Results of a three evaporator cryogenic helium Pulsating Heat Pipe

Abstract A three stage Pulsating Heat Pipe has been successfully operated using helium as the working fluid at fill ratios ranging from 20% to 90%. More than 2000 test runs were performed and results showed that an optimal thermal performance was achieved at a fill ratio of 69.5%, producing a maximum effective thermal conductivity keff around 50,000 W/m-K. The PHP was operated in a vertical orientation where the condenser section is located at the top position. The condenser section of the PHP was thermally anchored to a cryocooler with a cooling capacity of 1 W at 4.2 K and was operated from 2.9 K to 5.1 K. A total of 9 germanium type GR-200A and one Cernox® model CX-1050 were used to measure the temperature distribution, and a pressure transducer was used to record the fluid’s pressure oscillations. Each PHP section consists of 14 turns and an adiabatic length of 300 mm. This innovative design consists of two sub-evaporator sections for each PHP, resulting in a total number of six evaporators. This configuration was chosen in order for future testing in a varied heat load arrangement. This paper presents results based on equal heat load distribution throughout the evaporator sections.