EP0870998A1 - Boiler with return water injection in the lower part of the heat exchanger - Google Patents

Abstract

A water heater (1) has an outlet (9) for the heated water feed at the top and an intake (10) for a return flow feed at the bottom. The return flow feed is connected to an injection tube (13) with a closed end (17) and a series of orifices all facing in the same direction, so that the water returning to the heater at low temperature is mixed with the reheated water inside it. The injection tube orifices are equipped with nozzles which are positioned to direct jets of water along rising channels (2-6) at the back or front of the heater. In addition the channels can have restrictions at their lower ends to give an increased Venturi effect from the return flow nozzles.

Description

The present invention relates to a boiler with low water injection back into the heater.

Current heating systems central by heat transfer fluid operate mostly at lower temperatures than old.

This state is the consequence of several factors.

First the losses linked to distribution are directly proportional to the temperature of the coolant. To reduce losses, it should operate at a lower temperature.

Then, the insulation of the dwellings allows to operate at a lower temperature while keeping an impression of comfort.

Finally, the installation and use more frequent underfloor heating has changed the design of facilities and their level of operation with regard to the temperatures of the coolant.

This request brought the manufacturers of boilers to modify their product to make it compatible and resistant for this operating mode at lower return water temperatures, generally between 25 ° C and 40 ° C.

These temperatures cool the walls of the combustion chamber and sometimes products of combustion condense on the walls of this combustion chamber causing acceleration of the corrosion of the heating body.

The object of the present invention is to limit these condensations while allowing a lowering sensitive return water temperatures and this in inducing inside and around each exchanger from the hearth a rotating homogenization current with water being reheated. So the water in contact with the walls of the hearth is at a temperature higher than that entering the boiler in from the return circuit.

To this end, the invention relates to a boiler whose heating body partially has upper hot water outlet constituting the departure for the heating circuit and its part lower water inlet at lower temperature for the return of water from the heating circuit characterized in that the lower part of the heater a hollow longitudinal injection tube developing over the entire length of the body from the return port of the body heats up to the opposite end of this heating body, said tube receiving the return water has on the one hand a closed rear end and a front end mounted on the return port and on the other hand a plurality of injection nozzles directed on the same side to generate a current turn intended to mix and homogenize the water of incoming return at low temperature with ambient water already reheated or in the process of reheating.

The absence of corrosion and the possibility of operation without loss of reliability at lower return water temperatures constitute the main advantages of the invention.

• la figure 1, une vue en coupe d'un échangeur asymétrique d'un corps de chauffe d'une chaudière sectionnable, les flèches montrant la circulation de l'eau à l'intérieur de l'échangeur ;
• la figure 2, une vue en coupe d'un échangeur symétrique d'un corps de chauffe d'une chaudière sectionnable, les flèches montrant la circulation de l'eau à l'intérieur de l'échangeur ;
• la figure 3, une vue agrandie de la zone d'injection dans le cas de l'échangeur asymétrique ;
• la figure 4, une vue agrandie de la zone d'injection dans le cas de l'échangeur symétrique ;
• la figure 5, une coupe schématique en long d'un corps de chauffe sectionnable d'une chaudière équipée des moyens d'injection selon l'invention ;
• la figure 6, une coupe schématique en long d'un corps de chauffe monobloc d'une chaudière équipée des moyens d'injection selon l'invention.

Other characteristics and advantages of the invention will appear in the description which follows, given by way of example and accompanied by the drawings which represent:

• Figure 1, a sectional view of an asymmetric exchanger of a heating body of a sectionalized boiler, the arrows showing the circulation of water inside the exchanger;
• FIG. 2, a sectional view of a symmetrical exchanger of a heating body of a sectionable boiler, the arrows showing the circulation of water inside the exchanger;
• FIG. 3, an enlarged view of the injection zone in the case of the asymmetric exchanger;
• FIG. 4, an enlarged view of the injection zone in the case of the symmetrical exchanger;
• Figure 5, a schematic section along a sectionable heating body of a boiler equipped with injection means according to the invention;
• Figure 6, a schematic section along a one-piece heating body of a boiler equipped with injection means according to the invention.

The invention proceeds from the general idea inventive which consists in creating a circulation of water asymmetrical in the boiler to bring back a part hot water from the top to the bottom that comes mix with the return water. This general function is obtained by injecting the water back in one direction suitable for the base of each exchanger element.

