The additional frictional pressure drop for vertical tubes due to its connection with the bend was accounted into the frictional component due to return flow.

Experiments on heat transfer and frictional pressure drop of kerosene of single phase flow in the internally ribbed tube were conducted and compared with those of smooth tube.

To calculate discharge port pressure, this article considers the influence on frictional pressure drop in the gas and liquid two-phase flow between rod and tubing owing to rotation of rods.