1

NASA JSC Chamber-A

LN2 System Upgrade

ByJLab Cryo Group

Presenter: VenkataRao GanniSeptember 18, 2012

2

Space Environment Simulation Lab (SESL)

NASA JSC Chamber-A

3

• Originally designed and used to create a low earth orbit environment to perform thermal-vacuum testing for all Apollo era manned spacecrafts

• Chamber-A is unique and mammoth– Height of 36.6 m (120’)– Outside diameter of 19.8 m (65’)– Hinged door diameter 12.2 m (40’)

Background of Chamber-A

4

Chamber-A

5

• Liquid Nitrogen Shroud in Chamber A– Divided into 28 zones– Provides 80K background environment for LEO simulation

• Forced flow system utilizing three primary pumps and one auxiliary pump with 40 HP each

• In excess of 100 control and isolation valves, and 100 RV’s and Burst Disks

• Six (6) storage tanks, total capacity of 144,000 gallons

• One 6,000 gallon “Boil-Off-Tank” with Vent Stack

Original LN2 System

6

– Storage: 6 Vessels, 144,000 Gallons Capacity, two truck unloading– Delivery: 3+ pumps, 6000 Gallon Separator, Steam/LN2-GN2 Vaporizer– Distribution: 28 shroud control zones

Original LN2 System (cont.)

7

• JWST is planned to be launched in 2018, on board an Ariane 5 into an L2 (quasi) Halo orbit at 1.5 million km (1 million miles) from Earth

• Chamber-A was selected for JWST ground testing because of its unique size and characteristics

• Expected to cost ~$1million/day for the overall program during ground testing, planned to be 90 to 120 days

• Needed an upgrade of most systems to meet the physical and technically demanding test requirements

James Webb Space Telescope (JWST) Testing

8

• Chamber Structure

• Vacuum Systems– B32 Roughing– New High Vacuum

• LN2 Systems (JLab)– Storage and distribution– Thermo Siphon– LN2 Shroud

• Helium System (JLab)– Refrigeration– New distribution– New GHe shroud

Major Systems

9

• A long duration test (such as JWST’s 90 to 120 days) requires that all systems be highly reliable and robust– Current LN2 pumps have a maintenance cycle of 300 hours while JWST

timeline approaches ten times this amount– System is electrical power dependant– Large number of control valves and relief devises in the system have low

reliability

• Thermal stability and uniformity of the internal helium shroud will depend upon a uniform, stable LN2 shield temperature– Failure of a control valve will disrupt uniformity of not only LN2 shroud but the

internal helium shroud as well– Too many valves to control for uniformity

• System as existed was not an efficient user of LN2– Up to eight truck loads (48,000 gallons) of LN2 per day at steady state

Reason For Upgrade

10

• Replace existing pumps with new cryogenic pumps having longer maintenance cycles

• Put the new pumps on emergency power to increase availability

• Rebuild or replace all of the control valves, pressure control and relief devises

• Rework the control system to maintain temperature uniformity at all chamber levels

• Repair or replace and re-insulate LN2 distribution lines to improve efficiency

• Convert one of the six supply tanks to a phase separator tank to increase the phase separation efficiency of the Boil-Off-Tank

Initial Upgrade Approach

11

• Pumps with 3000 hour capability that met the flow and pressure requirements would be a special design

• Installation of new pumps with double block and bleed capability required for real time maintenance was expensive

• Placing the pumps on emergency power was driving up the need and cost of a new generator

• Rebuild and/or replacement costs for the number of valves and pressure control devices was very expensive

• Reworking the control system to maintain temperature uniformity at all chamber levels was a complex undertaking

• Converting a supply tank to a phase separator tank increased system complexity

Problems with Initial Approach

12

3

Original Forced Flow System

13

14

Shroud panel fluid temperatures estimated to operate between 85K and 89K

Pressure Enthalpy Analysis (cont.)

15

• While a gravity flow system had been discussed previously it had been discarded due to the perceived technical risk of gas blockage

• Due to the cost estimates provided during PDR for the modifications, participants started to discuss this option again and to study the possibilities more rigorously

• Jefferson Lab performed analysis that showed the technical risk was much lower than originally perceived

Thermo Siphon A Fresh Approach

16

• Thermal-siphon had been previously demonstrated on smaller facilities that were designed and built with that mode of operation in mind. Would it work on an existing large facility ?

