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Патент USA US3053972

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Sept. 11,1962
R. M. CHRISTMANN
3,053,959
APPARATUS AND METHOD FOR HEATING FLUIDS
Filed Dec. 15. 1959
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3,053,959
Patented Sept. 11, 1952
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3,053,959
APPARATU§ AND METHOD FOR
HEATING FLUIDS
Richard M. Christmann, 616 N. Main St, Pratt, Kans.
Filed Dec. 15, 1959, Ser. No. 859,645
12 Claims. (Cl. 219--I0.49)
This invention relates to an apparatus and a method
for heating ?uids, and, more particularly, to the heating
of ?uids inductively while they are ?owing in a conduit.
The principal object of the invention is to provide a
be employed for the conduction of a liquid such as water
from an entry point 11 to a discharge point 12. For the
purpose of inducing liquid flow in the piping system 10,
a pump 13 is provided. Also interposed in the piping
system 10 is a heater generally designated by the numeral
14, which is electrically energized by a generator 15. In
asmuch as a principal object of this invention is to pro—
vide a novel method and apparatus for the heating of
?owing ?uids, it is believed unnecessary to go into further
detail relative to the piping system it} or rami?cations
thereof. Many modi?cations of the system depicted will
method and apparatus for the heating of ?owing ?uids
occur to those skilled in the art as a result of a considera
which utilizes electrical energy but which is ‘free of any
tion of the instant teaching.
The system 10 may include conventional iron pipe
lengths such as are designated by the numeral 16. Also,
connections through the wall of the conduit through
which the ?uids may be ?owing. Although ?uid»carry
ing pipes have been electrically heated internally for a
long time, such operations have required the use of heat
the system 10‘ may include iron elbows 17 and a conven
tional union 18.
The portion of the system lltl including the heater 14
ing elements that were mechanically coupled to an elec
can be seen in enlarged scale in FIG. 2, Where the iron
trical source and this meant the provision of connections
extending through a pipe wall, or the like. This is ob 20 or other pipe 16 is seen connected as by threads 19 to a
pipe length 20. The pipe length 20 is seen to be shaded
jectionable, since it requires sealing means, involves shock
for a nonconducting material of construction such as
and/ or spark hazard and also has been responsible for de
creased e?iciency of the heater. Although attempts have
been made in the past to avoid this drawback, as by the
Fiberglas.
Disposed about the pipe 20 is a coil 21, a portion of
one winding 21:: being seen in the cross-sectional view
depicted in FIG. 3. The coil 21 is insulated from the
atmosphere by means of an insulating layer 22. The
disadvantages which have sharply limited the use of this
layer 22 also assures insulation of each winding or con
principle.
volution 21a from an adjacent Winding or convolution.
It is, therefore, another important object of this in
vention to provide a method and apparatus for heating 30 A variety of suitable materials can be used for the layer
'22 which are effective to “pot” the coil on the tube. A
?owing ?uids which utilizes the so-called “transformer"
commercially available material for this purpose is epoxy
principle ‘and which avoids the disadvantages and draw
resin and is effective to seal the coil 21 hermetically as
backs experienced in previous applications of this prin
well as electrically and thermally insulate the same. Also,
ciple. Broadly, the “transformer” principle comprehends
utilization of the “transformer” principle, these attempts
have been characterized by other, but equally undesirable,
the provision of a primary winding external to the liquid
carrying pipe and a secondary isolated from the primary
and interposed within the pipe. In the past, attempts to
utilize this principle have relied upon a dielectric effect
the layer 22 mechanically ruggedizes the pipe-coil com
bination. In this manner, the primary of the transform
er provided by the coil 21 is integrated with the ?uid
conducting pipe 20. The coil 21 is connected by means
of leads 23 to a source of alternating current which, for
stemming from the character of the liquid being heated.
This sharply limited the liquids that could be heated, and 40 the sake of convenience, is depicted as a generator 15.
The generator 15 may be either adjacent to or remote
further necessitated the employment of complex apparatus
in order to generate the high frequency voltage required.
