US2468903A - Vertical tubular heat exchanger - Google Patents

Description

May 3, 1949. E. VlLLlGER 2,463,903

VERTICAL TUBULAR HEAT EXCHANGER Filed Aug. 28, 1946 lnu enior Eugen Villiger I By I Fig AFtorpcga Patented May 3, 1949 UNITED STATE VERTICAL TUBULAR HEAT EXCHANGER Eugen Villiger, Zurich, Switzerland, assignor to Aktieng'esellschaft Fuer Technisehe Studien,

Zurich, Switzerland,

a corporation of SWIIGI'! land Application August 28, 1946, Serial No. 693,451 In Switzerland September 22, 1945 1 Claim. (01. 257-222) 2 This invention relates to a vertical tubular to be heated passes first through the said annular heat exchanger in which a medium is to be heated on the contraflow principle by flue gases which arrive at a considerable height above ground.

Tubular heat exchangers of this kind are erected for example in thermal power plants of the type, in which the working medium traverses a closed cycle and heat derived from an external source is to be supplied to this working medium indirectly by a main combustion heater. Combustion heaters for plants of this kind are usually of considerable height, and the flue gases frequently leave the heater at the upper end thereof so that they emerge at a considerable height above ground. Particularly in heaters which are fired with oil or pulverised coal the fresh air required for the support of combustion has then likewise to be supplied from above to the burners arranged in the upper part of the heater. If therefore a preheater for theair required for the support of combustion has to be erected in conjunction with a combustion heater of this kind, so that said air shall be heated therein by the waste gases arriving from the combustion heater, the connections on the air preheater provided for the incoming flue gases and the outgoing heated air are preferably placed at the top of the preheater, since an arrangement of this kind permits of long connecting pipes being dispensed with. The fresh air to be heated in the preheater is advantageously drawn off from the upper part of the engine room as the temperature near the ceiling of this room is higher by a few degrees than that directly above the floor.

In connection with tubular heat exchangers of this kind, used as a preheater, the problem arises of how to make it'possible to bring about in a vertical tube nest an exchange of heat between the fresh air that is to be heated and the heat of the outgoing flue gases on the contraflow principle, and also how to utilise the thermal content of the waste gases issuing from the combustion heater to as great an extent as possible for the heating up of the air required for the support of combustion. In order to satisfy these various requirements, the problems above referred to are solved according to the present .invention by building into a tubular heat exchanger of the kind above described concentrically with a tube nest firstly achimney tube as the innermost body and then a second tube which surrounds the latter and leaves an annular space round it free. In this arrangement the medium space, and the flue gases which issue from the said tube nest and have been already brought therein to a lower temperature, pass in the op- 5 posite' direction to said medium through the chimney tube on the contraflow principle thereby giving up still more heat'to the medium to be heated.

When the present invention is used no separate high chimney stack with its own foundation needs to be provided. The type of construction employed according to the present invention also enables the heat ofthe escaping flue gases to be utilised to a very large extent, which is favourable from an economical point of view.

A constructional form of the subject matter of the invention is illustrated by way of example in the accompanying drawings in which:

. Fig. 1 shows on an enlarged scale an axial longitudinal section through said tubular heat exchanger, and

Fig. 2 shows in the'left hand half a section on the line IIII of Fig.1 and in the right hand half a plan view of Fig. 1.

The structure illustrated in Figs. 1 and 2 is not the main combustion heater. but is a preheater used to derive heat from combustion products discharged by the'main combustion heater (not shown), near the top thereof and hence at a substantial elevation, and transfer said heat to combustion air flowing to the main combustion heater.

The numeral l5 denotes the cylindrical shell of the preheater constructed as a vertical tubular heat exchanger, in which fresh air entering through a connection is is to be heated in a vertical tube nest I! by the exchange of heat with flue gases. These latter are derived from the main combustion heater. These flue gases, which arrive at a considerable height above ground, en ter from above through a connection 18 (Fig. 1) into the interior of the shell l5 of the heat exchanger and pass from the top downwards through the tubes of the nest I! which is annular in cross section. A chimney tube l9, part of which extends above the shell l5 of the heat exchanger, forms the innermost body of this latter and is built into the heat exchanger coaxially with the tube nest l'l. Into the heat exchanger is also built a second tube 20, which surrounds the chimney tube l9 and leaves an annular space 2| between said chimney tube and itself. The fresh air entering through the tube l6 passes from the top downwards through the annular space 2|, while the flue gases, which escape at the bottom of the tubes of the nest i1 and in which they have been cooled down already to a great extent, pass through the chimney tube I! from the bottom upwards. In this way an exchange. of heat with the fresh air flowing in the opposite direction takes Place, so that the flue gases become cooled down still further as they pass through the chimney tube l9, that is to say more heat is abstracted from them which however is usefully employed for heating up the fresh air which has entered through the connection It. The fresh air preheated in the annular space 2| passes at the bottom into the tube nest l1, flows around the tubes of this nest in the opposite direction to the flue gases and finally emerges in a heated state through the connection 22 near the top of the heat exchanger, after which it is conducted to the burner of the main combustion heater (not shown).

The, lower supporting plate 25 to which the lower ends of the tubes of the nest i1 and the chimney tube IQ of the heat exchanger are fas'- tened, is rigidly mounted, since it comes into con tact with comparatively cold gases only. The plate 25 is also supported by a number of columns 28 so that it may be comparatively hin which is desirable from the standpoint of thermal stresses and the large number of holes which have to be drilled in it. The top plate 21 of the tube nest I1 is on the other hand connected to the shell 15 by an elastic length of tube 28 so that it can expand upwards. As therefore this plate 21 is not subjected to any additional stress due to thermal expansion, it may be thin so that it can more easily follow any unequal thermal expansions which may possibly take place. the chimney tube [9 is also constructed as a piece of elastic tube. 7

What is claimed is:

A vertical tubular heat exchanger, in which a medium is to be heated on the contrafiow principle by flue gases which arrive at a considerable The part 29 of height above ground, comprising a vertical cylin drical shell; a vertical tube nest built into said shell and comprising an upper and lower plate into which the tubes of this nest are fixed; an upper header provided at the top end of said shell and having an inlet for flue gases, said header serving to distribute said gases over the upper extremity of the tubes of said nest; a lower header in communication with said tubes; a chimney tube built into said shell coaxially with said tube nest as the innermost body, in communication with said lower header and leading to a point external to the heat exchanger; a second tube surrounding said chimney tube and leaving an annular space between the, latter and itself and communicating at its lower end with the space which is bounded by said shell, said upper and lower plates of the tube nest and said chimney tube; a second inlet provided at the top of said shell for the incoming medium to be heated and connected to said second tube; and an outflow connection for heated air leading from the upper end of the space bounded by the shell, the upper and lower plates of said tubenest and they chimney.

EUGEN VILLIGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 752,994 McKee Feb. 23, 1904 1,142,495 Clisdell June 8, 1915 1,856,771 Loefller May 3, 1932 FOREIGN PATENTS Number Country Date 17,255 Great Britain July 24, 1909 41,206 Germany Oct. 18, 1887

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