US3270182A - High temperature fluid heater - Google Patents

Description

Aug. 30, 1966 P. HYNES v HIGH TEMPERATURE FLUID HEATER Filed March 26, 1964 I! N II III] Ill Y United States Patent 3,270,182 HIGH TEMPERATURE FLUID HEATER Lee P. Hynes, Haddonfield, N.J., assignor to Hynes Electric Heating Company, Kenilworth, N.J., a corporation of New Jersey Filed Mar. 26, 1964, Ser. No. 355,034

Claims. (Cl. 219-382) The present invention relates to electric heaters for fluids, especially gases and vapors, and more particularly to high temperature heaters.

A purpose of the invention is to obtain improved heat transfer from a resistor to gases or vapors.

A further purpose is to heat gases or vapors to extremely high temperatures.

A further purpose is to expose maximum area of a resistor to gases or vapors in contact with the resistors and to get a maxi-mum velocity of flow of the gases or Vapors over the exposed surfaces of the resistor.

A further purpose is to form a resistor in the shape of a helically wound or continuous wall tube and pass gases or vapors through the inside and along the outside walls of the tube.

A further purpose is to support a resistor by means of longitudinally spaced insulators which form flow passages around the resistor.

A further purpose is to support a helically wound or continuously walled tubular resistor by insulators which permit gas or vapor flow through the tube and around the exterior of the tube.

A further purpose is to utilize insulators to both support the resistors and form continuous passages around the resistor to channel gases or vapors along the resistor.

A further purpose is to support a helically wound or continuously walled tubular resistor from insulators in a manner whereby a minimum amount of resistor surface is in contact with the insulator surface.

A further purpose is to heat any desirable gas, gas and vapor, or vapor medium to a high temperature for subsequent use.

A further purpose is m enclose helically wound or continuously walled resistors, supported by suitable insulators, within a pressure tube or chamber to permit heating of gases or vapor at high pressures.

A further purpose is to avoid heat losses by providing reverse flow passages in a pressure tube around the resistors and insulators to preheat the incoming gas or vapor prior to con-tact with the resistors and insulators.

A further purpose is to use vapor in an electric heater without danger of short circuiting from condensation.

A further purpose is to provide a high temperature fluid heater which can be readily assembled or disassembled.

A further purpose is to expose maximum surface of the resistor to gases or vapors flowing at maximum velocities in order to prevent undue rise in temperature of the resistor beyond its structural thermal capacity.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the numerous embodiments in which my invention may appear, selecting the form shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

FIGURE 1 is a fragmentary longitudinal section of the heater of my invention.

FIGURE 2 is an axial section taken on the line 2-2 of FIGURE 1.

FIGURE 3 is an end elevation of an insulator of the invention showing a plurality of orifices.

FIGURE 4 is a fragmentary end elevation showing a Patented August 30, 1966 resistor of the invention supported in an insulator ori fice.

FIGURE 5 is a fragmentary perspective view of a helically wound tubular resistor wound from resistance wire or flat ribbon.

FIGURE 6 is a fragmentary perspective view of a continuous walled resistor tube.

FIGURE 7 is a schematic block diagram showing the use of a heater in a system for heating of combined gas and vapor- Describing in illustration but not in limitation and referring to the drawings:

The present invention is concerned with electric heaters for fluid which may permissibly be gases or vapors. When reference is made herein to gases, it is intended to include air and mixtures of gases being preheated for any use, including use as a heat transfer medium, use in a chemical reaction, or any other purpose where high temperature gas is required. When reference is made to vapors, it is intended to include steam, ammonia, vapors used in chemical reaction, and vapors used for heat transfer. Where the gases or vapors are used as a heat transfer medium, they can be used either in .a closed circuit system or in a system wherein the heat transfer medium is exhausted to the atmosphere after heat exchange.

In the prior art, demands have been primarily for large volumes of gases which, for instance, could be used in production processes such as the synthesis of ammonia from nitrogen and hydrogen. These demands have been successfully met by electric heaters of a type, for instance, shown by my Patents Nos. 2,790,889 and 3,108,174, where large inputs of electric power have been utilized in resistor elements which have been of substantial cross section and size. More recently, high temperature heated gases or vapors in relatively small volume-s at very high pressures and very high velocities of flow have been required in many operations, such as heating dies in the molding of small plastics and other materials, pilot plant operations, and laboratory ope-rations where hot gases or vapors are necessary to perform tests, experiments and other functions. Gas or vapor temperatures required may be, for instance, in the range of l800 Fahrenheit or higher. In these pilot or experimental operations, conditions analogous to commercial or industrail or military operations are simulated to achieve test data on materials under controllable conditions.

