U.S. patent number 3,619,559 [Application Number 05/011,986] was granted by the patent office on 1971-11-09 for steam generator.
Invention is credited to Nat Camp.
United States Patent |
3,619,559 |
Camp |
November 9, 1971 |
STEAM GENERATOR
Abstract
A steam generator has a boiling chamber receiving water from a
reservoir through a capillary tube and discharging steam through an
outlet having a selectively variable orifice size. A pair of spaced
electrodes in the form of metal strips are suspended within the
chamber and are connected across a voltage source. The lower
portion of each metal strip has conductive portion of larger area
than the upper portion thereof. The enlarged area extends from the
vicinity of the chamber bottom to about the middle third of the
chamber. The electrodes can be formed by a pair of flat metal
strips disposed in parallel vertical planes and each having an
enlarged portion of either constant or variable width.
Alternatively, each electrode can be formed from a strip bent in
its dimension of thickness to form a "J" configuration. The pair of
J-shaped electrodes are vertically supported in nested relationship
in either identical or inverted orientation.
Inventors: |
Camp; Nat (Harrison, NY) |
Family
ID: |
21752830 |
Appl.
No.: |
05/011,986 |
Filed: |
February 17, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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826870 |
May 22, 1969 |
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Current U.S.
Class: |
392/336; 239/136;
392/338 |
Current CPC
Class: |
F22B
1/30 (20130101) |
Current International
Class: |
F22B
1/00 (20060101); F22B 1/30 (20060101); H05b
003/60 () |
Field of
Search: |
;219/284-295,271-276
;21/118,119 ;239/133,135,136 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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241,130 |
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Oct 1962 |
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AU |
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108,664 |
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Oct 1943 |
|
SW |
|
Primary Examiner: Bartis; A.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of my application Ser.
No. 826,870, filed May 22, 1969 now abandoned.
Claims
What is claimed is:
1. A steam generator comprising an upright heating chamber with an
inlet in the region of its lower end and an outlet in the region of
its upper end, feed means at said inlet for supplying water to said
chamber, discharge means connected to said outlet for emitting
steam therefrom, support means in said chamber and a pair of
juxtaposed electrodes in said chamber connectable to a source of
heating current for vaporizing the water therein; said electrodes
being constituted by elongate elements of generally J-shaped
configuration having each a substantially vertical long leg
depending from said support means near said upper end, a bight
portion in the vicinity of said lower end and an upstanding short
leg rising from said bight portion, said elements being spacedly
nested with their J's in coplanar relationship and with their short
legs terminating at substantially the same level above their bight
portions.
2. A steam generator as defined in claim 1 wherein said J's are
relatively laterally inverted with alternation of their long and
short legs.
3. A steam generator as defined in claim 1 wherein said elements
are metal strips with a dimension of width transverse to the plane
of the J's.
4. A steam generator as defined in claim 3 wherein said strips are
transversely curved at the upper extremities of said long legs.
5. A steam generator as defined in claim 4 wherein said support
means comprises two members with matingly curved surfaces in
contact with said upper extremities.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to a steam generator of the type
described in my prior U.S. Pat. No. 3,267,678, issued Aug. 23,
1966, which discloses a vapor-generating device wherein water from
a relatively large body of liquid in a storage tank, or the like,
is electrically heated in a relatively small boiling chamber, the
evaporating liquid being continuously replenished by way of a
capillary tube connecting an inlet of the boiling chamber to the
supply tank.
Such a system works well when the outlet from the steam chamber
terminates in a fixed nozzle orifice generating a substantially
constant back pressure which, together with the substantially
constant inlet pressure delivered by the capillary tube, maintains
the water within the boiling chamber at a more or less constant
level at which the liquid influx due to the pressure differential
just balances the rate of evaporation. If, however, the effective
orifice opening is changed to vary the width of the emitted jet,
the liquid level in the boiling chamber may change so much as to
lead to a flooding or a draining of the chamber unless a
compensatory adjustment is made in the wattage consumed.
SUMMARY OF THE INVENTION
Generally speaking, it is an object of the invention to provide
improved water-heating means in a boiling chamber which will
stabilize wattage and substantially reduce the possibility of
flooding or draining of the boiling chamber.
