LMSC-D877499

INVESTIGATION OF A PARA-ORTHO

HYDROGEN REACTOR FOR APPLICATION

TO SPACECRAFT SENSOR COOLING

FINAL REPORT

JANUARY 1983

by T.C.Nast

FOR NASA GODDARD SPACE FLIGHT CENTER

CONTRACT NAS 5-25792

Dr. Allan Sherman, Technical Officer

• f PALO AITO

RESEARCH LABORATORY -f

PAL O ALT O RESEARC H LABORATORIE S

LOCKHEED K«SS«.ES & SPACE COMPANY, INC. • A SUBSIDIARY OF LOCKHEED CORPORATION

PALO ALTO. CALFORNW
LMSC-D877499

INVESTIGATION OF A PARA-ORTHO

HYDROGEN REACTOR FOR APPLICATION

TO SPACECRAFT SENSOR COOLING

FINAL REPORT

JANUARY 1983

by T. C. Nast

FOR NASA GODDARD SPACE FLIGHT CENTER

CONTRACT NAS 5-25792

Dr. Allan Sherman, Technical Officer

Applied Materials and Technology Laboratory

Lockheed Missiles & Space Company, Inc.

3251 Hanover Street

Palo Alto, California 94304
LMSC-D877499

FOREWORD

The Lockheed Palo Alto Research Laboratory is submitting this final report in

fulfillment of the requirements of Contract NAS 5-25792. Mr. T. C. Nast was

Lockheed Project Manager, and Dr. Allan Sherman was the NASA-Goddard Space

Flight Center Technical Officer. Mr. 6. Bell did the initial work on the

design of the test apparatus. Mr. R. Grayson performed the literature search

and trade studies on the reactor. Mr. L. Naes performed a detailed thermal

analysis of the reactor assembly, and Dr. I. Hsu assisted in the testing and

data reduction.
LMSC-D877499

CONTENTS

Section Page

ILLUSTRATIONS iii

TABLES iv

1 INTRODUCTION 1-1

2 DESIGN AND ANALYSIS 2-1

2.1 Application to Instrument Cooling 2-1

2.2 Catalyst Selection and Reactivity 2-6

2.3 Reactor Design Trades 2-11

2.4 Selected Converter Design 2-17

3 TESTING 3-1

3.1 Test Apparatus 3-1

3.2 Test Results 3-6

4 CONCLUSIONS 4-1

REFERENCES R-l
LMSC-0877499

ILLUSTRATIONS

Figure Page

2-1 Para-Ortho Heat of Conversion Versus Conversion

Temperature 2-2

2-2 Overall System Process Diagram 2-3

2-3 Adiabatic Process Diagram 2-4

2-4 Isothermal Process Diagram 2-5

2-5 Equilibrium Composition for Hydrogen 2-8

2-6 Catalyst Activity Studies; e Versus Pressure,

Experimental Data 2-15

2-7 Cylindrical Bed Reactor Pressure Drop 2-18

2-8 Radial Flow Reactor Pressure Drop 2-19

2-9 Cylindrical Bed Reactor Configuration 2-20

2-10 Radial Flow Reactor Configuration 2-20

2-11 Selected Converter Design 2-22

2-12 Photograph of Reactor Showing Retention Screen 2-23

2-13 Photograph of Reactor-Outer Tube 2-23

3-1 Single Stage Solid Cooler 3-2

3-2 Catalytic Reactor Test Schematic 3-3

3-3 Reactor Assembly Cross Section 3-4

3-4 Reactor Assembly Photograph 3-5

3-5 Flow Diagram for Para-Ortho Reactor Tests - Series I 3-7

3-6 Calibration of GOW-MAC Gas Analyzer 3-8

3-7 Efficiency of Catalytic Reactor Versus Flow Rate of Hydrogen 3-10

3-8 Reactor Efficiency Versus Temperature 3-12

3-9 Percent Parahydrogen at Reactor Outlet Versus Catalyst

Temperature 3-13

3-10 Flow Diagram for Series-II Tests at Low Reactor Pressure 3-14

3-11 Correlation of Pressure Drop Through Bed 3-16

iii
LMSC-D877499

TABLES

Table Page

2-1 State Point Enthalpies 2-7

2-2 Comparison of Heat Absorption by Various Processes 2-7

2-3 Activities of Various Catalysts 2-10

2-4 Activities of Some Other Catalysts 2-11

2-5 APACHI-1 Catalyst Activity 2-12

2-6 Summary of Reactor Characteristics 2-20

3-1 Reactor Pressure Drop Data 3-16
LMSC-D877499

Section 1

INTRODUCTION

The utilization of solid hydrogen in space for sensor and instrument cooling

is a very efficient technique for long-term cooling or for cooling at high

heat rates. The solid hydrogen can provide temperatures as Tow as 7-8 K to

instruments. Vapor cooling can be utilized to reduce parasitic heat inputs to

the 7-8 K stage and can be effective in providing intermediate cooling for

instrument components operating at higher temperatures. The use of solid

hydrogen in place of helium may lead to weight reductions as large as a factor

of ten and an attendent reduction in system volume.

Hydrogen exists in two different molecular states: the para form in which the

protons have opposing spins, and the more energetic ortho form which has

unidirectional spins. At room temperature, normal hydrogen consists of

approximately 25 percent para and 75 percent ortho, while at the normal

boiling point temperature of 20.4 K and lower, the mixture is greater than

99 percent para. The endothermic conversion from 99 percent para to the

equilibrium composition, which is temperature dependent, is an extremely slow

reaction requiring hundreds of hours. Use of an appropriate catalyst can

reduce the reaction time to fractions of a second. It is, therefore, possible

to develop a catalytic reactor which can be located in the hydrogen vent line

of a dewar and will use the endothermicity of the para to ortho conversion to

enhance instrument cooling with hydrogen.

This report presents the results of an investigation of a catalytic reactor

for use with a solid hydrogen cooling system. Trade studies were performed on

several configurations of reactor to meet the requirements of high reactor

efficiency with low pressure drop. Results for the selected reactor design

are presented for both liquid hydrogen systems operating at near atmospheric

pressure and the solid hydrogen cooler operating as low as 1 torr.

1-1
LMSC-D877499

Section 2

DESIGN AND ANALYSIS

2.1 APPLICATION TO INSTRUMENT COOLING

A class of infrared instruments (Refs. 1 and 2) requires detector cooling to

10-13 K and also incorporates a cooled baffle which must operate in the

80-150 K temperature range to limit the background photon flux. The solid

hydrogen provides the focal plane cooling, while the baffle is cooled with

vapor from the sublimation of H2. A substantial increase in baffle cooling

can be achieved by incorporation of the endothermic catalytic converter at the

baffle. Fig. 2-1 shows the heat of conversion in the reactor as a function of

reactor temperature. As the curve shows, the maximum heat of conversion

occurs at 105 K.

