Pressure Drop in Gas-Liquid Flow

1) the homogenous model with mean flow velocity similar to single-phase flow, and 

2) the separated flow model with an artificially separated gas and hquid flow. 

Model (1) One of the most commonly used models to characterize the pressure drop in microchannels is that proposed by Lockhart and Martinefli [63] iov gas-liquid horizontalflow in pipes, which is used for all regimes. It employs two friction multiphers for gas and liquid, 4 g and I , as given by the following equation  

The two equations given above are correlated in terms of a dimensionless number called the Lockhart-Martinelli parameter (. It is the ratio of the singlephase pressure drop of liquid to that of the gas and given by 

Here Lp jL) and KpjjL)g are the frictional pressure drop gradients when liquid and gas are assumed to flow in the microchannel alone, respectively. They are calculated as 

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