US2680600A

US2680600A - Heat interchanger

Info

Publication number: US2680600A
Application number: US190735A
Authority: US
Inventors: Rothemund Max
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1950-05-10
Filing date: 1950-10-18
Publication date: 1954-06-08
Anticipated expiration: 1971-06-08

Description

June 8, 1954 M. ROTHEMUND HEAT INTERCHANGER 2 Sheets-Sheet '1 Filed Oct. 18. 1950 lllll l l lliili INVENTOR MAX ROTHEMUND IIIIIHH l. I

mwjm v- ,3 4 4 AT TORNE Y3 June 8, 1954 RQTHEMUND 2,680,600

HEAT INTERCHANGER Filed Oct. 18. 1950' 2 Sheets-Sheet 2 "lllllilll 1 W1 "MIMI mill m minimum, mmml INVENTOR MAX ROTHEMUND ATTORNEYS i atented June 8,

UNITED STATE 1 OFFICE HEAT INTERCHANGER Application October 18, 1950, Serial No. 190,735

Claims priority, application Germany May 10, 1950 6 Claims.

This invention relates to heat interchangers and has particular reference to heat interchangers of large dimensions.

In such heat interchangers, also referred to as heat exchangers and used, for instance, in gas turbine plants, it is oftentimes difiicult to provide a construction reconciling the requirements as regards mechanical strength with those concerning the possibility of free thermal expansion. Such heat exchangers mostly are constructed so as to operate either as a countercurrent, or as a crosscurrent, or as a combined countercurrent and crosscurrent heat exchanger. Usually they are mounted in a vertical direction. The exhaust or waste gases thus are able to pass through the heat exchanger and especially through a nest of tubes in the heat exchanger from bottom to top while the air which is under a higher pressure and to which the exhaust gases are intended to transmit their heat as completely as possible, surrounds the nest of tubes from outside. In this case the individual wall parts will have different temperatures both at the start and during operation. It follows that constructional steps must be taken in order to permit free development of the heat expansion occurring, so that no detrimental thermal tensions can be set up.

Arrangements are known in which the inserted nest of tubes is fixedly connected to one end of the shell or casing of the heat exchanger so that the relative expansions between the shell or casing and the nest of tubes have to be taken up 'in a stufiing box at the other end of the heat exchanger. This arrangement has the disadvantage that large temperature potentials are existing at the fixing point of the nest of tubes and that at this fixing point which is for instance in the lower part of the container, the

tube plate is subjected to a bending stress not i only by the weight of the nest of tubes but also by the forces originating from the internal gas pressure, whereby constructional diificulties are caused. Simultaneously provision must be made for a free radial expansion at the fixing point between the cover and the inserted nest of tubes. Hence, the conditions are very unfavourable at this point in regard to the strains to which the material is exposed.

-It is an object of the present invention to provide a construction by which these disadvantages are avoided.

With this object in View according to the present invention the support for the nest of tubes consists of a supporting structure, for instance, in

the form of a pressure-compensated tube or a plurality of stay bolts taking the whole weight of the nest of tubes at the upper or lower tube plate. For instance, the nest of tubes may be supported in the shell or casing in such a way that it rests, by means of a pressure-compensated sheet metal cylinder disposed coaxial to the container case, in a flange arranged approximately at one half of the height of the casing. In this way the vessel or casing is subdivided in a manner which is desirable for transport purposes and a symmetrical arrangement for the relative thermal expansions between the nest of tubes and the outer casing is obtained. Moreover, the inner parts of the heat exchanger, more particularly, the nest of tubes with the tube plates are dis posed in a field of homogeneous temperature, whereby detrimental temperature potentials are avoided. The cross sections of the ducts in this case are dimensioned in such a way, as will be hereinafter described in greater detail, that the tube plates in regard to gas forces are nearly pressure-compensated and the plate has merely to take up the dead weight of the nest of tubes at the fixing point. The forces produced in the interior of the vessel by the gas pressure on the contrary are taken exclusively by the casing in the form of tensile stress. In the heat exchanger according to the invention the inner inserted nest of tubes is free to relatively expanel approximately uniformly and symmetrically in an upward and downward direction in relation to the outer casing. Accordingly stuffing box devices are provided both at the upper and at the lower end of the upright vessel, 1. e. in the supply and exhaust piping, in order to make the stufi'ing boxes as handy as possible in regard to their manufacture and operation.