The following describes the comparative benefits associated with various

reactor employments. For comparison with vapor cooling only it is assumed

that an optics module is cooled to 30 K with Ho vapor.

Figures 2-2, 2-3, and 2-4 are enthalpy-temperature plots representing the

overall thermodynamics of the catalytic conversion system. Figure 2-2 shows

lines of 100 percent para and equilibrium compositions. Figures 2-3 and 2-4

show an equilibrium composition line and percent para lines from 0 to

100 percent in increments of 10 percent.

Two operating process alternatives are of interest: an adiabatic catalytic

converter and an isothermal reactor. Both options use heat exchange from the

baffle to warm the hydrogen gas from 30 K (optics temperature) and then to

100 K (baffle temperature) (points (1) to (2) on the process diagrams). At

this point, because of the slow rates of equilibration, the gas stream is

still almost completely in the form of para-hydrogen. In the adiabatic

reactor, the catalyst causes the gas to quickly reach near 100 percent of its

2-1
LMSC-D877499

60 80 100 120 140 160 180 200 220 2UO 260 280 300

CONVERSION TEMPERATURE (K)

Fig. 2-1 Para-Ortho Heat of Conversion Versus Conversion Temperature

2-2
LMSC-D877499

ISOTHERMAL

CONVERSION

END POINT

38.

PARA P3

END POINT

42.9% / /\ ADIABATIC

PARA

, / I

49% "

PARA

2A

'ADIABATIC

CONVERSION

HEAT EXCHANGE WITH BAFFLE

VAPOR IN EQUILIBRIUM

WITH SOLID H2 AT 10 K

VAPOR WARMED BY HEAT 309.5- 100 = 209.5

EXCHANGE IN OPTICS

MODULE TO 30 K

HEAT EXCHANGE WITH

BAFFLE

ADIABATIC CONVERSION

HX AFTER CONVERSION

ENDOTHERMIC REACTION

AND HX IN REACTOR

HEAT EXCHANGE

WITH OPTICS 1416.4 - 1102.4 = 314

1490.8 - 1102.4=388.4

80 90 100 110

TEMPERATURE (K)

Fig. 2-2 Overall System Process Diagram

2-3
LMSC-D877499

TEMPERATURE (K)

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

_Q

Q_

800

700

600

500

400

300

200

100

0

I I I I I I

I

EQUILIBRIUM

EQUILIBRIUM

80 100

90

I I I I I

% PARA

10 30 50

0 20 40 60

I I I I I I I I I

2000

1900

1800

1700

1600

1500

1400

1300

1200

1100

1000

900

800

700

600

500

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280

TEMPERATURE (°R) _

Fig. 2-3 Adiabatic Process Diagram

Q_

2-4
LMSC-D877499

TEMPERATURE (K)

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

800

700

600

500

CO

Q_

X

Z

400

300

200

100

I I I I I 1 I I

EQUILIBRIUM

80 100

90

I I I I

% PARA

10 30 50

0 20 40 60

I

I I I I I I I I I I I I

2000

1900

1800

1700

1600

1500

1400

1300

1200

1100

100(5

900

800

700

600

500

400

300

200

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280

TEMPERATURE (°R)

Fig. 2-4 Isothermal Process Diagram

2-5
LMSC-D877499

equilibrium composition along a line of constant enthalpy. Since the para to

ortho conversion is an endothermic process, energy is removed from the gas,

causing the temperature to drop to about 79 K. The equilibrium composition at

this point ((2a) on the process diagrams) is 49 percent para. Because of the

very slow uncatalyzed reaction rates in the exit line, the gas is warmed by

the baffle along a line of constant composition (49 percent para) to a final

temperature of 100 K (point (4) on the process diagrams), a process which

contributes an additional 314 J/g cooling capacity to the uncatalyzed case

(1107 J/g versus 793 J/g, respectively). Ten watts of cooling may therefore

be attained by the adiabatic reactor with a hydrogen mass flow rate of

0.00903 g/s. With a flow rate equal to 0.01 g/s, 11.1 W may be extracted from

a 100 K baffle.

The isothermal reactor utilizes heat from the baffle to maintain a constant

gas temperature during a continuous conversion to the equilibrium composition

of 38.6 percent para at 100 K (point (3) on the process diagrams). There is

no further heat exchange in the exit line.

The enthalpy values for the various processes and a comparison of the heat

absorbed in the various processes are shown in Tables 2-1 and 2-2.

The test reactor will be designed for adiabatic operation, due to the

difficulties inherent in ensuring adequate heat transfer in the small catalyst

space as is required by the isothermal condition. However, because of heat

leaks from the test apparatus to the reactor, actual operation will be between

the adiabatic and isothermal conditions.

2.2 CATALYST SELECTION AND REACTIVITY

At low temperatures, the spontaneous conversion of para-H2 to the

equilibrium composition is very slow and is attributed to magnetic

interreactions between the ortho molecules. The kinetics follow a standard

o

bimolecular rate law of -dx/dt = Kx , with an uncatalyzed rate constant

2-6
LMSC-D877499

Table 2-1 STATE POINT ENTHALPIES

State/Process

1

2

1» 2

2

2> 2A

3

2> 3

4

2A» 4

c

H(J/g)

309.5

1102.4

1102.4

1490.8 ,

1416.4

AH(J/g)

792.9

0

388.4

314.0

(

Description

30 K gas from optics

100 K gas from baffle

', Cooling of baffle without catalytic

converter 78.9 K, 49 percent para

Adiabatic conversion 100 K, 38.6 percent

para

Isothermal conversion 100 K, 49 percent

; para

Heating of state 2A gas to final

temperature

Table 2-2 COMPARISON OF HEAT ABSORPTION BY VARIOUS PROCESSES

Process

Heat absorption by

vapor from 30 K to 100 K

Heat absorption with

isothermal reactor at 100 K

Heat absorption with

adiabatic converter

AH. J/g

793

388

314

K = 0.114 (Ref. 3), and where x represents the concentration of ortho or

para H2'. The equilibrium composition of H2 versus temperature is shown in

Figure 2-5.

An extensive literature search yielded data on activities of various catalysts

including metal films, metal hydride gels, and metals supported by alumina,

silica, oxides, or zeolites. In terms of a kinetic rate parameter such as Km

2-7
LMSC-D877499

80 100 120

TEMPERATURE (K)

140 160 180 200

Fig. 2-5 Equilibrium Composition for Hydrogen

2-8
LMSC-D877499

(molecules HU converted per second per mg catalyst), the most active

catalysts consist of Ni, Cu, or Fe films supported by alumina or silica. Most

researchers subscribe to a form of the Wigner theory of catalyst activity

whereby absolute conversion rates are proportional to the square of the

magnetic moment of the metal ion.