The invention mainly applies but not exclusively for sectional boilers, i.e. to those comprising a heating body 1 formed heat exchanger elements such as 2, 3, 4, 5, 6 including a front heat exchanger element 2 and a rear facade exchanger element 6, for example in cast iron, joined together in juxtaposition longitudinal by means of hydraulic connections 7 using junction pieces called nipples such as 8.

The heating body conventionally presents, a hot water outlet 9 called outlet at the orifice top of the last exchanger element 6 and a water inlet cold 10 called return to the bottom port of the same last exchanger element 6.

Output 9 and input 10 are connected hydraulically to a water distribution circuit heated by a heat source burning a fuel in a fireplace 11.

Under certain conditions, the water returned to low installation temperature can cause formation in the rear exchanger element of a zone condensation at the water injection back and to the foyer level.

It is known that this condensation zone causes corrosion which leads to reduction notable in the lifetime of the last exchanger element and, starting from the entire heating body of the boiler.

Now, it turns out to be desirable and interesting, for all the reasons stated above, to operate with the lowest return water temperatures possible.

The present invention allows for a boiler formed by a plurality of exchanger elements, and more generally for a heating body any 12 (Figure 6), accept temperatures particularly low return water located by example between 40 ° C and 25 ° C, i.e. use water at direct return temperatures of the circuits heating by radiators, but also and above all direct return of the meanders of the heating ducts by the ground that operate at low temperatures because intended to establish a basic ambient temperature low.

An embodiment will be described below. of the invention with reference to the figures of the drawings. he it is understood that the scope of the invention extends in particular to boilers with heating bodies 12 no sectionable as shown in Figure 6.

We mount from the front or from the back of the boiler in the channel represented by the alignment of underpasses of the exchanger elements a tube longitudinal hollow injector-distributor 13 which preferably extends over the entire length of the heating body 12. This injector-distributor tube 13 is of sufficiently small cross-section than that of low orifices such as 14.15 of the exchanger elements to allow good water circulation on the part and other of these heat exchangers. The tube injector-distributor 13 arises at the level of the bottom orifice of the last exchanger receiving on input 10 the connection of the return circuit. he includes, for example at this level, a flare or a flange or any other means allowing its end 16 to occupy the entire section of this connection and therefore to receive the entire flow of return liquid. The tube injector-distributor 13 is for example closed or with a restriction that is to say a passage to lower section at its other end 17 opposite to its entry into the heating body of the boiler.

Of course, mounting or configuration reverse may exist namely an entry into the body boiler heating from the front of this last.

This injector-distributor tube 13 comprises at right of each lower chamber 18 of each exchanger delimited by the lower orifices 14 and 15 at least one outlet 19 for example equipped an outlet nozzle. The orifice (s) 19 are located on the same side of the exchanger element, by example the one on the right side in Figures 1 and 2. These nozzles are intended for injecting and diffusing water back to the very base of each of the elements exchangers.

These nozzles are preferably oriented so as to direct the injection jet in the direction general of the uplink channel (s) such as 20 delimited by the walls immediately adjacent to ports 14 and 15. The nozzle outlet sections are determined based on the power of the boiler, the number of heat exchangers and return and departure water temperatures.

The injector-distributor tube 13 forms a real injection ramp through which preferably all of the return water.

Depending on the type and geometry of the exchangers, the inner conformation of this lower part differs. There are shown in Figures 1 and 2 two basic variants of exchanger elements, on the one hand asymmetrical, and on the other hand symmetrical.

It is first of all asymmetric exchangers such as 21 with throttling zone 22 (FIGS. 1 and 3), that is to say those whose internal conformation has a rising channel at the right of the orifices, the interior volume has a throttle 23 by the approximation of the walls. This conformation comes from also of its general exterior form.

We will preferably choose the volume along which naturally propagates the rising flow. he in the case of this type of exchanger element rising volume defining channel 20 on the right in Figures 1 and 3. As shown, this volume present for mechanical and foundry requirements a constriction 23 constituting the adapted conformation to achieve the conditions for a Venturi effect. There where the nozzles of the orifices 19 is or are directed from so as to be centered in relation to these forms for benefit from the Venturi effect, that is to say in the middle zone of the ascending channel 20 inside the exchanger element. This results in an acceleration local water speed and a consecutive call of water favoring the circulation of water in the direction arrows.

Due to the rotating movement of the water thus generated within each exchanger element, the water hot from the top of the heat exchanger element is driven down by a call depression. This movement, indicated by arrows in Figures 1 and 3, presents a certain force allowing homogenization to be done quickly. Cold water return is no longer in direct contact with adjacent walls because injected into the center of the canal amount 20 opening at the bottom of each element exchanger but quickly mixed with water already hot.

