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Publication numberUS3575581 A
Publication typeGrant
Publication dateApr 20, 1971
Filing dateMay 15, 1969
Priority dateMay 15, 1969
Publication numberUS 3575581 A, US 3575581A, US-A-3575581, US3575581 A, US3575581A
InventorsMasao Ando
Original AssigneeChisso Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Heat-generating pipe utilizing skin effect current controlled locally in heat generation by short-circuiting bridges
US 3575581 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United States Patent [72] Inventor Masao Ando Yokohamashi, Japan [21] Appl. No. 824,975 [22] Filed May 15,1969 [45] Patented Apr. 20, 1971 [73] Assignee Chisso Corporation Osaka, Japan [54] HEAT-GENERATING PIPE UTILIZING SKIN EFFECT CURRENT CONTROLLED LOCALLY IN HEAT GENERATION BY SHORT-CIRCUITING BRIDGES 2 Claims, 3 Drawing Figs.

[52] 11.8. CI 219/301, 219/1051 [51] Int. Cl 1105b 5/08 [50] Field ofSearch 219/1051, 240, 241, 300, 301; 128/303.12

[56] References Cited UNITED STATES PATENTS 1,964,732 7/1934 Homan 128/303.12

2,225,354 12/ 1 940 Schmalenbach 2 l 9/300X 3,293,407 12/1966 Ando 219/301 3,377,463 4/1968 Rolfes 219/300 FOREIGN PATENTS 866,096 4/ 1961 Great Britain 219/300 Primary Examiner-R. F. Staubly Attorney-Fred C. Philpitt ABSTRACT: In a heat-generating pipe comprising a highly ferromagnetic pipe and an insulated conductor line inserted therein and having such a connection that AC flowing through the insulated conductor line is equal in intensity and opposite in direction to the AC flowing concentratedly through the inner wall portion of the pipe due to the skin effect of AC, the heat-generating pipe is characterized in that a certain section of the inner surface of the pipe is brought to short circuit state by a conductor line optionally including a thermostatic or other switch and having an impedance which is selected according to the requirement for decreasing or elimination of heat generation in said section, to control the heat generated in said section.

wherein (Qcm) is resistivity, is specific permeability and f HEAT-GENERATING PIPE UTILIZING SKIN EFFECT CURRENT CONTROLLED LOCALLY IN HEAT GENERATION BY SHORT-CIRCUITING BRIDGES This invention relates to heat-generating pipe utilizing askin effect of AC flowing through the inner wall portion of a ferromagnetic pipe such as a steel pipe, which enables to control heat-generation in a certain section of the inner surface of the pipe.

When the skin effect is pronounced, the depth of the skin S(cm) which is an index showing the range of flow of current in a conductor is represented by a following formula,

S=5030 1/P/Mf is frequency of current per second.

Such a skin effect caused in a ferromagnetic pipe, such as a steel pipe, will be hereinafter explained by referring to an attached drawing.

In FIG. I, an insulated conductor line 1 passes through the inside of a ferromagnetic pipe 3. One end of the conductor line is connected to one terminal of AC source 2 and theother end thereof is connected to one end 4 of the ferromagnetic pipe 3. The other end 5 of the ferromagnetic pipe 3 is connected to the other terminal of the AC source 2 by a conductor line 6.

If a relationship represented by the following formula:

1 t 2s, D S and l D (2) wherein D(cm) is an inner diameter of the steel pipe, [(cm) is its length, and t(cm) is its thickness, exists between I, D and S, the current is concentrated on the inner surface of the ferromagnetic pipe having a large specific permeability, and does not appear onto the outer surface of the pipe, and such an apparatus can be utilized as a heat-generating body. This is a publicly known fact disclosed in Japanese Pat. No. 460,224 (Patent Publication No. l2l28/l965) whose counterparts in USA. and Canada are U.S. Pat. No. 3,293,407 and Canadian Pat. No. 760,556.

In such a heat-generating pipe, it is impossible to decrease or stop heat generation in at least one section of the pipe, for example, between X and Y as indicated in FIG. 1.

An object of the present invention is to provide a heatgenerating pipe in which the above-mentioned drawback is overcome, namely, a heat-generating pipe capable of controlling heat generation in an optional section of the pipe made of a highly ferromagnetic steel or the like.

Now, it has been found that the above-mentioned object can be attained by the apparatus of the present invention.