The physical mechanism of the conversion is believed to involve adsorption of

the \\2 molecules on paramagnetic sites, with the overall kinetics generally

following a first order Arrhenius rate law (Km = B exp (-E/RT)), where

Km is the catalyst specific reaction rate; Bm is the pre-exponential

factor; E is the activation energy in cal/mole; and R is the specific gas

constant. In addition to this mechanism, various chemical mechanisms have

also been proposed. Whereas in the paramagnetic mechanism the adsorbed pHp

molecule is magnetically switched to oH2, the chemical mechanisms involve

the splitting of the pH2 molecule into two H atoms, each on an uncovered

surface metal site of low binding energy, and then the recombination to

oH2. These are forms of the Bonhoeffer-Farkas (Ref. 4) mechanism which has no

diffusion retardation since the activity is due to the catalytic surface. The

chemical mechanisms are also approximately first order reversible Arrhenius

reactions. Because of the nature of the conversion mechanism, the para to

ortho conversion is the kinetically reversible reaction to ortho to para

conversion.

Table 2-3 lists various catalysts, experimental temperatures, pressures, and

relative activities found in the literature for the primary pressure range of

interest (1-10 torr). In formulating a common basis of units for K , all

2 catalysts were assumed to have an active surface area of 40 cm /mg, which is

an approximate value obtained from the literature. Also shown are the values

of 3, which is the ratio of grams of catalyst to grams per second of hydrogen

flow. This parameter is commonly used in reactor design.

Table 2-4 presents data which could not be converted to the common .1C

basis. It gives an indication of the relatively high activities of the

O catalysts. However, note that the order of the most active

2-9
LMSC-D877499

>-

, < I

i g

o

O

oo

ro

CM

cu

_a

(O

s^

o

c*

+J

Z3

^£

•

CO

cu

O CO

n \ ^^ Cf ^^

i— en

0 £

— -E

i *

en •

r—1

<T3

-t-> CO

O CM

-T~

C7) Q)

Ss_

0

l_>

+•**

0-

-— ^

^^

*— •*

4->

CO

>>

^~

rO

4->

rC

C_>

-

Lf>

r*^ =

en CD

t— H ^^

(_>1 ^

•> i— 1

e

ro c

-C = 2 =

-o o

3 S_

C£ CO

un «3

<+-' "^

• cu cu

^ s.

I-H I— 1 I— 1 I— 1

o o o o

X X X X

•3- CM LO CT>

i-H LQ 00 l£>

— -_-

IO LO <3- «£fo o o o

I— 1 I-H i-H I— 1

X X X X i— i oo LO ro

CM «3" CO «3-

1^ = = =

;

o

en

\ — ~ ~

r^"*

cu

>

cu

CO •(-

4-* t/^

•i- CU

•— > cu

O CU i —

CU O) -i- O

+-> I^J OO 2!

•r- "^^ "^^

i — CM CU CO

0 + •— +

QJ TD ^3 "^D

rsj Q. 2: z

i— i

uo r^.

r^ = = = en

en t— i <^ji~H ^^

" cn

Ct f^ , 1

E ^£

rO o f

f— — z ~ -r- >N

•O J3 CU

o: i^ LT]

j

cu cu cu

r** rv' fV

i— 1 I— H i — 1 i— 1 ,— 1 t—H

0 O 0 0 O 0

X X X X X X

V.O CVJ OO LO C*~^ f~^

O^ ^^ ^^ ^"^ ^^ CO

^^~ ^^~ ^J~ ^^ CO CO

o o o o o o

i— 1 i— 1 I-H i— 1 i— 1 < — 1

X X X X X X i— i LO oo o un <o

CO CM CM CM (^ ^H

o

= = = = i — I »J3

o r~-^

j |

CO

CO

= = = = II

l~^

iO)

CU O) CU CU "O

4-J 4-> -l-l 4^ ^

•1 — *r- "r- «r- O

r— r— i— 1— Q_

O O O O

CU CU O) CU E i^si r^j r^vi i^i ~^

"^^ "^^ *^^ "^^ 'r— CO

CSJ CM CvJ CM CO

+ + + + CU CM

2! C_) 21 0 Qi Q

LO

2

n

N

•r— r — to =

5 Cn O%

CU i— I i— i

•i—^ •> ri

C >) >->

rO CU CU

S- i— i— =

Li_ UJ LU

« » 2

cu cu ^

* ' * . ^

r— 1 I— 1 i — 1^- 1

O O O O

t-H i — 1 I — 1 t-H

X X X X

CO ^- LO LO

CO CVJ (NJ CM

0 O 0 0

t— 1 ,— 1 ,— 1 ,-H

X X X X

-H ^ LO LO

CM VD CM CM

r^ , ,

LO

en

i-H

1 1 O CO

o en r~~

r*- CM i— i

CO

E

•r—

Ll_

CM

., —

"Z. CO

o

CM

•Zi -ZZ LJ- LL.

(T>

i-H

**r

- = c

0

•— 4->

M i—

-M en

~ — GJ *i~~

**^ t/}

t-H CM

r— 1 i— 1

tl tl

Q^ QJ

r^^ r^N oo oo

i— 1 ,— 1 r— 1 ^H

O O O O

t-H t-H i — 1 t — 1

X X X X

VD l^~ CO CO

CM CM i-H t-H

O O O O

t— 1 I— H t-H t— 1

X X .X X

^ ^ 00 CO

— £ ?'-. " — ' Q- i t ]

o o,'

CM CM' ^ ^

t 1_H r^. r^

^D ^^r

oJ 'CM,

— —

'a!

CD

cv

0

r— OO

CU

CD LO

CO CM

O

CM O

•Z. l_> U- -Z.

('

„

'

li)

t— i \ x

<*5

CO '

I— 1

2-10
LMSC-D877499

catalysts (Ni/Al203 and hydrous ferric oxide gel) vary according to each

author and method of preparation.

Table 2-5 presents a summary of test data on a high surface area Ni on

silicate catalyst (APACHI-1) at pressures in the range of 3.52 x 105 ~ 1.03

x 10 Pa. The data are summarized in Fig. 2-6 in terms of e versus

pressure. Only & values for near complete conversion (^95 percent) are shown.

The available data on the catalysts indicate the APACHI-1 is among the most

active if not the most active catalyst available. In addition it is

commercially available, whereas most of the others are available in

experimental batches or not at all. Based on these considerations, APACHI-1

was selected for reactor studies. Unfortunately, data on the APACHI-1 at low

pressure is not available. Therefore an extrapolation to the operating

pressure of ~ 2 torr is required.

