The comments present an assessment of formulations for frictional pressure gradient correlation of moderately viscous lubricating oil–water two-phase flow through a horizontal pipe of 0.025 m internal diameter, which was obtained by Dasari et al. [1]. Their modified Lockhart–Martinelli correlation was
φW2=0.019X3+0.06X2-0.006X+1.397
(1)
Recently, Muzychka and Awad [2] developed an alternative approach for predicting two-phase frictional pressure gradients using superposition of three pressure gradients: single-phase liquid, single-phase gas, and interfacial pressure gradient. Muzychka and Awad [2] obtained an expression for the two-phase frictional interfacial multiplier for the liquid phase (ϕl,i2) as follows:
φl,i2=φl2-1-1X2
(2)

From Eq. (2), it is clear...

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