Heat sensing instrument, using thermocouple junction connected under heavy conducting materia

Harvey, W. D.

Miller, H. B.

English

NASA Technical Reports Server

H. 8. M!LLER E I A L  
HEAT-SENSING INSTRUMENT 
Filed Dec. 29, 1964 
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INVENTORS 
BY 
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3,382,714 
Howard B. Miller, Nampton, arnd William D. Harvey, 
Newport News, Va., assignors to the United States of 
America as represented by the Administrator of the Na- 
tional Aeronautics and Space Administration 
Filed Dec. 29, 1964, Ser. No. 422,092 
3 Claims. (Cl. 73-190) 
HEAT-SENSING INSTRUMENT 
ABSTRACT OF THE DISCLOSURE 
A device for sensing infinitesimal amounts of heat 
flowing onto a surface at several locations. A support 
body having several holes drilled in it at each of said 
locations has a sheet of heat conducting material bonded 
to it over said holes. A thermocouple junction is con- 
nected to the underside of said sheet in each of said 
holes to sense the heat flowing onto the surface at the 
several locations. 
The invention described herein may be manufactured 
and used by or for the Government of the United States 
of America for governmental purposes without the pay- 
ment of any royalties thereon or therefor. 
The invention relates generally to a heat-sensing in- 
strument and more specifically concerns a heat-sensing 
instrument for sensing or detecting infinitesimal amounts 
of heat flowing onto a surface. 
In aerodynamic heat transfer studies, it is necessary 
to measure infinitesimal amounts of heat flowing onto 
a surface at many locations on the surface. In the past, 
this has been done by installing individual capsule-type 
instruments in the surface. Each of these instruments 
consists of a thin disk (one or two mils thick) of a 
known material to the back of which is attached a ther- 
mocouple. The disk is supported at its perimeter by a 
suitable insulator, and this assembly is installed inside 
a thin case. The thin case is then installed in a hole in 
the surface under test in such a manner that the disk 
is flush with the surface. These instruments or gages 
have tQ be made individually and installed sepanately 
in a series of holes located in the surface under test. 
These prior art instruments have many disadvantages. 
First, since they are individually constructed, a consid- 
erable amount of time is used in constructing land in- 
stalling them. The methods used in fabricating the gages 
are necessarily slow because of the many operations and 
numerous parts involved. Second, accurate control of the 
disk thickness or mass per unit area is a problem since 
either may be altered during assembly and these param- 
eters are then not accurately known. Third, the disk is 
easily dimpled during construction and installation. And 
fourth, it is difficult to aline the disks with the test sur- 
face, especially when the surface is curved. For best re- 
sults, the surface should be smooth and continuous with 
no irregularities. 
It is therefore an object of this invention to provide 
an improved means for sensing infinitesimal amounts of 
heat flowing onto a surface. 
Another object of this invention is to provide a means 
for sensing the heat flowing onto a surface using indi- 
vidual gages in which the individual gages are not indi- 
vidually constructed and installed. 
A further object of this invention is to provide a means 
for sensing the heat flowing onto a surface in which the 
thickness or mass per unit area of the sensing element 
material is accurately controlled and previously deter- 
mined. 
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Still another object of this invention is to provide a 
means for sensing the heat flowing onto a surface in 
which the sensing element material is easily alined with 
the contour of the surface. 
A still further object of this invention is to provide 
a means for sensing the heat flowing onto a surface in 
which the sensing element material is not likely to be 
dimpled during construction and installation. 
Yet another object of this invention is to provide a 
means for sensing the heat flowing onto a surface which 
is sufficiently sensitive to eliminate expensive amplifica- 
tion of its output signal. 
To realize the above objects, this invetnion takes the 
form of +attaching a continuous thin sheet of a material 
having a previously known thickness, density and specific 
heat to a supporting surface through which a series of 
holes of a known diameter has been previously made. 
Thus, each perforated area, with the known material 
stretched across it, forms a calorimeter. By iattaching 
thermocouples to the under surface of the thin material 
through each perforated area, the heat flowing onto the 
surface can be measured. Since very high sensitivity is 
needed to detect heat in infinitesimal amounts, the suc- 
cessful application of this invention depends on being 
able to attach over the perforation sheets of sensing 
material having a total thickness of two mils or less. In 
cases where the time of rate of change is measured in 
milliseconds, or the amount of heat present produces 
only a fractional degree of total temperature change, then 
this invention becomes practical because the sensing ma- 
terial stretched across the perforated openings acts like 
individual calorimeter gages for sensing low heating rates. 
Other objects and advantages of this invention will 
further become apparent hereinafter and in the draw- 
ings, in which: 
FIG. 1 is ,a top view of a preferred embodiment of this 
invention; and 
FIG. 2 is a sectional view taken substantially along 
the line 2-2 of FIG. 1. 
In describing the preferred embodiment of the inven- 
tion illustrated in the drawing, specific terminology will 
be resorted to for the sake of clarity. However, it is not 
intended to be limited to the specific terms so selected, 
and it is to be understood that each specific term includes 
all technical equivalents which operate in a similar man- 
ner to accomplish a similar purpose. 
Turning now to the preferred embodiment of this in- 
vention shown in FIGS. 1 and 2 of the drawing, the num- 
ber 11 designates a support body through which several 
