A heat exchanger of increased effectiveness is disclosed. A porous metal matrix is disposed in a metal chamber or between walls through which a heat-transfer fluid is directed. The porous metal matrix has internal bonds and is bonded to the chamber in order to remove all thermal contact resistance within the composite structure. Utilization of the invention in a rocket chamber is disclosed as a specific use. Also disclosed is a method of constructing the heat exchanger

Fortini, A.

Kazaroff, J. M.

English

NASA Technical Reports Server

United States Patent 
Fortini et al. 
4,108,241 
[45] Aug. 22, 1978 
r54i HEAT EXCHANGER AND METHOD OF 3,170,512 2/1965 Smith ........................... 165/DIG. 10 
3.211.133 10/1965 Valvi ........................... 165/DIG. 10 - -  MAKING 
[75] Inventors: 
[73] Assignee: 
[21] Appl. No.: 
[22] Filed: 
3;262;190 7/1966 Rosioker ..................... 165/DIG. 10 
Anthony Fortini, Cleveland; John M. 3,289,756 12/1966 Jaeger .......................... 165/DIG. 10 
3,306,353 2/1967 Burne ........................... 165/DIG. 10 
The United States of America as 3,364,951 1/1968 Burne ........................... 165/DIG. 10 
represented by the Administrator of 3,798,902 3/1974 Butter .................................... 60/267 
the National Aeronautics and Space 
Administration, Washington, D.C. 
559,846 
Mar. 19, 1975 
Kazaroff, Rocky River, both of Ohio 3,302,704 2/1967 Valyi ........................... 165/DIG. 10 
Primary Examiner-Charles J. Myhre 
Assistant Examiner-Margaret A. LaTulip 
Attorney, Agent, or Firm-N. T. Musial; J. R. Manning; 
J. A. Mackin 
[51] Int. (3.2 .............................................. F28F 13/00 
[52] U.S. c1. .................................... 165/146; 165/169; 
60/267; 239/127.1 
[58] Field of Search ............... 165DIG.  10, 146, 169; 
60/267; 239/127.1 
~561 References Cited 
U.S. PATENT DOCUMENTS 
2,401,797 6/1946 Rasmussen .................. 165/DIG. 10 
2,448,315 8/1948 Kunzog ....................... 165DIG. 10 
2,487,435 11/1949 Goddard ...................... 165DIG. 10 
3,161,478 12/1964 Chessin ........................ 165DIG. 10 
29 
[571 ABSTRACT 
A heat exchanger of increased effectiveness is disclosed. 
A porous metal matrix is disposed in a metal chamber or 
between walls through which a heat-transfer fluid is 
directed. The porous metal matrix has internal bonds 
and is bonded to the chamber in order to remove all 
thermal contact resistance within the composite struc- 
ture. Utilization of the invention in a rocket chamber is 
disclosed as a specific use. Also disclosed is a method of 
constructing the heat exchanger. 
5 Claims, 5 Drawing Figures 
I 
https://ntrs.nasa.gov/search.jsp?R=19790005118 2020-03-20T17:52:20+00:00Z
U.S. Patent Aug. 22, 1978 4,108,24 1 
I 
.-----_____---- 
FIG. 2 
FIG. 5 ‘22 
4,108,241 
1 
In summary, it is an object of the invention to provide 
HEAT EXCHANGER AND METHOD OF MAKING a heat exchanger of high effectiveness which is simple 
in construction and which may be easily altered to pro- 
vide areas of increased heat transfer and which is rela- ORIGIN O F  THE INVENTION 
This invention was made by employees of the U.S. 5 tively simple to construct. 
BRIEF DESCRIPTION OF THE DRAWINGS Government and may be manufactured or used by or for the Government of the United States for govern- 
mental purposes without any payment of royalties FIG. 1 is an axial section of the heat exchanger em- 
thereon or therefor. 
