1. MINIATURE ENGINEERING SYSTEMS GROUP: MINIATURE ENGINEERING SYSTEMS GROUP: COST ANALYSIS OF PRE-CHILLING AND HEAT LEAKAGE DURING OPERATION FOR LH2 VJ STORAGE & TRANSFER FACILITIES AT NASA KSC Presented by – Presented by – K.V.Krishna Murty

2. References : A report on ‘NASA KSC Base Center Hydrogen Operations’ by Dr.Addison Bain, 2001-2002. Communication of Mr.Thomas Tomsik (NASA GRC). Communication of Mr.Bill Notardonato (NASA KSC).

3. LH2 Storage and Transfer facilities:  LH2 Storage Tank: Outer Diameter of the outer shell = 70 ft, Inner Diameter of the inner shell = 62.5 ft, Material – Stainless Steel.  LH2 Transfer Line:  Fill Rate to ET = 8,400 gpm to 10,000 gpm,  Outer Jacket m/l – Stainless Steel,  Inner Jacket m/l – Welded Invar,

4. Economic Analysis of Pre-Chilling of metals: Assumptions and Values: Latent Heat of Vaporization of LH2 (L): 56 W-hr/lb Cost of Electricity = 0.05 $/kW-hr LH2 cost = 2 $/lb Specific Heat of 304 SS at cryogenic temperature = 144 J/lb-K Density of 304 SS = 0.285 lb/in 3 = 7,900 kg/m 3 Specific Heat of Welded Invar at cryogenic temperature = 149 J/lb-K Density of Welded Invar = 0.291 lb/in 3 = 8,055 kg/m 3 Thickness of storage tank = ½ in (assumed for calculations), VJ Transfer Line Length = 1500 ft Cooling Power of 1 RTBC = 1 kW @ 19K

5. Cost of Pre-Chilling: 304 SS: Cost of pre-chilling per lb of SS: 310K  80K 80K  19K LH2 Boil-off $0.328 $0.087 RTBC $0.004 $0.018 Cost of pre-chilling 304 SS over the complete range (310K  19K): cost/lb of SSSavings Boil-off$0.414 0 % 310K to 80K by RTBC, rest by boil-off$0.09178 % 310K to 19K by RTBC$0.02295 %

6. Pre-chilling with top stage  to 80 K Time Mass (min) (lb) 7½ 208 15 417 22½ 625 30 833 Pre-chilling with bottom stage  to 19K Time Mass (min) (lb) 37½ 208 75 417 112½ 625 150 833 Pre-Chilling of 304 SS (with 1 RTB): Pre-chilling with 2 stages  Time Mass (min) (lb) 45 208 90 417 135 625 180 833

7. Cost of Pre-Chilling: Welded Invar: Cost of pre-chilling per lb of Welded Invar: 310K  80K 80K  19K LH2 Boil-off$0.339 $0.090 RTBC $0.004 $0.019 Cost of pre-chilling Welded Invar over the complete range (310K  19K): cost/lb of WISavings Boil-off$0.429 0 % 310K to 80K by RTBC, rest by boil-off$0.09478 % 310K to 19K by RTBC$0.02395 %

8. Cost savings in maintaining the system at LH2 temperature by RTBC Cost savings in maintaining the system at LH2 temperature by RTBC : Considering 1 kW of heat leakage, If LH2 is let to boil-off: Rate of LH2 boil-off = 430 lb/day Cost of LH2 boil-off = 860 $/day If RTBC is used to prevent LH2 boil-off: Number of RTBC required = 1 Total cost of input power for 1 RTBC = 180 $/day The savings from complete boil-off to RTBC use for Pre-Chill = (860-180)/860 ≈ 79 %

9. Input power required to maintain the Storage Tank (Pad B) at LH2 temperature: LH2 Boil - Off = m = 600 gallons/day = 355 lb/day, Cost of LH2 Boil-Off = $ 260,000/yr, Input power required to maintain the Storage Tank (Pad B) at LH2 temperature: LH2 Boil - Off = m = 600 gallons/day = 355 lb/day, Cost of LH2 Boil-Off = $ 260,000/yr, Input power required = P where, P= m*L = (355*56)/24 = 830 W. So, a nominal cooling power of about 1 kW at 19K would be appropriate.

10. Time required to pre-chill the storage tank to 19 K with 1 RTB = 770 hr, Cost of LH2 Boil-Off for Pre-Chill = $ 105,000 Pre-Chilling of Storage Tank: Pre-Chilling of Transfer Line: LH2 Boil-Off Cost = $ 17,000, Number of RTBCs required to pre-chill the transfer line to 19K in 9 hrs, I.e., with both stages = 15 (1 for every 100 feet of the transfer line), Number of RTBCs required to pre-chill the transfer line to 80K in 9 hrs, I.e., if only the top stage is used = 3 (1 for every 500 feet of the transfer line).

11. Conclusion: The calculation shows that it is economically effective to use cryo- coolers for cooling the Liquid Hydrogen Vacuum Jacket storage & transfer facilities at NASA KSC. Please NOTE: This analysis considers only the running costs associated with the cryocoolers. It does not take into account the installation and maintenance costs associated with the cryocoolers.