• JLab successfully built thermo-siphon cooling system for the 2K cold compressors

• A thermal model was developed for the existing system– The accuracy of the model was confirmed by comparison to actual

LN2 usage history in order to develop confidence in the modeling methods

Proof of Concept

17

Proof of Concept (Cont.)A Simplified Thermo Siphon Example

Phase SeparatorHead (1-2) 100 ft

30.5 m

Pressure 1.2 atm

Liq. Density 799 g/LVap. Density 5.4 g/L

1.2 atm

Density Ratio = 150

18

• A thermal model of the thermo-siphon system showed that the concept was feasible– Some features in the existing facility raised a concern

• Transition lines between sections of elevated shroud panels were small in diameter and in some non-vertical positions

– Some features of the facility were very favorable • Supply tank pressure ratings were sufficient to allow the use of vaporizer

pressure to push the LN2 to the phase separation tank on the top of the chamber

• Most distribution lines and headers were large enough in diameter to operate in this mode

• Building was tall enough to elevate the phase separation tank sufficiently to maintain sub cooled liquid (up to 2/3 of the height and thus helping flow distribution) well above areas where gas blockage was of concern

• System heat load was reduced significantly due to shorter transfer lines, fewer valves, and elimination of pumps

Proof of Concept (Cont.)

19

Thermo-siphon Analysis

20

• Most critical transition piece (node 15B) remains in the sub-cooled region

• Increased heat load the on shroud will decrease fluid density which automatically increases the fluid flow through the system

Pressure Enthalpy Analysis

21

Liquid Nitrogen – System Progress

LND PRE Apr 2007

LND PDR (Forced Flow)Jul 2007 Trade Study

(Forced Flow & Thermo-Siphon) Nov 2007

LND PDR (Thermo-Siphon )April 2008

CostTrade Study (Phase Separator-Truss Assy)Jan 2009

LND CDRThermo-SiphonMay 2009(Option 2A)

LND URRJune 2012

LN2 Shroud PDRApril 2007

LN2 Shroud CDRNovember 2007

LN2 Shroud CompleteNovember 2010

LN2 System Time Line

22

• Rationale for changing from forced flow (Pumps) to natural flow (Thermo-Siphon)

– Reliability• No major power draws• No rotating equipment• No short life limiting parts• Substantially reduced components (valves & relief valves)• Very few components require un-interruptible power

– Lowest Installation Cost

– Reduced Operation & Maintenance Cost

– This process provides lower temperatures in the chamber, while consuming less LN2

Decision for Thermo-Siphon April ‘08

23

Thermal Analysis

24

Quality vs. Pressure Distribution

25

Quality vs. Pressure Distribution

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0% 2% 4% 6% 8% 10% 12% 14% 16% 18% 20%

Saturated Liqu

id Position

 (l) [non

‐dim

.]

Pressure [a

tm]

Exit Quality (xe) [non‐dim.]

Available Dp Press. at #3Press. at #4 Press. at #5Sat. Liq. Position

26

Perameter Units Total ZONE A ZONE B ZONE C ZONE D ZONE E ZONE F ZONE G ZONE JZONE H-KLUNAR FLM. LOCKSSPARE 1SPARE 2

Load kW 181 17.4 17.4 18.3 24.4 20.9 21.2 16 8.7 19.1 11 1.5 2.5 2.5Ln2_Vap g/s 919 88.4 88.4 93.0 124.0 106.2 107.7 81.3 44.2 97.1 55.9 7.6 12.7 12.7Assumed quality % 5 5 5 5 5 5 5 5 5 5 5 5 5 5Ln2_Suply g/s 18385 1768 1768 1860 2480 2124 2155 1626 884 1941 1118 152 254 254Ln2_Sup_Valve_CV 2" 54 54 54 54 54 54 54 54 54 54 54 54 54Ln2_Warm-up_Valve_ 2" 54 54 54 54 54 54 54 54 54 54 54 54 54Supply line _Dp psi 5.74E-01Ln2_Sup_Valve_Dp psi 0.4 0.4 0.4 0.8 0.6 0.6 0.3 0.1 0.5 0.2 0.0 0.0 0.0Total Sup. Dp psi 1.0 1.0 1.0 1.3 1.1 1.1 0.9 0.7 1.0 0.7Zone_Load_Dp( retur psi 1.6 1.6 1.8 3.2 2.4 2.4 1.3 0.4 1.9 0.6Availabel_Dp psi 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3Dp_Margin psi 3.7 3.7 3.5 1.7 2.8 2.8 4.0 5.1 3.3 4.9Dp_Ratio (Total/Avail psi 41.2% 41.2% 44.2% 72.9% 55.7% 56.0% 35.6% 17.8% 47.2% 21.0%

