Thermal energy storage converter with rhenium capsul

Merra, S. G.

Van Someren, L.

English

NASA Technical Reports Server

(NASA CR OR TMX O R  AD N U M B E R )  ICATEQORY) 
I 
T H E R M 0  E L E C T R O N  
E N G I N E E R I N G  C O R P O R A T I O N  
https://ntrs.nasa.gov/search.jsp?R=19650018229 2020-03-17T01:32:05+00:00Z
I *  
I 
I 
I 
I 
I 
i 
I 
I 
Report  No, TE84-65 
THIRD MONTHLY PROGRESS REPORT FOR 
THERMAL ENERGY STORAGE/CONVERTER 
PROTOTYPE DESIGN, FABRICATION 
AND TESTING 
Contract No. 950976 INAS7 - 1 -- 
3 May through 2 June 1965 
by 
S .  G. Mer ra  
L. van Someren 
Prepared fo r  
Jet  Pr opulsion Labor at or y 
Pasadena,  California 
A pp r ov e d by : 
P. G. Pantadklos, Manager 
Engineering Department 
TABLE O F  CONTENTS 
Section Page  
INTRODUCTION. e . . . e e ,  . e . , . . , . . . . . . 1 
SUMMARY. .  . . * .  . e * .  . , * .  , . . * .  . . . 2 
PURIFICATION O F  MgO AND B e 0  POWDERS , e . . . e 3 
3Be0-2MgOOXIDE PREPARATION ~ . , . , . ~ . ~ ~ . ~ 7 
FEASIBILITY MODEL. . , . . . '. . , . . . . . . . . e 11 
CONVERTER . . . . . , . . . . . . . . . . . . . . . 16 
I '  
I 
I 
I 
I 
I 
Figure 
1 
2 
3 
4 
5 
6 
7 
LIST OF FIGURES 
Page -
Rhenium Crucible Mounted for R F  Heating . . . . . . . , . 4 
3Be0-2Mg0 Eutectic f r o m  Melt# 3 e . a . , e ., . e 10 
Exploded View of Major Thermal Shield Subassemblies 12 
Thermal  Shield Assembly . . e . e e , , , e . e . . e . 13 
Electron Bombardment Heater for  TES Container e e e 14 
TES Feasibil i ty Model .  . . e e e e a e 17 
Niobium Flange Beam Welded to a Rhenium Sleeve, e . . . . 18 
iii 
T H l R M O  E L E C T R O N  
E l C l R E E R l N G  C O R P O R l l l O N  
I -  
1. INTRODUCTION 
This  repor t  represents  the Third Monthly P r o g r e s s  Report  of the work being 
performed under Contract No. 950976/NAS7- 100 with the Je t  Propulsion Laboratory.  
The objectives of this program cal l  for  the design and fabrication of one ther -  
mal energy s torage feasibility model. / This model shal l  include an electron beam 
weldment sealed rhenium capsule containing 3Be0- 2Mg0 oxide, one thermionic 
converter of the Se r i e s  VI11 o r  TE-100 design of J P L  Contract No. 950671 modified 
to accommodate the capsule, capsule heater ,  and thermal  shielding. ~ 
7 
--*-.* ” -- - 
r, 
-- ~ -- w.-* . 
#2a**lU;r 
The model  shal l  be tested in the presence of a JPL representat ive fo r  not l e s s  
than 16 cycles  a t  50OC above and below the melting point of the oxide. 
1 
2. SUMMARY 
During the month of May purification of MgO and B e 0  powders I was continued, 
rc' 
and the vacuum firing procedures used resulted in an  overal l  decrease  in the im- 
purity levels of the two "as received" MgO powders f rom F i she r  Scientific and 
Morton Chemical. 
made using the MgO f rom the two different suppliers.  These two melts  a s  well 
a s  the first melt  (made with Morton MgO) were made in vacuum and subsequent 
determination of the BeO/MgO rat io  indicated that the required stoichiometry 
was retained. 
in comparison to the other mel t s ,  and i s  presently being analyzed. 