FIG. 2 is a half axial section of the rocket chamber 
BACKGROUND OF THE INVENTION 
This invention relates to apparatus for transferring FIG. 3 is a Partially CuatawaY oblique view of a 
heat from a first environment to a second environment 
of lower temperature and is directed more particularly 
to devices known as heat exchangers. 
Basically, a heat exchanger includes a wall of high 
heat conductivity metal separating two environments of 
different temperatures. If the wall is the shell of a device 
such as a rocket chamber, for example, which must be 
protected from destruction by the combustion inside the 2o 
rocket chamber, a coolant medium or fluid may be Referring now to FIG. 1, there is shown a heat ex- 
directed or flowed over the outer surface of the wall to changer '' which comprises a l1 con- nected through a supply conduit 12 and through a pump absorb the heat. 
25 the heat exchanger will be discussed as being in a high mobile radiator which comprises a plurality of tubes temperature environment and with the coolant being through which there is directed the liquid coolant from supplied from the heat-transfer medium supply 14, it 
lized to transfer heat in the opposite direction, that is the air directed against the radiator tubes. 
included roughening the surface of the wall in contact than the environment outside of the heat exchanger. 
with the flowing fluid, increasing the fluid velocity by ne coolant flows from supply 14 through the conduit decreasing the cross-sectional area of the coolant tubes 12 and pump 13 and the heat exchanger as shown by 
or channels and/or increasing the pressure drop across the 
each channel to increase fluid velocity. Additionally, 35 Disposed in the tube 11 is a porous metal matrix 16 
the use of fins on the dividing wall or which extend which has a greater density as at 17 than it does at the 
have been utilized. metal matrix at 17 increases the internal heat-transfer 
from previous coefficient of the porous matrix in an area where the 
prior art attempts to increase the heat tmnsfer include 40 temperature of the environment is much greater than at 
lack of control of surface roughness, low cycle thermal the end of tube 11 where the coolant enters or at the 
fatigue problems which result from joining different opposite end where the coolant is exhausted. The high 
sections of material by welding or brazing or the like, temperature and/or heat flux is represented by arrows 
the difficulty of machining suitable size channels in thin 18 while the lower temperatures and/or heat flux 
walls and confined spaces, and the difficulty of machin- 45 toward the ends of tube 11 are represented by the short 
bodying the invention. 
embodying the invention. 
rocket Chamber embodying the invention. 
10 
FIG. 4 is a partial cross section of the rocket chamber 
FIG. 5 iS a View Of a modification to the structure 
15 of FIG. 3 taken along the lines A. 
shown in FIG. 4* 
DESCRIPTION OF A PREFERRED 
EMBODIMENT 
Other examples of heat exchangers include the auto- l3 to a heat-transfer medium Or fluid 14* 
an engine' The temperature Of the is reduced by will be understood that the heat exchanger can be uti- 
to increase the heat transfer have 30 heat-transfer medium would be of higher temperature In the Past, 
15. 
radially inwardly or outwardly from the tubes ends of the tube 11. This increased density of the porous 
Some Of the Problems which 
ing fins in small channels. 
OBJECTS AND SUMMARY OF THE 
INVENTION 
It is an object of the invention to provide a new and 
novel heat exchanger having heat-transfer enhance- 
ment. 
It is another object of the invention to provide a heat 
exchanger wherein the velocity of a flowing heat-trans- 
fer medium is maintained at a relatively low magnitude, 
thereby avoiding the need for special pumps to develop 
a high pressure for the heat-transfer medium. 
Still another object of the invention is to provide a 
heat exchanger and a method of making the exchanger, 
both of which are relatively simple as compared to the 
prior art. 
Yet another object of the invention is to provide for 
a rocket engine, a heat exchanger which will cause 
maximum heat transfer to a coolant fluid at the rocket 
throat where inner wall temperatures are the highest. 
