EP0403326B1 - Warm water storage heater and installation equipped with such a storage heater - Google Patents

Abstract

The invention concerns an installation for the distribution of hot water comprising a tank (1) fitted with a cold-water inlet pipe (2) emerging into the lower section, with a hot-water outlet pipe (3) opening into the top section and with a third pipe (9) opening at an intermediate level and intended for the heating and reheating of the tank, the said third pipe (9) being connected in series with the secondary (102) of a heat exchanger (10), the primary (101) of which is a heat source, and with a circulating pump (11) causing the water to circulate in the direction of the tank, the upstream end of this third pipe (9) being connected at (P) to the cold-water inlet pipe (2). <IMAGE>

Description

The invention relates to a hot water distribution installation comprising a hot water tank, that is to say a closed tank capable of containing, for the purpose of storing the corresponding calories, a body of water. hot under pressure intended in particular for sanitary drawing, the volume of this mass generally being of the order of a hundred liters and its temperature generally being between 50 and 80 ° C.

In known embodiments, the balloons of the kind in question are served by two tubes, one of which, assigned to the intake and supplied by a network of pressurized cold water, opens into the lower part while the other , assigned to the drawing and connected to at least one hot water distribution tap, opens in the upper part.

Any opening of the tap results in a distribution of hot water drawn from the upper part of the tank, the volume of water withdrawn being automatically compensated by admission of an equivalent volume of cold water under pressure in the lower part of the tank.

The calories necessary for heating the water contained in the flask, at least for the most part, are generally supplied to it by an independent closed water circuit comprising in series a coil embedded in the flask, a pump circulation and a heat exchanger associated with a heat source such as the burner of a boiler

The coil in question is relatively expensive and the efficiency of the heat exchange which it makes possible is low.

To remedy these drawbacks, we have already proposed, in a solar heating installation equipped with a balloon of the kind defined above, to remove the coil embedded in the balloon, the two ends, of the heating pipes, which were previously connected to the two ends of this coil, then opening directly into the balloon.

This solution leads to a more favorable thermal balance than the previous ones.

However, it still has the drawback of requiring the use of four separate connections sealingly passing through the wall of the balloon for, respectively, the four tubes serving the balloon in cold water and in hot water.

To reduce this drawback, it has already been proposed to limit the number of the above connections to three.

But in the embodiments proposed for such installations (see document DD-A-239 844) the heating or reheating of the tank is relatively slow when the two operations of drawing and reheating the tank are simultaneous, that is to say - say when hot water is drawn up during a period of reheating of the tank.

The invention makes it possible, above all, to eliminate this drawback.

To this end, hot water distribution installations of the type in question according to the invention are characterized by all of the following provisions: they comprise a hot water tank equipped in total with three water supply tubes, namely a first tube connected to the cold pressurized water inlet and opening into the lower part of the tank, a second hot water withdrawal tube opening into the upper part and a third heating tube opening into the tank lower than the tube sampling, this third tube being mounted in series with the secondary of a heat exchanger and with a circulation pump mounted so as to drive the water towards the balloon, the upstream end of this third tube being connected to the first tube, and a non-return member being mounted on the section, from the first tube, included between the mouth of this tube in the balloon and the point of connection to said tube of the upstream end of the third tube, in a direction such that this section can only be traversed by water leaving the balloon.

In preferred embodiments, in addition, the end of the third tube which opens into the balloon is plugged at the end and hollowed out from lateral slits whose width is greater than the mutual spacing.

The invention includes, apart from these main provisions, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.

In what follows, we will describe preferred embodiments of the invention with reference to the accompanying drawing in a manner of course not limiting.

Figure 1 of this drawing shows very schematically a domestic hot water drawing installation comprising a tank and established in accordance with the invention, this installation being shown during a period of heating the tank without drawing.

Figure 2 similarly shows in Figure 1 a portion of the same installation, shown when drawing hot water without heating the tank.

