Thermal stress analysis for heat exchangers and its support system of cold box for a helium liquefier/refrigerator

The performance of a helium refrigerator or liquefier is influenced significantly by different kinds of losses associated with the Cold Box and Dewar. The main losses are pressure loss and heat in-leak from the surroundings. The heat in-leak can be minimized by proper placements of different parts in the cold box based on temperature, design of the support system, piping systems, Multi-Layer Insulation (MLI), valves, turbo-expanders, and the Dewar body mainly at the neck region. The design of the internal piping and support system is done by reducing different losses in the system. Therefore, a 3-D model of the cold box is developed with a motive to obtain the temperature contour for all the components and also to obtain the thermal stress for all the heat exchangers used and its supporting system. Based on this 3-D model, the temperature contour is obtained by using ANSYS Steady State Thermal and the stress analysis is done using Ansys Static Structural analysis. This analysis gives a clear view of the thermal study of the heat exchangers and its support system. From this study we can know the location of maximum and minimum stress concentration which is very important to know as far stability is concerned. (author)