A still further object of the invention is to provide a 
method of making a rocket chamber having maximum 
heat transfer at the throat area. 
arrows 19. 
While the increased density of the porous metal ma- 
trix as at 17 will increase the heat transfer, it will also 
reduce the volume of coolant flowing through tube 11 if 
50 it is of constant diameter. To the end that the reduction 
of coolant flow volume caused by the increased density 
of the porous metal matrix at 17 will be minimized or 
eliminated, the diameter of tube 11 is increased as at 20, 
thereby providing a maximum cross-sectional area 
55 where the density of the porous metal matrix is greatest 
so that the overall flow rate and pressure drop is equiva- 
lent to that of a straight tube. 
Ideally, the density of the porous metal matrix 16 
should increase or decrease proportionately in accor- 
60 dance with the temperatures and/or heat flux being 
impressed on the tube 11. In other words, the density of 
the porous metal matrix 16 preferably follows the tem- 
perature profile of the heat flux along the length of the 
tube 11. Likewise, the increased diameter of tube 11 at 
65 20 preferably followed the temperature and/or heat flux 
profile curve and, of course, will be maximum where 
heat flux and/or temperature is maximum and minimum 
where heat flux and/or temperature is minimum. 
4,108,241 
3 4 
The heat exchanger 10 may be constructed by form- from destruction. It will be understood that the slugs 30 
ing a body of porous metal, as for example, sintered shown in FIG. 3 may extend the full length of rocket 
metal powder, sintered fibers, woven sintered wire chamber 21 or any part thereof, as desired. Also, in 
cloth or foam metal, or other porous metal bodies such accordance with the construction shown in FIGS. 1 and 
as photoetched plates or laser drilled plates with ran- 5 2, the density of the porous metal matrix may be selec- 
domly arranged pores or openings into the desired tively varied to provide additional heat transfer where 
shape which may be cylindrical and which may include desirable. In the event that ribs 31 are not to be used, the 
one or more of the increased diameter Dortions, as porous metal matrix may likewise extend the full length 
shown at 20 in FIG. 1. A tube 11 may then be formed 
over the porous metal matrix by electroforming, sput- 
tering or the like. 
As an alternative, the heat exchanger 10 may be con- 
structed by first forming tube 11 including, if desired, 
one or more portions of increased diameter. Such meth- 
ods are well known in the art. Tube 11 may then be 
filled with sintered metal powder, metal fibers or the 
like. The tube 11 and its contents are then heated to a 
temperature high enough to cause bonding or welding 
of the contents of tube 11 to form a porous metal matrix 
and to bond or weld to the tube 11. The bonding or 
welding of all points of metal to metal contact provides 
maximum heat transfer by eliminating normal high ther- 
mal resistance contact points. 
The metals used for the tube 11 and for the porous 
metal matrix 16 are those having the best heat-transfer 
characteristics. However, the selection of metals will 
depend upon the environment and other materials with 
which the heat exchanger comes in contact, and will 
also depend upon the coefficients of expansion of the 
metals used for the porous matrix 16 and the tube 11. In 
forming the heat exchanger 10, sputtering may have 
some important advantages in that a greater number of 
alloys can be deposited over the porous metal matrix 
than can be deposited by electroforming. 
Referring now to FIG. 2, there is shown a half axial 
section of a rocket chamber 21 having an inner annular 
wall 22 and an outer annular wall 23 configured so as to 
produce a throat 24. The space between the inner wall 
and the outer wall 23 contains a porous metal matrix 25 
which is bonded or welded to the inner and outer walls 
22 and 23, respectively, by suitable bonding or welding 
techniques. A coolant fluid is directed to a manifold 28 
at the downstream end of the rocket nozzle and flows 
through the matrix 25 in an upstream direction, i.e., 
opposite to the flow of combustion gases exiting as 
shown by arrow 29. Of course, the coolant flow may be 
in the opposite direction to that shown in FIG. 2, if 
desired. The distance between walls 22 and 23 is much 
greater at the throat area as indicated by arrows 26 than 
it is at the upstream or downstream ends, as indicated by 
arrows 27. Additionally, the density of the porous metal 
matrix 25 may be much greater at the throat area 24 
than it is at the upstream or downstream ends of the 
chamber, as is shown in FIG. 2. 
