Pressure drop in fully developed, turbulent, liquid-vapor duct flows at zero gravity
Sridhar, K.R.
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https://hdl.handle.net/2142/20851
Description
Title
Pressure drop in fully developed, turbulent, liquid-vapor duct flows at zero gravity
Author(s)
Sridhar, K.R.
Issue Date
1990
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Aerospace
Engineering, Mechanical
Language
eng
Abstract
Reliable prediction methods for the frictional pressure drop in liquid-vapor flows at zero gravity are essential to the design of two-phase thermal control and fluid transfer systems aboard spacecrafts. The present investigation is concerned with the prediction of the frictional pressure drop in steady, fully developed, turbulent liquid-vapor duct flows in both dispersed and annular flow regimes. The dynamics of such flows are simulated by using two immiscible, neutrally buoyant liquids, water and n-butyl benzoate, in an earth based flow facility.
In the case of dispersed flow, simulation experiments were conducted with n-butyl benzoate droplets in flowing water. The theoretical basis of the simulation is given. Experiments showed that, for a fixed combined flow rate of water and benzoate, the frictional pressure drop is unaffected by large changes in the volume fraction of benzoate drops and their size distribution. Measured power spectra of the static wall pressure fluctuations induced by the turbulent water-benzoate flow also revealed that their dynamics is essentially unaltered by the presence of the droplets. These experimental findings, together with the theoretical analysis, led to the conclusion that the pressure drop in fully developed, dispersed liquid-vapor flow in straight ducts of constant cross section at 0-g is identical to that due to liquid flowing alone at the same total volumetric flow rate and, therefore, can be readily determined.
A method for predicting the frictional pressure drop in liquid-vapor annular flows in 0-g has also been developed. Based on an analysis and published correlations, a means of relating the measured 1-g frictional pressure drop in water-benzoate flow to the liquid-vapor pressure drop in 0-g was developed. The use of empirical correlations was necessary because of the lack of rigorous theoretical analysis for the dynamics of annular flows. Two different correlations were used, and it was found that the results were in good agreement.
Based on the results of this investigation, the frictional pressure drop in steady, fully developed, turbulent, liquid-vapor duct flow in 0-g is found to be consistently less than that in 1-g under otherwise identical conditions. This holds for both dispersed and annular flow regimes. Physical arguments in support of this finding are given.
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