Thermal performance assessment of cryogenic transfer line with support and multilayer insulation for cryogenic fluid

Abstract

Cryogenic transfer lines are very important to transport cryogenic fluid in the fields of fusion energy and hydrogen energy. The main aim of this work is to assess and minimize heat leakage of cryogenic transfer line. A three-channel coaxial liquid helium pipe with three support structures and typical multilayer insulation (MLI) materials was designed. Cryogenic transfer lines installed three support structures and MLI with different layer density & number of layer were studied based on a horizontal cryogenic transfer line test platform with liquid nitrogen. Thermal performance including heat leakage and temperature distribution of straight and elbow pipe have been numerically and experimentally analyzed for boundary temperature 77 K–293 K. By comparing simulated results with experimental heat leakages of supports, MLI and cryogenic transfer lines, the largest deviations are less than 10%, 10.7% and 6.6%, respectively. Based on above analysis, the minimal heat leakages of two-plate support and MLI with 50 layers and 25 layers/cm are 0.200 W and 0.488 W, respectively. Furthermore, the minimal heat leakages of straight pipe and elbow pipe were acquired as the values of 0.688 W and 0.858 W with two-plate support and MLI under 50 layers and 25 layers/cm. The results have been successfully applied in 250 W@4.5 K helium cryogenic refrigerator. The new and useful assessment method could also be applied to minimize heat leakage of cryogenic transfer lines with different size, support and MLI, etc, and then to improve the energy efficiency of system.