US1958364A - Heat transfer tube - Google Patents

Description

May 8, F. X GOVERS 1,958,364

HEAT TRANSFER TUBE File d Aug. 26, 1951 Patented May 8, 1934 PATENT OFFICE 1,958,364 HEAT TRANSFER TUBE I Francis X. Govers, Vincennes, Ind., assignor to L Indian Refining Company, Lawrenceville, 111.,

a corporation of Maine Application August 26, 1931, Serial No. 559,360

3 Claims.

My invention relates to heat transfer tubes,v more particularly to tubes adapted to be used in a group and mounted in the path of a heating fluid such as the hot products of combustion,

5 and has for its principal object the provision of ing a pointed-oval cross section and adapted to be secured rigidly to the circular tube. The heat transfer member is preferably provided with fins which aid in transferring heat from the gases to the tube. The tubes having the heat transfer members and fins secured thereto or cast thereon are so mounted in the path of the hot gases that the gases will pass around the tubes in a streamline direction so that a complete wiping action will take place over the entire'external surface and dead spaces and eddy currents will not exist near the rear side of the tubes.

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 is a plan view of a tube embodying my invention; Fig. 2 is a sectional elevation taken on line 2--2 of Fig. 1, while Fig. 3 is a diagrammatic showing of the streamline path of the gases passing around a tube.

Referring to the drawing I have shown a pipe 10 of substantial circular cross section and preferably formed of seamless steel or wrought iron tubing capable of withstanding considerable pressure. Around the pipe 10 is cast a heat transfer element 11 having a pointed-oval or gutti-form peripheral cross section as shown more clearly in Figs. 2 and 3. The element 11 is preferably formed with a relatively thin layer at the forward side of the pipe 10 and with a considerably greater thickness at the rearward side. It will be observed that the element 11 is designed to present a large surface of contact with the hot gases and to eliminate dead spaces, that is, portions of the tube surface over which there is relatively little movement of the heating fluid. In order to secure efiicient heat transfer between the hot gases and the fluid which is passed through the pipe 10, it is desirable that there be a tight and uniform contact between the pipe and the heat transfer element and it has been found that such a contact will be obtained when the member 11 is cast around the preformed pipe 10.

'In order to further increase the efiiciency and rate of heat transfer, the element 11 is providedwith a plurality of flat, parallel fins 12 having substantially the same shape as the element 11 in cross section and arranged transversely to the length of the pipe. The fins 12 are preferably cast integral with the element 11.

Preferably the cast element 11 will be shorter than the pipe 10 so that there will be suflicient lengths of the pipe extending at the ends for attachment to suitable headers. A tube can thus be readily removed for replacement or repairs. It is to be understood that the tubes will usually be arranged in groups and that they may be manifolded so that the fluid to be heated will either pass through them in series or in parallel, or perhapsthrough smaller groups connected in a series-parallel relation.

As will be observed with reference to Fig. 3 the tube is arranged in the path of the hot gaseous products of combustion transversely to the direction of travel to these gases with the pointed edge extending in the direction of flow of the gases. Due to the streamline shape of the periphery of the element 11 and fins 12 the gases will flow with a wiping contact with the surface and will not form eddy currents or dead pockets at the back side of the tube. Due to this arrangement heat will be transferred from the hot gases to the pipe 10 from all directions rather than merely from the leading side of the pipe as is often the case when the pipe is of circular cross section. Moreover, the heat transfer element 11 will prevent the accumulation of soot or carbon at the rear side of the pipe 10, which accumulation would tend to decrease the amount of heat transfer. Another important advantage lies in the fact that dueto the shape of the element 11 the hot gases will be subject to less resistance to flow, thus decreasing the power consumption of circulating fan or blower equipment.

By using preformedseamless tubing or pipe of wrought iron'or steel as the liquid containing member 10 it is possible to maintain this pipe of uniform thickness and having an absolutely uniform bore.

While I have illustrated my invention as par- I er s, pre-heaters, super-heaters and similar heat exchange devices wherein one fluid is heated from the outside by another fluid. The fins 12 serve not only to present a large heat absorbing surface to the heating fluid but to a certain extent to guide the flow of the heating fluid and to prevent eddy currents.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A heat transfer tube comprising a preformed elongated member for conducting a fluid to be heated across the path of a heating fluid, said member having a circular cross section, a heat transfer element cast entirely around and in contact with said member, said heat transfer element having substantially a guttiform cross section so as to present an external streamline surface to said heating fluid with a relatively thin layer of said heat transfer element at the forward or contact side of said member and with a greater thickness of said element at the rearward side of said member, and a plurality of fins projecting from the outer surface of said heat transfer element, said fins extending entirely around the relatively thin layer of said element at the forward edge of said elongated member and arranged transversely to the length of said member.

2. A heat transfer tube comprising a preformed pipe adapted to convey a fluid to be heated. through the path of a heating fluid, a casting surrounding and in contact with said pipe, said casting having a pointed-oval cross section and arranged in the path of said heating fluid so that the pointed edge is in the direction of flow of said heating fluid and a plurality of fins of pointed-oval contour formed on the exterior surface of said casting and entirely surrounding the same, said fins being arranged to correspond to said casting with the pointed edge in the direction of flow of said heating fluid.

3. A heat transfer tube comprising a preformed pipe of ductile .metal adapted to convey a fluid to be heated through the path of a heating fluid, a heat conducting element of cast iron surrounding and in rigid contact with said pipe, said element having a pointed-oval cross-section and arranged in the path of said heating fluid so that the pointed edge is in the direction of the flow of said heating fluid, and a plurality of fins cast integral with and having'substantially the same shape as'said heat conducting element in

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