Visualization research on a pentane loop thermosyphon for shaft cooling

The loop thermosyphons has advantages of high heat transmission efficiency and needing no additional power. It can quickly draw out the heat in the motorized spindle with no coolant getting into the shaft, and has a good application prospect in the field of motorized spindle cooling. However, the evaporation and condensation sections of a loop thermosyphon will be in the same pipe and at the same height under the heat conduction of the shaft. These structural changes will directly affect the flow characteristecs and heat transfer performance of the loop thermosyphon. This paper experimental studied the vapor-liquid two phase flow characteristics in a pentane loop thermosyphon. The effects of the heat input power and fill ratio on the flow characteristics were analyzed. Results show that the two-phase flow pattern transitions from stratified flow to wavy flow and finally to plug flow as fill ratio increases. The velocity of the liquid flow in the upper adiabatic section of the loop thermosyphon is on the order of 0.1 m·s-1, and it decreases with increasing heat input when the fill ratio is between 30 and 70 %.