US1808619A - Heat exchanger - Google Patents

Description

June 2, 1931. RL UHDE 1,808,619

HEAT EXCHANGER Filed Feb. 2o, 1929 Fig'. 1.

Patented June 2, 1931 s UNITED STATES PATENT OFFICE ROBERT UHDE, OF CASSEL-WILHELMSHOHE, GERMANY, ASSIGNOR TO S'CHMIDTSCHE HEISSDAMPF-GESELLSCHAFT MIT BESCHRNKTER HAFTUNG, OIEy CASSEL-WIL- HELIMSHOHE, GERMANY, A CORPORATION 0F GERMANY HEAT EXCHANGER Application led February 20, 1929, Serial No. 341,505, and in Germany March 8, 1928.

My invention relates to heat-exchangers and particularly to interstage superheaters with several groups of heatingtubes connected in series.

The construction of interstate superheaters for large power installations presents considerable difficulties, principally on account of the large dimensions necessitated by the volumes of steam to be dealt with and of the considerable differences of' temperature to which the individual parts of` the superheater are subjected.

In order to keep the dimensions of the superheater as small as possible, care must be taken to obtain an eilicient'transfer of heat from the heating steam to the interstage steam and to utilize as uniformly as possible the space available within the superheater container. These requirements are fulfilled for example, by U-tubes connected to headers, if the groups of out-flow and return heating tubes are arranged in sections or divisions, likewise in series, determined by partition walls within the superheater container, because in that case the interstage steam to be superheated is maintained for its entire path in uniform contact with the tubes carrying the heating steam.

In such an arrangement, however, very considerable differences of temperature occur in the individual sections of the superheater. The temperature in the section receiving the interstage steam from the engine and receiving also the heating steam after it has already given up a considerable part of its heat, preferably on the counterflow principle, is naturally considerably lower than in that section which the highlyheated interstage steam leaves and to which the heating steam is admitted at its highest temperature. y.

In order to avoid inadmissible` stresses in the heating-tube system and the container walls, according to the present invention provision is made for the individual parts subjected to unequal expansions to` move freely in relation to one another. l

With this object,the heating tubes open into headers displaceable in relation to one another, of which yonly one end header,

.pass to the condensate-eduction' pipe.

namely, the end header connected with the heating-steam outlet pipeor the end header connected with the heating-steam inlet pipe, is fixed in relation to the container, so that in consequence of the freedom of one end of the heating tubes, no in-admissible stresses ycan occur in the intermediate headers through differential expansion of the groups of tubes.

It is already known in heat-exchange apparatus, to provide `a wall of tubes movable in a header, to which all the heating tubes are connected at their ends. This construction, however, with large dimensions presents considerable technical difficulties. In particular very heavy stresses are produced in the tube system because groups of tubes of very different' temperatures are connected to a common wall. l

It is also known to connect the tubes of heat-exchangers in groups to headers movable in relation to one another. In this form-both end headers are fastened to the container wall and in consequence cannot move in relation thereto. This construction is therefore unsuitable for large interstage superheaters with very considerable differences of temperature between the first and question, the heating steam has to pass through a comparatively long serpentine course where it is in part condensed by giving up heat to the medium to be heated,

while the condensate must-flow through successive tubes to the .end header in Aorder izo n the parts of the tubes covered by condensate, heat transmission is, however, substantially less efficient than in the tubes 4containing no condensate, so that the condensate flowing through the tubes, in effect, renders a part vWalls of the heating tubes, so that the arrangement according to the present invention leads to an improvement in the efliciency of working of the heat-exchanger.

In the accompanying drawings a form of the invention is shown by way of example. Y Figure 1 is a longitudinalsection; while Figure 2 shows to a larger scale, as rei gards itsleft-hand half a section on the broken line II-II of Figure 2, and as regards its right-hand half a section on the line III-III of Figure 1. The heat-exchanger shown comprises a cylindrical container, 1, which is closed at one end by an end piece, 2, and at the other end by a readily removable cover, 3. An inlet connection, 4, is provided for the inv terstage steam to be heated and an outlet connection, 5, for the superheated interstage steam.

The heating-tube system lying in the container, l, consists of two groups of U-tubes, 6, 7, and 8, 9, disposed in series. The outflow lengths, 6, of the first group of tubes are connected to a distributor header, 10, while the vreturn leng'ths, 7 of this group deliver into an intermediate header, 11, from which the outflow -lengths of tube, 8, of the second group extend, the corresponding return lengths, 9, being connected to the end header, 12. f

Between the outflow and return groups of tubes, partitions, 13, 14 and 15, are arranged in such a/way that U-shaped sections `orv divisions in series are provided, through which the interstage steam flows on its way from the inlet, 4, to the outlet, 5.