Still another object of the invention is to provide a
from the heater 14—the latter being the case where com
method and apparatus for the inductive heating of ?owing
been designed to operate effectively with ordinary power
line frequency, i.e., 60 cycles per second. Other low
?uids wherein a relatively low frequency electrical cur
mercial electric power is employed.
The heater 14 has
frequency currents can be also employed to advantage,
rent is employed. Frequencies of the order employed in
such as 25 or 400‘ cycles per second. Through the use
power transmission, i.e., 60 cycles per second, are uni
of this frequency energy, it is possible to develop up to
formly available, and the use of such electrical energy
20 kilowatts of power in a pipe heater while still retain
for inductive heating according to the so-called “trans
50 ing modest size and insuring that the over-all installation
former” principle is an object hereof.
is desirably rugged.
Yet another object is to provide a method and apparatus
The secondary is provided in the form illustrated as
for inductive heating of liquids ?owing in a pipe, or the
,an inner pipe 24 which is spaced or supported interiorly
like, in which a novel transformer secondary is installed
in the pipe to provide a desirably high e?iciency in the
of the pipe 20 by means of spacers or supports 25. In
55 the illustration given the secondary comprises an ele
ment made of mild steel which is seen to be a tube. How
Other objects and advantages of this invention may be
ever, the secondary element 24 may be provided equally
.seen in the details of construction and operation as set
heating operation.
forth in the ensuing speci?cation.
The invention will be described in conjunction with an
satisfactorily in the form of a solid bar. The secondary
element 24, however, must be constructed of a magnetic
illustrative embodiment in the accompanying drawing in 60 material such as iron so that the same may be heated by
which~
FIG. 1 is a schematic representation of a fragment of a
piping system to which the instant invention has appli
cation;
FIG. 2 is ‘an elevational view, partially broken away
and in section, of an induction heater employing the
teachings of this invention; ‘and
FIG. 3 is a cross-sectional view taken along the line
3—3 of FIG. 2.
the development of eddy currents. In operation, a cer
tain amount of heat is engendered in the element 24
.(when the primary coil 21 is energized) through a cir
culating current in the surface shell of the secondary
element 24 as if the same were acting as a one turn sec
ondary. Here, it is to be appreciated that the secondary
element 24 is in effect a core which provides its own
secondary, and, thus, if desired, a special secondary Wind
.ing may be omitted.
Referring now to the drawing, the numeral 10 desig 70 This core element 24 may be treated in a variety of
manners to insure chemical inertness, e.g., gold plating
nates generally a ‘fragment of a piping system which may
3,053,959
3
4
may be used for water-heating cores; or for oil, copper.
could be used. A variety of inert materials may be em
ployed for the spacers 25, such as Te?on. From this, it
to a pipe of about 3/; inch I.D. In most ?uid ?ow opera
tions, it is undesirable to introduce frictional resistance
will be seen that the heating element is effectively insul
ated both from the pipes 16 of the piping system 10
and from the primary-providing coil 21.
Through the use of a single element providing both
the secondary and the core, it is now possible to provide
a device employing the “transformer” principle which is
but the same is often necessary to reduce ?lm coef?cient
so as to achieve substantial heat transfer. With the in
stant invention, streamline-—as contrasted to turbulent
?ow-—can be employed without effecting the achieve
ment of maximum efficiency of heat transfer.
While in the foregoing speci?cation I have set ‘forth
a detailed description of an embodiment of the invention
capable of dissipating heat at a reasonable power level 10 for the purpose of completely describing the same, it
within the pipe carrying the liquid to be heated and while
will be apparent to those skilled in the art that many
yet retaining a very desirable compactness and ruggedness
variations of the details herein given may be made with
out departing from the spirit and scope of the invention.
possible to provide an “in-line” pipe heater through the
I claim:
assembly of three single parts—the pipe, the winding, 15
1. In a ?uid heater, a conduit constructed of electrical
and the core. Alternatively, this could be done through
insulating material, an electrical winding about said con
the employment of two major parts—the potted pipe
duit, a source of low frequency voltage coupled to said
winding and the treated core.