Two additional 3BeO- 2Mg0 mel t s  of unpurified oxide were  
The mel t  using F i she r  MgO has  a very clean external appearance 
I I An electron bombardment heater  was built and tes ted using various d iameters  
of tungsten and rhenium wire.  
for the feasibility model heater.  
wi re  did not demonstrate the same life capability as tungsten. 
Fifteen mil  tungsten appears  to  be the best  choice 
Under s imi la r  operating conditions rhenium - 
j 
2 
A full  scale  version of the thermal  shield assembly was built for evaluation. 
.sp \ 
Since thin rhenium sheet which is on order  for shielding was not available, tanta- 
lum was used in  its place on the inner surfaces. 
ordering of all pa r t s  required for the test  set-up was accomplished during this 
reporting period. 
Pre l iminary  fabrication and 
With the exception of the rhenium sleeve fo r  the converter which is on order  
and due for  delivery ear ly  in June all par ts  have been built, and a r e  available for 
converter  fabrication. A l l  the ma te r i a l  required fo r  the container is either on 
hand o r  due ear ly  in June. 
on Set converters ,  a component t e s t  was made using a n  available ( la rger  d iametcr )  
rhenium sleeve and a niobium flange. 
welder. 
that this design is quite sound for the model. 
Since rhenium sleeves have not been previously used 
.*..-..a x- 
The joint was made in the electron beam 
Subsequent cycling of the assembly to operating temperature  demonstrated 
I 
2 
T H R R M O  E L I C T R O N  
E N G I N E E R I N G  C O R P O R A T I O N  
I 
3. PURIFICATION O F  MgO AND B e 0  POWDERS i 
Magnesia and beryll ia with which t o  make  the oxide slug have been fired at 
high tempera ture  by heating uncompacted oxide in a me ta l  bucket in vacuum. An 
unreactive container is required,  and rhenium is found to  fulfill this requirement 
adequately. Purification is effected by evaporation of volatile impurit ies,  which 
condense in  a cooler pa r t  of the system. It is therefore  necessary  for  the whole 
mass of oxide and its container t o  be isothermal,  and hotter than some nearby 
par t  of the system, which can ac t  as a condenser. 
Electron-bombardment heating of the bottom of the right cylindrical  container 
was found to  leave the upper open end much cooler,  and to  be r a the r  inconvenient 
to  manipulate, Radio frequency induction heating was therefore  utilized. Howeverg 
i f  the container was supported on a pedestal in  the usual manner ,  the center of the 
bottom was cool owing to  heat loss  by conduction down the pedestal, and the center  
of the top was cool owing to  radiation loss f rom the open top of the container. 
much c loser  approach to isothermal  conditions was obtained by supporting the 
container on tantalum wi res  just  above the pedestal ,  and closing the top with a 
loose fitting lid of rhenium. See F igure  1. This  eliminated the da rk  patch on top 
of the oxide, which had presumably been caused by condensation of contaminants 
there.  
A 
Upon fur ther  heating, a dark deposit was found on the underside of the lid. 
A l l  of this  work was complicated and slowed by the tendency of the dry  uneom- 
pacted oxide to "explode" and spatter a11 over the vycor and baseplate during the 
ear ly s tages  of evacuation and heating. 
p rocess  is obvious. 
achieving i so thermal  conditions throughout the container,  since the heat is devel- 
oped only in the walls of the Container. 