This invention consists in a heat-generating pipe comprising a highly ferromagnetic pipe and an insulated electric line inserted therein and passing therethrough and having such a connection that AC flowing through the insulated conductor line is equal in intensity and opposite in direction to the AC flowing only through the inner wall portion of the pipe due to the skin effect of AC which is characterized in that a section or plural sections of the inner surface of the pipe are brought in short circuit state by a wire or wires having an impedance which varies according to the requirement for decrease or stoppage of heat generation in said section or sections, in order to control the heat generated in said section or sections.

In addition, it is also possible to use with great deal of advantage the apparatus of the present invention in which a switchgear is interposed at an arbitrary position within the above short circuit to realize its on-off cycles, which may be activated automatically by a thermostat.

The present invention will hereinafter be illustrated with reference to the attached drawings.

FIG. 1 shows a schematic view of a publicly known heatgenerating pipe utilizing skin effect current, which is given as a reference, to enable persons skilled in the art to understand the principle and the construction of the present apparatus.

FIG. 2 shows a schematic, cross-sectional view of a heatgenerating pipe having a short circuit apparatus in a section thereof, according to the present invention.

FIG. 3 shows a schematic, cross-sectional view of a further embodiment of the present invention.

In FIG. 2, an insulated conductor line I is inserted in and passes through the inside of a ferromagnetic pipe 3, One end of the conductor line is connected to one terminal of an AC source 2 and the other end thereof is connected to one end 4 of the ferromagnetic pipe 3. The other end 5 of the ferromagnetic pipe 3 and the AC source are connected by a conductor line 6.

Terminals 7 and 8 are provided at both the ends of a section where heat generation is to be stopped, or controlled, and the section between both the terminals is shorted by a conductor line 9 having an impedance much lower than that of the inner surface of the section of the ferromagnetic pipe. (The section between both the terminals corresponds to the section between X and Y in FIG. 1.) Flanges I0 and 12 and covers 11 and 13 are installed for the convenience of connecting both the ends of the conductor line 9 to the terminals 7 and 8.

The current from one terminal of an AC source 2 passes through the insulated conductor line 1 and flows through the inner surface of the ferromagnetic pipe 3 from one end 4 of the ferromagnetic pipe 3 to the terminal 5 while generating heat, but it passes mostly through the conductor line 9 during the part from the terminal 8 to the terminal 7 and flows only through the inner surface of the pipe 3 again from the terminal 7 to the other end 5 of the pipe 3 while generating heat again;

and returns to AC source 2 through the conductor line 6.

In this case, the current flowing through the insulated conductor line 1 is almost equal in intensity, and opposite in the direction of flow, to the current flowing through the conductor line 9, and there is hardly any skin current occurred in the section of the pipe between the terminals 8 and 7. Thus, heat generation hardly occurs in this part.

If the impedance of the conductor line 9 is made larger than that in the case where the above-mentioned heat generation is almost stopped, the intensity of the current flowing through the conductor line 9 becomes smaller than that flowing through the insulated conductor line 1. In this case, some extent of skin current occurs in the section of the ferromagnetic pipe between the terminals 8 and 7, and hence some extent of heat generation occurs there.

Thus, in accordance with the variation of the impedance of the conductor line 9 from an extremely low value to a very higher one, the heat generation in the short-circuited section of the pipe may be controlled from almost no heat generation to the value attained without such short circuiting.

FIG. 3 is a schematic representation in which a switchgear is interposed at a position within the short circuit described above. In this FIG., the short circuit, as set forth, is made by shunting the section X-Y by at least one insulated conductor line 9 in the inside of pipe 3, and the conductor line 9 is drawn out from said pipe so as to connect with a switchgear 15 in series. When the switch 15 is open, the shunting effect is eliminated; therefore, heat is generated to the extent of full capacity. On the other hand, when the switch 13 is closed, the heat generation will be restrained in the shunted section from generating heat because a greater amount of the current is shunted by the line 9. Thus, actuation of the switch in on-off cycles can adjust the heat generation. It goes without saying that the control of on-off cycles may be done by an attached thermostat.

When the impedance is made much higher, the heat generation in the section becomes almost the same with that of other sections of the ferromagnetic pipe 3 where no short circuit is made.

The above-mentioned explanation has been given in case of the control of heat generation in one section of a heat generating pipe utilizing skin effect based upon such a circuit as in FIG. 2. In cases of any number of plural section, it is also possible to control heat generation in each section so as to make it take the same or a different value in each of the sections.