A minimum value of e of 1000 based on a study of the data was selected for

design. This value is shown in Fig. 2-6.

2.3 DESIGN TRADES

Having selected a value of e of 1000 g catalyst per g H^/s flow rate, which

our extrapolation of available data indicates will yield complete conversion,

the primary problem is minimizing the pressure drop in the reactor. The

catalyst volume required is based on a catalyst density of 0.45 g/cm .

Pressure drop through the catalyst bed was calculated using the Ergun

relationship for pressure drop through packed beds with negligible static head

and for particles of similar size and shape. The relationship may be

expressed as:

2-11
LMSC-D877499

Table 2-4 ACTIVITIES OF SOME OTHER CATALYSTS

Mos

on

Catalyst

Sampl e

1 9% Cr 0 /Al 0 2 3 2 3

\ ,

0.5% CuO/Al90,

tL o

;

 0.5% N10/A1,0,

tL 6

0.5% Cu/AKO,

L J

0.5% N1(A)/A190,

y "." c. J

i .J

Ferric Oxide Gel

(Weitzel)

t Active 0.5% Ni(B)/Al?03

a Wt. basis

0.5% Mn202/Al203

0.5% Tb90.,/Al 90,

(L 6 <L 6

0.5% Pd/Al90,

2 3

5.0% NHDAUO,

L. J

5.0% Ni(X) A1203

0.5% Tb09/Zr02

^

,

T

77'K

Density

(g/cm3)

1.34

1.26

1.43

1.26

1.43

1.33

1.28

1.69 ,

1

|

1 .41 I1

i ,

1.84

i !

1 .91 '

i

3.63

Wt

(g)

9.30'"

••'

';

3.86

3.66

3.86

3.66

3.21

3.38

4.70

4.11

3.84

1

2.55 !

6.58

Pres-

^sure

xlO^a)

/r 1

'2.86

0.79

0.45

278lf

0.79

2.86

0.79

2.86

0.79

2.86

0.79

0.45

2.86

0.45

2.86

0.79

2.86

0.79

2.86

0.79

2.861

0.79

2.86

0.79i

2.86

0.79

0.45,

Act. '

Ener.

(E) -

kcal/mol(

0.99

0.99

0.99

0.97

0.98

0.95

0.96

_

-

0.77

0.81

0.85

0.70

0.81

0.94 ,

0.95

0.93 .

0.94 ;

I

1

 _ \

i

0.85

0.86

0.42

0.45 ,

0.96

 :

0.97

0.98 .

K

3 '

0.099x10"!

0.076x10"!

0.060x10

0.33x10"!

0.27x10

0.51xlO"J

0.34xlO"4

0

0

3.0x10"!

2.2x10"!

1.7x10"^

n

5.2x10^

0.76x10"!

0.63x10"^

0.41x10"!

0.32x10

0

0

0.84x10"!

0.69xlO"H

8.9x10"!

5.7x10"^

0.20x10"!

0.17x10";

0.11x10"^

Relative

Activity

1 .0

3.3

"

: 5.2

0

30

4.0

53

7.7

4.1

i

,

1 o

8.5

90

i

1

 2.0

i

2-1-2
LMSC-D877499

Table 2-5 APACHI-1 CATALYST ACTIVITY

Point

1 ,

2

3

4

5

6

7

8

9

•10

lla

lib

12 ,

13

14

15

16

17a

17b

18 ,

19

20

21

22

23

24

25

26

27

28

L .. . -

Tin( K)

86.7

97.8

76.7

110

97.2

86.7

86.7

70.6

132.8

132.8

119.4

119.4

90.

67.2

56.1

147?8

110.

88.9

88.9 •

79.4

67.2

56.7

133.9

88.9

122.8 •

111.1

100.

66.7

56.1

147.2

' P(Pa )

3.50xl05

3.72xl05

3.72xl05

3.72xl05

3.72xl05

3.72xl05

3.72xl05

3.72xl05

3.65xlOS

3.50xlOs

3.72xl05

3.72xl05

3.72xl05

3.72xl05

3.72xl05

3.65xl05

3.65xi05

3.65xl05

3.65xl05

3.65xi05

i

3.65xl05

3.65xl05<

3.78xi05

3.72xl05

3.78xl05

3.72xl05

3.72xl05;

3.72xl05

3.72xl05

3.72xl05

i _

M(g/s)

.668

.643

.655

.630

.630

.643

.428

.643

.668

.435

.605

.605

.643

.655

.655

.504

.580

.605

.605

.605

.630

.643

.643

.491

.416

.454

.491

.567

.580

.340

Dp(mesh)

16-25

30-40

30-40

. 30-40

30-40

30-40

t

30-40

 l

1 30-40

! 16-25

16-25

1 30-40

30-40

30-40 ,

30-40 i

: 30-40 ,

50-80

50-80

50-80

50-80

 ;

50-80

50-80

! 50-80

16-25

80-140

80-140 ;

;

 80-140 :

80-140

80-140 !

80-140

 ;

80-140

/g catalystx

9H2/S:

104.

61.8

80.8

84.

82.4

82.4

124.

61.8

104.

160.

110.

87.7

82.4

80.8

80.8

117.

81.6

78.

74.9

78.

74.9

73.5

102.

83.9

99.

90.8

83.9

52.5

51.3

121.

y equilibrium ,

0

 conversion \

94.3 ''

100

98.5

99.9

99.8

96.5

98.8

99.2 '

1 96.0

99.7

99.7 \

99.0

100.

100.

99.5

98.3

99 . 6

100.

100.

100.

100.

100.

99.5

93.9

64.7

81.5

• 90.

96.4

96.4

26.7

'

2-137*
LMSC-D877499

Table 2-5 APACHI-1 CATALYST — • — - ( '_,

Point

29

30

31

32

33

34

35

36

37

f

3 8

39

40

41

42

43

44 j

45 '

46 ,

47

48

49

50

51

52 !t

,53 '

54

55

56

JTin ( K)

144.4

141.7

138.9

1 76.1

100.

;

 99.4

143.9

121.7

100.

j 78.9

i 99.4

100.6

1100.

122.2

111.1

88.9

77.8

144.4

122.2

100.

100.

122.2

99.4

100.

77.2

100.

