Thermal performances of a meter-scale cryogenic pulsating heat pipe

The combination of dry superconducting magnet using cryocooler as a cold source is becoming a standard. As the magnetic field highly decreases the cryocooler performances, the distance between the hot and cold spot is preferable to be higher than 1 m to maintain these performances. Thanks to their operation simplicity, compacity, lightness, and of course thermal performances, Pulsating Heat Pipes (PHP) are good candidates, as long two-phase thermal link, for these kind of systems. PHP can also work without gravity, in multiple orientations, with a small amount of liquid/gas and at a temperature around the saturation state of the working fluid inside. These devices are studied at different temperature to mostly cool down small electronic devices. At cryogenic temperature, PHPs have been studied in vertical and horizontal position filled with nitrogen, helium and neon mixtures. The longest one ever tested at these temperature is about 30 cm long. In this paper, we present the thermal performances of a 1 m long horizontal PHP made of 36 stainless steel parallel tubes. The tube internal diameter is 1.5 mm, close to the critical diameter (~1.7 mm) to maintain capillarity forces necessary to the PHP operation. ... mehrBoth evaporator and condenser section are copper made and are separated by an adiabatic section. Each section is 33 cm long and 40 cm large. This PHP has been studied with nitrogen with the condenser temperature maintained at 75 K. Several pressure and temperature sensors placed in the three different sections allow to monitor the thermodynamic behavior of the PHP. The maximum equivalent thermal conductivity measured is about 150 kW/(m.K) with a liquid ratio of 0,7 inside the PHP. This system can transfer a maximum heat power of 30 W before reaching its operation limit.