Recent Advances in Cryogenic Pulsating Heat Pipes

Research activities regarding cryogenic pulsating heat pipes (PHPs) are quickly springing up around the world. The strong interest is motivated in part by the exciting potential of PHPs for many cryogenic applications where effective heat transfer over large distances is required. In this regard the PHP supplies a complimentary functionality to regenerative cryocoolers that produce localized cooling at their cold tip. This report provides an update on recent experimental and modeling activities with cryogenic PHPs, demonstrating effective thermal conductivity values exceeding 50,000 W/m-K, and transferring heat over distances on the order of a meter. In addition, the report highlights the unique features associated with cryogenic PHPs, such as temperature dependent fill ratios, system pressures exceeding multiple bars, and operation up to and beyond the critical point. Preliminary investigations into the ability of a PHP to spread heat from one region to another are also reported.