78.3

98.9

1

i

1

1

'

I

1

V(PaV

J3.72xl05

3.72xl05

3.72xl05

3.72xl05J

'6.93xl06

7.17xl06

1.05xl07

1.06X107

1.05xl07

1.04xl07

l.OSxlO7

7.01xl06

3.46xl06

6.87xl06

1.05xl07

1.04xl07

6.96xl06

1 l.OSxlO7

! l.OSxlO7

l.OSxlO7

1.04xl07

6.94xl06

7.09xl06

7.04xl06

7.05xl06

3.53xl06

1.03xl07

1.04*1 07

M(g/s) '

.340

.353

.325

.567

.630

1.273

.630

.617

.617

.617

1.273

.592

.592

.617

.630

.630

.592

.617

.630

.617

1.285

.617

.617

1.273

.617

.617

.617

.617

Dp(mesh)

I

,' 80-140

80-140

80-140

80-140

50-80

50-80 '

50-80

50-80

50-80

50-80 i

50-80

50-80

50-80

50-80

50-80

50-80

50-80

30-40

30-40

30-40

30-40

30-40

30-40

30-40

30-40

30-40

30-40

16-25

/

c /g catalyst^

gH2/s' ,

121.

117.

113.

53.7

23.6

11.8

23.6

24.2

24.2

24.2

11.8

25.1

25.1

24.2

23.6

23.6

25.1

26.8

26.2

26.8

12.9

26.8

26.8

13.0

26.8

26.8

26.8

27.5

i

0, equil ibrium

conversion

b

 26.7 .

32.1

36.6

99.3

92.7

68.9

j 77.7

' 87.8

94.8

96.0 .

70.5

,91.5 ;

92.5

1 83.5

89.0

94.8 j

90.8

89.4 '

93.0 |

96.0 I

75.0

92.5

94.5

75.0

97.6

96.1

95.8

94.0

(

.

2-14,
LMSC-D877499

'-X,.

10"

5 10 TO

PRESSURE (torr)

1

 IO3 10^ IO

10"

l/l

U

1

 10W

o>

IO

10

^T

IO

"

2

SYMBOLS

X ZEOLITES

O MOLE SIEVE

® RHENIUM POWDER

D (l)Dy203; (2)Nd2C>3

O Ni, NiH2 FILMS

A Fe

0 Ni

• Co

-SELECTED

DESIGN POINT

= 1000

j 1 APACHI-1

APACHI-1

l,9,llo,21

3,4,5,6,lib,8a,12,

35 TO 38

43,44,46,

0.5 5.0 50 500

IO

"

1

10 10 10Z

PRESSURE (psi)

IO

5000

IO4

Fig. 2-6 Catalyst Activities Versus Pressure - Experimental Data

2-15
LMSC-D877499

where

2

G = pU mass flowrate of fluid in tube (Ib /ft s)

Um = superficial fluid velocity at average pressure (ft/s)

D = particle diameter (ft)

e = fractional void volume in bed

u = fluid viscosity at average temperature and pressure (Ib /ft s)

= pressure drop per unit length (Ibf/ft2/ft)

U = superficial fluid velocity based on empty column cross section

(ft/s)

2

Since G = pU - m/A, g = 32.2 ft Ib /lbf s , and e was assumed equal to 0.45

t* rn T

(a value obtained from the literature), the Ergun equation may be simplified

to:

0.1874G •

V

The first term is the viscous contribution, while the second part is the

energy term. The pressure drop is dependent upon the size and shape of the

catalyst particles and not upon the material. Therefore, this equation is

valid for any catalyst.

Two design options were considered: a cylindrical and a radial flow reactor.

Because of the low pressure drop requirements for a solid H2 cooler, the

cylindrical design must be thin and have a large cross-sectional area, much

like a pancake. In the radial flow reactor, gas enters through a central tube

and flows radially outward through the toroidal catalyst bed and into the

outer annulus, where it flows axially out of the reactor section. For an

2-16
LMSC-D877499

equivalent reactor diameter and catalyst weight, the radial flow reactor has

much less pressure drop than the cylindrical. The only advantage inherent in

the latter lies in its relative simplicity. To achieve pressure drops about

equal to those in the radial flow reactor, the cylindrical reactor must have a

bed diameter of 2.5 in. This leads to a very thin bed (0.28 in.) under the

constraint of a fixed & = 1000.

Figures 2-7 and 2-8 show reactor pressure drop as a function of particle mesh

size, reactor length, and radial size. Each line represents a combination of

particle and radial size; inner tube diameter and annulus width for the radial

flow reactor and bed diameter for the cylindrical. The abscissa for the

cylindrical reactor is reactor length. Fixing an appropriate length

determines e for each specific bed diameter. For the radial flow reactor, the

abscissa is the catalyst thickness, which together with the other two radial

dimensions and the catalyst packing density determines e.

For a radial flow reactor which has an inlet tube diameter of 0.5 in., a

catalyst bed radial thickness of 0.25 in., and an axial length of 2.073 in.,

and an outer annulus of 0.25 in., the total inside diameter is 1.5 in., with a

packed catalyst weight of 10.0 g. Pressure drops through the reactor for 10,

15 and 20 mesh particles are predicted to be 0.13, 0.23, and 0.37 torr,

respectively, for a mass flow rate of 0.01 g H2/s, an inlet temperature of

100 K, and an inlet pressure of 2 torr, which is the vapor pressure of gas

over solid hydrogen at about 10 K. The general configuration of the reactor

designs is shown in Figs. 2-9 and 2-10.

2.4 SELECTED CONVERTER DESIGN

The final catalytic converter design is shown in Fig. 2-9. The catalyst is

retained with fine mesh stainless steel screen. Threaded plugs in the end cap

permit loading and unloading of the catalyst. The volume of the catalyst

space is 51.5 cm3. This design gives a e value of 2,490 s"1 based on a

flow rate of 0.01 g/s H2 and a measured catalyst quantity of 24.9 g. This

value exceeds the estimated required value of 1000 s"*.

2-17
LMSC-D877499

o

0.25

BED THICKNESS, L (cm)

0.5 0.75 1.0 1.25 1.50

REACTOR DIAMETER = 2.5 (in.)

= 1000 s (6.45 cm)

0. 10 J 0.20 0.30 0.40

BED THICKNESS, L (in.)

0.50 0.60

Fig. 2-7 Cylindrical Bed Reactor Pressure Drop

2-18

c\
LMSC-D877499

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

~ 1.2

i 1.1 <§.

_, 1.0

O 0.9

^f-1 0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

CATALYST-THICK NESS, AX (cm)

1.0 2.0 3.0

D1 = 1/2 in., Ad = 1/4 in.

D] = 1/4 in., Ad = 1/8 in.

O 10 MESH

D 15 MESH

A 20 MESH

® 30 MESH

D1 =1/4 in., Ad = 1/8 in.

1/4 \n., Ad = 1/8 in.

Dj =- 1/2 in., Ad=» 1/4 in.

Dj -1/2 in., Ad = 1/4 in.

