US3563303A

US3563303A - Method and apparatus for increasing uniformity of heat transfer

Info

Publication number: US3563303A
Application number: US785491A
Authority: US
Inventors: Paul Viktor Gilli; Kurt Fritz; Walter Roznovsky
Original assignee: Waagner Biro AG
Current assignee: Waagner Biro AG
Priority date: 1968-01-15
Filing date: 1968-12-20
Publication date: 1971-02-16
Anticipated expiration: 1988-02-16
Also published as: GB1239854A; DE1811596B2; DE1811596A1; CH496225A; AT278863B

Abstract

A method and apparatus for increasing the uniformity of heat transfer in a heat exchanger. The flow of the medium which is to be heated is regulated in such a way as to provide a uniform outlet temperature of this medium at the outlet ends of the tubes. This is achieved by throttling the flow of the medium into the inlet ends of the tube. After measuring the temperature of the medium at the outlet ends of the tubes, a throttling at the inlet ends is provided to achieve uniform temperatures at the outlet ends, respectively.

Description

United States Patent METHOD AND APPARATUS FOR INCREASING Inventors Paul Viktor Gilli Vienna; Kurt Fritz, Klosterneuburg; Walter Roznovsky, Vienna, Austria Appl. No. 785,491 Filed Dec. 20, 1968 Patented Feb. 16, 1971 Assignee Waagner-Biro Aktiengesellschaft Vienna, Austria Priority Jan. 15, 1968 Austria UNIFORMITY OF HEAT TRANSFER 13 Claims, 6 Drawing Figs.

US. Cl 165/1, 165/ 101 Int. Cl F 28f 27/02 [50] Field ofSearch 165/1, 39, 40,101,163,l74

[56] References Cited UNITED STATES PATENTS 2,070,427 2/1937 Faunce 165/174 3,406,745 10/1968 DeCastelet 165/40 Primary Examiner-Charles Sukalo Attorney-Steinberg and Blake \M lk I2 l6 [IE ,4 s"

PATENIED ram 6&9?!

SHEET 2 0F 3 1' A/ MIN 76/? 5 mm mm? fl/LL WA fE-R jaw R0 NoVsK y ATENTEU FEB I 6 I97! SHEET 0F 3 BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for increasing the uniformity of heat transfer in heat exchangers.

in particular, it is an object of the invention toprovide a method and apparatus which will increase the uniformity of operation of a heat exchanger wherein part. of the tubes through which the heated medium flows are necessarily rendered inoperative. f i

Thus, for example, it sometimes-happens during operation of a heat exchanger that a certain part of the tubes thereof become defective due to the occurrence of an accident, for example, and the situation is often one where the location of the defective tube or tubes is such that it is inaccessible. Under these conditions it becomes necessary to terminate the operation of such defective tubes.

It has already been proposed to terminate this operation by plugging up the defective tubes so that they will nolonger participate in the heat exchange. Such plugging of the defective tubes necessarily results in a decrease in the extraction of the heat from the heating medium at predetermined locations. The heat-exchanging operations will now take place with a sharp decrease in uniformity with those tubes :in the immediate vicinity of the plugged defective tubes which are no longer used becoming heated to an extent greater than other tubes. A similar effect can in fact be encountered during starting up operations when the design of the system has been carried out in such a way that not enough care was taken to achieve, uniform discharge temperatures at the individual tubes, or in the case where during manufacture of the individual tubes localized narrowing or reductions in the cross section of the path of flow result from. factorssuch as a welding bead which is toolarge and whichis improperly situated so that it extends into and undesirably restricts the path of flow at a localized area. Yet another source for a deviation in the structure resulting in nonuniform operation is the different internal diameters of the heat-exchanging tubes necessarily resulting from conventional manufacturing tolerances. Furthermore, it is not possible to avoid certain deviations from an ideal construction in the design of a given system, particularly in the case of bundles of helical tubes forming part of a system where the helical tubes define pipe cylinders of different diameters. in an actual construction it is essential to provide such a pipe cylinder with a given whole number of tubes while according to theory,.a fractional number of tubes, rather than a whole number of tubes, will be required to achieve uniform operation. Thus, for all of these reasons it is unavoidable that a lack of uniformity will be encountered in the operations of heat exchangers. Of particular significance, however, is the case where one or moreindividual tubes must be excluded from the operations as a result of damage to such tubes with the damaged tubes located where they cannot be repaired either because the location of the damaged tube or tubes is inaccessible, or because of the presence of radioactivity in the region of the damaged tube or tubes. Thus, in certain through-flow steam generating constructions, which are heated with gases, liquids or liquified metals from a nuclear reactor, it is either not possible to carry out repairs directly in a given bundle of tubes or repairs can only be made after a long waiting time has expired, Such difficulties are also encountered in conventional installations, however, where the tubes of the bundles are packed with a particularly high density. All of these latter effects are encountered to a particularly large extent in the case of through-flow steam generators which do not have any intermediate collection of the heated fluid.

