Study of the thermal performance of multilayer insulation used in cryogenic transfer lines

• DOI: 10.1016/j.cryogenics.2019.01.005
• Publication Date: 2019-01-25T02:52:21Z
• Authors: Bicai Deng; Shaoqi Yang; Xiujuan Xie; Yunlong Wang; Xing Bian; Linghui Gong; Qing Li
• Keywords: 0202 electrical engineering, electronic engineering, information engineering; 02 engineering and technology; 7. Clean energy

Abstract We studied the relation between the thermal performance of multilayer insulation MLI used for cryogenic transfer lines and the layer density, number of layer and material of reflectors and spacers theoretically and experimentally. An optimum combination of layer density and number of layer of MLI is proposed. The heat flux and effective thermal conductivity of MLI are calculated using modified Lockheed Equation. Based on the theoretical studies, a horizontal cryogenic transfer lines test platform was built, thermal performance of MLI, including heat leakage per meter, heat flux and effective thermal conductivity were experimentally studied for layer density from 20 to 50 layers/cm and number of layer from 30 to 80 layers. Four MLI systems with different material of reflectors and spacers were tested. Both theoretical and experimental results show that heat flux decreases with the increases of number of layer and the decrease of layer density. The differences of heat flux between theoretical and experimental values when layer density is 20, 25 and 40 layers/cm are 23%, 20% and 39% for number of layer from 40 to 70, respectively. By comparing calculated and experimental results, optimum layer density and suitable number of layer are obtained for MLI used in cryogenic transfer lines at the temperature range for 293–77 K. In the four MLI systems constructed with different materials, the combination of Double-aluminized Mylar and Fiberglass paper (MP) has the best performance. Effective thermal conductivity and heat flux of MLI are 0.135 mW/(m·K) and 1.43 W/m2, respectively. And the heat leakage per meter of cryogenic transfer line is reduced to 0.49 W in suitable condition.