The temperatures achieved by the gases and vapors heated according to the invention are of a temperature which could, for instance, be achieved by a jet of burning gases but such jet would not be acceptable for the purposes stated above because the products of combustion of such jet may be chemically objectionable. The heated gases or vapors provided by the heater of the present invention, on the other hand, can be selected to yield any chemical result or effect desired or in other instances can be desirably inert.

In the present invention, the concept of a helically wound or continuously walled tubular resistor has been used wherein such resistor is supported from an insulator which provides passages along the outside of the tube as well as through the center of the tube. By this means,

maximum area of the resistor is exposed to the gases or vapors so that very high temperature effects can be achieved at relatively low volume. The flow area along the outside of the tube is proportioned to the flow area through the center of the tube to provide a balance in heat transfer between the resistor and the gas or vapor flowing in contact with the entire resistor surfaces. The insulators are provided with orifices which have small projections which support and position the resistor. Each insulator has a plurality of orifices which provide parallel flow passages through a series of adjoining insulators. In turn, the preferably disc-like insulators are snugly supported within a pressure tube or chamber which channels the complete flow of gases or vapors through the heater. The resistors within the orifices of the insulators can be electrically connected in a parallel or series relationship as desired.

The pressure tube or chamber may have reverse flow longitudinal passages on its exterior surface so that input gas or vapor can be preheated.

By virtue of the present heater, substantially the full heat output of the tubular resistor is delivered to the gas or vapor, since the flow is over the entire inside surface and substantially the entire outside surface of the resistor. Additionally, any heat which is radiated from the external wall of the resistor to the surrounding insulator is subsequently transferred to the gas or vapor. The flowing gas or vapor wipes heat from the walls of the insulator orifices which have absorbed the radiant heat.

Considering now the drawings in detail but not in limitation and looking at FIGURES l to 7, a heater 20 has an outer tubular pressure wall or shell 21 which is preferably circular in cross section but desirably of any suitable shape. The wall 21 is joined as by welding or the like at 22 to an end face 23 at one end, and to an end face 24 at the other end by, for instance, welds at 25. The wall 21 is structurally adequate to support pressures which may be several hundred pounds per square inch or greater. The end face 23 has an outlet at 26 through which the heated gases or vapors pass to their intended use.

The wall or shell 21 has contained therein baflles 27 and 28 which are suitably concentrically positioned with respect to the outer wall 21 and which are in the form of shields or jackets which channel the inlet gases along the pressure shell 21. Longitudinal spacer strips 29 are inserted between bafiles 27 and 28 and between bafile 27 and wall 21 to provide a spacing relationship between the baffies and wall 21 to achieve passages for flow of the gases or vapors along the passages as described above.

The inlet gases enter at 30 and pass longitudinally through the heater between balfie 27 and Wall 21. An end space at 31 manifolds the area between baffle 27 and wall 21 with the area between baflles 27 and 28 so the gas or vapor passes in a reverse flow direction at 32 back toward the end of the heater at 33. It should be understood that any number of such baffies and flow passages may be used to obtain preliminary flow to preheat the entering gases with any stray heat which may be emitted from the resistors themselves. The heater portion 34 comprises an end element 35 which is supported from end face 24 by cap screws 36 which engage threaded holes 37 in end face 24. The support element 35 has threaded therein a longitudinal rod 38 which has a threaded portion 40 threaded into support element 35. A lock nut 39 locks the rod to the element 35.

Ceramic insulators 41 as best seen in FIGURE 3 are supported on the rod 38 which passes through a center hole 42 located at the center of the insulator element. The insulators 41 are held in spaced relationship from the support element 35 by means of a spacer sleeve 43 which surrounds rod 38. The insulator elements 41 are supported in abutting relationship to one another longitudinally along the rod 38 as best seen in FIGURE 1. A washer 44 and nut 45 threaded onto rod 38 at the end opposite support element 35 retains the insulators in longitudinally adjacent relationship along the rod.

Each insulator element 41 has a plurality of insulator orifices 46 which are generally circular in cross section as at 47. When the insulators 41 are assembled on rod 38 as described above, the insulators are rotationally positioned so that the orifices 46 are longitudinally aligned to provide a plurality of straight flow passages. Each of the orifices has circumferentially spaced thereon projections 48, suitably three in number, which desirably have an angular surface but which may be permissibly of any configuration such as pyramid shape or the like.