SUMMARY OF THE INVENTION It is accordingly a primary object of the invention to provide a method and apparatus which will avoid the above drawbacks. a

In particular, it is an object of the invention to provide a method and apparatus which will achieve uniformity in the operation of a heat exchanger even in the case where part of the tubes thereof must be excluded from the operations.

in particular, it is an object of the invention toprovide a method and apparatus which will result in a substantial increase in the uniformity of the temperature of a heated medium where it discharges from heating tubes in the case where part of the latter tubes must be excluded from the operations.

It is especially an object of the invention to provide a method according to which it is possible to determine how to modify a given heat-exchanging system so as to achieve uniformity in the operation thereof after a given part of the heating tubes have been damaged so as to require part of the tubes to be rendered inoperative. I p

Also, it is an object of the invention to provide an exceedingly simple structure which can be added to an existing installation for the purpose of rendering the operation thereof more uniform in the case where it is necessary to exclude certain tubes from the operation.

In accordance with the invention the heat exchanger has a plurality of tubular means respectively provided with inlet and outlet ends. ln accordance with the invention the medium which is to be heated is directed through the plurality of tubular means in such a way that the temperature of this medium at the outlet ends of the tubular means is substantially uniform. in accordance with the invention, this result is achieved by throttling the flow of the medium which is to be heated into the inlet ends of the plurality of tubular means in such a way that this medium will have a uniform temperature at the outlet ends. Each tubular means may take the form of a single tube or a group of tubes. The throttling at the inlet ends of the plurality of tubular means is brought about by a throttling means which preferably takes the formof a suitably apertured plate having throttling apertures which respectively communicate with these inlet ends. in the event thatthere are tubes which for any reason no longer operate, then the aperture plate has throttling apertures which respectively have such a size that the extent of flow of medium through tubes in the immediate vicinity of those which no longer operate is greater than the extent of flow through the tubes which are more distant from the part of the tubes which have been rendered inoperative. Temperature measurements are carried out at the individual outlet ends of the plurality of operating tubular means for determining the temperatures at these several outlet ends, respectively, and in accordance with the latter temperatures a given throttling means is situated at the inlet ends to achieve the uniform temperature at the outlet ends. Thus, where there are tubes which no longer operate, the apertured throttling plates can have at the inlet ends immediately adjacent those tubes which no longer operate throttling apertures which are greater than more distant throttling apertures either absolutely or with respect to the latter apertures. Thus, in the case of heat exchange between a medium within longitudinally extending tubes and a hot fluid at the exterior of the tubes, the lesser extent of throttling is provided at those tubes which surround any inoperative tube or tubes. In the case where the heating fluid flows transversely across a bundle of tubes through which the heated medium flows, the lesser extent of throttling is provided at those tubes situated in the direction of flow of the medium which gives up its heat as well as, to a lesser extent, at those tubes which are in the immediate vicinity of any damaged tubes which no longer operate.

Thus, with the structure of the invention a throttling means is situated at the inlet ends of the plurality of tubular means to throttle the flow of the heated medium through the plurality of tubular means in a manner determined by the discharge temperatures at the outlet ends of the plurality of tubular means for regulating the flow of the heated medium through the operating tubes to achieve uniform temperatures at the outlet ends of the tubular means. The throttling means, according to a further feature of the invention, preferably takes the form of an apertured plate which is situated in front of an inlet plate to which the inlet ends of the several tubular means are connected. In order to measure the temperature of the medium discharging at the outlet ends of the tubular means, a thermocouple means situated in accordance with the invention at the region of an outlet plate to which these outlet ends are connected, and the thermocouple means is capable of measuring the temperature of the medium which discharges at the outlet ends of the individual tubular means.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. I is a partly sectional schematic elevation of a heat exchanger having helical heat-exchanging tubes;