Unfortunately, no way of accelerating the 
To use a l a rge r  diameter  container would in te r fe re  with 
I-- 
3 
I -  
F i g u r e  1. Rhenium Crucible Mounted for R F  Heating 
4 
I’ 
I 
I 
I 
I 
I 
I 
I 
~ 
T H E R M 0  E L E C T R O N  
E N G I H L L R I I I G  C O R P O R L T ~ O R  
I -  
Most of this purification work w a s  done with BeO, while awaiting resu l t s  of 
analyses of two samples  of MgO ( f rom different sources)  purified by firing. These  
resul ts  a r e  shown in Table 1. It is seen that considerable purification of the Morton 
MgO with respec t  to  S i  and T i  was achieved, while the F i she r  MgO lost  Na, but 
gained Fe and some Ca, and remained cleaner overall .  The earlier hypothesis 
that F i s h e r  MgO lost  Na on firing was therefore substantiated. 
In summary ,  some purification of MgO was achieved. F i she r  m a t e r i a l  lost  a 
substantial  amount of Na, but appeared to gain some F e  and Ca, perhaps during 
handling. 
lost  S i  and Ti ,  while remaining less pure overall.  
Morton material appeared t o  gain small amounts of F e  and Ca too, but 
On the s t rength of this data, it was decided to p repa re  a mel t  using F i s h e r  
MgO. (Melt # 3 ) .  
5 
I -  
T H E R M 0  E L E C T R O N  
L W G l l E E R I W C  C O R P O R A T I O W  
I 
Ca 
Si 
F e  
Ti  
Re 
c u  
Na 
Sr  
TABLE I 
IMPURITIES I N  MgO BEFORE 
AND AFTER FIRING TO 2000°C I N  VACUUM ' 
Mort on 
Before After 
1100 
650 
220 
90 
- -  
3 
< 5  
< O  
1200 
150* 
250 
40 * 
30 
5 
3. 5 
5 <o.  5 
Fishe r  
Before After 
280 
180 
15 
< 2  
< 10 
3 
110 
1. 5 
350* 
150 
30 ;:c 
< 5  
< 10 
4 
2* 
1. 0 
Significant changes a r e  indicated by * 
These a r e  quantitative spectrographic analyses,  all  made by TEECO's 
analyst. 
6 
T H R R M O  E L E C T R O N  
L N G I N C f I I N G  C O R P O R A T I O N  
1 
By National Spectrographic Lab. , Cleveland, Ohio 
1 
4. 3Be0-2MgO OXIDE PREPARATION 
1 
The first mel t  (Melt #1, Morton MgO) made was examined for  impurit ies and 
to  determine the BeO/MgO ratio. Spectroscopic analysis revealed that the mel t  
had picked up Re to  the extent of 0.5 - 5.070, and had lost  some iron. 
explanation that can be offered for the Re pickup is in t e r m s  of the high tempera-  
tu re  to which this mel t  had been exposed (26OOOC). A l l  other impurit ies detected 
were  present  in a similar amount in the start ing oxides. 
The only 
Most interesting was the estimate of the wt BeO/MgO rat io  as  1 : 1. The 
target  ratio,  corresponding to 3Be0 : 2Mg0, is 0.931 : 1. 
temperature  obtained by this mel t ,  l i t t l e  MgO had been lost  by evaporation. 
is  felt to be very encouraging, a s  trouble was anticipated owing to the high vapor 
p re s su re  of MgO at the eutectic temperature.  However, in  case  it proves neces- 
s a ry  to hold the composition of the melt  very close to that of the powder mixture ,  
plans have been made to  operate R F  heating in a n  iner t  a tmosphere such as argon, 
and a n  appropriate piece of equipment i s  under construction. 
So despite the very high 
This 
A cross-sect ion of this melt ,  examined under the microscope was found to 
contain some very la rge  bubbles, but very few fine pores .  
s t ruc ture  was seen. 
as- received unpurified oxides ear ly  in the program. 
of this first mel t  was the contraction which occurred on melting. 
ta iner  had been filled with mixed oxides, af ter  melting there  was not enough to  
wet the whole of the bottom of the container. 
tion of low density powder to  fully dense liquid. 