Figure 3 shows a detail of said balloon.

In a manner known per se, the tank 1 is arranged so as to contain a mass of hot water under pressure while retaining the calories of this mass by appropriate thermal insulation, the volume of said mass being for example hundred order liters.

The tank 1 is equipped with a first tube 2 opening into its lower part and a second tube 3 for drawing hot water opening into its upper part.

The end, of the tube 2, furthest from the tank 1, is connected, by means of a safety group 4, to a network 5 of cold pressurized water distribution.

The downstream end of the tube 3 is connected to a tap 6.

There is also an aquastat 7 associated with an operating circuit 8 capable of controlling the heating of the water contained in the tank as soon as the temperature of this water to a predetermined level drops below a predetermined threshold.

In addition, a third tube 9 is provided which opens into the balloon at an intermediate level thereof, but generally fairly close to the bottom of the balloon: this level is therefore generally located at a vertical distance H of between 0 and 200 mm above the average level of the mouth of the tube 2, for a cylindrical balloon whose diameter is between 400 and 500 mm.

The continuous flow path defined in part by said tube 9 for the heating water of the tank successively passes through a heat exchanger 10, constituting by itself the secondary 10₂ of this exchanger, and a circulation pump 11 connected so to send the water to the balloon.

The upstream end of the tube 9 is connected to the tube 2 at a point P thereof which is arranged downstream of the safety group 4, generally below the balloon 1.

The heat exchanger 10 could be directly the heating body of a boiler, the primary of this exchanger then being formed by the various passages offered to the hot gas originating from the combustion of an appropriate fuel.

In the preferred embodiment illustrated, this exchanger 10 is an exchanger with good thermal efficiency, the primary 10₁ of which is mounted in series with the exchanger 12 of a boiler 13 such as that which has just been defined and forms a closed circuit. with the latter and with a second circulation pump 15.

As for circuit 14, it advantageously forms the "short" loop of a mixed heating installation, that is to say provided to provide both central heating by circulation of hot water in radiators and the drawing of 'sanitary water, the "long" loop 16 of this installation, fitted with radiators 17, being mounted in parallel on the loop 14 and the tilting of one of these two loops to the other being automatically controlled by a three-way valve tracks 18.

Is further mounted on the section, of the tube 2 between the point p and the mouth of this tube in the balloon 1, a non-return member 21 oriented so as to make the circulation of water possible in said section only in the direction coming out of the balloon.

This member 21 can be placed on the mouth of the tube 2.

The operation of the installation described above is as follows.

At start-up, the temperature of the water contained in the tank is cold, that is to say lower than the setpoint to which the operating circuit 8 is controlled.

This circuit is therefore excited, which has the effect of simultaneously driving the two pumps 11 and 15 by placing the valve 18 in its position corresponding to the "drawing", that is to say the communication of the " short loop "14 with the exchanger 12 of the boiler.

The drive of the pump 15 has the effect of igniting the burner 19 of the boiler 13, which heats the water in the loop 14 as well as the exchanger 10.

The driving of the pump 11 has the effect of circulating the water in the closed circuit comprising in series the tube 9 (and therefore said pump 11 and the secondary 10₂ of the exchanger 10), the bottom portion of the tank 1 and the section of the tube 2, between point P and the end, of the said tube, opening into the balloon.

The water in question is drawn off in the coldest bottom zone of the tank 1, then it is reheated in the exchanger 10 and thus reintroduced reheated in the tank from the downstream end of the tube 9.

This operation in the tank heating mode continues until the temperature detected by the aquastat 7 reaches a given threshold and, from this instant, the circuit 8 controls the stopping of the pump 11 as well as that of the pump 15 if the latter is not otherwise requested.

Therefore, to draw hot water, simply open the tap 6.

Such drawing of hot water through the tube 3 is immediately compensated for by introducing an identical volume of cold water into the tank through the tube 9.

