Experimental study on a hydrogen closed-loop pulsating heat pipe with two turns

Abstract

A closed-loop pulsating heat pipe (PHP) with hydrogen as the working fluid has been tested at 10 different filling ratios (10–80%) and three condenser temperatures (19, 21, and 23 K) in vertical position. The PHP is made up of a capillary tube (internal and outer diameters of 2.3 and 3.3 mm, respectively) bended into a serpentine shape with 2 turns at each end. The lengths of the condenser, adiabatic and evaporator sections are 50, 500 and 50 mm, respectively. Experimental results show that the effective thermal conductivity of the PHP is between 30,000 and 70,000 W/(m·K), indicating that the PHP with 2 turns can run efficiently. The optimal filling ratio corresponding to the maximum effective thermal conductivity is different under different heat loads. Higher condenser temperatures are beneficial for the heat transfer, but do not affect the start-up.