EP1154216B1 - Steam heated liquid heater - Google Patents

Description

The invention relates to a steam-heated liquid heater with one cuboid-shaped, composed of several profiled plates Heat exchanger package with a first group of channels for the saturated or superheated steam and a substantially cross-flow second Group of channels for the heat-absorbing liquid, both the Channels of the first as well as the channels of the second group each on two opposite sides of the heat exchanger package open, and arranged on the other two sides of the heat exchanger package pressure plates are that brace the profile plates arranged between them against each other.

Such apparatuses, for example known from CH-A-296797, are mainly used in power plant operation Liquid preheater used. In a single, profiled plate composite and in its basic design, for example in EP 0 658 735 B1 described heat exchanger package is the superheated or saturated steam cooled and condensed, the released heat over the profiled Plates are released to the liquid flowing in cross flow, which causes this heats up.

The thin-walled profiled plates joined by welding are characterized by good heat exchange performance, but stand out This design also has problems in terms of strength, because above all when starting and shutting down the heat exchanger as a result mechanical structure multi-axis stress states can arise both on the prevailing pressure differences, as well as on those from the Strain stresses arising due to temperature differences. The expansion stresses arise between the core of the heat exchanger and the housing parts, especially those with regard to the to be recorded Print relatively thick-walled side panels. The thermal expansions work especially in the transition zones to the welds due to high local Tensions. Welds are not only between the individual Sheets of the heat exchanger package, but also in the area of the edges where So-called corner welds are to be provided to ensure the necessary mechanical To create strength and connectivity for the housing. in addition come material vibrations caused by pressure fluctuations in the media are excited and also lead to high local voltage peaks can. These thermal and mechanical loads must be from Strength association of the heat exchanger are included and lead above all with frequent starting and stopping of the device too early voltage or Vibration fractures. To make matters worse, that outer plates of the heat exchanger package compared to the further inside lying plates due to external cooling different Are exposed to temperature fluctuations.

The invention has for its object to provide a steam-heated liquid heater, which is characterized by a long service life even with frequent start-up and shutdown.

To solve this , it is proposed in a liquid heater with the features mentioned at the outset that a double wall defining a gap is arranged between each pressure plate and the outermost profile plate, and that the gap can be flowed through by a partial flow of the heat-absorbing liquid.

As a result of cooling the double wall by means of a partial flow of heat-absorbing liquid can reduce the wall temperatures and thus reducing the tensile stresses between the parts involved. The Number of load changes of the liquid heater until reaching Symptoms of fatigue become greater, and the lifespan becomes total elevated.

Preferred embodiments of the steam-heated liquid heater are in the Subclaims 2 to 14 specified.

So it is preferred that the gap between a manifold and a collector extends for the heat absorbing liquid. As a result, additional, separate connections for feeding and discharging through the double wall coolant flowing through avoided. To that extent aimed at Structural simplification also helps if the double wall on their one End in the housing of the distributor, and at its other end in the housing of the collector protrudes.

The holding the individual profile plates together and here under certain Prestressing pressure plate must be sufficient to achieve an adequate Flexural rigidity can be made relatively thick-walled. Consequences of this are strong different thermal expansions compared to the thermal expansions of the profiled plates. To the mutual influences and thus the Thermal stresses between the pressure plates on the one hand and the plates of the On the other hand, keeping the heat exchanger package low is another Embodiment of the invention proposed that the outside of the Double wall supported pressure plate made of at least two plate segments composed by a transverse to the longitudinal extension of the Heat exchanger package extending joint are spaced apart. The Parting line serves here as an expansion joint and enables temperature-related Expanding the adjacent plate segments so that strain stresses be effectively broken down.

The heat exchanger package is preferably one with a steam inlet and a container provided with condensate outlet, and the Liquid supply as well as the liquid discharge for the heat absorbing Liquid is sealed through the container wall. Preferably there is also the distributor and the collector for the heat absorbing Liquid inside the container.