Other and further objects, features and advantages of the invention will be pointed out hereinafter and appear in the appended claims forming part of the application.

In the drawing Fig. 1 illustrates a heat exchanger embodying the invention, in section; and

Fig. 2 illustrates a heat exchanger embodying the invention in slightly modifiedform, also in section.

Referring to the drawing, showing a longitudinal section of the heat exchanger, it will be seen that the same consists of an: upright casing composed of two cylindrical parts I and 2 and two end plates 3 and 4, and standing on supports 5. The medium under pressure which is to be heated, for instance air, enters through the branch 6 and is discharged through the branch 1. Arranged in the interior of the cylindrical casing is a nest of tubes 8 whose tubes are open at their ends and carried by tube plates 9 and 10. Through those tubes flows the heating agent, for instance, exhaust or waste gas, intended to transmit as much as possible of its heat to the medium to be heated and surrounding the tubes. The path of the medium to be heated is artificially extended by guide plates ll, I2, l3 so that the delivery or absorption of heat is increased accordingly. The hot medium enters at the lower end through the branch of duct it and the funnel-shaped extension l5 into the tubes 8, leaving the same through the funnel-shaped connection piece l6 and the branch or duct 41 at the upper end of the heat exchanger. The nest of tubes 8 with the tube plates 9 and I is carried by a supporting or suspending system l8, e. g., in the form of a carrier tube l8 supported on the lower cylindrical part I of the casing approximately in the middle of the heat exchanger. The carrier tube i3 is provided with passageways IQ for compensation of pressure so that the same pressure of the medium to be heated is prevailing on both sides.

By way of alternative, the supporting structure for the nest of tubes may comprise a plurality of stay bolts 22 or the like supporting plate 9 on a flange 23 affixed to the casing 2 at substantially the longitudinal midpoint thereof, as indicated in Fig. 2.

The different heat expansion between the nest of tubes 8 having a substantially higher temperature, and the outer casing i, 2, 3 4 of the heat exchanger is compensated at both sides by means of the stuffillg boxes 20 and 2i at the upper and lower ends of the heat exchanger.

In order to compensate the forces due to the gas pressure of the air or other medium under pressure surrounding the tubes 8, the outer cross section of the branches or ducts l4 and I7 (whose outer diameter is D) is preferably made equal to the sum of the circular areas covered by the tubes 8, which sum is where n is the number of tubes and d is the outer diameter of the tubes 8. In this case, the pressure forces acting on the conical funnels i and 18 on the one hand and on the tube plates 9 and ID on the other hand are equal and the nest of tubes 8 is freely floating in the casing i, being only under action of its own weight.

While the invention has been described in detail with respect to a now preferred example and embodiment of the invention it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is claimed is:

l. A device for interchanging heat between two fluids comprising an outer casing, a substantially upright system of tubes including an upper tube plate and a lower tube plate inserted therein and adapted to be surrounded by the first of said fluids being at a higher pressure and to be traversed by the second of said fluids, and a 4 supporting system comprising a plurality of stay bolts supporting one of said tube plates and transmitting the weight of the tube system to the middle part of the casing.

2. A heat exchanging device of the character described adapted for heat exchange from a high t mperature fluid medium to a lower temperature fluid medium which is at substantially higher pressure than said high temperature medium comprising in combination an outer casing adapted to contain said higher pressure lower temperature medium, a nest of heat exchange tubes within said casing for passage of said high temperature medium therethrough and adapted for heat expansion movement relative to said casing, means forming a support for the entire nest of tubes extending from an end of said nest to substantially the middle portion of said casing for reducing said relative heat expansion movement, said supporting means having provision for equaliaing the pressure on opposite sides thereof, ducts for introducing said high temperature medium into said tubes through said casing and for leading said medium away from said tubes, and enlarged connecting members interconnecting said tubes with said ducts, oppositely directed surfaces of said connecting members being exposed to said higher pressure medium and having substantially equal effective areas for equalizing oppositely directed pressure forces from said higher pressure medium.

