Experimental Investigation of an R134a Loop Thermosiphon for Shaft Cooling

Abstract

Shaft cooling based on a loop thermosiphon is an ideal method for cooling of motorized spindles since it transfers heat with high efficiency and does not require an external power supply. In this study, an experiment was conducted on an R134a single-loop thermosiphon when the evaporation and condensation sections were on the same pipe. Results indicated that the single-loop thermosiphon was still operational with a minimum average thermal resistance of 0.51 W/°C when the filling ratio (FR) was 40%. The temperature distribution of the test specimen was determined predominantly by the amount of heating power, and not the mode. The optimum liquid filling ratio was 40% – 60% under this special condition, and both the thermal resistance and the heat transfer limit increased with the increase of FR in this range. The maximum temperature of the 150SD motorized spindle decreased 29% with the use of the R134a shaft cooling structure.