The fatigue strength of a liquid preheater against frequent ones Load changes are not only caused by the voltages in the heat exchanger itself determined, but also by the distance between the heat exchanger and the tank adjusting thermal stresses. The mechanical forces that arise here keeping it low is proposed with a preferred embodiment that in With respect to the container, one end of the heat exchanger package is fixed and the other end is arranged with play in the container. The end of the heat exchanger package leading into the collector is preferably stationary, the liquid supply line between the container wall and distributor has a longitudinally elastic line section.

Another critical area in terms of thermal stress is that edge of the Heat exchanger packages, which are located in the area of the connecting edge between Steam room and liquid room is located. Therefore, with another Design proposed that the heat exchanger package in the area of Connecting edge between the vapor space and the liquid space with between the individual profile plates projecting wedges is provided, the wedges massive shaped and both with the adjacent profile plates, as well as with the respective Partition to the distributor or collector are welded. The profile plates and Use wedges and any additional double walls and internal walls the tensile forces due to internal pressure.

Fig. 1:

Einen Längsschnitt durch einen Flüssigkeitsvorwärmer;

Fig. 2:

Einen Längsschnitt durch denselben Flüssigkeitsvorwärmer in einer gegenüber Figur 1 um 90° gedrehten Ansicht;

Fig. 3:

Eine Draufschicht auf den Flüssigkeitsvorwärmer nach Fig. 1;

Fig. 4

Einen Detailschnitt der in Fig. 2 mit IV bezeichneten Einzelheit und

Fig. 5:

Einen Detailschnitt der in Fig. 2 mit V bezeichneten, horizontalen Ebene.

Details of a liquid heater according to the invention are explained below with reference to the drawing. In it show:

Fig. 1:

A longitudinal section through a liquid preheater;

Fig. 2:

A longitudinal section through the same liquid preheater in a view rotated by 90 ° with respect to FIG. 1;

Fig. 3:

A top layer on the liquid preheater according to Fig. 1;

Fig. 4

A detail section of the detail designated IV in FIG. 2 and

Fig. 5:

A detail section of the horizontal plane designated V in FIG. 2.

The drawings show a container 1, which consists of a cylindrical Container shell 2, an upper hood 3 and an upper hood 4, a heat exchanger package 5 being arranged in the container 1. The hoods 3, 4 are provided with several nozzles. With D is in the upper hood 3 Steam entry, and designated K in the lower hood 4 of the condensate outlet. The steam can be saturated or superheated steam Act power plant turbine.

The hoods 3, 4 are also provided in the center with further nozzles, with a liquid feed line 6 for the liquid inlet FE and one Liquid discharge line 7 for the liquid outlet FA. About the liquid entry FE the liquid to be warmed up enters the heat exchanger via the Liquid outlet FA leaves the heated liquid from the heat exchanger. The Liquid to be heated therefore flows through the container 1 essentially along its longitudinal axis. Finally there are 3 in the upper hood and the lower hood 4 each have a standpipe 8.

A heat exchanger package 9 is arranged almost centrally in the container 1. On the lower end of which is connected to the liquid inlet FE Distributor 10, at its upper end with the liquid outlet FA connected collector 11. The heat exchanger package 9 is a stack of plates made of profiled, d. H. deformed plates 12. The individual plates 12 are designed identically and are each mirror images connected to each other to form a pair of plates. This connection is made to the Longitudinal edges of the plates, with a pair of plates between each single plates forming a wavy channel for one Medium participating in heat exchange, and an essentially tubular one Channel for the other medium participating in the heat exchange results, the both media are essentially cross-flow. Details of the Plate design of such a heat exchanger package are in the European one Patent EP 0 658 735 B1 from the same applicant.

The liquid to be heated therefore passes from the distributor 10 through the channels formed between the plates and into the collector 11 heated here by the steam conducted in countercurrent. The steam arrives via the steam inlet D into the upper hood 3, which initially serves as a distributor, and of which on both sides in the area of the heat exchanger package 9 the arrows 13 recognize that the saturated or superheated steam from two each other opposite sides into the steam channels of the heat exchanger package 9 flows. This leads to an advantageous symmetrical temperature load on the Heat exchanger package 9. On the other hand, the steam would only enter the one-sided Incoming steam channels of the heat exchanger package, this would become one-sided high temperature load on the inflow side and thus too unfavorable Lead to temperature stresses.

