Experimental investigation of an R600a two-phase loop thermosiphon to cool a motorized spindle shaft

This paper has presented a novel method for cooling a motorized spindle shaft based on two-phase loop thermosiphons (TPLTs) which have a high heat transfer performance and work without external power. The evaporator section and the condenser section of the TPLT were on the same pipeline due to the thermal conduction of the shaft in the process of exporting the heat inside the shaft. An experimental investigation of a copper TPLT was carried out using R600a as the working fluid, under the special heating and cooling conditions in a stationary. Then the heat transfer performance of an R600a TPLT was compared with that of an N-pentane TPLT. According to the experimental results, the cooling effect on the shaft was numerically calculated. The results showed that the TPLT worked well and the average equivalent thermal conductivity was 3712-8048 W·m−1·K−1 under the special cooling and heating conditions, which was higher than that of an N-pentane TPLT when the temperature of the evaporation section was below 387 K. The optimum liquid filling ratio of the R600a TPLT was 40%-60%, in this filling ratio range the R600a TPLT had a growing thermal conductivity and a falling heat transfer limit. The maximum temperature rise of the motorized spindle shaft was reduced by 44%, from 55 K to 31 K after using the R600a TPLTs cooling structure.