2. Distributed 2-stage RTBC LH 2 Pipeline Cryocooler System Design LEI ZHOU MMAE UCF

3. Basic features of LH 2 Cryocooler For prechilling/cooling of the transportation pipeline of liquid Hydrogen Capable of removing heat at 19K Distributed mid-size cryocoolers are the best solution for the long LH 2 pipeline

4. Distributed RTBC cryocooler Reverse Turbo-Brayton cryocooler has higher efficiency than JT cryocooler With oil-free design, Turbo-compressor/expander has high reliability Distributed mid-size cryocoolers can be –Easy installable and manageable –Expandable –Redundant –Efficient

5. Cryocooler cooling power analysis How much cooling power needed to chill down a 50-ft-long-pipe in 24 hours Q=1908 kJ /ft P=Q*50/24*3600=1104W How much heat should be removed? The Invar LH 2 pipeline should be chilled down from 310K to 19K. Size: 10-inch diameter D, 8 mm pipe wall thickness th (estimated)

6. 2-stage RTBC: — a way to reduce chilling time Chill down with top cycle to 80K Switch the top cycle flow to cool the bottom cycle, use bottom cycle to chill down to 19K Total time: 7.4 hr Chill down with the both stages simultaneously to 19K Total time: 24.2 hr

7. 2-stage RTBC cryocooler Flow switch Top cycle Inter-heat exchanger / bottom cycle Cooling load interface

8. 2-stage RTBC cryocooler: — working mode1 CLI temperature: 80K Cooling power: 9.95 kW ; Cooling time: 2.2 hr Cooling load interface Flow switch Top cycle Inter-heat exchanger / bottom cycle

9. 2-stage RTBC cryocooler: — working mode2 CLI temperature: 19K Cooling power: 1.1 kW ; Cooling time: 5.2 hr Flow switch Top cycle Inter-heat exchanger / bottom cycle Cooling load interface

10. System configuration Recuperator DC Power Supply Motor/ 2 Stage intercooled compressor Intercooler Q rej Motor/ 2 Stage intercooled compressor Recuperator Turboalternator Q rej Turbo expander/brake Load Interface DC Reg- ulator/ Power Suppl y External HX

11. Thermodynamical schematic design

12. System Optimization System requirements: –Cooling temperature: 19K –Cooling power: 1100 W –Working temperature: 310 K Optimizable parameters: –Bottom Cycle pressure ratio: Pr

13. COP vs. Pr Ti=80K

14. Spec. of Components Bottom cycle: –Compressor: centrifugal 2-stage intercooled, Pr=3 –Motor: 15 kW, efficiency>=0.85 –Heat regenerator: 0.96 effectiveness, 11.7 kW –Turbine: turbo-expander with gas brake, 1.5 kW Top cycle: –Compressor: centrifugal 2-stage intercooled, Pr=2.42 –Motor: 85 kW, efficiency>=0.85 –Heat regenerator: 0.987 effectiveness, 121 kW –Turbine: turbo-expander with generator, 11.2 kW

15. Conclusions With system optimization, the proposed system can have a COP around 0.01 W/W Cooling power analysis shows that the cryocooler system is a mid-size system which is capable of chill down a 50-ft transfer line to 19K in about 8 hours