A Study of Anular Flow Characteristics in Microgravity and Hyper- Gravity Conditions

Statistics – Applications

Scientific paper

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Scientific paper

Annular flow is an important flow regime in many industrial applications. The need for a better understanding of this flow regime is driven by the desire to improve the design of many terrestrial and space-based systems. Annular two-phase flow is frequently present in the mining and transportation of oil and natural gas, boilers and condensers, and in heating and refrigeration systems. The flow regime is also important for the refueling of space vehicles, and heating and refrigeration systems for space use. On ground, gravity plays a major role in the process of heat and mass transport across the liquid film. In the presence of a gravitational pull, the film tends to be unstable and chaotic. This hinders accurate experimental measurements in the film and causes the process of deposition and entrainment unstable. In addition, the flow in the absence of gravity is axi-symmetrical and could be easily treated as a two-dimensional flow. These conditions allow for a convenient environment to study film characteristics. Past studies on annular flow have dealt with varying the gas or liquid Reynolds numbers and studying the effect of such changes on the flow regimes and pressure drops. Other studies by the same group focussed on the effect of reversing the direction of the gravity vector on the film flow characteristics. Two other relevant dimensionless groups, namely the gas-to-liquid density ratio and the gas-to-liquid viscosity ratio, are noticeably absent. The present study explains the effect of the density ratio on the film characteristics. In particular, the film thickness and pressure drop were examined in the present study. The film thickness was measured using two-wire conductance probes. Experimental data was collected in microgravity aboard the Novespace Zero-G Airbus microgravity simulator. Data were collected for a range of annular flow set points by changing the liquid and gas mass flow rates, the liquid-to-gas density ratio and the gravitational acceleration. The liquid-to-gas density ratio was examined by collecting data using Helium-water and air-water mixtures. The gravitational effect on the film thickness characteristics was examined by collecting the data during the microgravity and pull-up (hyper-gravity) portions of each parabolic flight.

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