US2402970A - Heater - Google Patents

Description

July 2, 1946.

H. J. DE N. MCCOLLUM HEATER Filed Sept. 5, 1942 3 Sheets-Sheet l jzn apemmc ozzum July 2, 1946.

H. J. DE N. MCCOLLUM 2,402,970

HEATER Filed sew, 5, 1942 s Sheets-$heet 2 J l 2, 1946. H, J. DE' N. MCCQ LU 2,402,970

HEATER s sheets-sheets Filed Sept. 5., 1942 Patented July 2, 1946 HEATER Henry J. De N. McCollum, Chicago, 111.; Theima.

McCollum executrix of said Henry-J. De N.

McCollum, deceased Application September 5, 1942, Serial No. 457,447

4 Claims. 1

My invention relates to heaters and more particularly to heaters 01 the internal combustion type, although it is not necessarily limited to this type of heater.

In heaters'of the internal combustion type, it is common to provide finned heat transfer means for transferring heat from the products of combustion to the ventilating air directed over the heat transfer means by a blower or other means for circulating air.. The heated products of com:

bustion are ordinarily directed against the fins at one end of the heat transfer means and where the hot products of combustion first come in contact with the fins, these fins are raised to a I temperature which is much in excess of the temperature of other portions of the fins and particularly that portion adjacent the outlet end of the heater. There is a practical limit to the temperature to which the fins can be heated and this limits the total quantity of heat which can be given off by a heater of any given size and shape.

An-object of my invention is to provide a heater wherein the heat transfer means is heated to a substantially uniform temperature throughout its length and thereby provide a more eificient heater having a higher heat output for a given size.

Another object of my invention is to provide a heater wherein the temperature range between difierent parts of the heater is reduced to a minimum and stresses and strains caused by great variations in temperature of the different parts are avoided. Another object of my invention is to provide an extremely light and compact heater having'a high heat output and particularly adapted forv use in aircraft.

Another object of imr invention is to provide a heater wherein the parts are so designed, as to have a. m \tlmum strength for a minimum weight and wherein these parts may be made as strong as desired to heat the requirements of any given type of service.

Another object. of my invention is to provide a new and improved heater which can be economically manufactured by conventional equipment and using conventional methods.

Another object of my invention is to provide a new and improved heater having more efficient means for transferring heat from the gases of combustion to a' heat exchanger and from this heat exchanger to ventilating air.

Another object of my invention is to provide anew and improved heater which more efficiently transfers heat from a gas-to a metal surface.

Another object of my invention is to provide a new and improved. heater which more efiiciently transfers heat from a metal surface to a gas.

Other objects and advantages Will become apparent as the description proceeds.

In the drawings:

Fig. 1 is a side elevational view of 'a preferred embodiment of my invention. In this view, part of'the casing for the ventilating air is broken away.

Fi 2 is an enlarged end view looking in the direction of the arrow 2 in Fig. -1. In Fig. 2, the inlet part or the casing for the ventilating air has been omitted to show more clearly the arrangement of -the external fins for heating this air.

- Fig. 3 is an enlarged longitudinal, sectional view on an enlarged scale and is taken on the line 5-5 of Fig. 3. The drawings disclose an embodiment of myinvention wherein the body In of the heater is enclosed in a casing H for directing ventilating air thereover. The body In comprises a pair of conical'castings l4 and I6 of aluminum or other suitable material. The castings l4 and I6 have telescopic .ends l8 and 20, respectively, and in telescoping these ends the casting l6 and its end 20 are heated and slipped over the cold casting M to form a shrink fit which firmly attaches the casting Hi to the casting to form a unitary structure. 7 r The casting M has an annular wall 22 integral with and located between a radially projecting series of interior fins 24 and a series of radially directed exterior fins 26. The forward end of the wall 22 is constructed and arranged to provide a rectangular recess or combustion chamber 28 and terminates in a threaded boss 30.

The casting l6 has an annular wall 32 integral .with and located between a series of radially diair. This ventilating air is supplied to the inlet end 40 of the casing by a ram, blower, or any g I 3 other suitable means and is discharged through the outlet 42, which may communicate directly with the airplane cabin or other space to be I heated or may be connected to a system of ventilating ducts for directing the heated air in any desired manner. In lieu of providing a blower or ram for forcing ventilating air into the inlet end 48 of the casing, a suction blower may be provided for the outlet 42 to create flow of ventilating air through the casing l2.