FIG. 2 is a schematic sectional elevation of that type of heat exchanger where the tubes are respectively arranged in planes to form partition walls in the heatexchanger;

FIG. 3 is a fragmentary longitudinal sectional elevation schematically illustrating one embodiment of a throttling DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, the heat-exchanger installation illustrated therein includes a plurality of helical tubular means through which the medium to be heated flows. In the illustrated example the plurality of tubular means are in the form of individual helical tubes 5 which define tube cylinders I4. The tube cylinder 1 is surrounded by the tube cylinder 2 which is itself surrounded by the tube cylinder 3, and this latter tube cylinder is, of course, surrounded by the outer tube cylinder 4. Each of these cylinders is defined by a plurality of helical tubes 5 having convolutions of the same diameter. Thus, the tubes which define the cylinder 1 have convolutions of the smallest diameter, while the tubes which define the cylinder 4 have convolutions of the largest diameter, and of course the cylinders 2 and .3 have tubes of corresponding diameters between those of the cylinders l and 4. Within each cylinder the several tubes which define the same are connected in parallel and within each cylinder all of the tubes which define the same have the same length. Thus, each tube cylinder is composed of a given number of parallel-connected helical tubes all ofwhich are of equal length.

The heating medium, in the form of a hot gas, enters at the top of the installation through the gas inlet 6, and heat is extracted from the hot gas entering through the inlet 6 to generate steam. The heat is extracted from the gas through the walls of the helical tubes 5, and the cooled gas leaves the steam generator at the lower outlet 7 thereof. The installation is situated within the elongated housing 8 which has the inlet 6 at its top end and the outlet 7 at its bottom end.

The number of parallel-connected tubes 5 in the several tube cylinders l--4 is different in the respect 'of cylinders. Thus, at the outer cylinder 4 which has the largest diameter there will be more parallel-connected tubes than in the remaining tube cylinders which successively have decreasing numbers of tubes from the outer to the inner cylinder 1, the latter of course having the smallest number of tubes. The difference between the numbers of tubes of the several cylinders is such that the longitudinal pitch of all of the helical tubes 5 is identical for all of these tubes in the several cylinders l-4.

The feedwater flows from the feedwater inlet I5 into the supply chamber l3where the feedwater is collected. At this chamber 13 the feedwater has access to an inlet plate ll formed with bores which receive the inlet ends of the plurality of tubular means 5. The throttling means of the invention is situated in front of this inlet plate 11 and the several tubular means 5 include, in addition to the helical portions thereof. the tubular extensions 9 respectively communicating with the several helical tubes and terminating in the bores of the inlet plate 11 in which the inlet ends of the extensions 9 are received in a fluidtight manner. Thus, through the several extensions 9 of the plurality of helical tubular means a communication is made with the feedwaterwhich is preheated, heated. converted into steam, and superheated within the helical tubes 5.

The live steam discharges from the plurality of tubular means 5 into tubular extensions 10 respectively communicating with and extending from the tubular means 5 and received in bores of an outlet plate 12 where the outlet ends of several tubular means are located, these outlet ends being defined by the outlet ends of the extensions 10 of the several tubular means. Thus, the live steam will flow from the helical tubes 5 respectively through the extensions 10 thereof and the outlet plate 12, which fluidtightly receives the extensions 10 in bores of the plate 12, respectively, into the live-steam collecting chamber 14, from which the live steam flows to the conduit 16. The outer cylindrical housing 8 for the entire installation is capable of withstanding high pressure and is suitable for use with gas at high pressure, particularly with gas issuing from a nuclear reactor.

In the type of heat exchanger which is illustrated in FIG. 2, the several tubular means are respectively arranged in planes so that the assemblies of tubular means form partition-walls. Thus, several bundles 17 of individual tubular means are assembled together to form a partition wall such as that which is schematically illustrated in FIG. 2. In each of these tubular partition walls the several tubes are curved so as to have horizontal portions extending back and forth in the manner shown in FIG. 2. Therefore, while with the embodiment of FIG. 2 the downwardly flowing heating gas will flow transversely across the horizontally extending portions of the several tubular means 17, in the embodiment of FIG. I the downwardly flowing heating gas will flow transversely across the helically extending portions of the several tubular means 5. Except for the fact that the several tubular means 17 have the configurations indicated in FIG. 2 so as to form walls of tubes, the construction of FIG. 2 is identical with that of FIG. 1 and the corresponding components are indicated with the same reference characters. It is of course apparent that with FIG. 2 the feedwater inlet 15 and chamber 13 are situated at the opposite side of the housing 8, but this of course is an immaterial distinction.

