Heated element sensor for fluid flow detection in thermal conductive conduit with adaptive means to determine flow rate and directio

Bell, D., III

English

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REPLY TO 
A'FTN OF: G p  
NATIONAL AERONAUTICS AND SPACE AD.MINISTRATION 
WASHINGTON, D.C. 20546 
November 6, 1970 
~ ~ ~ / ~ c i e n t i f i c  & Technical Information Division 
xtrentAont M ~ B L  WAnnim &I. Morgan 
F ROM s ~ ~ / 0 f f i c e  of A s s i ~ t a p t  General Counsel for  
Patent Matters 
T 
SUBJECTt Announcement of NASA-Owned U. S. Patents i n  STAR 
I n  accordance with the procedures agreed upon by Code GP 
and Code USI, the attached NASA-owned U. S.' Patent is being 
forwarded for  abstracting and announcement i n  NASA STAR. 
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NASA Patent Case No. 
NOTE - If  t h i s  patent covers an invention made by a corporate 
employee of a NASA Contractor, the following is applicabler 
yes 0 NO H' 
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Space Act, the name of the Administr.ator of NASA appears on 
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inventor (author) appears a t  the  heading of Column No. 1 of 
' _ t h e  Specification, following the,words a, , . w i t h  respect t o  
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https://ntrs.nasa.gov/search.jsp?R=19710008094 2020-03-17T02:37:58+00:00Z
March 17, "%TO B. BELL 111 3,500,686 
HEATED ELEMENT FLUID FLOW SENSOR 
Fi led Sept, 25, 1968 
FIG. 1 
FIG. 3 David Bel i ,  83 
f/VVE/VTOl<. 
United States Patent Ofice 3,500,686 Patented Mar,  1% 11990 
to. Electrical sensing means are provided for srnsing the 3,500,686 
HEATED ELEMENT PiFilD FLOW SENSOR electrical energy produced by the thermocouples to thereby 
David Be11 111, Houslon, Tex., assignor to the United detect fluid flow Ihe conduit. 
States of America as represented by (he Adntinistrator In the preferred form of the invention, the electrical 
of the I\la(ional Aeronautics and Space Admjnistratioll sensing means includes means for comparing the electrical 
Filed Sept. 25, 1968, Ser. No. 762,438 energy produced by the thermocouples and providing a 
Int. C1. Golf 1/00 read out of the rate and direction of the fluid flow through 
U.S. @I. 73-204 1Claim the conduit. The thermocouples and the heating element 
are preferably mounted in a portable housing which may 
be easily placed adjacent to  or against the conduit through 
ABSTRACT OF THE DISCLOSURE which flow is to be measured, whereby the heating element 
A hoated element fluid flow sensor for sensing the fluid 
flow in a thermal conductive conduit. It includes a pair of 
spaced-apart thermocouples arranged for contact with ax- 
ially spaced-apart points on the outside surface of the con- 
duit, with the heating element spaced therebetween and 
arranged for heating a portion of the conduit to thereby 
heat fluid in the conduit. Electrical sensing means are con- 
nected to the thermocouples for sensing the flow of fluid in 
the conduit. 
The invention described herein was made by an em- 
ployee of the United States Government and may be manu- 
factured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
This invention relates to a heated element fluid flow 
sensor for sensing the fluid flow in a thermal conductive 
conduit. 
When sensing fluid flow in a conduit it is desirable to 
have a unit which may be easily attached to the conduit 
(preferably portable) and arranged such that the fluid flow 
can be detected without inserting a probe into the conduit 
itself, which would otherwise disturb the fluid flow, create 
sealing problems, and the like. It is also important to 
detect not only the rate of fluid flow, but the direction of 
fluid flow, where it is not desirable to have a permanent 
flow meter. This is particularly true in the space environ- 
ment and on space crafts where it has been common prac- 
tice during checkout to utilize external power to operate 
various flow systems. In such event, normal spacecraft 
instrumentation is riot available. Thus, to determine if 
there is flow, the spacecraft would have to be powered in- 
ternally. Such a method requires additional operational 
time of spacecraft systems and is considered a safety 
hazard. 
Certain prior art attempts have been made toward find- 
ing a solution to the foregoing, but none have been as 
entirely satisfactory as the present invention. For example, 
external coils have been mounted about a conduit through 
which flow is to be tested and hest is applied at certain 
locations spaced therefrom. However, this type of device 
is not readily portable nor is it as simple in construction 
and operation. Other prior art devices have attempted to 
utilize thin metal film which are expos-d to a fluid stream 
and heated by an electrical current. Again however, this 
type of unit would not be portable, nor wo~rld it be suit- 
able lor the iniendcd purpose of the prese~it iriverrtlon. 
It is therefore an object of this invention to proviile an 
improved heated elenlent fluid flow sensor for sensing the 
fluid flow in a therri131 conclrrctive conduit v~iiich con- 
stitutes a substantial improvement aver the prior art and 
which provides a solution for the problen~s ennmerateci. 
Briefly stated, this invention is for a heated element fluid 
flow sensor for sensing the fluid floiv in a thermal con- 
ductive conduit. It includes the conlbination of a pair of 
spaced-apart therri~ocouples arranged far thermal contact 
with axially spaced-apart points on the outside surface of 
the conduit. A heating elenlent is spaced bet~ieen the pair 
of thermocouples and arranged for heating a partion of the 
conduit to thereby heat fluid in the conduit adjacent there- 
and the thermocouples are placed in thermal contact there- 
with. One form of an electrical sensing means includes a 
galvanometer calibrated to show direction and rate of flurd 
