FR2484070A1 - Heat exchanger for condenser - has sprayer at top of cylinder and condensing plates with water sump - Google Patents

Abstract

The heat exchanger has a cylindrical tower (11). The top of the tower is fitted with a sprayer (12). Below the sprayer, is a top plate (13). The surface of the plate is V-shaped and allows the spray to fall around the edge onto the lower plates (14a,b). The plates have identical sections and are equi distant. The lower plates (15) allow the spray onto the gas inlet pipe (16). Air is admitted through this pipe by openings underneath. The water is collected through a sump (17) with a sloping floor and an outlet flange.

Description

 The present invention relates to a condensing heat exchanger intended in particular to allow the recovery of the heat carried by the combustion gases.

 Heat exchangers are already known which make it possible to recover a large amount of heat from the combustion gases by condensation of most of the water vapor contained in these gases.

 This is how heat exchangers have been described, which include a tower in which flow against the current, on the one hand hot combustion gases, and on the other hand, a cold fluid sprayed at the top. from the tower, means for recovering the fluid at the bottom of the tower and means for circulating the fluid to a use circuit.

 The present invention aims to improve an exchanger of this type, in particular by simplifying and improving the construction of the intermediate baffles which make it possible to increase the contact surfaces between gas and fluid and thus to increase the heat exchange.

 To this end, the present invention relates to a heat exchanger comprising a tower in which circulate against the current, on the one hand, hot and humid gases entering the lower part of the tower, on the other hand, water droplets which are sprayed at the top of the tower, means for recovering water at the bottom of the tower and means for filtering and then circulating the water to a circuit of use , characterized in that the height of the tower between the spraying zone and that of the hot gas inlet is divided into a number of superimposed stages separated by trays intended to collect all or part of the water falling above it 'them and return it towards a lower tray or walls in the form of water curtains, these trays being arranged so as to delimit between themselves, with the walls and with the water curtains a succession of superimposed rooms through which pass gas.

 Thus, the trays used in the present invention are intended to collect all or part of the water falling above them, originating either from the spraying or from the upper tray, and to return this water to the lower part under form of curtains.

 Each curtain thus forms, flowing from one plate to another or from one plate to the walls, a continuous surface between the walls, or in the case of cylindrical devices, a surface of revolution around the axis of the tower.

 The entire space of the tower is then divided by the trays and the curtains into a number of gas chambers through which the gases pass successively and whose temperature and partial pressure of water vapor can vary by l to one another.

 The tower can be likened to a set of successive exchangers or, with the leaks near the curtains, different equilibria are established on the different floors.

The exchanger according to the present invention has, compared to an ordinary exchanger, the following advantages: - It is comparable to several simple exchangers my
tees in series. So we can get an excellent cross
temperatures of the two fluids. We can thus
obtain a higher heated water temperature
at the outlet temperature of the cooled gases (which
is not possible with an ordinary exchanger or
only gets one pressure and time balance
temperature.

Its size is reduced, much smaller than that
an exchanger of the same power or equal performance.

The circulation of fluids occurs naturally in
the body of the device: by gravity for water, by
draft for gases. Pumping costs for water
are therefore limited to the pressurization necessary to
the upper sprinklers (while in the appliances
in series, water must be pumped between each pass).

Similarly, the pressure drops at the gas level
are limited to crossing water curtains and
upper cones of water spray.

This low pressure drop (of the order of 100
pascals) allows in most cases to place these
recuperators behind classi thermal appliances
ques (boilers, ovens, internal combustion engines)
without having to change the means of circulating the gases.

The natural upward circulation of gases allows
this power exchanger can be considered a sim
chimney element when water circulation is
arrested
This provision is particularly used
when the gases to be treated contain solu elements
in the water and give corrosive products. he
stop the water to avoid the risks
corrosion.

So, on boilers with mixed burners
natural gas-fuel oil: in normal gas operation
natural, recovery is used. On the march from
oil rescue, the water circulator is stopped
to avoid the creation of sulfuric acid in water
from fuel sulfur.

The exchanger can therefore be placed behind any
mixed boiler without the need for a bypass with all the disadvantages that this additional equipment entails.

 In an advantageous embodiment of the present invention, the trays have the shape of an inverted V and on the walls of an inverted half V and the trays of a stage are staggered relative to those of the stage superior.

 In addition, the water flow and the distance between the stages are advantageously adjusted in such a way that the trays on one floor receive the water curtains coming from the trays on an upper floor in the vicinity of their top, so as to use the maximum possible exchange surface.

 With the aim also of increasing the exchange surface, a circulation of water on the walls is advantageously provided either by a discontinuous welding of the trays in inverted half-V on the walls, or by means of trays in inverted half-V , welded to the walls and provided with buckets on their upper surface and holes creating water jets towards the walls.

 In addition, hot and humid gases are advantageously introduced into the lower part of the tower through openings arranged directly above each inverted V of the last lower plate.

Other characteristics and advantages of the present invention will appear during the description which follows, made with reference to the appended drawing in which:
Fig. 1 is a sectional view of an exchanger according to the present invention;
Fig.2 is a sectional view of a larger diameter exchanger according to the invention;
Figs. 3 to 5 are sectional views of variants of trays fixed to the walls.