1/2 in.

Ad => 1/4 in.

= 1/4 in., Ad = 1/4 in.

3/8 in.

Ad - 3/8 in.

1/2 in., Ad = 1/4 in.

-DESIGN POINT

I I I I

0.7

'0.6

0.5

0.4

IO

Ir- Q-l-l

'0.3 <d

0.2

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 ,1.3 1.4

CATALYST THICKNESS,AX (in.)

Fig. 2-8 Radial Flow Reactor Pressure Drop

2-19^,
*«!>

•r

LMSC-D877499

-•—L

CATALYST^

D

SCREEN

Fig. 2-9 Cylimjrical Bed Reactor Configuration

INLET TUBE

CATALYST

SCREEN

STAINLESS STEEL

FILL HOLE

PLUGS

Fig. 2-10 Radial Flow Reactor Configuration

24,20
LMSC-D877499

Figs. 2-12 and 2-13 show the reactor during fabrication. The outer retaining

screen is visible on Fig. 2-12 as is the outer thermocouple rake for

measurement of gas temperatures. Fig. 2-13 shows the outer tube of the

reactor. The vacuum tight wire feed-throughs are also visible. Two pressure

ports to measure inlet and outlet temperatures can also be seen. The end cap

with the filling plugs is visible.

The reactor was loaded with HSC-197 (APACHI-1) catalyst available from Air

Products and Chemicals, Inc. The catalyst was 30 x 50 mesh from batch

no. 198CX6-2 which was tested for reactivity by Air Products. The chemical

formulation is NiSi04 ' (Si03)3 2 ' (H2°^5 6'

 A summary of reactor

characteristics is presented in Table 2-6.

Table 2-6 SUMMARY OF REACTOR CHARACTERISTICS

Catalyst Type:

Catalyst Quantity:

Overall Diameter:

Overall Length:

Catalyst Volume:

Effective Density as Loaded:

HSC-197 (APACHI-1), Nickel on Silica

0-P H2 Shift (30 x 50 Mesh) Sample

No. 198Cx6-2

24.9 g

2 in. (5.08 cm)

5.5 in. (14.0 cm)

51.5 cm3

0.484 g/cm3

2-21
LMSC-D877499

E

o

PO

CO

en

i/>

a

O)

sO)

T3

0)

O

<U

OO

I

CM

2-22:
LMSC-D877499

Section 3

TESTING

3.1 TEST APPARATUS

The tests utilized a solid cryogen cooler from a prior program. The cooler

was loaded with solid hydrogen and utilized as a low-pressure gas source to

the reactor. Details of this cooler and the solid hydrogen tests conducted

with it are given in Ref. 13. The cooler's configuration is shown in Fig. 3-1.

The overall test schematic of the system is presented in Fig. 3-2. Details of

the reactor setup and the gas analyzer will follow. The test setup provides

for evacuation of the insulation space around the hydrogen tank to a vacuum

level of 10 or lower, transfer lines to fill the tank with liquid

hydrogen, and a coolant loop which may be utilized to freeze and subcool the

liquid hydrogen with helium. The liquid hydrogen may also be solidified by

direct vacuum pumping of the ullage space. The reactor is located in the vent

line of the cooler. The hydrogen tank can be utilized as a source of gas to

the reactor at pressures from approximately 1.38 x 105 Pa down to 1 torr by

varying the valve settings, primarily valve VI to the mechanical pump and

valve V4 to the facility vent.

The catalytic reactor assembly consists of the reactor described in

section 2.4 along with a LN^ guard pot and an intermediate shroud with

heater to maintain nearly adiabatic conditions for the reactor. The inlet and

outlet pressure of the reactor was measured with a Wallace and Tiernen gage

with a 0 to 20 torr range. A pair of thermocouple rakes containing 4 absolute

and 5 differential thermocouples were mounted on the reactor and can be seen

in Fig. 2-12. The cross section of the reactor assembly can be seen in

Fig. 3-3. The photograph of the reactor assembly is shown in Fig. 3-4.

3-1
LMSC-D877499

ccomtJT

2MTISU6L4.S

DOUBLE AUtUINIZED

MYLAR

IM-iTRUMEMT

CONNECTION

•ilMGLE ST\GS SOUO

COOLE.R

XICOOtlDCNTI DtuuMIM NO I M

|l7Q77|:TII790'-.OS |l

fig. 3-1 Single-Stage Solid Cooler

3-2
LMSC-D877499

SYMBOLS

V

AV -

RV -

RP -

DP -

CP -

WTM -

PG -

SC -

QD -

C

TS

HE -

PS -

GHe -

LN2 -

LHe -

LH2 -

CT -

VT -

VM -

Cl -

CO -

FV -

CV -

VJ -

CRA -

MANUAL VALVE

AUTOMATIC VALVE

RELIEF VALVE

ROUGHING PUMP

DIFFUSION PUMP

COLD TRAP

WET TEST METER

PRESSURE GAUGE

SWAGELOK CONNECTOR

QUICK DISCONNECT

CRYOSTAT

TEMPERATURE SENSOR

HEAT EXCHANGER

PURGE SHROUD

GASEOUS HELIUM

LIQUID NITROGEN

LIQUID HELIUM

LIQUID HYDROGEN

CRYOGEN TANK

CRYOGEN VENT

VACUUM SPACE

COOLING INLET

COOLING OUTLET

FACILITY VENT

CALIBRATED VOLUME

HELIUM INLET

VACUUM JACKET

CATALYTIC

REACTOR

ASSEMBLY

V16H

Fig. 3-2 Catalytic Reactor Test Schematic

3-3
LMSC-D877499
LMSC-D877499

During the tests a GOW-MAC Model 24-150 thermal conductivity gas analyzer was

utilized. This instrument inferred the para-ortho concentration at the

reactor outlet by a measurement of the thermal conductivity of the gas stream.

3.2 TEST RESULTS

Initial tests were conducted without the gas analyzer, relying instead on the

temperature measurements in the inlet and outlet streams and performing a heat

balance to determine the reactor efficiency. This technique was not

successful. Subsequent detailed thermal analysis of the reactor showed that

the apparatus was not sufficiently adiabatic for this approach.

The tests with the gas analyzer were conducted in two series: Series I

conducted with liquid hydrogen at a pressure of approximately 1.38 x 10 Pa,

and Series II with solid hydrogen down to pressures as low as 1 torr.

Series I Tests

The flow diagram for these tests is shown in Fig. 3-5. Numerous combinations

of the valves 1-6 can be utilized for calibration of the GOW-MAC to obtain

reactor efficiency data and to verify calibration during any point in the

test. Initial calibration of the GOW-MAC consisted of passing normal hydrogen

gas (25 percent para) through inlet B and boil-off from liquid hydrogen

(99.9 percent para) from the test cooler through inlet A.

