Experimental Investigation of the Flow Field of Gas-Liquid Slug

The oscillating motion occurring in an oscillating heat pipe (OHP) can enhance heat transfer. The fluid flow of liquid plugs trapped between the vapor bubbles play a key role in an UHF. Understanding the flow field of liquid plug moving in a capillary tube will provide an insight into the oscillating motion occurring in an OHP. An experimental setup of a liquid plug moving in a capillary tube was established to determine the flow field of a liquid plug using the microscale particle image velocimetry (mu PIV) system. The motion of liquid plug was controlled by a computer-controlled system, which can produce a velocity ranging from 0.5 mm/s to 9 mm/s. The diameter of the capillary tube investigated herein is 1mm with a liquid plug length from 1.0 mm to 5.0 mm. The mu PIV data clearly indicates the complex nature of liquid plug flow in a capillary tube trapped between two gas bubbles. Experimental results show that there exist circulations near the contact line. The circulation strength in a liquid plug depends on the liquid plug length and velocity of the liquid plug.