US3619559A

US3619559A - Steam generator

Info

Publication number: US3619559A
Application number: US11986A
Authority: US
Inventors: Nat Camp
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-02-17
Filing date: 1970-02-17
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

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.

Description

United States Patent [72] Inventor Nat Camp Homestead Place, Harrison, N.Y. 10528 [21] Appl. No. 11,986 [22] Filed Feb. 17, 1970 [45] Patented Nov. 9, 1971 Continuation-impart of application Ser. No. 826,870, May 22, 1969, now abandoned.

[54] STEAM GENERATOR 5 Claims, 7 Drawing Figs.

[52] US. Cl. 219/288, 219/273, 219/293, 239/136 [51 Int. Cl 1105b 3/60 [50] Field 01 Search ..219/284-295,

. 271-276;2l/ll8, 119; 239/133, 135,

[56] References Cited UNITED STATES PATENTS 2,806,932 9/1957 Conlin et a1. 219/275 2,885,527 5/1959 Tone et al 219/289 X 2,818,486 12/1957 Schmitt et al.. 218/288 X 1,782,069 11/1930 Henning 219/289 3,219,796 11/1965 Grafet a1 219/273 X 3,267,678 8/1966 Camp 219/272 UX FOREIGN PATENTS 241,130 10/1962 Australia 219/288 108,664 10/1943 Sweden 219/285 Primary Examiner-A. Bartis Attorney-Karl F. Ross 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 1" configuration. The

pair of J-shaped electrodes are vertically supported in nested relationship in either identical or inverted orientation.

STEAM GENERATOR CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-impart of my application Ser. No. 826,870, filed May 22, 1969 now abandoned.

BACKGROUND OF THE INVENTION This invention relates generally to a steam generator of the type described in my prior U.S. Pat. No. 3,267,678,1aued Aug. 23, I966, 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 objectof 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 to 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 elementsare 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 anenlargement 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 adiagrammatic 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. I 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 the line 77 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 I0 having a drain II connected via a capillary tube 12 to an inlet 13 of an upright boiling chamber 14. A strainer 15 overlies the drain II to keep impurities away from the tube 12. Chamber I4 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 I4 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 2] 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 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 which may be in the middle third of its length. Other levels indicated in FIG. 2 are the chamber bottom L the lower end of the electrode at L,, the upper edge of the transverse bar 21b of the J at L and the top of the electrode at L 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 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:,L has twice this magnitude in the region L L in which the effective width is doubled, and is still greater in the bottom region L,L

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, and L 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 having the magnitude shown in FIG. 2(B). This current is only slightly greater than the current 1;, flowing when the liquid is at the intermediate level L;,.

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 with reduction of the current to magnitude I Further evaporation reduces the current faster than the volume until, at a liquid level L,, the current I, 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,., 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 and L so that the operating current Ix will range between magnitudes I, and I 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 and L 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 I. 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 US. patent identified above.

If the electrode extensions above level L; were insulated rather than exposed, the heating current would remain at the value I; for any water level between marks L, and L,.

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 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 .I-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 .l'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 FIG. 2) of the two short legs.

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 .l-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 Js 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

Claims

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 Jshaped 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.