The partitions, 13, 14 and 15, in the form shown, are supported by angle irons, 16, which are fixed to the wall of the container, 1.

To the inlet header, 10, is connected the heating-steam inlet pipe, 18, which passes steam-tight through an aperture in the end,

2, ofthe container, this inlet pipe being expansion.; From the end header, 12, leads curved within the container to provide for af heating-steam and condensate-eduction pipe,'19, which ylikewise passes steam-tight 'to'the outside of the container through an aperture inf-its end,"2. The educton pipe,

19, forms a rigid connection between the i end header, 12, and the end of the container, 2, so that the heating tubes secured to this header may be considered fixed in relation The tubes of the different groups through-` out their length are inclined at a certain small angle to the horizontal so that the condensate which forms in them can flow away under gravity.

Between the klower end of the intermediate header, 11, and the endheader, 12, a by-pass, 21, is provided throu h which condensate that has formed in t e upper lengths of ktubes can iow direct from the header, 11,

into the Aend header, 12. This by-passed condensate, therefore, in order to pass to vthe condensate outlet need not flow through the lower group of tubes lwhere it would exercise an unfavorable influence on the elficient transfer of heat. v

The correct relative position of the tubes 4is ensured in the usual way by distance pieces and clamps, 22, which like the collector headers are supported in a suitable manner on the lower part of the container wall.

As a heating-tube system is not fastened to the wall of the container, it can be readily withdrawn after disconnecting the pipes, 18 and 19, and removing the cover, 3.

The arrangement of the heating tubes and the manner of connecting them to the heating-steam inlet and outlet pipes can be modified without exceeding the scope of the invention. For example, the heating tubes can be fastened to the heating-steam inlet and be freely movable in relation to the heating-steam outlet, the fixed connection `to the heating-steam outlet being, however,

preferred on account of the lower temperature at that point. In addition, at the movable end, a straight pipe movable in a stuiing-box can be used instead of an expansion pipe for the connection of thel heating-steam pipe, the essential feature being that the kind of connection permits a straight-line movement of the end header at one end of the tubes in order to avoid dan gerous stresses on the tubes and especially tilting of the intermediate header.

What I claim is:

1. In a heat exchanger the 'combination of a closed container provided with an inlet connection and an outlet connection for the medium to be heated and with an inlet connection and Lan outlet connection for the heating medium, with afplurality of series connected groups of parallel connected heating tubes disposed within said container, said groups of heating tubes communicating with a plurality of headers movable with respect to the container, one of the end headers being connected to the inlet and the other end header being connected to the outlet of the heating medium, one of said two end headers beingvfixed and the other end header being freely movable in relation to the container.

2. A heat exchanger accordingV to claim l, the freely movable end header being connected to one connection for the heating medium by an expansion pipe.

3. In a heat exchanger the combination of a closed container provided with inlet connections and outlet connections for the medium to be heated and for the heating medium, the interior of the container being divided into sections formed by partitions' and arranged in series, with heating tubes disposed in the said sections of the container, said heating tubes opening into relatively movable headers and being arranged in series, one end header being connected to the inlet and the other end header being connected to the outlet of the heating medium, one of said two end headers being fixed and the other end header being freely movable in4 relation to the container.

4. In av heat exchanger the combination of a closed container provided with inlet and outlet connections for themedium to be heated and for the heating medium, with heating tubes disposed within -said contalner, said tubes opening into headers and being arranged in series, the one end header 4 vided with inlet and outlet connections for end' headers being fixed and the other end header being the container.

6. A- heat exchanger comprising the combination of a closed container provided with inlet and outlet connections for the mediumJ to be heated and with an inlet connection and an outlet connection for the heating medium, groups. of superposed freely movable. inrelation to `U-shaped heating tubes within the con'- tainer, the tubes'iof each group being so arranged that their planes are substantially parallel and the groups being so arranged that the tubes of one group are in substantially the same planes as the tubes of its adjacent group, said groups of tubes being connected in series -by superposed headers comprising two end headers and at least one intermediate header, partitions between said groups of tubes and between the bends of each group, said partitions being arranged to provide openings at alternate ends of the,A container whereby the container is divided into sections arranged in series, one of the aforesaid end headers being connected to the inlet and the other end header being connected to theoutlet of the Heating medium, one of said end headers A,being fixed and the other being freelymovable in relation to the container. 4.

In testimony whereof I` aiix my signature.

ROBERT UHDE.

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