Pressure drop prediction in annular two-phase flow in macroscale tubes and channels

Abstract

A new prediction method for the frictional pressure drop in annular two-phase flow is presented. This new prediction method focuses on the aerodynamic interaction between the liquid film and the gas core in annular flows, and explicitly takes into account the asymmetric liquid film distribution in the tube cross section induced by the action of gravity in horizontal tubes operated at low mass fluxes. The underlying experimental database contains 6291 data points from the literature with 13 fluid combinations (both single-component saturated fluids such as water, carbon dioxide and refrigerants R12, R22, R134a, R245fa, R410a, R1234ze, and two-component fluids such as water-argon, water-nitrogen, alcohol-argon, water plus alcohol-argon and water-air), vertical and horizontal tubes and annuli with diameters from 3 mm to 25 mm, and both adiabatic and evaporating flow conditions. The new prediction method is very simple to implement and use, is physically based and outperforms existing pressure drop correlations (mean absolute error of 12.9%, and 7 points out of 10 captured to within ±15%).2

Adiabatic frictional pressure gradient during flow boiling of pure refrigerant R1233zd and non-azeotropic mixtures R448A, R452A and R455A

“…This method produces a slight underestimation for the refrigerants R1233zd, R448A and R452A, whereas it slightly overestimates the R455A database, with more of 52% of the whole data points falling into a range of error of ±30%. Cioncolini-Thome (2017) [12] and Friedel (1979) [13] correlations consider a separated flow approach of the two-phases for the prediction of the frictional pressure drop: it is found that these methods provide a very good agreement with the whole dataset, with more of 70% and 73% of data points falling into a range of error of ±30% respectively. It is worth noting that the Cioncolini-Thome [12] correlation was originally developed only for annular flow: for this reason, the assessment is carried-out by excluding points that are likely (a visualization section is not available) to fall into the bubbly flow region and in the stratified region.…”

“…Cioncolini-Thome (2017) [12] and Friedel (1979) [13] correlations consider a separated flow approach of the two-phases for the prediction of the frictional pressure drop: it is found that these methods provide a very good agreement with the whole dataset, with more of 70% and 73% of data points falling into a range of error of ±30% respectively. It is worth noting that the Cioncolini-Thome [12] correlation was originally developed only for annular flow: for this reason, the assessment is carried-out by excluding points that are likely (a visualization section is not available) to fall into the bubbly flow region and in the stratified region. Practically, Figure 7b includes only experiments with vapor qualities higher than 0.3 and at the same time mass flux values higher than 150 kg/m 2 s. The statistics of this annular flow correlation slightly worsens when applied to the whole dataset, with a MAPE of approximately 30% for all the investigated substances.…”

The Calculation of Heat and Mass Transferring Processes in the Fan Cooling Tower Sprinkler Channels in Case of a Section of Saturated Humid Air

“…Исследованию особенностей течения двухфазных кольцевых дисперсных потоков посвящен ряд трудов зарубежных авторов [1][2][3][4][5][6][7][8][9][10][11]. В этих работах рассмотрены особенности течения и межфазного взаимодействия жидкой и газообразной сред, проанализировано влияние режимов течения жидкости и газа на интенсивность процессов тепломассообмена.…”

Oscillations During Flow Boiling in Single Microchannels

“…Similar results of the bubble nucleation frequency with small dependence on the wall superheat in pool boiling was presented in Hutter et al 24 A small effect of the heat flux on the nucleation frequency during vertical subcooled flow boiling was encountered by Chu et al 25 The employment of numerical analysis to flow boiling in microchannels is being studied by various research groups, however a fully functional numerical model is still far from being reached due to the complexity of the boiling phenomena. Numerical modelling of pressures, temperatures and velocities is commonly associated with twophase non-boiling flows Cioncolini and Thome, 26 specific flow patterns in predominantly larger circular microchannels Magnini and Thome, 27 single bubble growth and bubble merger in larger square microchannels Mukherjee et al 28 and Ling et el., 29 single bubble analysis Ferrari et al, 30 and is therefore not entirely relatable to the solely annular flow observed during boiling in our experimental work.…”