More specifically, my invention aims at providing means for
maintaining a substantially constant water level in a boiling
chamber of a steam generator to which water is fed at a controlled
rate by way of a restricted supply conduit, such as the
aforementioned capillary tube, and to maintain a low water level
while enabling control of the vapor stream over a wide range of
widths by merely varying the nozzle size without any other
adjustment.
It is known that water can be heated by the immersion of two
spaced-apart electrodes connected across a voltage source, the rate
of heat generation being proportional to the current flow, which
increases progressively with the depth of immersion and the
resulting decrease in the effective electrical resistance of the
water bath if the width of the electrodes is substantially constant
throughout their height. If the electrodes terminate at the bottom
of the chamber in such a manner as to have greater facing areas,
the current flow along their stems becomes negligible and the rate
of heating is almost independent of the depth of immersion.
Although electrodes of the first-mentioned type could be used to
regulate the water level in the presence of a constant supply
voltage, they tend to draw excessive current if the boiling chamber
is filled to an extent considerably above the normal level before
the current is turned on.
It is, accordingly, a more specific object of my present invention
to provide level-regulating electrodes for the purpose set forth
which minimize "spitting" resulting from too rapid boiling and
which do not overload the power supply though allowing for a
considerable variation in the current rate, depending on the water
level in the boiling chamber, to generate the requisite amount of
heat for overcoming different back pressures created in the boiler
through a restrictable outlet.
The aforesaid objects are realized, pursuant to my present
invention, by the provision of a pair of generally upright parallel
electrodes reaching from above into a water bath within a boiling
chamber which receives its water supply through a restricted inlet,
such as a capillary tube, and which is provided with an adjustable
outlet, the two electrodes including a pair of parallel conductive
elements rising to an intermediate level of the chamber. These
conductive elements are constructed and arranged to form facing
portions of greater area, as by having enlarged or internested
lower portions. More specifically, the enlarged areas should extend
from the vicinity of the chamber bottom to about the middle third
of the chamber to provide an adequate range of level variations
therealong while ensuring the existence of a sufficient vapor space
above the water level to prevent boiling out or "spitting" of hot
water.
With a pair of such electrodes, control of the water level within
the lower part of the chamber is possible since any rise of that
level along the immersed conductive elements results in a rapid
increase in the effective electrode area with a consequent rise in
heating current and greater vaporization rate; if, upon a lowering
of the back pressure due to an enlargement of the effective chamber
outlet, liquid enters the chamber more rapidly through the
capillary inlet tube, the rise in water level sharply increases the
magnitude of the heating current so as to restore the balance.
Once the liquid has reached the upper boundary of the main
electrode portions, a further rise in water level entrains only a
relatively slight increase in heating current, or none at all if
the exposed electrode surface does not rise above the middle region
of the chamber, so that the power supply will not be overloaded
even if the chamber is completely filled when the circuit is
closed. In that event, the level gradually drops back, at a rate
depending upon the width of the nozzle orifice, until the
aforedescribed balance is attained.
BRIEF DESCRIPTION OF THE DRAWING
For a fuller understanding of the invention, reference is had to
the following description taken in connection with the accompanying
drawing, in which:
FIG. 1 is a diagrammatic sectional view of a steam generator
generally similar to that described in my aforementioned U.S. Pat.
No. 3,267,678, but provided with a boiling chamber containing a
pair of electrodes constructed in accordance with an embodiment of
the present invention;
FIG. 2 shows at (A) a diagrammatic face view of an embodiment of
the electrodes of FIG. 1 and at (B) a graph serving to explain the
operation of the system;
FIGS. 3-5 are views similar to FIG. 2(A), illustrating different
electrode shapes capable of being used in the system of FIG. 1;
FIG. 6 is an enlarged sectional view of a boiling chamber
incorporating another embodiment of electrodes constructed in
accordance with the instant invention; and
FIG. 7 is a sectional view taken along line 7-7 of FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, I have illustrated a steam generator comprising a liquid
reservoir in the form of a tank 10 having a drain 11 connected via
a capillary tube 12 to an inlet 13 of an upright boiling chamber
14. A strainer 15 overlies the drain 11 to keep impurities away
from the tube 12. Chamber 14 has a top 16 in the form of a
detachable lid from which an outlet tube 17 leads to a head 18
carrying a turret 19 with a set of nozzles 20 of different orifice
sizes. Turret 19 may be rotated to align any one of the nozzles 20
with the outlet tube 17 in order to throttle the discharge of steam
therefrom to a predetermined extent.