Both of the heat exchangers of FIGS. 1 and 2 operate in the same way, the only difference being that the embodiment of FIG. 2 is particularly suited for a heat exchanger adapted to operate with a heating gas of relatively low pressure and having a rectangular or square cross section whereas the heat exchanger of FIG. 1 is ofa cylindrical cross section and is particularly adapted for operation with high pressure gas.

Assuming now, that, for example, as a result of a defect encountered in one of the tubes of FIG. I, it is necessary to remove this one tube from the operations, then the defective tube will be plugged up at its inlet and outlet ends so as to be rendered inoperative. The same considerations will apply in an analogous manner to FIG. 2 when a defective tube thereof must be rendered inoperative. This elimination of a defective tube from the operations will, as has already been mentioned, influence the transfer of heat to the adjoining tubes as a result of the fact that heat is no longer extracted in the inoperative, defective tube, so that more heat must be extracted by the adjoining tubes. Therefore, in accordance with the invention, the tubes in the immediate vicinity of the inoperative tube, for example the operating tubes of the cylinders I, 2, and 3 in the case where a tube of the cylinder 2 has been rendered inoperative, have the amount of medium flowing therethrough increased either absolutely or relatively with respect to the tubes in the cylinder 4, in this particular example. Thus, the throttling apertures of a throttling means at the inlet ends of the several tubular means will respectively have diameters which are enlarged at the inlet ends of the tubular means in the immediate vicinity of the inoperative tubular means either absolutely or relatively with respect to the diameters of the plurality of tubular means relatively distant from the inoperative tubular means.

In the case of bundles of tubes across which the heating gas flows, such as straight tubular portions in tube walls such as those shown in FIG. 2 or in involute bundles of tubes, or in the case where there is primarily transverse flow of the heating medium across the tubes, as in the case of the helical tubes 5, the relative and/or absolute reduction in the extent of throttling at the inlet ends takes place at allof the tubes which are situated directly behind the inoperative tube in the direction of flow of the heating gas, so that in the case where a tube of the tube cylinder 2 is rendered inoperative, for example, allof the remaining tubes of the cylinder 2 will have the flow of heating medium therethrough throttled to a lesser extent than all of the other tubes of the assembly. Thus, a particular wall of tubes 17 which has one of its tubes rendered inoperative will have the flow of heating medium through the remaining tubes of this wall throttled to an extent less than through the tubes of all of the other walls. Thus, within the same tube cylinder, tube wall, or series of involute tubes, all of the remaining operative tubes will have the flow of heating medium therethrough throttled to an extent less than in all of the other tubes of the entire assembly However, the immediately adjacent tubes, whether in a pair of immediately adjacent tube walls 17 or immediately adjacent involute or helical tubes will also be throttled to a lesser extent, but the extent of throttling in such immediately adjacent tubes will be somewhat greater than those tubes which remain in the same cylinder or wall. Thus, in the above example where a tube of the cylinder 2 has been rendered inoperative, the tubes of the cylinders I and 3 will be throttled to a lesser extent than the tubes of the cylinder 4 but a greater extent than'the'remaining operative tubes ofthe cylinder 2. j

The change in the operation of the heat exchanger to achieve the proper amounts of heated medium respectively flowing through the several tubular means to provide uniform discharge enthalpies is brought about by way of a throttling means situated at the inlet ends of the several tubular means, this throttling means being omitted from FIGS. 1 and 2 for the sake of clarity. In order to facilitate the construction of the heat exchanger and in order to have available the possibility of subsequent adaptation of the heat exchanger to the actual conditions which are subsequently encountered after the assembly is initially built, it has proved to be highly desirable to assemble together the inlet ends of the several tubular means of the heat exchanger fluidtightly within the bores of an inlet plate such as the inlet plate 11 indicated schematically in FIGS.-l and 2 and shown schematically at an enlarged scale in section in FIGS. 3 and 4. The same considerations apply to the case where there are a larger number of supply chambers for the heat exchanger. The throttling means, according to one embodiment of the invention, takes the form of an apertured plate situated in front of the inlet plate 11. A change in the structure subsequent to the building and operation thereof can then be fully carried out by providing several apertured plates having different arrangements and sizes of apertures therein, so that by exchanging one apertured plate for another it is possible to adjust the operations. A sealing means is provided to achieve a fluidtight connection between such an apertured throttling plate and the inlet plate 11, and this sealing means preferably takes the form of precisely flat ground surfaces of the throttling plate and inlet plate 11 directly engaging each other to form a fluidtightly sealed interface therebetween. An