A part of the air flow in the inlet 48 enters a I ,Venturi-tube 44, which is screwed into a bushing 46 in the boss 38 of casting I4. The Venturitube 44 has a restricted throat 48 to which fuel issupplied through openings 58 in a-fuel supply pipe 52, which may be connected either to any suitable fuel tank or to a source for supplying an unduly rich mixture of fuel and air. The raw fuel or rich mixture of fuel and air supplied by the pipe 52 mixes with air flowing through Venturi-tube 44 and forms a combustible mixture which is delivered with a whirling motion to the combustion chamber 28 through openings 54 in a burner tube 56.

The combustible mixture'supplied to the combustion chamber 38 is ignited by electrical igniters 58 which are supplied with current from any suitable source. In the drawings, I have illustrated a-heater having three igniters 58 closely grouped, but my heater is not limited to this number and arrangement and any other desired number and arrangement of these igniters may .be utilized. The hot wires 68 of these ignlters are in communication with the combustion chamber 28 through openings 82 which are protected from 3 cut out.

A mullier 68 is confined between the internal of-these fins and cooperates therewith to form passages ll through which the burned gases flow A tubular abutment 86 is screwed into the threads 81 at the outlet end of wall 32 and has a tapered portion 88 formingaan abutment for the flared end 88 of the exhaust pipe 14. A sleeve 92 surrounds the pipe 14 and has a tapered end 94 which engages the flared end 98 of the exhaust pipe and clamps it against the abutment 88 under the force exerted by a tubular nut 95. The

lefthand end of the sleeve 82 is inclined, as indicated at 88, as I have found that this inclination reduces the tendency of the exhaust pipe 14 to break oil? adjacent the endof the sleeve 92 under continued vibration.

' In the operation of my'invention, a portion of '52 to form a combustible mixture which is delivered to the combustion chamber 28 with a whirling motion through openings 54 in burner tube 56. This combustible mixture is ignited by the igniters 58. The heat thereby created in the combustion chamber 28 is partially absorbed by the walls of this combustion chamber and transmitted to the adjacent portions of the fins l4.

bustion chamber 28 to the outwardly flaring portions of the passages H located between the internal fins 24. The gases leaving the combustion chamber 28 are at a maximum temperature and tions of the fins 24 and the wall 22.

The rate of heat transfer from the ga to a metal surface varies greatly with the direction at which the gas strikes the metal surface and is highest when the gas scours the surface by being projected substantially vertically against this surface. The hot gases of combustion are not directed against the outwardly flaring wall 22 and i fact tend to hug the adjacent wall of the muiller shell so that relatively little heat is transfin 24 and 34 of the two castings and has a sheet metal shell 18 which abuts the inner'edge's i from the combustion chamber 28 to the exhaust pipe 14. The interior of the shell 18 is filled with glass wool or stainless steel wool, orother suitable heat resisting and sound absorbing material and elongated slots 12 in the shell 18 provide acousti-couplings between the passages 1| and the interior of the muiller.

That end of the muiiler shell which is adjacent the combustion chamber 28 is rounded as indicated at [3 and serves to direct the burned gases into the passages H with a minimum of resistance to the flow of these gases. This end of the muiller-is provided with an airspace 16 which protects the glass wool against the intense heat occasioned by the combustion chamber 28. Opening's I8 in a partition 88 form acousti-couplings between the space 18 and the portion of the muffler shell in which the glass wool is located. The

other end of the muiller shell-is illustrated as being provided with a rounded cap 82, which forms an air space to the left of the partition 84 defining the lefthand end of the compartment containing the glass'wool.

. gases flow through the passages H, they give'up ferred directly from the gases to the outwardly flaring portion of the wall 22 and most of the heat received by this wall is conducted to it by the adjacent portions of the internal fins 24.

On the other hand, the ventilating air is directed against the outwardly flaring wall 22 and scours this wall to remove great quantities of heat, therefrom. In other words, the heat transfer directly betwee the hot gases of combustion relatively inefficient, whereas the heat transfer fromthe outwardly flaring portion of this wall to the ventilating air is highly efficient, with the result that this outwardly flaring v portion ofthe a wall 22 and the adjacent portions of the internal fins 34 and exterior fins 28 are maintained at substantially the same temperature as other portions of this wall and these fins at the same tem- .perature as the corresponding wall and fins of the other casting.

