Liquid entrainment, droplet concentration and pressure gradient at the onset of annular flow in a vertical pipe

Studying the influence of refrigerant type on thermal efficiency of annular two-phase flows; mass transfer viewpoint

“…Interfacial waves are assumed to be sinusoidal upon the observations of previous experiments [10,11,18,19]. Upon the recent observations of Alekseenko et al [20], there are some fine ripples known as secondary waves on the sinusoidal interfacial waves.…”

“…for N µ >0.0667 (11) N µ , in the above correlation is the viscosity number, g is the gravitational acceleration, and ∆ρ is the liquid and vapor densities difference.…”

“…Most of the accomplished researches in this field are experimental and have been carried out at restricted operating conditions and on some special fluids like water and some limited number of refrigerants [10][11][12][13].…”

A new method of entrainment fraction measurement in annular gas–liquid flow in a small diameter vertical tube

“…Results show that the removed gas flow rate accounts for 11%-25% of the total supplied gas flow rate in the tested data range. Assuming that the droplets are evenly distributed over the tube cross-sectional area (Barbosa Jr et al [7]), it is then assumed that the missed droplets are accounted for in the 11%-25% of the total entrained droplets. Corrections were made to the calculated entrainment fractions based on the above assumption.…”

“…Later, many investigators adopted this method in their research; e.g. Andreussi and Zanelli [4], Asali [5], Paras and Karabelas [6], and Barbosa Jr et al [7]. One of the limitations of this method is its inability to take measurements near the interface due to the sampling of part of the liquid in the waves.…”