FIG. 3 is a partial cutaway view of a rocket chamber 
similar to that shown in FIG. 2 and corresponding parts 
are identified by like numerals. In the rocket chamber 
21 of FIG. 3, elongated porous metal matrix slugs 30 are 
disDosed in an annular configuration around the throat 
of the rocket chamber and may have selective areas of 
The elongated ribs 31 establish flow channels for the 
coolant but are not necessary to obtain the advantages 
of the invention. Accordingly, a rocket chamber may be 
constructed wherein a continuous, annular ring, config- 
15 urated to form a throat for the rocket chamber is used in 
place of the slugs 30. As will be explained hereinafter, 
the slugs may be formed by cutting slots in the porous 
metal ring. 
FIG. 4 is a partial cross-sectional view taken along 
20 the line 4-4 of FIG. 3 and shows the ribs 31 disposed 
between the inner and outer walls 22 and 23 and the 
porous metal matrix slugs 30. 
FIG. 5 is a cross-sectional view similar to FIG. 5 
showing an embodiment without the ribs 31 wherein 
25 the slugs are replaced by a continuous annular ring 30 of 
porous metal. 
The rocket chamber 21, as shown in FIG. 3, may be 
constructed as described hereinafter. Various tech- 
niques involving electroforming, sputtering, diffusion 
30 bonding and various machining steps have been used in 
the past to construct rocket chambers. However, new 
steps are now involved due to Applicants’ use of porous 
metal matrix between the inner and outer walls of a 
rocket chamber to increase the heat transfer effective- 
35 ness. In one method of making a rocket chamber ac- 
cording to the instant invention, the inner wall 22 of the 
rocket chamber is constructed on a suitably shaped split 
mandrel by either electroforming techniques or by spin- 
ning; that is, by forcing a metal sleeve or cylinder to 
40 conform to the mandrel while the mandrel and the 
sleeve are rotating. A porous metal matrix in the form of 
a ring, as shown at 300 in FIG. 5 is next formed around 
the rocket chamber inner wall 22 after the outer surface 
of the wall 22 is machined to the desired dimensions. 
45 The porous metal matrix may be formed by wrapping 
wire around the wall 22, by disposing the two halves of 
a split porous metal matrix ring around the chamber 
wall 22 or by positioning slugs 30 of porous metal 
around the wall 22, as shown in FIGS. 3 and 4. 
If no ribs 31 are to be utilized, either a layer of wax or 
a layer of leachable material, depending on whether the 
outer wall is to be formed by electroforming or sputter- 
ing, is formed on the exterior of the rocket chamber 
wall 22 but excluding the porous metal ring 300. The 
55 outer rocket chamber wall 23 is formed by electroform- 
ing or sputtering and, of course, will bond to the porous 
metal matrix ring 300 or slugs 30 if the latter are used. 
If ribs 31 are desired to form coolant channels, 
grooves must be machined in the wax layer or leachable 
10 increased density for greater heat transfer. 
50 
24 between inner and outer walls 22 and 23. The slugs 60 
30 are separated by longitudinal ribs 31 which extend 
substantially the full length of the rocket chamber. Ribs 
31 and the slugs 30 are bonded or welded to the inner 
wall and to the outer wall and, in addition, each rib is 
bonded or welded to the slugs 30 adjacent to it. The 65 
slugs 30 increase the heat transfer in the area of the 
throat where inner wall temperature is maximum to 
provide maximum protection of the rocket chamber 
layer prior to forming the outer wall 23. This groove- 
machining operation may also be extended to the po- 
rous metal matrix ring 300 whereby the ribs 31 will also 
be deposited between the slugs 30 thus formed and will 
be bonded to those slugs. 