' additional seal is achieved because of the differential pressure existing before and after the apertured plate which forms the throttling means. In some cases, a seal can be omitted. In this latter event the orifices of the apertured plate are dimensioned in such a way that the amount of medium flowing through the orifices together with leakage losses between the orifices provides the right amount of medium.

Referring to FIG. 3, the feedwater inlet region of the heat exchanger is shown in detail. In this embodiment the throttling means takes the form of the apertured plate 19 provided with the throttling orifices 20. The inlet extensions 9 of the several tubular means which form the inlet ends thereof are welded into the bores of the feedwater inlet plate 11. The apertured plate 19 with its orifices 20 is bolted to the inlet plate II. To improve the seal the surfaces of

plates

11 and 19 which engage each other are ground at their interface.

In the case of FIG. 4, the illustrated embodiment has a throttling means in the form of individual throttling nozzles 21 threaded directly into the bores of the inlet plate 11. Where the extensions 9 extend all the way to the upstream end face of the plate 11, the nozzles 21 can be threaded directly into the extensions 9, respectively.

Whenit has been determined that the outlet enthalpies or the discharge temperatures of the heated medium at the outlet ends of the several tubular means deviate from the desired uniformity, the throttling means either in the form of the individual nozzles of FIG.-4 or apertured plate of FIG. 3 is made in a precalculated manner so that approximately identical discharge conditions will be achieved at the several outlet ends of the individual tubes or strings of tubes. In general, the deviation from uniform outlet temperatures will be determined by measuring the outlet temperatures of the heated medium at the outlet ends of the individual tubes. After these outlet temperatures are measured it is possible in a known way to estimate the throttling required for the individual tubes or the extent of throttling can be newly calculated. Under certain circumstances, however, it is desirable to carry out an estimate of the required throttling structure. Then the throttling structure constructed as estimated is used and the discharge temperatures are measured. If required, the estimated throttling structures is changed a second time for a new throttling structure which will give the required uniform discharge temperatures. Thus, an empirical trial-and-error method may be used.

Referring now to FIG. 5, the live-steam collector is illustrated therein. With the construction shown in FIG. 5 it is possible to measure the temperature of the steam at the outlet ends of the several individual tubular means, respectively, upon discharge of the steam into the: collecting chamber. The live-steam tube extensions 10 of the several tubular means are fluidtightly welded, for example, to the outlet plate I2 in bores of the latter, respectively, the welding being located at the interior of the bores of the outlet plate, 12. An auxiliary plate 22 is bolted to the outer, downstream end face of the outlet plate 12, and this auxiliary plate 22 is formed with openings respectively forming extensions of the bores of the plate 12. A plurality of relatively short tubes 23 are fixed, as by welding, to the auxiliary plate 22 in a manner where these several short tubes 23 respectively form coaxial extensions of the extensions 10. Moreover, the inner diameters of the short tubes 23 are respectively equal to the inner diameters of the bores of the outlet plate 12. The temperature measuring means takes the form of a plurality of thermocouple means 24 in the form thermocouple elements situated in suitable openings formed in the short tubes 23, and these thermocouple means 24 are capable of measuring the temperature of the discharging live steam in a well-known manner. The several thermocouple means include the thermocouple cables or conductors 26 which are shielded from live steam by way ofa relatively large boxlike shielding sleeve 25 which is bolted to the auxiliary plate 22 in the manner shown schematically in FIG. 5. In this way the sleeve 25 forms a protecting means to protect the conductors 26 from the heated medium.