The flow rates were balanced and controlled by valve adjustments and

observations of the flow meters. A second calibration point was obtained by

passing the normal hydrogen gas through both sides. In this manner the

GOW-MAC was set up to run with normal hydrogen gas as the reference gas for

all tests, and the unknown or calibration gas was passed through inlet A. The

resulting calibration is shown in Fig. 3-6. Various additional checks on the

GOW-MAC operation were also made. For example, LH^ boil-off was passed

through both sides to ensure a zero output of the meter. During the tests the

3-6
LMSC-D877499

0)

O)

C/)

I

Kl

10

01

o

+J

(J

«3

(I)

o

I

(O

fO

D.

So

(O

en

fO

s

o

in

ro

CT)

3-7
LMSC-D877499

3.0

u

<2.0

i

o

o

u.

O

hCL

Io 1-0

20

EQUILIBRIUM

CONCENTRATION OF

PARAHYDROGEN WITH

RESPECT TO TEMPER

ATURE

CALIBRATION

A 6-16-82

D 6-17

O 6-18

COW-MAC T.C. CELL

FILAMENT CURRENT = 100 mA

I

20

100

200

LLJ

Qi

a:

LU

a.

LU

300

40 50 60 70 80

PERCENT OF PARAHYDROGEN

90 100

Fig. 3-6 Calibration of GOW-MAC Gas Analyzer

3-8
LMSC-D877499

calibrations were checked, for example by opening valve 1 to bring

99.9 percent para to the GOW-MAC to check its output. It was felt that checks

of this type were essential to rule out contamination of the gas due to leaks

or other sources. The output is very sensitive to minute quantities of

foreign gases. During the tests the test cooler was loaded with LHp and

allowed to self pressurize to approximately 1.38 x ICr Pa and the boil-off

gas was passed through the reactor where it was monitored at the GOW-MAC for

percent parahydrogen content.

Fig. 3-7 presents the conversion efficiency of the reactor as a function of

the volumetric flow rate of H2. The efficiency is defined as:

Percent Efficiency =

 Cinlet - Cout1et x 10Q

inlet equilibrium

During a test series the reactor temperature tended to change slowly, as it

was difficult to establish steady flow and temperature conditions independently. Changes in the flow rate led to changes in reactor temperature. The

data were grouped into three temperature regimes shown on the figure. The

reaction rate (percent efficiency) is shown to be a strong function of both

temperature and flow rate.

The catalyst which was used in the reactor spent a substantial time (several

months) exposed to the atmosphere during the various assembly stages and was

not heated prior to the tests. Some of the test points were repeated after

purging of the catalyst for approximately six hours with room temperature

helium. These repeat points showed a negligible effect of this purging as

indicated on the figure. Recharging the catalyst with gas at elevated

temperatures was not performed.

The data show a strong effect of reactor temperature. The activity at

103-120 K is much higher than at 226-297 K.

3-9
LMSC-D877499

DI1AHV1VD JO ADN3IDIJJ3 !N3Dy3d

3-10
LMSC-D877499

Figure 3-8 presents the efficiency of the reactor as a function of the

catalyst temperature for various flow rates. The data seem to indicate a

maximum reactivity at or near 100 K.

Figure 3-9 presents the percent para-hydrogen at the reactor outlet as a

function of the catalyst temperature at various flow rates. The low-pressure

data are also shown. The equilibrium concentration of para-hydrogen with

temperature is also shown.

During the Series-I tests the pressure drop through the reactor was not

measured.

Series II Tests

For the Series II tests the apparatus was modified so that the GOW-MAC

apparatus could be calibrated and operated at pressures below atmospheric

pressure. The flow diagram for the tests is shown in Fig. 3-10. The

calibration of the GOW-MAC was repeated at pressures below 1 atmosphere. Good

agreement with the prior calibration was obtained for pressures down to about

1/2 atmosphere absolute. Below this pressure the calibration became

unrepeatable and unstable.

During the tests the test cooler was filled with NBP hydrogen and then pumped

with vacuum pump A until it was solidified. Once adequate solid hydrogen

temperatures were established, the gas sampling proceeded in the following

manner: the flow stream from the reactor after passing through the mechanical

pump was split into two streams, one going to the flow meter for measurement

and the other going to the GOW-MAC. This stream was passed through a LN2

cold trap to remove contaminants from the pump and then was throttled to a

lower pressure prior to passing through the GOW-MAC, where it was metered

passing through the GOW-MAC and through a second mechanical pump B, and then

to the facility vent. A second LN2 trap guarded the GOW-MAC from back

diffusion of contaminants from this pump. This procedure was necessary to

obtain a sufficient pressure head through the GOW-MAC. The pressures in the

3-11
LMSC-D877499

0.

H

!«/)

•SI

jfSV

f^

(N

o

•

o

V

•>

V

1

1 fN

o

•

o

R>

ST '

H i

> (/) \ S • -

>-£ n \ M

(0 "-p

^ 3 n 2 °. n -

x ? 0 ^

 z

M n

 2 i

-' «fm* 0 < n

II °

;

 ui " 0 n &. .-> ! LJ

~.^» ""^ —

O CO (/) •• XS ^1

a- 0 Jn k. NX <J 1-1

o o J2 i- u

• • XJ o o o K *-•

V V * ~ <3 < H Z i ^ _ •> •> uj _ n

(J

V V 0

M 2 "

 "* ^ x^ ^<

S g 0 rM O <]

• • ^* ^ 0 0 I Q.

0 < ~"n^

 <

<^*^

6>

^

v _

o

oo

0

r^

ID

O

in

X

S i-

^ 10

>

<1

o t PO ^

- U

U.

O

0 HI

(N C£

*~ D

1-

<

£

O*TM 1 " LU 1 1

^ ^S

III

1-

o

o

0

O)

o

oo

1 1 1 1 1 1

O O O o o O

o oo to a- <M

(U

S-

(O

OJ

CL

o;

s_

<u

O)

<J

so

' 4->

o

(O

OJ

o;

oo

CD

CJ31H3ANOD DI1A1V±VO JO ADN3IDIJJ3 !N3Dy3d

3-12
LMSC-D87749

9

i—r

CL

1-

t/>J.

isrij£oo v m o e

n

m i£> r^j =r ffi o o o o o

--^ o o o o o

j_ V V V V V £ > > » > V V V V V

*«."F <N t- i— co in

tC5.' m a- rg ro co

c o o o o o

U, -SSS 00000

r" oooo'-

r~ . . . • Q.

< O O O O J_

<£ LO II II II II » 5 — I , O Q- U.