3. A heat exchanging device of the character described adapted for heat exchange from a high temperature fluid medium to a lower tempera ture fluid medium which is at substantially higher pressure than said high temperature medium comprising in combination an outer casing adapted to contain said higher pressure lower temperature medium, a nest of heat exchange tubes within said casing for passage of said high temperature medium therethrough and adapted for longitudinal heat expansion movement in two directions relative to said casing, means connect ing with the middle portion only of said casing forming a support for the entire nest of tubes, said supporting means having provision for equalizing the pressure on opposite sides thereof, ducts for introducing said high temperature medium into said tubes through said casing and for lead ing said medium away from said tubes, and enlarged connecting members interconnecting said tubes with said ducts, the outer cross-section of each of said ducts being substantially equal to the aggregate outer cross-section of all said tubes for maintaining the effective area of opposite surfaces of said connecting members substantially equal to equalize oppositely directed pressure forces from said higher pressure medium,

4. A heat exchanging device of the character described adapted for heat exchange from a high temperature fluid medium to a lower temperature fluid medium which is at substantially higher pressure than said high temperature medium comprising in combination an outer casingadapted to contain said higher pressure lower ten perature medium, a nest of heat exchange tubes within said casing for passage of said high temperature medium therethrough and adapted for limited heat expansion movement relative to said casing, means forming a support for the entire nest of tubes extending from an end of said nest to substantially the middle portion of said casing for reducing said relative heat expansion movement, said supporting means having provision for equalizing the pressure on opposite sides thereof,

ducts for introducing said high temperature medium into said tubes through said casing and for leading said medium away from said tubes, the outer cross-section of each of said ducts being substantially equal to the aggregate outer crosssection of all said tubes for equalizing oppositely directed longitudinal pressure forces from said higher pressure medium on the joints between said tubes and said ducts, and pressure resistant heat expansion joints between said ducts and said casing for compensating for relative heat expansions between said casing and said tubes and ducts. r

5. A heat exchanging device of the character described adapted for heat exchange from a higher temperature gaseous medium to a lower temperature gaseous medium which is at sub' stantially higher pressure than said high temperature medium and comprising in combination an outer casing adapted to contain said high pressure lower temperature medium, a plurality of heat exchange tubes within said casing for passage of said high temperature medium therethrough, a perforated cylinder for supporting said tubes in said casing to provide equalized pressure of said higher pressure medium on all sides of said tubes and said supporting cylinder, means for hanging said tubes from one end of said cylinder, means for supporting the other end of said cylinder within said casing at the middle portion only thereof, ducts for introducing said high tem perature medium into said tubes and for leading said medium away from said tubes, and enlarged connecting members interconnecting all of said tubes with each said duct, opposite surfaces of said connecting members exposed to oppositely directed longitudinal forces from said higher pressure medium having substantially the same efiective area for equalizing said oppositely directed forces.

6. A heat exchanging device of the character described adapted for heat exchange between a igh temperature lower pressure medium and a low temperature higher pressure medium and comprising in combination an outer casing transversely subdivided into two major segments, means for joining said segments to form said casing, a nest of heat exchange tubes within said casing for passage of said high temperature medium therethrough, means for supporting the entire nest of tubes at one end only thereof within said casing to provide substantially equalized pressure of said high pressure medium on all sides of said nest of tubes, means for affixing said support means to said casing only at the joint therein between said two segments, ducts for introducing said high temperature medium into said tubes and for leading said medium away from said tubes, opposite transverse surfaces of the joints between said tubes and said ducts subjected to oppositely directed longitudinal forces of said higher pressure medium having substantially equal effective area for equalizing said forces.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,649,120 Kniskern Nov. 15, 1927 2,549,093 Huber Apr. 1'7, 1951 FOREIGN PATENTS Number Country Date 32,560 Germany Aug. 3, 1885 45,496 France May 27, 1935