1. Cryogenic Engineering Lab. 팀 3 김경중, 박창기 2016. 6. 2. Current researches in Cryogenic Engineering Laboratory

2. Major research areas 2 Refrigerator  Magnetic refrigerator  Pulse tube refrigerator  Mixed refrigerant Joule-Thomson refrigerator Space cryogenics  No vent filling  Line chill-down  Space cryogenics

3. Refrigerator 3

4. Magnetic refrigerator 4  Application of the magnetocaloric effect  High thermodynamic efficiency : reversible process  Use of solid magnetic refrigerant

5. Pulse tube refrigerator 5  Solid expander replaced by gas expander, orifice and reservoir  Similar to Stirling cycle

6. Joule Thomson cryocooler 6  Simple construction  High operation reliability  Application  Cooling infrared sensors  Cryosurgery  LNG liquefaction Heat exchanger

7. Cryogenic Engineering Lab. Efficiency improvement of BOG re-liquefaction cycle by using phase separator and exergy analysis 박창기

8. Contents 8 Problem definition Introduction Exergy analysis

9. BOG (Boil-off gas) Problem definition LNG Evaporation Heat inleak LNG evaporation because of heak in-leak from environment Pressure increase in the tank Venting of the evaporated NG Liquefaction of the evaporated NG http://www.shippipedia.com/ships/ship-types/tanker/gas-carrier/

10. Efficiency definition of BOG re-liquefaction cycle

11. BOG liquefaction cycle Introduction C A HX V C: Compressor A: Aftercooler HX: Heat exchanger V: Joule-Thompson valve V

12. Introduction 12 BOG liquefaction cycle with phase separator Phase separator Mixer C A HX V V C: Compressor A: Aftercooler HX: Heat exchanger V: Joule-Thompson valve

13. Freezing point of NFMR Mole fraction 고체 액체 기체 삼중점임계점  Freezing point problem is solved by mixing several refrigerants C. Lee, J. Yoo, J. Lee, S. Jeong, "Visualization of the solid–liquid equilibria for non-flammable mixed refrigerants", Cryogenics, 75, pp. 26-34, 2016.

14. Efficiency analysis at various conditions Ar : R14 : R218 = 0.3 : 0.2 : 0.5 LP150 kPa HP2700 kPa Specific work consumption 0.6194 Phase separating temperature - Without phase separatorWith phase separator LP200 kPa HP2800 kPa Specific work consumption 0.5795 Phase separating temperature 300 K 6.5 % 100 kW

15. Exergy analysis about the results Without phase separator HX Useful effect Total exergy input = 1548 kW

16. Exergy analysis about the results With 300 K phase separator HX Useful effect Total exergy input = 1448 kW

17. Conclusion Phase separator Mixed refrigerant Freezing point measurement

18. Space cryogenics 18

19. No-vent filling 19 Supply tank Receiver tank Vent Unexpected momentum International space station Space vehicle Technologies On-orbit technology Cryogenic propellant storage technology Fluid transfer technology NVF  Reduction Space Launch Vehicle mass  Difficulty of vent filling under micro-gravity condition

20. Transfer line chill-down 20  Indispensable process of undertaking cryogenic mission and establishing a normally operated cryogenic system  Less cryogenic liquid consumption  Shorter chill-down time Ref. http://www.nasa.gov/sites/default/files/thumbnails/image

21. Cryogenic expander 21  Generally key component of cryocooler  Enthalpy reduction without entropy change  Reduction boil-off gas (BOG) of cryogenic propellant

22. Cryogenic Engineering Lab. Analytic model of No-vent Filling (NVF) 김경중

23. General filling method Problem definition Cryogen Vent Injection Cryogen Normal gravity Cryogen Micro-gravity Fuzzy liquid-vapor interface Unwanted momentum generation Limitation

24. Problem definition Previous research  Variables study  Experiment for liquid nitrogen(LN 2 ) and liquid hydrogen(LH 2 )  Experiment for variables change(wall temperature, liquid temperature, mass flow rate and pressurization pressure)  Analysis  Equilibrium model  Optimized model for specific experimental device  Non-dimensional map to find feasible initial condition Previous model can predict NVF result, but NVF process Process predictable model independent on experimental device is needed.

25. NVF processes Introduction 2. Pressurization due to tank cool down 3. Pressure equilibrium due to condensation and evaporation balance 1. Pressurization due to flash evaporation 123

26. Experimental apparatus Transfer line Supply tank Receiver tank

27. Analysis Wall coordinate 1 2 n n-1 n-2 … Top bulk Bottom bulk Convection Conduction

28. Analysis Evaporation Flash evaporationPool boiling YesNo P receiver <P sat Nucleate boilingFilm boiling YesNo receiverReceiver tank satSaturation state LeidenfrostLeidenfrost point

29. Analysis Condensation No condensation Condensation by heat transfer Yes No Yes No P receiver >P sat T v >T in receiverReceiver tank satSaturation state vVapor inIncoming

30. Results and discussions Comparison  Bottom temperature tendency 30 caseT wall [K]T supply [K]P supply [kPa] 117515540016.8 218015840072.1 3170138400114.77 418015040041.3 Requirement of axial conduction of bottom

31. Results and discussions Comparison  Middle temperature tendency 31 caseT wall [K]T supply [K]P supply [kPa] 117515540016.8 218015840072.1 3170138400114.77 418015040041.3 Conduction (wall coordinate) is reliable.

32. Results and discussions Comparison  Pressure tendency 32 caseT wall [K]T supply [K]P supply [kPa] 117515540016.8 218015840072.1 3170138400114.77 418015040041.3 Well-predicted pressure overshoot

33. 33

34. Appendix

35. Principle of JT refrigerator 35

36. NFMR(Non-flammable mixed refrigerants) Comparison with FMR  Lower isothermal enthalpy difference  No risk of explosion and flammability

37. Exergy analysis about the results Ar : R14 : R218 = 0.3 : 0.2 : 0.5 A A B B C C With phase separator A: Total flow B: Vapor fraction after phase separating C: Liquid fraction after phase separating 240 K

38. Exergy analysis about the results Ar : R14 : R218 = 0.3 : 0.2 : 0.5 A A B B C C Refrigerant Mass flow [kg/s] Ar2.15 R143.16 R21816.87 Mass flow [kg/s] 2.07 2.95 12.6 Mass flow [kg/s] 0.08 0.21 4.27 Refrigerant Mass flow [kg/s] Ar2.06 R143.02 R21816.12 With 300 K phase separator Without phase separator Sum22.1817.624.56 Sum21.2

39. Exergy analysis about the results Ar : R14 : R218 = 0.3 : 0.2 : 0.5 With 300 K phase separator Without phase separator 5335 kW 4679 kW 656 kW

40. Temperature profile in HX T2T2 T1T1 Venkatarathnam, Gadhiraju. Cryogenic mixed refrigerant processes. Ed. Klaus D. Timmerhaus. New York: Springer, 2008. Exergy loss during heat transfer