MINIATURE JOULE-THOMSON CRYOCOOLERS FOR PROPELLENT MANAGEMENT MINIATURE ENGINEERING SYSTEMS GROUP MINIATURE JOULE-THOMSON CRYOCOOLERS FOR PROPELLENT MANAGEMENT TASK I: Thermodynamic Cycle Analysis and System Optimization Presented by  K.V.Krishna Murty MMAE

Schematic Layout of the Flow Setup and the proposed Cryogenic System [1: proposed cryo cold head, 2: common compressor for the JT cryogenic system, 3: common heat exchanger for external heat rejection, 4: recuperative heat exchanger for regeneration, 5: JT expansion valve – this would be located physically next to item 6, 6: cold head heat exchanger, 7: vacuum jacket, dark arrows indicate flow of neon, open arrows indicate flow of LN2]

JT Cryocooling System External HX Cold head JT expander Load Interface Recuperator Motor and Compressor Qrej JT expander Load Interface External HX Cold head

Schematic representation of Joule-Thomson Cycle with respect to the current system

Specifications Compressor: Pressure Ratio = 10, Efficiency = 85%, Working Fluid = Neon, Operating pressure range = 3 bar to 30 bar, Electric Power required to run the motor for compressor = 12 kW. Recuperative Heat Exchanger: Temperature drop/rise = 227 K, Pressure difference between Hot side and Cold side = 27 bar. JT Valve: JT coefficient = 0.259, Temperature drop across JT Valve = 7 K. Heat Sink: Heat Load = 2196 W, Working pressure = 30 bar. Cold Head: Cooling power = 20 W, Working pressure = 3 bar. Overall system: Working Fluid = Neon, Working pressure range = 3 bar to 30 bar, Mass flow rate/cold head = 3.953 g/s, System COP = 0.0078.

Selection of JT coefficient

Other considerations and Optimization

Other considerations and Optimization Lowering of the inlet temperature to the compressor from 300 K to 280 K  No use. Instead it lowers the COP value. Increasing Pressure Ratio to 70 (operating pressure range of 1 bar to 70 bar)  Improves COP and JT coefficient. But the option is discarded owing to the difficulty in designing the miniature heat exchanger for a pressure difference of 69 bar.

Companies contacted for purchase of off-the-shelf Compressor and JT Valve Fluitron, Inc. – negotiation in active progress. RIX Industries – negotiation in active progress. Sundyne Corp., Gas Equipment Engg. Corp.(GEECO), Burton Corblin, Inc. ProcessFlo, Inc. Hydro-Pac Inc. – negotiation in active progress. CPC-Cryolab(tm) – negotiation in active progress.

Future Work To accomplish Task II: Development and Fabrication of a Highly Effective, Compact Recuperative Heat Exchanger. NOTE: Cycle specifications are optimized based on the fact that LN2 test bed would be used for conducting the experiment.