Further, this invention can be also applied to a circuit other than the above-mentioned ones, for example, such a circuit as described in Japanese Pat. Application No. 20427/1966, entitled Heat-generating Pipe Utilizing Skin Effect Current,

whose counterparts are US. Ser. No. 627,086, Canadian Pat. Application No. 986.43 l, West German Pat. Application No. P l6l5 l92.l, British Pat. Application No. 23142/68 and French PV 154842.

The above-mentioned Japanese patent application relates to a heat generating pipe having an arrangement including a primary circuit of an electric conductor line connected to a source of AC supply and inserted within at least one pipe of ferromagnetic metal throughout the entire length thereof in electrically insulated relation from the inner wall portion of said pipe and a secondary circuit consisting of said at least one pipe of ferromagnetic metal and at least one conductor having an impedance as low as possible and connecting the ends of said pipe, the secondary alternating current induced in the secondary circuit by the primary current being concentrated on the inner wall portion of said pipe on account of the skin effect while satisfying the relations expressed by equations (1 and (2).

The apparatus of the present invention can be applied with great commercial advantage in various cases. For example it can be applied to booster pumps, valves or the like installed in the liquid transportation pipe described in Japanese Patent No. 460,224.

lclaim:

1. in the known type of heat generating apparatus comprising a length of ferromagnetic pipe, a first length of an electrical conductor line disposed within said ferromagnetic pipe but insulated therefrom, and electrical and power connections so that upon the passage of alternating voltage through said first length of electrical conductor line there is a concentrated flow of current along the inner skin of the ferromagnetic pipe to thereby generate heat in said ferromagnetic pipe, the improvement which comprises:

a. at least one additional length of electrical conductor line disposed within said length of ferromagnetic pipe,

b. said additional length of electrical conductor line being shorter than said first length of electrical conductor line and arranged generally parallel to at least a portion of said first length of electrical conductor line,

c. said additional length of conductor line being connected to said ferromagnetic pipe at two spaced apart-points whereby the concentrated flow of current along the inner skin of the ferromagnetic pipe is at least partially short circuited along the inner surface thereof between said two spaced apart points to an extent dependent upon the impedance of said additional length of conductor lin. between said two spaced apart points.

2. A heat-generating pipe according to claim 1 wherein at least one switchgear is interposed at a position within the short circuit shunting said inner surface so as to control the heat generation within said section of said heat generating pipe on an on-off basis.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1964732 *Mar 21, 1930Jul 3, 1934Kirk William JDilator
US2225354 *Nov 10, 1937Dec 17, 1940Koppers Co IncProcess and apparatus for the manufacture of carbon black
US3293407 *Nov 7, 1963Dec 20, 1966Chisso CorpApparatus for maintaining liquid being transported in a pipe line at an elevated temperature
US3377463 *Jun 21, 1965Apr 9, 1968Trans Continental ElectronicsPrefabricated electric resistance pipe heating system
GB866096A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3706872 *May 15, 1970Dec 19, 1972William J TrabilcySystem for electrically heating fluid-conveying pipe lines and other structures
US3755650 *Nov 16, 1971Aug 28, 1973Chisso CorpElongated heat-generating apparatus providing for a reduction in the highest voltage to be applied
US4110599 *Feb 5, 1976Aug 29, 1978Chevron Research CompanyMethod and means for decreasing the heat output of a segment of a heat generating pipe
US4132884 *Feb 14, 1978Jan 2, 1979Chevron Research CompanyMethod and means for segmentally reducing heat output in a heat-tracing pipe
US4142093 *Feb 14, 1978Feb 27, 1979Chevron Research CompanyMethod and means for segmentally reducing heat output in a heat-tracing pipe
US4408117 *May 28, 1980Oct 4, 1983Yurkanin Robert MImpedance heating system with skin effect particularly for railroad tank cars
US4645906 *Mar 4, 1985Feb 24, 1987Thermon Manufacturing CompanyReduced resistance skin effect heat generating system
EP0130671A2 *Apr 30, 1984Jan 9, 1985Metcal Inc.Multiple temperature autoregulating heater
Classifications
U.S. Classification392/469, 392/478, 219/630
International ClassificationH05B6/10, F24H1/10
Cooperative ClassificationF24H1/105
European ClassificationF24H1/10B2D