After the outer wall is formed, the split mandrel is 
removed and the inner surface of the inner wall 22 may 
be machined to a desired contour. At this point, the 
porous metal matrix ring 300 or slugs 30 are not bonded 
4,108,241 
5 6 
to the inner wall 22. To accomplish such bonding, the 
rocket chamber assembly may be heated to a tempera- 
ture sufficiently high to produce bonding between the 
porous metal matrix ring 300 or slugs 30. 
invention without departing from the spirit and scope 
thereof, as set forth in the claims appended hereto. 
What is claimed is: 
1. A Heat exchanger for transferring heat from an 
To reduce the temperature of the diffusion bonding 5 environment at one temperature to a heat-transfer fluid 
or vice-versa, said fluid being supplied from a heat- 
a chamber formed of a metal having high thermal 
conductivity and having an inlet and an outlet, 
a porous metal matrix of high thermal conductivity 
disposed in said chamber, said porous matrix being 
metallically bonded to said chamber; all points of 
contact within said metal matrix being metallically 
bonded; and 
means for directing a heat-transfer medium into said 
inlet, said heat-transfer medium flowing through 
said chamber and exhausting through said outlet, 
said chamber and said porous media having a 
greater cross-sectional area at areas of high heat 
exchanger than at positions of low heat exchange, 
and wherein both the density of said porous metal 
matrix and the cross-sectional area of said chamber 
vary along the direction of coolant flow in said 
chamber in proportion to the variation of heat flux 
of said chamber along the direction of coolant 
flow. 
2. The heat exchanger of claim 1 wherein said metal- 
lic bond of said chamber and said matrix is a sputtered 
bond. 
3. The heat exchanger of claim 1 wherein said metal- 
lic bond of said chamber and said matrix is an electrode- 
posited bond. 
4. The heat exchanger of claim 1 wherein at least one 
of said metals is a metal alloy. 
step s' that Of the inner 22 transfer fluid source, said heat exchanger comprising: 
may be avoided, a relatively low temperature solder 
material of the types which are well known in the art 
areas where the porous metal matrix is to be positioned. 
The solder material will bond the porous metal matrix 
material to the inner wall 22 without resorting to the 
relatively high diffusion bonding temperatures nor- 
mally required. 
The diffusion bonding step may be advantageously 
eliminated by machining away the inner wall 22 com- 
pletely after the mandrel is removed. The inner wall 22 
is then reformed, either by electroforming or sputtering 
techniques and is applied directly to the surface of the 
porous metal matrix ring 300 or the slugs 30. The wax 
or leachable material is then removed from between the 
inner wall 22 and the outer wall 23, as well as from all 
other areas of the rocket chamber. 
The inlet manifold at the downstream end of the 
rocket chamber and the coolant exit manifold at the 
upstream end ofthe rocket chamber are added by any of 
the well-known techniques of the prior art. 
with the invention need not be to one tech- 
nique such as electro-forming but may include other 
methods. For example, it may be desirable to form the 
may be applied to the outer surface ofthe wall 22 in the 10 
15 
20 
25 
The construction of a rocket chamber in accordance 30 
inner wall of any alloy which may be advantageously 35 
sputtered, this being done after the outer wall has been 
electroformed. On the other hand, there are instances 
where it would be preferable to sputter-deposit the 
outer wall. 
make changes and modifications to the above-described 
5. '& heat exchanger of claim 1 wherein both the 
density of said porous metal matrix and the cross-sec- 
tional area of said chamber vary along the direction of 
coolant flow in said chamber in proportion to the varia- 
tion of heat flux on said chamber along the direction of 
It will be understood that those skilled in the art may 40 coolant flow. * * * * *  
45 
50 
55 
65 


Heat exchanger and method of making

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server