 The exchanger shown in FIG. 1 comprises a vertical cylindrical tower 1 provided at its upper part with spraying booms 2 which spray water towards its lower part. Under these ramps, the tower 1 is provided with an upper central conical plate 3 whose point is directed upwards, a plate 4 welded to the walls of the tower constituted by a truncated cone whose point is directed towards the bottom and a central conical plate 5 identical to the plate 3. Under the plate 5 opens a horizontal duct 6 for supplying hot and humid gases. Under the conduit 6 for supplying the gases, there is a tank 7 for collecting water.

 The water to be heated which is sprayed by the ramps 2 is partly collected by the tray 3. The water flow is adjusted so that the water which flows on the tray 3 is returned in the form of a curtain of continuous water the upper part of the lower plate 4.

The water flows over this plateau which returns it in the form of a second continuous curtain towards the top of the lowest plateau. The tower is thus divided into four rooms separated by water curtains.

 The hot gases which come from the tube 6 pass successively through these four chambers. Four different equilibria are thus obtained, which makes it possible to obtain a temperature of the heated water which is higher than the temperature of the cooled gases leaving the tower.

 The exchanger shown in FIG. 2 is a cylindrical exchanger with a larger diameter than that shown in FIG. 1.

 I1 comprises a cylindrical tower 11 provided at its upper part with spraying booms 12 Under these booms, the tower 11 comprises an upper plate 13 whose surface is a surface generated by an inverted V rotating around the axis of the tower. On the floor immediately below the tower has two plates 14a and 14b The plate 14a welded to the walls of the tower is of the same type as the plate 4 welded to the walls of the tower 1 but of larger diameter and the plate 14b placed in the center is similar to the central plate 3 of tower 1.

The lower stage comprises a plate 15 similar to the plate 13.

 The sections of the plates 13, 14b and 15 are identical and the diameters of the plates 13 and 15 are such that the points of the intermediate plates 14a and 14b are equidistant from the points of the plates 13 and 15.

 Under the lower plate 15 is disposed a supply conduit 16 having at its lower part openings 16a and 16b arranged under the plate 15. Under this conduit is arranged u # n tray 17 for recovering water.

 The operation of this exchanger is similar to that shown in FIG. 1, the only difference being that double curtain surfaces are obtained per floor.

 It is clear that we can multiply the number of trays per floor and thus multiply the areas of water curtains crossed by the gases.

 The towers may not only have a cylindrical shape as shown in Figs. 1 and 2 but also a parallelepiped shape. In this case, the plates comprise flat surfaces having in section the: # same shape of inverted V as that represented in FIGS. 1 and 2 and which extend from a side wall to the opposite wall.

To improve the exchange surfaces between water and gases, the side plates such as plates 4 and 14a can be produced as shown in the
Fi.g. 3, 4 and 5.

 The. plate 21 shown in FIG. 3 has in section the shape of an inverted half V. It is welded discontinuously to the wall 22 to allow a partial flow of the water coming from the upper parts along the wall 22.

 The plate 23 shown in FIG. 4 has also in section the shape of an inverted half V. It is welded completely to the wall 22. At the bottom of its upper part is welded a vertical wall 24 forming a weir. The plate 23 and the wall 24 thus define a bucket. The tray is provided at the bottom of the bucket with holes 25 in the direction of the wall 22. The height of water above these holes makes it possible to obtain jets of water which come to cry out on the wall. 22; The rest of the water flows in the form of a curtain of water at the top of the wall 24.

 Alternatively as shown in FIG. 5, the wall 24 is provided at its lower part with slots 26 from which the water comes out, trickles over the lower part of the plate 23 and leaves this plate in the form of a curtain of water.

Claims (7)

- CLAIMS  1.- Heat exchanger comprising a tower in which circulate against the current, on the one hand, hot and humid gases entering the lower part of the tower, on the other hand, water droplets which are sprayed at the upper part of the tower, means for recovering the water at the lower part of the tower and means for filtering and then circulating the water to a use circuit, characterized in that the height of the tower between the spraying area and that of the hot gas inlet is divided into a number of superimposed stages separated by trays (3, 4, 5; 13, 14a, 14b, 15) intended to collect all or part water falling above them and returning it towards a lower plate or walls in the form of water curtains, these plates being arranged so as to delimit between them, with the walls and with the water curtains, a succession of superimposed chambers through which the gases pass.  2.- Heat exchanger according to claim 1, characterized in that the plates --have the shape of an inverted V (3, - 5; 13, 14b, 15) and on the walls of a half Inverted V (4, 14a) and the stages of a stage are staggered with respect to those of the upper stage.  3.- Heat exchanger according to claim 1 or 2, characterized in that the water flow and the distance between the floors are adjusted so that the trays of a floor receive the water curtains from the trays d 'an upper floor near their summit.  4.- Heat exchanger according to any one of the preceding claims, characterized in that it comprises a circulation of water on the walls.  5. Heat exchanger according to claim 4, characterized in that the circulation of water on the walls is obtained by a discontinuous welding of the plates (21) in half V reversed on the walls.  6.- Heat exchanger according to claim 4, characterized in that the circulation of water on the walls is obtained by plates (23) in inverted half V welded to the walls and provided with buckets on their upper surface and holes ( 25) creating water jets towards the walls.  7.- Heat exchanger according to claim 2 ourla claim 3, characterized in that the lower gas inlet is through openings arranged in line with each inverted V of the last lower plate.