The steam condenses on the plates 12 serving as heat exchanger surfaces, so that the droplets that form afterwards due to their gravity drain at the bottom and finally in the lower condensate collector Hood 4 can be accumulated. The resulting heat of condensation will come on the liquid rising into the collector 11 via the respective other channels issued.

The profiled plates 12 form an essentially cuboid plate pack, which by external pressure plates 14, which are parallel to the plates 12th extend, is held under a certain bias. To achieve this Preloads are tie rods 15 due to the opposite Pressure plates 14 inserted and tightened under a certain tension. Figure 1 shows that the tie rod 15 outside of the profiled by Plates 12 formed cuboids.

Figures 1 and 2 also show that not a continuous Printing plate is used, but each printing plate consists of a total of three Plate segments 16 composed. The plate segments 16 are by a Parting line 17 running transversely to the longitudinal extent of the heat exchanger package 9 spaced. In this way, the individual plate segments 16 in expand certain limits and compensate for thermal stresses.

Between each of the two sides of the heat exchanger package 9 arranged Pressure plates 14 and the outermost profile plate 12 is one Double wall 18 used for cooling purposes by a partial flow of heat Liquid can flow through. To accommodate the internal pressure in Tractive forces acting in the longitudinal direction are additional, one or more times existing inner walls 18a are provided. These are the same size and Shape like the double walls 18, divide the heat exchanger package in two or several modules, are single-walled (not flowed through) and are used for recording the tensile forces in the longitudinal direction due to the internal pressure on the liquid side. The Number is determined by the size of the tensile forces (generated by the internal pressure) Longitudinal direction determined

Figure 4 shows several of the paired profile plates 12, as well the outside pressure plate 14. Between the outermost profile plate 12a and the pressure plate 14 there is a gap 19 delimiting double wall 18 Double wall 18 is in the flow direction of the heat-absorbing liquid considered longer than the profile plates 12 of the heat exchanger package, which is why Double wall 18 protrudes at its lower end 20 into the housing of the distributor 10. Likewise, the double wall 18 projects with its other end into the housing of the Collector. The gap 19 between the two individual walls 20a, 20b Double wall 18 is approximately 2 to 5 mm with a thickness of the individual walls 20, 20b of approx. 3 mm. To ensure the thickness of the gap 19 are between the individual walls 20a, 20b extending in the flow direction Spacers 21. The spacers 21 are preferably only with the outer, welded to the pressure plate 14 single wall 20a.

FIG. 5 shows that the heat exchanger package 9 is in the area of FIG. 1 drawn connection edge 22 between the vapor space and the liquid space is provided with wedges 23 which are welded between them in pairs Profile plates 12 protrude. The wedges 23 are solidly formed from metal and both with the adjacent profile plates 12 and with the respective partition 24 to Distributor or welded to the collector.

Figure 1 finally shows that the heat exchanger package 9 via webs 25th is supported against the inner wall of the container shell 2. This support takes place in the upper area of the heat exchanger package 9 at the level of the collector 11. On the other hand, there is no corresponding rigid connection between Heat exchanger package 9 and tank wall in the lower area of the tank 1. On in this way it is possible for the heat exchanger package 9 to move within the Container and expand in relation to the container. To compensate for the here adjusting length change is the liquid supply line 6 between the formed by the hood 4 container wall and the distributor 10 with a provided flexible, longitudinally elastic line section 26. The Heat exchanger package 9 including manifold 10 and collector 11 is therefore as it were hung in the container 1 and can avoid Extend thermal stress downwards unhindered.

