A heat pipe heat sink which is possible to frozen start up at the lower than -20℃ by using a VCHP was designed, manufactured and tested. The VCHP uses water and nitrogen gas as the working fluid and non-condensable gas. The test results showed that the VCHP heat sink started up successfully at the range of -20 to -30℃ of the ambient temperature and 1000 to 2600W of the heat flow rate. The thermal resistance of the VCHP heat sink decreased as increased the heat flow rate and the ambient temperature since the active zone of VCHP increased.

The operational characteristics of a VCHP in the various operation conditions were investigated. A water heat pipe including nitrogen gas as a non-condensable gas was designed and manufactured using a copper tube with 12.7㎜ diameter and 480㎜ length. Experimental data showed that the length of non-active zone mostly depend on the temperature of the vapor and the non-condensable gas. And the heat flow rate was negligible parameter at the same vapor temperature in the range of the experiment. As the vapor temperature increase and the non-condensable gas temperature decrease, the non active zone was increased. The calculated data by using the flat front model and the experimental results showed same tendency.