The projections 48 support a resistor element 50 as best seen in axial section in FIGURE 4. It will be seen that the projections 48 center and support the preferably tubular resistor element 50 so that the complete inner surface of the resistor element is exposed to flow of the gas or vapor and substantially all of the outer surface 52 is also exposed to flow of gas or vapor as will be explained later.

Orifice 46 is of a size which provides a substantially uniform flow of gas or vapor through both the interior and along the exterior of the resistor. Under this condi tion of flow, the resistor delivers its thermal output uniformly over its inner and outer surfaces, thus allowing the resistor to deliver its maximum heat output at a lower operating temperature.

The tubular resistor elements may optionally be of a helically wound wire or fiat ribbon as shown in FIGURE 5. A ribbon 53 is helically wound so that the edges at 54 are generally adjacent. In an alternate embodiment of the resistor as seen in FIGURE 6, the resistor has a continuous thin wall 55. It should be understood that although the resistor has been shown in round cross section, any cross section tubular resistor may be used, including triangular, rectangular, or other shape.

The respective diameters of the tubular resistors in either of the embodiments of FIGURES 5 and 6, as well as the wall or ribbon or Wire thickness, is determined so that the necessary ohmic resistance to current flow is obtained to yield the desirable heating effect.

The resistor 50 extends throughout each of the aligned insulator orifices 46 in a manner as shown in FIGURES 1 and 4. As seen in FIGURE 4, either the embodiment as shown in FIGURE 5 or the embodiment as shown in FIGURE 6 may be used.

Each of the resistors which passes through each of the aligned orifices of the insulator elements is selectively manifolded electrically in any well known manner at each end of the heater at 56 and 57 to achieve either a parallel relationship or a series relationship between resistors. The resistor elements 50 are electrically manifolded into terminals at 60 and 61 suitably connected to fixed insulated terminal posts 62 and 63 which are held insulated and sealed within the support element 35 by insulated supports 64 and 65. A terminal box 66 encloses the terminal connecting posts 67 and 68 which are connected to an outside electrical source. Suitable mountings 70 and 71 support the box 66 from the support face 35. An end closure or an end cover, not shown, is connected or is secured at 72.

The outside diameter of the insulator 41 is such that it fits snugly within inner bafiie 28 so that substantial blockage of any flow is obtained through the heater except through the orifices 46 between the wall 47 of the orifice 46 and the wall 52 of the resistor 50, and flow through the interior of the resistor 50 at 51.

This relationship between the insulators 46 and baffle 28 in addition to blocking any flow of gases or vapors provides support to the insulators 46 from the bafiie 28.

In operation, suitable current is provided to the terminals at 67 and 68 to energize the resistors 50 which are chosen to provide the necessary ohmic resistance to current passage, thus generating a desired amount of heat energy. Gas or vapor or a combination thereof is introduced into the heater 20 at inlet 30 and passes in the direction of the arrows 73 along the wall 21 and bafile 27. This wall and baflie will be somewhat heated from the heat energy radiated from the resistors 50. The fiuid will reverse flow direction at 31 and pass in the direction of arrows 74 between the balfies 27 and 28 and will be further heated by the radiant energy provided to these baffles as well as any conducted heat to the baffle 28. The preheated fluid then passes into the longitudinally aligned orifices 46 of the insulators between the orifice wall 47 and the resistor wall 52 and also through the interior of the resistor at 51.

As the fluid passes through the orifices 46, a highly desired heating effect on the fluid is achieved. First, since the complete inner surface of the tubular resistor wall 52 is exposed to the flow of the fluid, an optimum heat transfer relationship is achieved. Additionally, a portion of the fluid passes along the outside of wall 52 of the resistor and within the orifice 46 in the passages formed at 75, 76 and 77 as seen in FIGURE 4. It will be seen that the fluid in its longitudinal passage both through the center of the tube and along the exterior of the tube in passages 75, 76 and 77 will absorb the heat energy created by the resistor and will tend to cool the resistor, thus allowing optimum use of the resistor while preventing undue high temperatures in the resistor which would be created under less optimum heat transfer conditions.

Additionally, much of the heat which is radiated to the walls of the orifice at 47 will be absorbed in the fluid, since the high velocity flow of the fluid wipes heat from the surface.

The size of the orifice passages 75, 76 and 77, is selected to achieve approximate uniform flow through the resistor as well as around the resistor, and likewise through all of the orifices and resistors, which as described, are in parallel. The gases after passing through the orifices and through the resistors mix in chamber 80 and pass out through discharge opening 26 of the heater 20 for any suitable end use.