LIST OF REFERENCE NUMBERS

1

container

2

container jacket

3

upper hood

4

lower hood

5

Heat exchanger package

6

liquid supply

7

liquid drain

8th

standpipe

9

Heat exchanger package

10

distributor

11

collector

12

plate

12a

outermost plate

13

arrow

14

printing plate

15

tie rods

16

plate segment

17

parting line

18

double wall

18a

inner wall

19

gap

20

The End

20a

Single wall

20b

Single wall

21

spacer

22

connecting edge

23

wedge

24

partition wall

25

web

26

longitudinally elastic line section

D

steam inlet

K

condensate outlet

FE

liquid inlet

FA

liquid outlet

Claims (14)

1. Steam-heated liquid heater with a cuboid heat exchanger stack (9) which is composed of a plurality of profiled plates (12) and has a first group of channels for the saturated or superheated steam and a second group of channels, which is routed essentially in cross-current, for the heat-absorbing liquid, wherein both the channels of the first and the channels of the second group in each case open out on two opposite sides of the heat exchanger stack (9), and pressure plates (14) are disposed at the two remaining sides of the heat exchanger stack (9), which plates brace the intervening profiled plates (12) against one another,
   characterised in that a double wall (18), which defines a gap (19), is disposed between each pressure plate (14) and the respective outermost profiled plate (12a), and that a partial stream of the heat-absorbing liquid can flow through the gap (19).
2. Liquid heater according to Claim 1, characterised in that the gap (19) extends between a distributor (10) and a collector (11) for the heat-absorbing liquid.
3. Liquid heater according to Claim 1 or Claim 2, characterised in that the double wall (18) projects at one end (20) into the housing of the distributor (10) and at its other end into the housing of the collector (11).
4. Liquid heater according to any one of Claims 1 to 3, characterised by distance pieces (21), extending in the flow direction, between the individual walls (20a, 20b) of the double wall (18).
5. Liquid heater according to Claim 4, characterised in that the distance pieces (21) are welded to one (20a) of the two individual walls.
6. Liquid heater according to any one of Claims 1 to 5, characterised in that, viewed in the flow direction of the heat-absorbing liquid, the double wall (18) is longer than the profiled plates (12) of the heat exchanger stack (9).
7. Liquid heater according to any one of Claims 1 to 6, characterised in that the pressure plate (14) supported externally at the double wall (18) is composed of at least two plate segments (16) which are spaced apart by a parting interstice (17) extending transversely to the longitudinal extent of the heat exchanger stack (9).
8. Liquid heater according to Claim 7, characterised in that each pressure plate (14) is composed of a total of three plate segments (16) which are divided by parting interstices (17).
9. Liquid heater according to any one of Claims 1 to 8, characterised in that the heat exchanger stack (9) is inserted in a container (1) provided with a steam inlet (D) and a condensate outlet (K), and that the liquid feed line (6) as well as the liquid withdrawal line (7) for the heat-absorbing liquid are passed in a sealed manner through the container wall.
10. Liquid heater according to Claim 9, characterised in that the container (1) is formed in a cylindrical manner with two covering hoods (3, 4), and the heat-absorbing liquid is passed through these essentially in the longitudinal direction of the container, wherein the liquid feed line (6) and withdrawal line (7) are passed centrally through the respective covering hood (4 and 3).
11. Liquid heater according to Claim 9 or Claim 10, characterised in that the distributor (10) as well as the collector (11) for the heat-absorbing liquid are also located inside the container (1).
12. Liquid heater according to any one of Claims 9 to 11, characterised in that, in relation to the container (1), one end of the heat exchanger stack (9) is disposed in a stationary manner and the other end is disposed with clearance of motion inside the container.
13. Liquid heater according to Claim 12, characterised in that the end of the heat exchanger stack (9) which leads into the collector (11) is stationary, and that the liquid feed line (6) comprises a longitudinally elastic line portion (26) between the container wall and the distributor (10).
14. Liquid heater according to any one of Claims 1 to 13, characterised in that the heat exchanger stack (9) is provided in the region of the connecting edge (22) between the steam space and the liquid space with wedges (23) which project between the individual profiled plates (12), wherein the wedges (23) are solid and are welded both to the adjacent profiled plates (12) and to the respective partition wall (24) for the distributor (10) and collector (11).

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