gage holes 12 are machined or drilled. Stretched on the 
top surface of support body 11 and bonded thereto is a 
sheet of sensing material 13. Thermocouple wires 14 are 
attached by spot welding to the under surface of the 
sheet of sensing material 13 at the centers of the holes 
12. Thermocouple wires 14 are also connected to thermo- 
couple leads 15 which are connected to suitable record- 
ing equipment (not shown). Each of the holes 12, with 
the sensing material 13 stretched over it, is a calorimeter. 
By attaching the thermocouple wires 14 to each of these 
calorimeters, the heat flowing into it can be measured. 
The diameters of thermocouple wires 14 should be smaller 
than the thickness of material 13 for best results. 
The shape of the holes 12 are shown as being round; 
however, they can be any shape without departing from 
the spirit or scope of this invention. It is only necessary 
that an accurate determination of the cross-sectional area 
of the holes can be made so that the amount of sensing 
material 13 covering the holes can be determined. The 
size and number of holes 12 that are used depends on the 
particular application of this invention. 
The sheet of sensing material 13 can be made from any 
3,382,714 
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good conductor of heat, such as, copper, platinum, silver spirit or scope of the invention as defined in the follow- 
or stainless steel. The thickness of the material 13 de- ing claims. 
pends on the particular application of this invention. What is claimed is: 
However, it should be noted that this invention becomes 1. An instrument for sensing infinitesimal amounts of 
much more useful when the thickness of material 13 is 5 heat flowing onto a surface area at several locations on 
two mils or Iess. Then a sheet of the material 13 can be said surface area comprising: 
handled much easier than small disks of the material a support body area including sharply contoured con- 
without damaging the material. The sheet of material figurations; 
13 is bonded to support body 11 by any suitable bonding holes formed in said support body area at each of said 
material. It is better that the bonding material be a ther- several locations; 
mal insulating material so that it will insulate the mate- a single, continuous, smooth sheet of heat conducting 
rial 13 from support body 11. If support body 11 is itself material bonded to said support body area over said 
a thermal insulator, this would not be necessary. holes to form the entire surface of said support body 
The support body 11 can be the body forming the area and all of the area being sensed; and 
surface onto which the measured heat is flowing, or it 15 a thermocouple for each of said several locations with 
can be a model fitted into the surface, or it can be a model each thermocouple consisting of two wires connected 
forming the surface. Support body I1 is shown as having together at one of their ends to form a themocou- 
a flat surface. However, it can have a curved surface. If pie junction which is attached to the under surface 
it has a three-dimensional curved surface, then it is neces- of said sheet of heat conducting material under one 
sary that the sheet of sensing material 13 be shaped before 20 of said several locations and with the other ends of 
it is bonded to support body 11. said two wires extending through the hole cor- 
The advantages of this invention are numerous. This responding to said one location whereby the voltage 
invention simplifies the construction and installation of generated across said thermocouple junctions are 
multiple heat gages thereby resulting in considerable indicative of the heat flowing onto said surface at 
time saving over the construction and installation of pre- 25 said several locations. 
viously used gages. The error of dimpling the sensing ma- 2. An instrument in accordance with claim 1 wherein 
terial is greatly reduced because of the much greater said sheet of heat conducting material is less than three 
bonding surface provided. In the individual capsule-type 
gage, bonding of the calorimeter disk is limited to a very 
small area around the circumference of the disk. A 
smoother contour of the surface where the heat flow is 
measured can be maintained with this invention. This 
invention provides for closer control of the sensing ma- 
terial that is stretched over the perforated areas. The 
sensing material can be accurately measured for thick- 
ness and the thermal properties known before assembly. 
In the previous individual capsule-type instrument, the 
possibility existed that each sensor disk could be altered 
during fabrication. This invention eliminates the need 
for amplification of its outputs because of the high sensi- 
tivities that can be obtained with it. 
It is to be understood that the form of the invention 
herewith shown and described is to be taken as a pre- 
ferred embodiment, Various changes may be made in the 
shape, size and arrangement of parts. For example, equiva- 
lent elements may be substituted for those illustrated and 
described herein, parts may be reversed, and certain fea- 
tures of the invention may be utilized independently of 
the use of other features, all without departing from the 
mils thick. 
3. An instrument in accordance with claim 1 wherein 
3o said thermocouple wires are attached to the under sur- 
face of said sheet at approximately the centers of said 
holes. 
References Cited 
UNITED STATES PATENTS 
35 2,921,972 111960 Kreisler et al. _ _ _ _ _ _ _  136-214 
3,008,029 1111961 Davis et al. _ _ _ _ _ _ _ _  73-15X 
3,194,071 7/1965 Hageir -____________ 73-341 
3,232,113 111966 Malone _ _ _ _ _ _ _ _ _ _ _ _ _  73-355 
3,280,626 1011966 Stempel _______-____ 73-190 
OTHER REFERENCES 
Gardon, R.: “An Instrument for the Direct Measure- 
ment of Intense Thermal ‘Radiation,” in the Review of Sci- 
entific Instruments (24), p. 366-370, May 1953. 
RICHARD C. QUEISSER, Primaiy Examiner. 
JAMES J. GILL, Examiner. 
J. C. GOLDSTEIN, EDDIE E. SCOTT, 
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45 
Assistant Examiners. 


Heat sensing instrument Patent

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