude of waves on the film surface, their length and velocity of displacement along the interface; and mean surface of the interface between gas-viscous liquid flows, as identified for all observed forms of annular oil-air two-phase flow
Summary
The two-phase flow of a gas and a highly viscous liquid includes a wide range of phenomena, which have attracted interest in both industrial and academic circles. It is relative to the structures formed that accompany the flow Research concerned with their determination has been carried out, among others, by Ebrahimi-Mamaghani et al [8], Liu et al [9] and Hamidi et al [10], in which the analysis involved heat transfer coefficients, as well as Smith et al [11] and Shen et al [12], who supplemented their analyses by determining the volume ratios of particular phases. The works of Qiao et al [23] and Xue et al [24] involved research dealing with the determination of flow structures occurring during two-phase gas-liquid downward flow in vertical pipes and developed flow maps corresponding to their occurrence.
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