-II- U

"-z!2 ^moo

IjLlJ ^.^-^^OfNOiam

— O U-U-U-U-^^o^-'m

£0 UUUU v v v v v

go ^ £ S 2 •>•>•>•>•>

D ^I do^m vvvvv

1 -L.

on. S3££§

> 0 ->•>->•> ^ ^ d ^ «

doa aooOO <

S^ b fct"T"

uj o 2 3 S «

0

Qi |— i£> ro r^ •—

^tfl S^ ^ ^ ^- x " £* ' " nr°- 1i £ U i/i0X ^ - 1 " 1 /v / "* Q 1 H / X / B / <S / >u / ?/ y/

i•i•ii•////ifk\\\U

. O

Zuj

0*Mt£ < \-

 OL

C UJ

"I

§O^X

st

DS i 0^DMOin<N§ 2 CM v_. H

i/)>_l <C<U

0 LL

S oHI o: 3^<

'

£UJCL

_ S § Hoin

DC rs

CQi

dcL

DaU

i

-p

<T3 o3

I/)S- <DO) s_o

•4->o(O<u

<T3 cO) enoS- "a

 I

(Oi-(Oo>oS- 01 Q. enI CO

o<0

ro

oCM

iv

3-13
LMSC-D877499

0)

ai

o.

so

4->

O

(O

OJ

o

(O

a>

0)

si

OJ

oo

fO

S3

O

I

CO

en

3-14
LMSC-D877499

GOW-MAC as measured with pressure gage PC were in the range of 5.08 -

10.16 cm of vacuum.

The reactor efficiency data obtained during these tests are presented in

Figs. 3-7, 3-8, and 3-9 along with the Series-I data at higher pressures.

Figure 3-7 shows the reactor efficiency for tests conducted at 1.4 to 2 torr

reactor pressure.

The data are grouped into three temperature ranges. If one compares the data

in the 160-163 K range with the data at high pressures (1.45 x 10^ Pa), the

data appear somewhat lower for the low-pressure runs (27 percent versus

35 percent). The effect of flow rate on efficiency is similar for both

pressure ranges.

Figure 3-8 shows efficiency versus catalyst temperature from 127-169 K. The

data do not appear to be extensive enough to draw any conclusions about the

effect of temperature on reactor efficiency. Because of the reactor operation

the lower temperature points are at the highest range of the flow

(0.062 rrr/h), and as the temperature increases the flow rates drop to

1.4 CFH at 169 K. Accounting for the flow rate effect on efficiency it

appears that there is relatively little effect of temperature on efficiency.

One data point is shown at 0.011 m3/h, 13 torr, and 163 K which indicates

approximately 86 percent reactor efficiency, indicating that for sufficiently

low flows the efficiency approaches 100 percent.

The low-pressure data for various conditions are also presented in Fig. 3-9 .

Pressure Drop

The pressure drop across the reactor bed was measured with a Wallace-Tiernan

gage with 0 to 20-torr range. A correlation between measured and predicted

pressure drop is shown in Fig. 3-11. The predicted pressure drop is shown in

Fig. 3-11. The predicted pressure drop was based on the Ergun expression

(page 2-15). The fractional void volume in the bed was assumed equal to

3-15
LMSC-D877499

0.2 0.1

PREDICTED PRESSURE DROP (torr)

0.6

Fig. 3-11 Correlation of Pressure Drop Through Bed

0.45. The particle diameter for the catalyst was assumed equal to 0.0594 cm.

This value was selected based upon the 30 x 50-mesh size particles. A 40-mesh

average was assumed. The estimated reading uncertainty of the gage is

indicated on the data points. The agreement is quite good and indicates the

small pressure drops achieved through the bed. The test conditions for this

data are summarized in Table 3-1.

Table 3-1 REACTOR PRESSURE-DROP DATA

Flow Rate

(m3/h) (STP)

0.074

0.058

0.052

0.263

Reactor

Temperature

(K)

85

101

142

167

'Average Reactor

Pressure

(torr)

2.47

2.06

1.79

7.65

Pressure

Drop

(torr)

0.05

0.12

0.22

0.50

3-16
LMSC-D877499

Section 4

CONCLUSIONS

The operating feasibility of placing a catalytic reactor in the vent line of a

solid Hp cooler (or liquid Ho cooler) has been demonstrated in this

contract. The measured pressure drop is quite low and agrees with predictions.

The measured reactor efficiency varied from 10 to 100 percent for the flow

rate range of this study. Comparisons with other investigators' data at one

atmosphere indicate lower efficiencies for this investigation. One possible

explanation of this difference may be the lack of elevated temperature

regeneration of the catalyst in this study.

Additional testing is needed to determine the requirements and sensitivity of

regeneration at elevated temperatures and to determine the effects of exposure

to various environments. The exposure effects and regeneration requirements

(if any) must be shown to be compatible with spacecraft ground operations. In

particular, the means and limitations on high-temperature regeneration while

mounted to an instrument component should be explored.

4-1
LMSC-D877499

REFERENCES

1 LMSC-0085818. CLIR Cooler Components Definition Study (Nov. 30, 1979).

2 LMSC-D811574. Upper Atmospheric Research Satellite Cryogenic Limb Array

Etalon Spectrometer (CLAES) (July 1981).

3 Scott, R. B., Cryogenic Engineering, D. Van Nostrand Co., Inc.,

Princeton (1959), p. 289.

4 Bonhoeffer, K. R., and Farkas, A., Trans. Faraday Soc., 28, 242 (1932).

5 Rudham, R., Tullett, A. D., and Wagstaff, K. P., J. Catalysis, 38,

488-^90 (June 1975).

6 Brown, D. E., Eley, D. D., and Rudham, R., J. Catalysis, 16, No. 3,

292-302 (1970).

7 Kubicka, H., J. Catalysis, 20, No. 2, 163-71 (Feb. 1971).

8 Eley, D. D., Forrest, H., and Rudham, R., J. Catalysis, 34, 35-40 (1974).

9 Frackiewicz, A., J. Catalysis, 40, No. 2, 184-9 (Nov. 1975).

10 Eley, D. D., and Shooter, D., J. Catalysis, 2, 259-73 (1963).

11 Weitzel, D. H., Draper, J. W., et al., Advances in Cryogenic

Engineering, Vol. 2, 12-18 (1956).

R-l
LMSC-D877499

12 Singleton, A. H., Lapin, A., and Wenzel, L. A., Advances in Cryogenic

Engineering, Vol. 13, 409-27 (1967).

13 Nast, T. C., Study of a Solid Hydrogen Cooler for Spacecraft Instruments

and Sensors - Final Report, LMSC-D766177 (Aug. 1980).

R-2