Perameter Units Total ZONE A ZONE B ZONE C ZONE D ZONE E ZONE F ZONE G ZONE JZONE H-KLUNAR FLM. LOCKSSPARE 1SPARE 2

Load kW 181 17.4 17.4 18.3 24.4 20.9 21.2 16 8.7 19.1 11 1.5 2.5 2.5Ln2_Vap g/s 919 88.4 88.4 93.0 124.0 106.2 107.7 81.3 44.2 97.1 55.9 7.6 12.7 12.7Assumed quality % 10 10 10 10 10 10 10 10 10 10 10 10 10 10Ln2_Suply g/s 9193 884 884 930 1240 1062 1077 813 442 971 559 76 127 127Ln2_Sup_Valve_CV 2" 54 54 54 54 54 54 54 54 54 54 54 54 54Ln2_Warm-up_Valve_ 2" 54 54 54 54 54 54 54 54 54 54 54 54 54Supply line _Dp psi 1.19E-01Ln2_Sup_Valve_Dp psi 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.0 0.1 0.0 0.0 0.0 0.0Total Sup. Dp psi 0.2 0.2 0.2 0.3 0.3 0.3 0.2 0.1 0.2 0.2Zone_Load_Dp( retur psi 1.5 1.5 1.6 2.9 2.2 2.2 1.3 0.4 1.8 0.6Availabel_Dp psi 12.2 12.2 12.2 12.2 6.3 6.3 6.3 6.3 6.3 6.3Dp_Margin psi 10.5 10.5 10.4 9.0 3.8 3.9 4.7 5.7 4.3 5.5Dp_Ratio (Total/Avail psi 13.8% 13.8% 15.1% 26.6% 39.4% 39.5% 24.4% 9.3% 32.0% 11.9%

ZonesParameter

Parameter

Pressure Drop Analysis for Each Zone

27

Press. Drop Available & Req’d vs Exit Quality

28

LN2 Fluid Temperature

29

• Bake out

• Cool down

• Steady state

• LN2 drain

• Warm up

with door & scavenger panel operation at 80K

Required Modes of Operation for JWST

30

AREA 2(Room 1904)

Pressure Build Up Vaporizer

LN2 RecoveryColdbox

Nitrogen Steam Trim

HeaterN

Purpose of Vaporizers:-Generate (vaporize) GN2needed for Chamber A Bakeout and repressurization. (Must pass thru Nitrogen Steam Trim heater First)

Purpose of Pressure Build Up Vaporizer:-Generate (vaporize) GN2needed to pressurize the bulk storage tanks and move the liquid into the facility.

AREA 1(Tank Farm)

Warm Up Vaporizers

T k

Skid

Tank Pressure

Control Valve Skid

Equipment Layout

AREA 3

31

Pressure Build Up Vaporizer

Warm Up Vaporizer

s

LN2 Distribution- Area 1

Tank Pressure Control Valve Skid

LN2 Distribution – Area 1

32

AREA 2(Room 1904)

LN2 RecoveryColdbox

Nitrogen Steam Trim

HeaterN

LN2 Valve Box

Purpose of LN2 valve Box:LN2 Distribution gateway to:-Hi-Vac-Chamber A-Helium Coldboxes-Ch A Door

Purpose of LN2 Cold Box:-Sub-cool Pressurized Liquidincoming from tank farm.-Utilize Vapor return from Chamber A other wise vented to further pre-cool the LN2 from tank Farm.-Reduce LN2 Consumption

Purpose of N2 Steam Heater:Condition N2 for bakeout orChamber Repressurization.

LN2 Distribution – Area 2

33

GN2 Steam Trim Heater

LN2 Recovery Coldbox

LN2 Distribution – Area 2 (Cont.)

34

7th

Leve

l –Ph

ase

Sepa

rato

r pip

ing

Zone

A C

ontr

ol

–1s

tN

E1s

tN

orth

sid

e Zo

ne C

ontr

olDistribution System - Area 3

AREA 3High bay Outside of Chamber (Cold & Warm Piping)

35

LN2 Distribution- Piping Inside of Chamber

0’ Elevation

31’ Elevation

62’ Elevation

100’ Elevation

0’ Elevation

31’ Elevation

62’ Elevation

100’ Elevation

0’ to 100’ Elevation Col

lect

ive

Hea

ders

Zone

Jum

pers

Zone

Jum

pers

LN2

Out

let P

ipe

Rec

ircul

atio

n Li

nes

Supp

orts

LN2 Distribution- Chamber Instrument Panels

Liquid Nitrogen - Inside of Chamber

36

Liquid Nitrogen – New Zones H & K

Zone KZone H

37

Liquid Nitrogen - Inside of Chamber

N

Modifications:- Installed new shroud zones (Zones H&K) which now covers the pre-existing Side and Top Sun Areas.-Tied vertical subzones together with fluid jumpers with one inlet and one outlet. - Photogrammetry and Air Flow access holes- Down rod access holes-JWST Test article clearances above the door