winding, a magnetic element within said conduit, and
For optimum operation, the core should have a size,
a nonmagnetic element about said magnetic element and
i.e., area and length, to operate just under saturation for 20 within said conduit, the inner walls of said conduit being
the voltage employed. This insures that maximum econ
spaced from the outer walls of said nonmagnetic element
omy of weight and over-all size may be maintained.
whereby ?uid is adapted to ?ow between said inner and
This also precludes operation in an area when there is a
outer Walls, said electrical winding being effective to in
nonlinear current voltage relationship which may prove
ductively heat ?uid ?owing past said elements.
injurious to the equipment. Also, the core is desirably 25
2. The structure of claim 1 in which said nonmagnetic
so as to make commercial utilization feasible. It is now
constructed to be at least as much longer than the wind
element is a brass cylinder.
ing on each end of the winding as is the inside diameter
3. In a ?uid heater, a conduit constructed of electrical
of the winding. This can be appreciated from a con—
insulating material, an electrical winding about said con
sideration of FIGURE 2 wherein the overlap of the core
duit, a source of low frequency voltage coupled to said
relative to the coil 21 is designated by the numeral 26
30 winding, and an element within said conduit in the path
this being indicated at only the left hand end of the core
of ?uid ?owing therein to direct ?uid ?ow about said
providing element 24 but which is seen to exist also at
element, said element being constructed of magnetic ma
the right hand end thereof. In this fashion, I am able
terial, said conduit being a circular pipe, said element
to minimize end ?ux loss effects and to maximize the
overlapping said winding at each end of the winding by
power factor. Lengths greater than that shown provide 35 at least about the inside diameter of said winding.
little, if any, additional improvement in power factor.
4. In a device for heating ?uids ?owing in a conduit,
Heaters have been constructed according to these condi
a length of conduit constructed of nonmagnetic electrical
tions operating with power factors of 0.9 or better and
insulating material, a length of electrical conductor
with conversion efficiencies of virtually 100%.
Wound about said length of conduit with each winding
If desired, the heating capacity of the heater 14 may 40 loop being insulated from the remaining loops, a source
be enhanced by interposing a one turn cylindrical shell
of alternating current coupled to said electrical conductor
of a non-magnetic conductor such as a brass tube. This
whereby the said electrical conductor is effective to serve
is indicated in dotted line in FIGURE 3 by the numeral
as a transformer primary, and a transformer secondary
27. Such a modi?cation, however, may tend to compli
constructed of magnetic material in said length of con
cate the structure and might only be advisable where an 45 duit and heatable primarily by eddy currents induced
absolute maximum in space economy is required. Usu
ally, however, such supplemental structure is not needed.
This may be appreciated from the fact that a heater effec
tive to deliver 37,500 Btu per hour need be only 30
therein by said primary, said secondary being interposed
in the path of ?uid ?owing in said conduit and having
its outer walls spaced from the inner walls of said con
duit, whereby said ?uid necessarily ?ows around said
inches long with a 24 inch long potted primary having an 50 secondary.
OD. of about 3 inches.
5. In a device for heating ?uids ?owing in a conduit,
Effective “instant” heating may be obtained by the
a length of conduit constructed of nonmagnetic electrical
addition of the interposed shell 27 or, to a lesser degree,
insulating material, a length of electrical conductor wound
by the plating or coating of a heavy ?lm of low resistivity
about said length of conduit with each winding loop being
material on the core 24. The normal time response of 55 insulated from the remaining loops, a source of alternat
the heater (2—3 seconds) may be improved by a factor
ing current of power line frequency coupled to said elec
of 3 or 4 in this manner.
trical conductor whereby the said electrical conductor is
The heater of the invention is exceptionally advanta
effective to serve as a transformer primary, and a trans
geous since it does not require costly frequency conversion,
former secondary constructed of magnetic material in
special winding procedures or core treatments, special 60 said length of conduit, said secondary being interposed
conduit shapes, or special separate components. It pro
in the path of ?uid flowing in said conduit and having
vides the heater with large heat exchange area for mini
its outer walls spaced from the inner walls of said con
mum “hot spot” effect. It is susceptible of being made
ductor, whereby said ?uid necessarily ?ows around said
as chemically inert as the user desires and may be made
secondary.