No  discernable micro-  
The mel t  w a s  a light gray color. This mel t  was made with 
The most  significant feature 
Though the con- 
This i s  due pr imar i ly  to the contrac- 
a 
T H I R M O  E L E C T R O N  
f W C l N E E l l N G  C O R P O R A T I O N  
A second melt  (Melt #2, Morton MgO) was made, a imed pr imar i ly  at achieving 
a l a r g e r  quantity of molten mater ia l .  
alcohol to m o r e  than f i l l  the bucket, and it was filled about 70% with oxide s lur ry .  
This was warmed to dr ive off mos t  of the alcohol, and then evacuated and heated 
to  the melting point. After  a minute o r  so at the melting point, the heat was r e -  
moved and, a f te r  cooling, m o r e  of the same batch of oxide was added, dr ied  out, 
pumped down, and remelted.  This procedure was repeated twice more .  
Sufficient unpurified oxides were  blended with 
The resulting slug occupied about 1 /3  of the containers slipped readily out of 
the container when cold, and solidified with a shallow rounded c ra t e r  at the top, 
implying that it contracted on freezing. 
made because of the i r regular  pores  in  the mater ia l .  
charac te r i s t ic  of the f i r s t  mel t  (both were made with unpurified oxides). 
examined fo r  BeO/MgO rat io  and spectroscopically for  t r a c e  impurit ies.  
principle t r ace  was i ron ,  followed by silicon, and these and the other traces were  
present  in amounts comparable with the start ing oxides, but purification with 
respect  to Ca was considerable,  and some T i  was lost. No rhenium was detected, 
despite the discoloration of the mater ia l ,  and a detectability l imit  of 1 ppm for  it. 
This me l t  was never at the temperatures  reached by the first melt .  The BeO/MgO 
weight ra t io  was found to  be 0 .947 ,  which ag rees  with the ta rge t  ra t io  0.931 within 
the l imits  of experimental e r r o r .  
problem. 
N o  quantitative measurement  could be 
It had the gray color 
It was 
The 
Again, MgO evaporation was not a significant 
Since air fir ing is a standard method of cleaning ce ramics ,  it was applied to 
p a r t  of the second slug. Fir ing was car r ied  out for  1 hour at ]1200°C in a i r s  sup- 
porting the sample on pure  A 1  0 ceramics .  Some cleaning of the specimec was 
2 
2 3  
By Skinner and Sherman,  Inc. Newton, Mass.  
8 
found, and it was therefore  fired for another five hour s  in the same  conditions. 
This left the specimen clean, that i s ,  of yellowish-white appearance,  throughout, 
except for  some metall ic gray flecks. A fur ther  examination i s  now under way to 
determine which impurit ies a r e  lost  on a i r  firing. 
which cause the gray color. 
These a re  presumably the ones 
A thi rd mel t  was made using Fisher  MgO in  place of Morton. This  was quite 
satisfactory and appeared very clean and f r e e  f rom gray  contamination on removal 
f rom the container, Figure 2. Apparently the pu re r  F i s h e r  oxide leads to a c leaner  
product when used without special  purification. During melting, considerable depo- 
sition occurred  on the bell- j a r ,  implying that purification and melting both occurred.  
Fu r the r  examination of this mel t  is underway. 
A piece of s c rap  0.02" Re sheet was included in the second mel t  made. It was 
extracted f rom the resulting slug, and sections were  examined metallographically. 
Some t r a c e s  of fast-etching areas and possible pores  or inclusions were  found 
along the center  line of the sheet. These a re  not normally present  in sound rhenium 
sheet. They a r e ,  however, found near  the edge of sheared rhenium sheet. F u r t h e r  
work is planned for placing rhenium in  melts a f te r  careful polishing of the rhenium 
along the edges to remove t r aces  of shearing. 
The external  and internal appearance of the rhenium containers used is s t i l l  
immaculate  and they a r e  perfectly leaktight and the polished sections show no s igns 
of a t tack at the sur faces  of the sheet,  though this would be the f i r s t  place to  be 
attacked i f  there was any interaction. 