Zone H (new)

Zone J

Zone K (new)

Lunar Floor

38

Overall Nitrogen System after Modifications

39

LN2 Tank Farm

40

Overall GN2 Distribution

41

LN2 Panel Temperatures at the Start

42

Bake Out After 1 Hr

43

Bake Out After 48 Hrs

44

Overall LN2 Distribution

45

LN2 Distribution in Quad-1

46

LN2 Panels at Steady State

47

Ceiling & Floor

48

Warm Up

49

QUADRANTS QUAD 1 QUAD 2 QUAD 3 QUAD 4 SCAVENGR

ZONES A,B, DIFF F,G, H-K ML, FLR., E C & D 40' DOOR J

START LEVEL (%) 45.0% 17.7% 27.0% 38.0% 31.0%START LEVEL (in H20) 19.5 8.7 14.6 18.1 14.8START TIME 10:08 AM 11:12 AM 11:38 AM 10:43 AM 9:29 AMDATE 8/16/2012 8/16/2012 8/16/2012 8/16/2012 8/16/2012TE-7155/TE-7177 (K) 83/79.2 86.9/79.2 85/86.6 83/79.2MILIAMPS 6.28mA 7.8 mA 8.8 mA

FINISH LEVEL (%) 93.90% 96.00% 94.00% 92.90% 92.90%FINISH LEVEL (in H20) 45.3 46.5 44.9 44.95 45MILIAMPS 16.16 mA 16.4 mA 16.2 mA 15.95 mA 16.02 mASTOP TIME 10.38 AM 11:36 AM 12:08 AM 11:07 AM 9:48 AMTE-7155/TE-7177 (K) 82.7/78.9 82.7/78.9 89/78.9 82/85 81.4/?

CLOSE MAKE VALVE 10.38 AM 11:36 AM 12:08 AM 11:07 AM 9:48 AM

PHASE SEP AT 0 % 12:05 PM 1:50 PM 1:54 PM 3:21 PM 4:30 PM

TIME TO VAPORIZE LN2 1 HR 2 HR 1 HR 4 HRS 6 HRS43 MIN 26 MIN 46 MIN 14 MIN 42 MIN

GALLONS USED 267 267 267 267 267

TOTALGallons/Hr 156 110 151 63 40 519Grams/s 134 94 130 54 34 447Heat Load (kW) 26.7 18.8 25.9 10.8 6.8 89

Heat Load in Each Zone

50

LN2 Consumption Comparison

51

– The overall heat load on the chamber has reduced…….• Radiant barrier on the old solar wall (30’x80’)?• Removal of drive shaft housing..?

– The pressure drop through panels less than predicted• Indicated pressure drop from 1960’s panels and piping is far

less than used in the model. (checking data)• This made the liquid quality about 1% vs design point of 3-5%

– Initially, this sent liquid to the vent lines– System designed with a recirculation valve to be capable to create

a pressure drop to adjust quality

Things we think we learned (need Verification..)

52

Pressure Taps

Importance of pressure tap elevation for liquid lines for pressure measurements

53

Test Objectives:• Validate Bakeout

- Goal: shroud average of > 45 ⁰C (30 ⁰C difference) [333-303K]

- Results: shroud average of 70 ⁰C(30 ⁰C difference)  [358-328 K]

• Validate Cool-down- Predicted: cool-down to steady-state ~12 hours- Results: cooled door to steady-state in 3 hours and main shrouds

in < 6 hours- Predicted: reduced LN2 usage for cool down from 58K gallons to

30K gallons- Results: Used ~18K gallons to cool panels

Functional Tests

54

• Validate Thermo-Siphon- Predicted: steady state usage 35K gal/day (vs. 48K gal/day)- Results: steady state use of LN2 ~24K gal/day

• Validate LN2 Drain- Drain liquid back to tank farm- Recovered ~1800 gallons to the tank farm

• Warm up with Door and Scavenger Panel at LN2 temperature- Operate door & scavenger panel at LN2 independently while all

the LN2 panels warm-up - Accomplished

Functional Tests (Cont.)

55

August 2012 Chamber-A successfully passed all the Ln2 system

functional tests

Exceed all expectations

Conclusions