In the embodiment of FIG. 6 a different construction of a live-steam collector 14 is illustrated. In this case the live-steam tubular extensions 10 are respectively welded in the bores of the outlet plate 12 by way of welding rods. Thus, while with FIG. the welding of the extremities of the tubes to the outlet plate 12 is carried out in the interior of the bores of the latter, in the case of FIG. 6 the welding of the tubes 10 takes place at the downstream end face of the outlet plate 12, and with the embodiment of FIG. 6 the auxiliary plate 22 is spaced slightly from the plate 12. The collecting chamber 14 for the live steam is defined by a wall means which includes a removable cover shown at the top of FIG. 6, and the auxiliary plate 12 is fixed to this removable cover by way of suitable bolts. As was the case with the embodiment of FIG. 5, the auxiliary plate 22 of FIG. 6 carries the relatively short tubes 23 which respectively form coaxial extensions of the extensions 10 and which carry the several thermocouple means 24. The conductors 26 of the thermocouple means in the embodiment of FIG. 6 are respectively guided through the interiors of protective tubes 27 along the bolts 28 which interconnect the plate 22 with the removable cover, so that in this case it is the tubes 27 which form the means for protecting the conductors 26 from the live steam. Further shielding of the conductors can be provided by way of a top shielding sheet 29 carried by the several connecting bolts 28 and formed withopenings receiving the upper open ends of the shielding tubes 27 in the manner shown in FIG. 6.

Thus, with the constructions of FIGS. 5 and 6 the measurement of the livesteam temperature is carried out at each individual tubular means, whether this tubular means is in the form of a single tube or a group of tubes, after the heated medium has passed through the outlet plate 12. The thermocouple means used to measure the temperature can be arranged in the path of gas flow or at the exterior of the heat exchanging tubes, in particular at the extensions 10 thereof.

The invention described above is of course not limited to use with steam generators. It can be used with heat exchangers such as, for example, those which use liquid metal for heat exchange or with regenerators in MHD circuits. Also, the invention is not limited to bundles of tubes arranged so that the heating gas flows directly across or primarily across the tubes. The invention also can be used in installations where the heating gas flows longitudinally along the heating tubes. In this latter case the method and apparatus of the invention are such that the tubes which immediately surround the tube which is rendered inoperative receive the larger amounts of the medium which is to be heated while the remaining tubes which are situated more distant from the inoperative tube receive the heated medium also in larger amounts but to a lesser extent than those tubes which immediately surround the inoperative tube.

It is apparent that when no steps are taken to compensate for an area where a tube or group of tubes are inoperative, the operating tubes in the immediate vicinity of such an area will be heated to a far greater extent that other tubes because of the greater amount of heat available at this particular area resulting from the failure of the nonoperating tubes to absorb their share of the heat. With the invention, because the extent of throttling in the tubes in the immediate vicinity of the nonoperating tubes is less than the throttling in tubes distant from the nonoperating tubes, a greater amount of heated medium flows through the tubes with the lesser throttling, thus reducing any tendency for overheating in the walls of the tubes in the immediate vicinity of the nonoperating tubes.

We claim:

I. In a method for increasing the uniformity in the transfer of heat in a heat exchanger having a plurality of tubular means through which the heated medium flows, said plurality of tubular means respectively having inlet ends and opposed outlet ends, the steps of respectively directing the medium which is to be heated through said plurality of tubular means from said inlet toward said outlet ends thereof, measuring the temperature of the medium at the outlet end of each of said plurality of tubular means, and then providing at the inlet end of each of said plurality of tubular means a nonadjustable throttle. to throttle said plurality of tubular means to extents, respectively, which will achieve substantially uniform temperatures of the heated medium at the outlet ends of said plurality oftubular means.

2. In a method as recited in claim 1 and wherein the amount of medium directed into the plurality of tubular means together with leakage losses determine the amount of medium required to flow through the plurality of tubular means.

3. In a method as recited in claim 1 and wherein said plurality of tubular means are respectively in the form of individual tubes, and said measurement of temperature respectively taking place at the outlet ends of the plurality of individual tubes.

4. In a method as recited in claim 1 and wherein the heated medium is water, the step of converting the heated water into steam within the plurality of tubular means without any intermediate collection of the heated medium and then superheating the resulting steam.

5. In a method as recited in claim 1 and wherein ifa part of said tubular means is no longer operative, the extent of throttling in those tubular means immediately adjacent the part thereof which is not operative is reduced so as to be less than the extent of throttling in those tubular means which are more distant from the part which is not operative, to reduce the tendency of overheating in the walls of those tubular means adjacent the part which is not operative.