A pair of electrodes 21, 22 are suspended from lid 16, hanging down
to almost the bottom of chamber 14 in spaced-apart, parallel
relationship. These electrodes are connectable by way of a switch
23 across a source of operating voltage diagrammatically indicated
at 24.
The water level in tank 10, whose volume greatly exceeds that of
boiling chamber 14, is above the top of the chamber so as to create
a sufficient hydrostatic pressure differential across capillary
tube 12 to drive water into the chamber. With the twin electrodes
21, 22 energized, the steam generated in chamber 14 creates a back
pressure whose magnitude depends upon the effective width of the
selected nozzle 20. The amount of heating current passing between
the electrodes 21 and 22 depends on the quantity of water bridging
these electrodes and is therefore a function of the height h of the
liquid in chamber 14. Thus, the water level in the chamber during
steady state operation must be such that enough heat is generated
to raise the temperature of the water bath above the boiling point
(which varies somewhat with the back pressure of the steam), taking
into account the constant influx of cold water from reservoir 10 to
balance the rate of vapor discharge via the selected nozzle 20.
In FIG. 2(A) I have shown an advantageous shape of the electrode
21, which, of course, is also representative of the similar
companion electrode 22. This electrode consists of a metal strip
(e.g. of steel) of substantial constant width w bent roughly into
the shape of a J, with the hook 21a of the J terminating at a level
L.sub.3 which may be in the middle third of its length. Other
levels indicated in FIG. 2 are the chamber bottom L.sub.0, the
lower end of the electrode at L.sub.1, the upper edge of the
transverse bar 21b of the J at L.sub.2, and the top of the
electrode at L.sub.4.
The operation of the system of FIG. 1, whose electrodes 21, 22 have
the shape illustrated in FIG. 2(A), will now be explained with
reference to the graph of FIG. 2(B). In this graph, I have plotted
the water volume v and the heating current I (on the abscissa)
against the height of the water level (on the ordinate), it being
understood that this showing is to be considered qualitative rather
than quantitative.
With chamber 14 of cylindrical or prismatic configuration, volume v
varies proportionately with height h as indicated by the straight
dot-dash line in FIG. 2.
The heating current I, and therefore the amount of thermal energy
generated, varies with the conductance of the water body between
the electrodes and is thus generally proportional to the immersed
electrode area. This is represented by the solid line in FIG. 2
according to which the slope dI/dh is proportional to the width w
of the electrode strip in the region L.sub.3 -L.sub.4, has twice
this magnitude in the region L.sub.2 -L.sub.3 in which the
effective width is doubled, and is still greater in the bottom
region L.sub.1 -L.sub.2.
Significant for the proper operation of the system of FIG. 1 is the
fact that the heating current rises more rapidly than the water
volume between levels L.sub.1 and L.sub.3, thereafter increasing
more slowly than that volume.
Upon prolonged standing with switch 23 open, water from reservoir
10 completely fills the chamber 14. When the switch is then closed,
electrodes 21 and 22 draw a starting current I.sub.4 having the
magnitude shown in FIG. 2(B). This current is only slightly greater
than the current I.sub.3 flowing when the liquid is at the
intermediate level L.sub.3.
After the necessary warmup period, which will be quite short if the
volume of chamber 14 is small, steam begins to evolve and to exit
from the chamber via one of the nozzles 20. When the rate of steam
generation outraces the water supply through tube 12, the water
flow through tube 12 reverses so that the liquid volume decreases
at a faster rate than the current flow as will be apparent from the
diagram from FIG. 2(B).
This condition is unstable so that the level rapidly drops to the
point 2I.sub.3, with reduction of the current to magnitude I.sub.3.