flow. Preferably the housing includes insulating means 
between the heating elements and thermocouples whereby 
the thermocouples are responsive prinlarily to heat con- 
ducted from the heater through the fluid in the conduit. 
Reference to the drawing will further illustrate the in- 
vention wherein like numerals refer to like parts and in 
which: 
FIG. 1 is a schematic central sectional view of one 
apparatus embodying this invention mounted adjacent a 
pipe through which fluid flow is to be tested. 
FIG. 2 is a view similar to FIG. 1, but showing in block 
diagram form the electrical sensing means of the inven- 
tion, with fluid in the pipe, but no flow therethrou&. 
FIG. 3 is a view similar to FIG. 2, but with fluid flow 
from left to right as shown in the figure. 
Referling to the drawing, the device of this invention is 
adapted for posiiioning adjacent a thermal conductive 
type pipe made of iron or the like such as pipe 10 with fluid 
11 therein. 
The apparatus consists of a portable housing 1% which 
is so shaped and dimensioned as to be easily portable and 
at the same time constructed so as to be held adjacent to 
and in contact with a longitudinal length of the outside 
su~face of pipe 10, as shown. 
Housing 12 has mounted therein a pair of thermo- 
couples 15, with one provided near each end of the hous- 
ing 12. Thermocouples 15 are so placed in housing 1% that 
they will be in thermal contact with pipe 10 when housing 
12 is placed thereagainst. Each of the thermocouples 15 is 
connected by appropriate conductors to sensing 111eans for 
detecting and reading out variations in electrical energy 
produced by the thermocouples as indications of flow 
through pipe 10. One such sensing means could be gal- 
vanometer 16 arranged for comparing the electricol energy 
produced by thermocouples 15 and providing a read out of 
variations in electrical energy produced by the the~mo- 
couples as an indication of the direction and rate of fluid 
flow in pipe 10. 
Housing 12 has a central well therein formed by cyl~ndpr 
20 in which is mounted heating means in the form of 
elect~ical heating coil 21 having a capacity of 40 watts, 
for example, and power by any convenient elecrr~cal 
soulce, such as source 22. 
In operation. the apparatus of this invention is placed 
in contact with pipe PO rn the position shown in FIG. 1. 
Thereaftei heat~ng element 21 is energized wh~ch thereby 
heats that poition of pipe 10 adjacent thereto, wllrch 
carLses the hcailng of the Piu~d lnsrde of pipe 10 111 a pat- 
tern s u ~ h  as is derr~onstmted by heat ltnes 25 In FIG 2. 
Since there is no flow through pipe 10 at this point, and 
since thelmocoup!es 15 ale substantially equally spaced 
apart from heat clement 21, thermocouples 15 produce 
approximately equal electrical enelgy. In any event, gal- 
vanometer 16 can be adjusted to a null pos~tron to com- 
pensate for any variations not caused by fluid flow thiough 
pipe 10. 
Thereafter, fluid flow can be commenced thiough 
pipe 10, as by p ~ ~ n ~ p i n g  and the like, with the result 
3,500,686 
3 a 
that heating eIernent Iil rends to heat up flrtid 11 in con- arranged for ~lierrnal contact pith axially spaced 
duit 10. Fluid flow in the direction of arrows 26, shown a p a ~ l  poillls on the outside surface of said conduit 
in FIG. 3, teaiis to cause the heated fiuid to move down when said housing i . ~  placed theleagainst; 
stream. The resuit is that the dowi~stream thermocouple a well positioned in said housing spaced between and 
$5 will detecl a higher temperatwe than the upstream insulated f ~ o m  said thermocouples, said well pene- 
thermocouple 15, which difference is then sensed and read trating through said housing and perpendicular to 
out by galvanometer 16. It is to be understood that gal- said conduit; 
vanometer 16 is calibrated to show both the direction and an electrical coil heating element mounted in said well 
rate flow by comparison of the electrical energies pro- and arranged for heating a small portion of said con- 
duced by the two thermocouples 15. duit to thereby heat fluid in said conduit adjacent 
It will thus be apparent that this invention provides an thereto when said housing is placed against said 
apparatus which can be used to determine the direction conduit; 
and rate of fluid flow in a conduit without penetration and electrical sensing means connected to said thernlo- 
thereinto. It  provides a safe system which reduces fire couples for detecting and reading out variations in 
hazards to a minimum. It is portable whereby it may be 15 electrical energy produced by said thermocouples as 
used in a number of different positions without damage indications of the direction and rate of fluid flow in 
to or intrusion into the conduit itself. It is s i m ~ l e  of con- said conduit. 
struction and extremely sensitive to changes iiflnid flow. References Cited Further modifications may be made in the invention 
without departing from the scope thereof. Accordingly, 20 UNITED STATES PATENTS 
the foregoing description is to be construed as illustrative 
only and is not to  be construed as a limitation upon the 2>4463283 8/1948 Hnlsberg ------------ 73-204 
invention as defined in the following claim. 2,525,197 10/1950 Beams et al. --------- 73-204 
What is claimed is: 3,229,522 1/1966 Benson -------------- 73-204 
1. In a heated element fluid flow sensor for sensing the 25 
rate and direction of fluid flow in a thermal conductive FOREIGN PATENTS 
conduit, the combination comprising: 601,298 5/1948 Great Britain. 
a portable housing having a trough-like surface for 45,872 12/1935 France. 
positioning against the outside surface of said con- 
duit; 30 JERRY W. MYRACLE, Primary Examiner 
a pair of thermocouples mounted in said housing and 


Heated element fluid flow sensor Patent

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