TECHNOLOGY AREAS: Materials/Processes

ACQUISITION PROGRAM: PMS 502, CGX Program, ACAT I

OBJECTIVE: Develop a low cost means of helium circulation for a High Temperature Superconducting system.

DESCRIPTION: HTS Degaussing Systems (HTSDG) make extensive use of helium circulators as the prime coolant mover. These circulation fans currently make up approximately 30-40% of the refrigeration system cost which is around 30-50% of the total HTSDG system procurement and installation costs. HTSDG systems require up to 40 helium circulators depending on the ship class. Each of the circulators will be integrated into a junction box that contains a cryocooler. The cables that make up the HTS degaussing systems are long length, cryostat, 44mm OD, with 40 HTS tape conductors contained in the 21mm ID corrugated stainless tube. The length of these cables can be up to 200 meters. Cables are cooled to 50K with an operating charge pressure around 7 bar.

The Navy seeks a more cost effective solution for cryogenic helium circulation fans that operate at 30-60K at 1L/sec with minimal heat leak into the cryogen. Under normal operation the unit would be under 7 bar of helium however 21 bar may be seen during storage and system warm up.

PHASE I: Demonstrate the feasibility of a low-cost helium circulation concepts to achieve the desire level of performance. Perform bench top experimentation, where applicable, as a means of demonstrating the identified concepts. Establish validation goals and metrics to analyze the feasibility of the proposed solution. Provide a Phase II development approach and schedule that contains discrete milestones for product development.

PHASE II: Develop, demonstrate and fabricate a prototype as identified in Phase I. In a laboratory environment, demonstrate that the prototype meets the performance goals established in Phase I. Verify final prototype operation in a representative laboratory environment and provide results. Develop a cost benefit analysis and a Phase III installation, testing, and validation plan.

PHASE III: Working with government and industry, install full scale prototype onboard a selected Navy ship and conduct extended shipboard testing.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: A cryogenic helium circulator has commercial application beyond the Navy. This product could provide cost savings when used in cryogenic refrigeration skids for HTS motors and generators. Reducing the overall cryogenic refrigeration costs makes smaller HTS machines feasible from a cost view. This product is a step toward having low power, 100�s of kWs, HTS machines which may see use in industrial environments.

REFERENCES:
1. Fitzpatrick, B. "High Temperature Superconducting Degaussing Demonstration and Development," to be published in the proceedings of ASNE Day 2007, June 2007.

2. Snitchler G., Gamble B., Kalsi S.S., "The performance of a 5 MW high temperature superconductor ship propulsion motor" Applied Superconductivity, IEEE Transactions on Volume 15, Issue 2, Part 2, June 2005 Page(s):2206 � 2209.

3. Curcic, T.; Wolf, S.A. "Superconducting hybrid power electronics for military systems" Applied Superconductivity, IEEE Transactions on Volume 15, Issue 2, Part 2, June 2005 Page(s):2364 � 2369.

4. Fitzpatrick, B.K.; Kephart, J.T.; Golda, E.M., "Characterization of Gaseous Helium Flow Cryogen in a Flexible Cryostat for Naval Applications of High Temperature Superconductors" Applied Superconductivity, IEEE Transactions on Volume 17, Issue 2, June 2007 Page(s):1752 � 1755.

KEYWORDS: Cryogenic; Superconductor; HTS; Cryocooler; Refrigeration; Fan;

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