6. In a heat exchanger, a plurality of tubular means through which medium to be heated flows, said plurality of tubular means respectively having inlet ends and opposed outlet ends. and throttling means situated at said inlet ends of said plurality of tubular means for throttling the flow of medium through the plurality of tubular means to an extent which will provide at the outlet ends of the plurality of tubular means substantially uniform temperatures the degree of uniformity of which is beyond that which would prevail without said throttling means, and a plurality of thermocouple means situated at and respectively coacting with said outlet ends of said plurality of tubular means for measuring the temperature of the medium discharging through the latter outlet ends, said throttling means having a construction selected in accordance with the temperatures .measured by the plurality of thermocouple means for achieving said degree of uniformity in the temperatures of the heated medium at the outlet ends of said plurality of tubular means.

7. The combination of claim 6 and wherein an inlet plate is formed with bores respectively receiving the inlet ends of the plurality of tubular means, and said throttling means including an apertured plate situated in front of said inlet plate and formed with a plurality of throttling apertures respectively communicating with the inlet ends of the plurality of tubular means.

8. The combination of claim 7 and wherein a sealing means is situated between said plates for providing a fluidtight coaction therebetween.

9. The combination of claim 8 and wherein said sealing means includes flat-ground surfaces of said plates which engage each other and form a fluidtight interface therebetween.

10. The combination of claim 6 and wherein an outlet plate is formed with bores respectively receiving the outlet ends of the plurality of tubular means, and a plurality of relatively short tubes respectively communicating with said outlet ends of said plurality of tubular means and at which said plurality of thermocouple means are respectively located.

11. The combination of claim 10 and wherein an auxiliary plate carries said tubes and fluidtightly engages said outlet plate while providing communication between said tubes and said outlet ends of said plurality of tubular means, respectively.

12. The combination of claim 10 and wherein a chamber means communicates with said outlet ends for receiving the medium discharging therefrom, said chamber means having a removable cover, and connecting means connecting said tubes tors extending through said wall means and protecting means coacting with said conductors for protecting the latter from the heated medium discharging from said outlet ends of said plurality of tubular means.

Claims

1. In a method for increasing the uniformity in the transfer of heat in a heat exchanger having a plurality of tubular means through which the heated medium flows, said plurality of tubular means respectively having inlet ends and opposed outlet ends, the steps of respectively directing the medium which is to be heated through said plurality of tubular means from said inlet toward said outlet ends thereof, measuring the temperature of the medium at the outlet end of each of said plurality of tubular means, and then providing at the inlet end of each of said plurality of tubular means a nonadjustable throttle, to throttle said plurality of tubular means to extents, respectively, which will achieve substantially uniform temperatures of the heated medium at the outlet ends of said plurality of tubular means.

5. In a method as recited in claim 1 and wherein if a part of said tubulAr means is no longer operative, the extent of throttling in those tubular means immediately adjacent the part thereof which is not operative is reduced so as to be less than the extent of throttling in those tubular means which are more distant from the part which is not operative, to reduce the tendency of overheating in the walls of those tubular means adjacent the part which is not operative.

6. In a heat exchanger, a plurality of tubular means through which medium to be heated flows, said plurality of tubular means respectively having inlet ends and opposed outlet ends, and throttling means situated at said inlet ends of said plurality of tubular means for throttling the flow of medium through the plurality of tubular means to an extent which will provide at the outlet ends of the plurality of tubular means substantially uniform temperatures the degree of uniformity of which is beyond that which would prevail without said throttling means, and a plurality of thermocouple means situated at and respectively coacting with said outlet ends of said plurality of tubular means for measuring the temperature of the medium discharging through the latter outlet ends, said throttling means having a construction selected in accordance with the temperatures measured by the plurality of thermocouple means for achieving said degree of uniformity in the temperatures of the heated medium at the outlet ends of said plurality of tubular means.

12. The combination of claim 10 and wherein a chamber means communicates with said outlet ends for receiving the medium discharging therefrom, said chamber means having a removable cover, and connecting means connecting said tubes to said cover for removal of said tubes and plurality of thermocouple means with said cover.

13. The combination of claim 10 and wherein a wall means defines a chamber receiving the medium discharging through said outlet ends, said thermocouple means including conductors extending through said wall means and protecting means coacting with said conductors for protecting the latter from the heated medium discharging from said outlet ends of said plurality of tubular means.