The heaters of the invention may be utilized individually or in combination to heat either gases alone, vapors alone, or a combination of gases and vapors. As seen in FIGURE 7, one of the numerous combinations of heaters is shown. A gas 80 enters a first heater 81 of the type described above and the gas is suitably heated and discharged from heater 81 at 82. The vapor from boiler 83 heated to its saturated condition passes through line 84 from boiler 83 and is mixed with gas from heater 81 at 85. This mixing stage of hot gas and saturated vapor insures that the combination vapor gas mixture entering heater 86 at 87 does not form a condensate which would short out the electrical elements of heater 86, since the vapor is superheated when it reaches heater 86. The combined gas vapor mixture passes through heater 86 through line 88 into a work vessel or the like 90 wherein the heat of the fluid medium is transferred to an end product or process. The somewhat cooled gas vapor mixture is discharged from the Work 90 through return line 91 into heat exchange jacket 92 of boiler 83, and is further cooled at this point by transferring more of its heat to the contents of boiler 83, after which it is discharged at 93. Feed line 94 supplies fluid to the boiler 83 as required. In the event that the return fluid through '91 is insuflicient to produce enough saturated vapor, additional electric heating elements 95 can be turned on in boiler 83 to make up the deficiency.

In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a heater for high temperature fluids, a longitudinally extending outer closed shell having a fluid inlet and a fluid outlet, a series of insulators having a plurality of apertures extending through each insulator arranged in longitudinally abutting and aligned relationship along the length of the heater within the shell to form a plurality of orifices having inner walls extending through the insulators, a tubular resistor having substantially continuous inner and outer surfaces extending longitudinally through each orifice, peripherally spaced projections extending inwardly from and longitudinally along the inner walls of the orifices for centrally supporting a resistor within each orifice and for spacing the resistor apart from the inner walls of the orifice so as to form inner and outer passageways with respect to the resistor through each orifice and external electrical connection to said resistors whereby fluid flowing through these orifices is heated by contact With both surfaces of the resistor and the walls of the orifice.

2. A heater of claim 1, wherein the tubular resistor is helically wound, the edges of each winding abutting with one another to form the continuous surfaces of the resistor.

3. A heater of claim 1, wherein the tubular resistor has continuous cylindrical walls.

4. A heater of claim 1, including baflle means between the shell and the insulators for directing flow of the fluid along the length of the heater to preheat it prior to passage through the orifices.

5. A heater according to claim 1, including means for centrally supporting the plurality of insulators Within the shell in aligned and abutting relationship.

References Cited by the Examiner UNITED STATES PATENTS 861,811 7/1907 Condon 219300 884,367 3/1908 Condon 2l9300 1,333,933 3/1920 Nichols 219-381 1,468,722 9/1923 Macy 2l9-307 1,738,164 12/1929 Zingg 219374 X 1,985,280 12/1934 Carleton 219380 2,868,944 1/1959 Koch et al. 219379 ANTHONY BARTIS, Primary Examiner.

Claims (1)

1. IN A HEATER FOR HIGH TEMPERATURE FLUID, A LONGITUDINALLY EXTENDING OUTER CLOSED SHELL HAVING FLUID INLET AND A FLUID OUTLET, A SERIES OF INSULATORS HAVING A PLURALITY OF APERTURES EXTENDING THROUGH EACH INSULATOR ARRANGED IN LONGITUDINALLY ABUTTING AND ALIGNED RELATIONSHIP ALONG THE LENGTH OF THE HEATER WITHIN THE SHELL TO FORM A PLURALITY OF ORIFICES HAVING INNER WALLS EXTENDING THROUGH THE INSULATORS, A TUBULAR RESISTOR HAVING SUBSTANTIALLY CONTINUOUS INNER AND OUTER SURFACES EXTENDING LONGITUDINALLY THROUGH EACH ORIFICE, PERIPHERALLY SPACED PROJECTIONS EXTENDING INWARDLY FROM AND LONGITUDINALLY ALONG THE INNER WALLS OF THE ORIFICES FOR CENTRALLY SUPPORTING A RESISTOR WITHIN EACH ORIFICE AND FOR SPACING THE RESISTOR APART FROM THE INNER WALLS OF THE ORIFICE SO AS TO FORM INNER AND OUTER PASSAGEWAYS WITH RESPECT TO THE RESISTOR THROUGH EACH ORIFICE AND EXTERNAL ELECTRICAL CONNECTION TO SAID RESISTORS WHEREBY FLUID FLOWING THROUGH THESE ORIFICES IS HEATED BY CONTACT WITH BOTH SURFACES OF THE RESISTOR AND THE WALLS OF THE ORIFICE.

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