The Challenge 0
Superconductor materials present zero electrical resistance at very low temperatures. The low temperatures must be maintained during operation, which requires advanced refrigeration (cryogenic) systems. A helium-helium heat exchanger system capable of cooling compressed helium gas from ambient temperature to 5K (~ -268°C) faces four main challenges:
- The heat exchanger system requires a thermal efficiency exceeding 99%.
- Temperatures below -196°C require special material, construction, and certification procedures.
- The application imposes high demands on freedom from leaks under a helium design pressure of 25bar (g).
- Thermal stresses due to the steep thermal gradient along the heat exchanger could cause material failure if not considered in the design calculations.
Due to the complexity and demanding requirements of this application, the customer, ILK (Institute for Air Handling and Refrigeration, Dresden, Germany), could not find a commercial off-the-shelf solution on the market. The Airec technical team designed a nearly pure counter-flow heat exchanger to achieve the high effectiveness and maximum compactness required by the application. Advanced CFD and FEM calculations were performed to predict system performance and reliability before manufacturing.
It was obviously impossible to test in these extreme conditions, so this was a one-attempt project with no room for technical mistakes.
In addition to the main heat exchanger, a special Compact 36 was also delivered for this large project as a separate step to cool helium with nitrogen to approximately -196 °C.
Both units have been successfully installed and tested, and several additional units are planned to be delivered in the future for the same customer.