The products of combustion pass from the outwardly flaring portions of the passages II to the straight or cylindrical portions of these passages and then to the entrained portions of these passages leading to the exhaust pipe 14. As these their heat to the interior fins and to casting walls and when these gases reach the inwardly directed portions of thepassages l these gases are allproachlng their minimum temperature. The heat transfer between these gases and the inwardly directed portion of the casting-wall 82, however, is a'maximum, since the gases of combustion are directed against and tend to scour this entrained portion of the wall. At the same the air flowing in the inlet 48 enters Venturi-tube. 44 and mixes with fuel supplied through pipe The hot gases of combustion flow from the com- I give up part of their heat to the adjacent por-- and the outwardly flaring portion of=wall 22 is time the heat removed from this entrained portion of the wall 32 by the ventilating air is a minimum and the resulting balance maintains the conical portion of casting 32 at substantially the same temperature as the conical portion of casting l4 and the connected cylindrical portions of both of these castings. In other words, my novel structure provides a heater wherein the heat transfer means is maintained at substantially uniform temperature throughoutits entire length and an extremely lightweight, compact and efficient heater can be provided by designing the heater so that all parts of the heat transfer mean operate at maximum temperature.

The heated ventilating air flowing through the casing outlet 42 may be discharged directly into the airplane cabin or other space to be heated, or may flow through a suitable duct arrangement for dividing up this heated air and delivering it to specific locations. The cooled gases of combustio are discharged to atmosphere through the exhaust pipe 14.

The muiller I0 absorbs sounds entrained in the ases of combustion. This muiiler also cooperates with the walls 22 and 32 to direct the flow of the gases of combustion and directs the relatively cool gases of combustion against the conical portion of wall 32 while permitting the extremely hot ases of combustion to flow along the conical portion of wall 22 in such a way as to give up relativel little heat to this wall.

In the embodiment of my invention'shown in the drawings, the several igniters 58 are provided with individual housings I00 which are attached to the casing I2 and have open lower ends communicating with openings I02 formed in this casing. The housings I00 have openings Hit through which the igniter wires I06 extend and while a small amount of ventilating air may escape through these openings I04, the provision of the housing I00 forms a convenient means for preventing the igniters 58 from reaching unduly high temperatures and at-the same time preventing the escape of large quantities of air from the casing l2 around these igniters.

My novel, double cone heat exchanger is not limited to use in 'a heater having a combustion chamber therein. This double-cone or opposed alignment therewith, inner and outer wall means forming a flow passage for conducting the hot products of combustion from said combustionchamber to said exhaust passage, said flow passage being of annular cross section, the inner and outer walls of said passage adjacent the combustion chamber flaring outwardly at an abrupt angle to the axis of said chamber, and said walls of said flowpassaige adjacent the exhaust end of the heater converging toward the axis of the exhaust passage at an abrupt angle to said axis, a. jacket spaced at an approximately uniform distance from the outer wall of said flow passage throughout its length, forming a passage for ventilating air between said outer Wall and said jacket, said air passage being of annular cross section with its 'walls flaring outwardly from the end adjacent the combustion chamber and con verging at the other end adjacent the exhaust passage so that the air passage substantially follows the contour of the flow passage, and means delivering ventilating air so as to flow through said passage in the same. direction as the combusbustion gases impinge forcibly against the con verging surface of said wall adjacent the exhaust cone type of heat exchanger may also be utilized in a heater which is supplied with exhaust gases from an internal combustion engine or which is supplied with heated fluid from any other suitable source.

While I have illustrated and described only a single embodiment of my invention, .it is to be understood that my invention is not limited to the details shown and described, but may assume numerous other forms. My invention is. to be construed as including all modifications and variations coming within the scope of the appended claims. i

I claim: 4

1. In a heater of the class described, wall means forming a cylindrical combustion chamber and a tubular exhaust passage in substantially axial end of the heater.

2. In a heater as defined in claim 1, said outer wallof the flow passage for combustion gases being of relatively thin metal and having integral fins circumferentially spaced, extending substantiallythroughout the length of the passage and projecting radially inward and substantially across it, subdividing said passage into a'plurality of longitudinal channels to which the flow of hot gases is confined, said wall having also a. series of outwardly projecting radial fins extending substantially throughout the length of the ventilating air passage and substantially across it to the said jacket, subdividing said passage into a plurality of longitudinal channels confining streams of ventilating air and transferring thereto the heat absorbed by said wall and its inwardly projecting fins.

3. Ina heater as defined in claim 1, the inner wall of said fiow passage or the combustion gases comprising a hollow metallic shell filled with sound absorbent material and having $112.11 perforations distributed over its lateral area.

4. In a. heater as defined in claim 1, the walls of said flow passage for the products of combustion intermediate said outwardly flaring-portions and said converging portions being substantially parallel to the common axis of the combustion chamber and exhaust passage, whereby said produots of combustion experience an abrupt change of direction in passing from the outwardly flaring portion of the flow passage into said intermediate portion and impinge forcibly against the

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