Reduction of liquid pumping power by nanoscale surface coating

The objective of the present study is to reduce the liquid pumping power by controlling the contact angle of the riser surface with the nanoscale surface treatment. The efficiency of a bubble pump is examined depending on the size of the riser, submersion ratio, gas inlet flow rate, and contact angle variations by nanoscale surface coating between 23.7° and 153.8°. By the nanoscale surface coating, the efficiency is improved by 22.5%, 25%, and 18%, respectively, for the 11 mm, 8 mm, and 5 mm risers compared to the uncoated surface. However, the superhydrophobic surface with a contact angle of 153.8° shows a lower efficiency compared to other surfaces due to the reversed liquid vibration flow. The highest efficiency of the liquid pumping power is obtained at the contact angle of 90.3°. An experimental correlation for the dimensionless volumetric liquid flow rate is developed with an error band of ±20%.