around other types of non-magnetic, non-conductor pipe 65
6. In a device for heating ?uids ?owing in a conduit,
a length of conduit constructed of nonmagnetic electrical
insulating material, a length of electrical conductor
wound about said length of conduit with each winding
loop being insulated from the remaining loops, a source
of alternating current coupled‘ to said electrical conductor
and treated to resist even such highly corrosive materials
as hydrogen ?uoride, aquaregia, etc. It is of advanta
geous use in full ?ow heating application, imposing mini
mum pressure drop, or to demand heating, such as in
hotels, homes, etc. Here, it is to be appreciated that
maximum e?iciency in transfer of heat to the ?uid ?ow
ing past the secondary is achieved without the need for
introducing substantial friction. Somewhat less than .5
psi. head is su?icient to attain approximately 30 g.p.m.
flow through a 10 kw. heater with a flow area equivalent 75
whereby the said electrical conductor is effective to serve
as a transformer primary, and a solid bar transformer
secondary constructed of magnetic material in said length
of conduit, said secondary being interposed in the path of
?uid ?owing in said conduit and having its outer Walls
3,053,959
6
the Winding by at least about the inside diameter of said
spaced from the inner Walls of said conduit, whereby said
?uid necessarily ?ows around said secondary.
winding.
7. In a device for heating ?uids ?owing in a conduit,
a length of conduit constructed of nonmagnetic electrical
insulating material, a length of electrical conductor
9. In a ?uid heater, a conduit
insulating material, an electrical
duit, a source of low frequency
Winding, and an element within
Wound about said length of conduit with each winding
loop being insulated from the remaining loops, a source
of alternating current coupled to said electrical conductor
constructed of electrical
winding about said con
voltage coupled to said
said conduit in the path
of ?uid ?owing therein to direct ?uid ?ow about said ele
ment, said element being constructed of magnetic mate
trial and adapted to be inductively heated by current ?ow
whereby the said electrical conductor is eiiective to serve
as a transformer primary, and a magnetic element serv 10 ing in said ‘Winding, said element being rigidly mounted
ing as a core of said transformer and located centrally
of said conduit, said magnetic element being equipped
in said conduit and de?ning with said conduit a ?uid ?ow
channel wherein the ?uid ?owing in said channel is heated
substantially entirely by electrical currents induced in
said element.
ary of said transformer, said secondary being interposed
10. The structure of claim 9 in which said element is
in the path of ?uid ?owing in said conduit and having 15
proportioned in area and length for operation just under
its outer Walls spaced from the inner walls of said conduit,
saturation for the voltage employed.
whereby said ?uid necessarily ?ows around said sec
with a nonmagnetic outer surface serving as the second
11. The structure of claim 9 in which said element is
elongated relative to said winding in the direction of
8. In a device 1for heating ?uids ?owing in a conduit,
a length of circular conduit constructed of nonmagnetic 20 ?uid ?ow and is positioned in said conduit to overlap said
winding at both ends of said Winding.
electrical insulating material, a length of electrical con
12. The structure of: claim 11 in which the ratio of
ductor wound about said length of conduit with each
ondary.
Winding loop being insulated from the remaining loops,
a source of alternating current of power line frequency
coupled to said electrical conductor whereby the said 25
winding length to winding diameter is about eight.
References tCited in the ?le of this patent
UNITED STATES PATENTS
electrical conductor is effective to serve as a transformer
primary, and a solid transformer secondary constructed
of magnetic vmaterial in said length of conduit, said sec
ondary being interposed in the path of ?uid ?owing in
said conduit and having its outer walls spaced from the 30
inner walls of said conduit, whereby said ?uid necessarily
?ows around said secondary, said element overlapping
the Wound length of electrical conductor at each end of
1,260,564
2,181,274
Magnusson et al _______ __ Mar. 26, 1918
Jackson et al. ________ __ Nov. 28, 1939
2,218,999
2,868,938
2,875,311
White ________________ .._ Oct. 22, 1940
Bar?eld et al __________ __ Jan. 13, 1959
Harkenrider __________ __ Feb. 24, 1959
2,904,664
Rothacker ___________ __ Sept. 15, 1959
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