9 
I -  
t 
I 
I 
I 
I 
F i g u r e  2.  3Be0-2Mg0 Eutect ic  from Melt  #3 
10 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
1 
5. FEASIBILITY MODEL 
To gain confidence in the proposed designs of the model 's  t he rma l  shielding 
and electron bombardment heater ,  both units were  built for evaluation with a 
dummy container,  
The the rma l  shielding design used a s  many concepts as possible f r o m  both 
An exploded the so la r  and isotope generators  which have performed very well. 
view of the ma jo r  sub-assemblies  used €or the shields i s  shown in F igure  3 while 
the completely assembled unit is shown in F igure  4. 
shown in the la t te r  f igure is  the portion that will be positioned around the emi t te r  
sleeve.  
was used in  i t s  place on the inner surfaces.  
inside the assembly,  and heated by the gun. 
The opening in the shields 
Since thin rhenium sheet which is on o r d e r  was not available,  tantalum 
A dummy capsule will be supported 
A m e a s u r e  of the shielding effectiveness, including edge effects ,  will be ob- 
tained by measuring the capsule temperature ,  surface tempera tures ,  and power 
input. 
l o s s  vs  capsule tempera ture  will be calculated. 
the outer su r f aces  will be obtained with a Leeds and Northrup thermopile.  
With known values of emissivity for the outer surfaces ,  the ra te  of heat 
A check of the heat loss f r o m  
An electron bombardment gun, Figure 5, was built and tested with six wi re s  
01511, and . 02011 Tungsten and .015" Rhenium in  four separa te  tes t s .  of . OIO1t, 
The . O I O t t  tungsten wi re  was not rigid enough, while the 
high values of s tar t ing filament cur ren t  - in  excess  of 100 amperes .  
tungsten w i r e  provided adequate rigidity without excessive filament cur ren ts .  
assembly  with ~ 015" wires  can be mounted, dismounted, and handled af ter  opera-  
tion. 
. 015" tungsten wi re s  is planned for the model, 'LSnder s m l i ? a r  c)p<-r3ting c c r r l i ' i q n s  
020" wires  required 
The 015" 
The  
The expected life of this  gun is of the o rde r  of 500 hours ,  A heater  wl th  
1 1  
I. 
I 
F i g u r e  3 .  Exploded View of Major T h e r m a l  Shield Subassemblies  
12 
I '  
F i g u r e  4. Thermal Shield Assembly 
13 
F i g u r e  5. Electron Bombardment Heater  for  TES Container 
14 
T H E R M 0  E L E C T R O N  
E N G I N E C R I N G  C O R P O R A T I O N  
I 
rhenium wire  did not demonstrate the same life capability as  tungsten. 
Pre l iminary  fabrication and ordering of all par t s  required fo r  the tes t  set-up 
, was accomplished during this reporting period. 
I 
15 
T H E R M 0  E L E C T R O N  
E I C I ~ f i n l N E  C O R P O R l T l O N  
6. CONVERTER 
Since rhenium sleeves have not been previously used on Set converters ,  a 
component t e s t  was made using an  available ( l a r g e r  diameter)  rhenium sleeve 
s imi la r  to pa r t  35, Figure 6,  to a niobium flange, pa r t  34. 
in  the electron beam welder,  and is shown in F igure  7. 
The joint was made 
The joint was cycled rapidly to 9OO0C twenty t imes,  and leak checked a f t e r  
the first and last ten cycles. 
the joint was cycled to 150OOC rapidly approximately thirty t imes.  
temperature  was selected as a possible operating condition for another application. 
The joint was still sound and leak t ight .  
The joint w a s  leak tight both t imes.  Subsequently, 
The increased 
F r o m  these tes t s  the joint design appears  to be very good. 
16 
F i g u r e  7 Niobium Flange Beam Welded to  a Rhenium Sleeve 
18 


Thermal energy storage/converter prototype design, fabrication and testing third monthly progress report, 3 may - 2 jun. 1965

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server