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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 – K.V.Krishna Murty. References : A report on ‘NASA KSC Base Center Hydrogen Operations’ by Dr.Addison Bain, 2001-2002.

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MINIATURE ENGINEERING SYSTEMS GROUP :

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  1. 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 – 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/in3 = 7,900 kg/m3 • Specific Heat of Welded Invar at cryogenic temperature = 149 J/lb-K • Density of Welded Invar = 0.291 lb/in3 = 8,055 kg/m3 • 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 SS Savings Boil-off $0.414 0 % 310K to 80K by RTBC, rest by boil-off $0.091 78 % 310K to 19K by RTBC $0.022 95 %

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

  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 WI Savings Boil-off $0.429 0 % 310K to 80K by RTBC, rest by boil-off $0.094 78 % 310K to 19K by RTBC $0.023 95 %

  8. 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 = 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. Pre-Chilling of Storage Tank: 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 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.

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