We understand the interest of the invention which avoids walls near the return water inlet to be subjected to a temperature favoring the condensation and therefore corrosion of the adjacent area of the outer wall of the exchanger. Lifetime of the exchanger is thus increased and it is possible without fear of operating the installation at lower return temperatures and therefore improve its performance.

They can also be so-called exchangers symmetrical 24 (Figures 2 and 4) according to which it there are two identical channels on either side of low orifices of the same exchanger element. In that case, we will create asymmetric water circulation by a injection nozzle directed upward towards the upstream channel 20 adjacent to the same side of the exchanger, for example the right side as shown in Figures 2 and 4.

Unilateral injection generates movement turning of the water represented by the arrows on the Figures 2 and 4 and a homogenization effect allowing cold water to mix quickly with water room and warm up enough to avoid the aforementioned drawbacks.

If necessary, to further increase the homogenization effect, we can predict neighborhood of each nozzle a second nozzle slightly offset in orientation with respect to the first.

As shown in Figure 6, this invention also applies to form boilers 12 different heaters, for example those in steel. For these boilers, the heating body 12 is no longer formed by the juxtaposition of elements successive exchangers but by an interior volume free or divided by total intermediate walls or partial.

The punctual injection of return water by a lower inner tube with orifices fitted with nozzles forming an injection rail also allows obtain sufficient vacuum for these boilers for the desired effect, namely the creation of a rotating current.

All advantages for this type of boiler above are also retained.

Claims (13)

Boiler with heating body has a water outlet (9) at the top warmed up constituting the start of the heating and at its bottom an entry (10) of water to be heated from the return of water from the heating circuit characterized in that one provides a hollow longitudinal injection tube (13) developing at the bottom on substantially the the entire length of the heater from the water return port to the heater to the level of the opposite low end of this heating body, and in that said hollow tube injection (13) which receives the return water from the circuit on the one hand has a first end obstructed or weakly passing and a second end mounted on and in communication with the inlet (10) of water to be heated and on the other hand a plurality orifices (19) directed on the same side to generate in each exchanger and therefore in the heating body from the boiler a rotating current intended to mix return water entering the boiler at low temperature with the ambient water inside the boiler already reheated or in the process of reheating and to homogenize the entire volume of water inside the boiler. Boiler according to claim 1, characterized in that all the return water arrives in the heating body via the tube injection (13). Boiler according to claim 1 or 2 characterized in that the orifices (19) are fitted nozzles. Boiler according to claim previous characterized in that the nozzles are oriented so as to direct the injection jet into the general direction of the ascending channel (s) (20) immediately delimited by the walls adjacent to the lower orifices (14) and (15) of the heat exchangers. Boiler according to any one of previous claims characterized in that the injection tube (13) has at each nozzle a second nozzle directed in a slightly direction different. Boiler according to any one of previous claims characterized in that the injection tube (13) is supplied with water to be heated by the water circuit returning to the boiler by the rear face of the rear exchanger thereof. Boiler according to any one of previous claims 1 to 5 characterized in that the injection tube (13) is supplied with water to warm up by the water circuit returning to the boiler by the front face of the exchanger before the latter. Boiler according to any one of previous claims, characterized in that the heating element is made up of heat exchanger elements heat assembled in longitudinal juxtaposition and having in the upper part of an exchanger end a hot water outlet and partly lower rear end exchanger one return of water to be heated, each heat exchanger element having lower openings (14) and (15) delimiting between them an open lower chamber (18), the heat exchanger elements being through the lower part by the injection tube (13) through the lower holes (14) and (15). Boiler according to any one of previous claims characterized in that the or the heat exchangers is or are asymmetrical and present (s) near its or their entrance lower a constriction (23) leading to a channel upright (20) and in that the orifice (s) of the orifices (19) is or are directed so as to be centered with respect to the forms defining the constriction (23) to benefit from the Venturi effect, that is to say in the middle zone of the rising channel (20) inside the heat exchanger element. Boiler according to claim 8, characterized in that the exchanger element is symmetrical and in that the injection tube (13) passes through each open lower chamber (18) located between two lower orifices (14) and (15) of each heat exchanger. Boiler according to claim previous, characterized in that the injection nozzle that the injection tube (13) has is directed along a median zone of the adjacent rising channel (20). Boiler according to any one of claims 1 to 7 characterized in that the body of boiler heating is in one piece and in that the injection tube (13) runs along the middle lower. Boiler according to claim previous, characterized in that the heater presents interior partitions delimiting rooms partially open and in that at least a nozzle is present at the right of each room.

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