Distributed 2-stage RTBC LH2 Pipeline Cryocooler System Design

LEI ZHOU

MMAE

UCF

Basic features of LH2 Cryocooler

For prechilling/cooling of the transportation pipeline of liquid HydrogenCapable of removing heat at 19KDistributed mid-size cryocoolers are the best solution for the long LH2 pipeline

Distributed RTBC cryocooler

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

Cryocooler cooling power analysis

How much cooling power needed to chill down a How much cooling power needed to chill down a 50-ft-long-pipe in 24 hours50-ft-long-pipe in 24 hours

Q=1908 kJ /ft

Q C D th 310 19( )

P=Q*50/24*3600=1104W

How much heat should be removed?How much heat should be removed?The Invar LH2 pipeline should be chilled down from 310K to 19K. Size: 10-inch diameter D, 8 mm pipe wall thickness th (estimated)

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 19KTotal time: 7.4 hr

Chill down with the both stages simultaneously to 19KTotal time: 24.2 hr

2-stage RTBC cryocooler

Flowswitch

Top cycle

Inter-heat exchanger / bottom cycle

Cooling load interface

2-stage RTBC cryocooler:—working mode1

CLI temperature: 80K

Cooling power: 9.95 kW ; Cooling time: 2.2 hr

Cooling load interface

Flowswitch

Top cycle

Inter-heat exchanger / bottom cycle

2-stage RTBC cryocooler:—working mode2

CLI temperature: 19K

Cooling power: 1.1 kW ; Cooling time: 5.2 hr

Flowswitch

Top cycle

Inter-heat exchanger / bottom cycle

Cooling load interface

System configuration

Recuperator

DC Power Supply

Motor/ 2 Stage intercooled compressor

Intercooler

Qrej

Motor/ 2 Stage intercooled compressor

Recuperator

Turboalternator

Qrej

Turbo expander/brake

Load Interface

DC Reg-ulator/ Power Su

pply

External HX

Thermodynamical schematic design

System Optimization

System requirements: – Cooling temperature: 19K– Cooling power: 1100 W– Working temperature: 310 K

Optimizable parameters: – Bottom Cycle pressure ratio: Pr

COP vs. Pr

Ti=80K

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

Conclusions

With system optimization, the proposed system can have a COP around 0.01 W/WCooling 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