2015 Volume 23 Issue 3 Pages 41-56
A loop heat pipe (LHP) with an evaporator that has multiple cylindrical wicks in parallel (MCP type) was newly developed for cooling the CPU installed in high performance servers. An MCP type LHP was compared with a LHP containing an evaporator with a pin array conduction structure (PACS type) that has been already developed with regard to heat transfer characteristics. It was observed experimentally that the heat transport performance of each type of LHP was practical because both could be operated in a stable manner and the evaporator temperature could be cooled to 70 °C or less in high power regions with more than 300 W. Upon comparison of both types of LHPs, the difference was seen in the performance in a low power region. And it is believed that the temperature relation between a reservoir tank and a condenser, and the influence on condensation thermal resistance is the cause of the difference in a low power region. Moreover, the evaporative heat transfer coefficient of an MCP type LHP and PACS type was calculated, and it was revealed that the MCP type has a higher evaporative heat transfer than the PACS type. To investigate this case, the thermal analysis of the heat leak occurring due to the difference in the temperature of the wick was carried out. As a result, it was revealed that the heat leak via the wick depends on the flow velocity of the working fluid on the wick surface.