Further evaporation reduces the current faster than the volume
until, at a liquid level L.sub.x, the current I.sub.x generates
just enough heat to balance the outflow of steam against the entry
of fresh water. During this period of instability, the pressure
differential across capillary tube 12 may be reversed to that
excess water is returned to tank 10. The location of the operating
level L.sub.x, depending upon such parameters as the hydrostatic
head in vessel 10 and the flow resistance of tube 12, varies for a
given system with the effective outlet opening as determined by the
selected nozzle 20. Generally, this level will lie between marks
L.sub.2 and L.sub.3 so that the operating current Ix will range
between magnitudes I.sub.2 and I.sub.3.
In FIG. 3 I have shown a modified electrode 21' with an enlarged
bottom portion 21a' of constant width which operates essentially in
the same manner as the electrode 21 of FIG. 2, except that the
current rise between levels L.sub.1 and L.sub.3 is constant.
FIG. 4 shows another electrode 21" whose enlarged bottom portion
21a" is rounded so that the sharp bends in the line I of FIG. 2 are
replaced by more gradual transitions.
Naturally, the specific shapes illustrated in FIGS. 2-4 are merely
representative of a wide variety of roughly equivalent
configurations.
While the electrodes described above were disposed in parallel
vertical planes, they could also be made from a pair of nested
strips bent into a J or similar configuration as illustrated at
121, 122 in the perspective view of FIG. 5. It will be apparent
that, in this case, the level L.sub.1 coincides with the lower
boundary of inner electrode 122, the operation being otherwise the
same as previously explained.
The use of strips bent in their dimension of thickness as shown in
FIG. 5, rather than enlarged in their dimension of width as seen in
FIGS. 2-4, has the advantage of simpler and therefore less
expensive manufacture of these electrodes which can be made from
standard stock of stainless steel or other suitable metal.
The storage tank 10 of FIG. 1 could also be supplemented or
replaced by a supply line of more or less constant water pressure,
greater than the hydrostatic head in the completely filled heating
chamber 14, as likewise shown in my prior U.S. patent identified
above.
If the electrode extensions above level L.sub.3 were insulated
rather than exposed, the heating current would remain at the value
I.sub.3 for any water level between marks L.sub.3 and L.sub.4.
A further configuration of electrodes is shown in FIGS. 6 and 7.
Electrodes 31 and 32 are suspended from top 16 and are connected to
operating voltage 24 in any suitable manner (not shown). The
electrodes have an arcuate cross section as shown in FIG. 7 and
have a J shape at the lower ends thereof which are invertedly
nested, one within the other, as shown in FIG. 6. By this laterally
inverted nesting, a substantial increase in the facing area of the
electrodes is obtained, while maintaining the upper portions of the
electrode at a substantial spacing in order to minimize the
increase in electrical conductance when chamber 14 is filled with
water above the level of the short leg of the J-shaped electrodes.
By minimizing the increase in electrical conductance, excessive
boiling which could result in spitting of hot water is limited.
Also, the increased spacing reduces electrical consumption as
compared with parallel spacing of electrodes such as in the
embodiment shown in FIG. 5. The embodiment of FIGS. 6 and 7
prevents excessive surge of steam output when the chamber is filled
with water and maintains a more equalized steam output at the
various water levels.
Depending from top 16 are a pair of nonconductive supports 33
having a surface which mates with the curvature of electrodes 31,
32 so that the electrodes may be mounted thereon, as by suitable
rivets 34. The close contact of the electrodes with the supports
provides means for maintaining the electrodes in parallel
relationship. The curvature of the electrodes improves the rigidity
thereof, which is further maintained by the conformation with the
supports.
It will be noted that the coplanar J's defined by the electrodes
31, 32 of FIGS. 6 and 7 have rounded bight portions, in contrast to
the angular ones of the electrodes of FIGS. 2(A) and 5, and that
their depending longer legs alternate with their upstanding shorter
legs; thus, the spacing between the two electrodes is considerably
smaller in the zone of overlap than in the region above the level
of termination (L.sub.3, FIG. 2) of the two short legs.
* * * * *