The two operations which have just been described most often occur at separate times since, on the one hand, the respective durations of the drawing-off and reheating periods are in practice relatively short and do not overlap and that, d on the other hand, the volume of hot water permanently available at the top of the tank is generally sufficient to meet the different hot water needs of the users of the installation.

However, the two operations indicated, corresponding respectively to hot water drawing and to reheating of the water in the flask, can be perfectly combined.

In all cases, the presence of the non-return member 21 on the tube 2 forces the entire volume of cold water admitted into the tank 1 from the network 5 to pass through the exchanger 10: the response times of the installation for heating the water is therefore always reduced to a minimum.

To avoid as much as possible disturbing, by the admissions of water heated in the balloon, the thermal stratification naturally created in the volume of water of this balloon, the downstream end of the tube 9 is advantageously arranged so that the water leaving through this end is distributed in horizontal directions as represented by arrows G in FIG. 1.

For this purpose, for example, said end is plugged axially and horizontal slots 20 as radially visible in FIG. 3 are hollowed out radially in its side wall.

These slots 20 advantageously have a width l greater than their mutual spacing e , so as to reduce the speed of exit of the heating water: the respective values of these two dimensions are for example 2 and 1.5 mm for a diameter of tube 9 of the order of 15 to 18 mm.

A construction with horizontal slits can also be adopted with advantage at the end of the tube 2 which opens into the balloon: this is what is indicated by the arrows F in FIG. 1. In such a case, the relationship between the lengths and gap spacing is generally reversed from that explained above.

As a result of which, and whatever the embodiment adopted, there is finally a hot water distribution system with balloon whose constitution and operation result sufficiently from the above.

• le nombre des tubes desservant le ballon en eau est réduit de quatre à trois, ce qui réduit semblablement le nombre des traversées étanches de la paroi (généralement inférieure) dudit ballon par lesdits tubes,
• la vitesse de réchauffage du ballon est maximum dans tous les cas de fonctionnement,
• le ballon est dépourvu du serpentin habituel,
• le rendement thermique global de l'installation est excellent du fait que l'on peut choisir pour l'échangeur thermique une construction à rendement thermique très élevé, ce rendement étant nettement supérieur à celui de l'échange thermique réalisé entre l'eau d'un ballon et l'eau qui circule dans un serpentin immergé dans ce ballon : c'est ainsi que, si l'on considère une installation de distribution d'eau chaude comprenant un ballon et une chaudière dont la puissance thermique est de l'ordre de 22 kW, il est possible de récupérer une puissance thermique de l'ordre de 15 kW avec la solution préconisée ci-dessus -correspondant à un débit d'eau de réchauffage compris entre 500 et 800 l/h lorsque la pompe 11 est excitée-, alors qu'il est difficile de récupérer plus de 7 kW avec les constructions antérieurement proposées.

This installation has many advantages over those previously known and in particular the following:

• the number of tubes serving the water balloon is reduced from four to three, which likewise reduces the number of watertight crossings of the wall (generally lower) of said balloon by said tubes,
• the speed of reheating of the tank is maximum in all operating cases,
• the balloon is devoid of the usual coil,
• the overall thermal efficiency of the installation is excellent because it is possible to choose a construction with a very high thermal efficiency for the heat exchanger, this efficiency being much higher than that of the heat exchange carried out between the water a tank and the water flowing in a coil submerged in this tank: this is how, if we consider a hot water distribution system comprising a tank and a boiler whose thermal power is around of 22 kW, it is possible to recover a thermal power of the order of 15 kW with the solution recommended above - corresponding to a flow rate of heating water of between 500 and 800 l / h when the pump 11 is energized -, while it is difficult to recover more than 7 kW with the constructions previously proposed.

Claims (2)

1. Hot water distribution installation comprising a hot water tank (1) equipped with a total of three water serving tubes, namely a first tube (2) connected to the pressurized cold water intake (4,5) and opening into the low part of the tank, a second tube (3) for drawing off hot water opening into the top part and a third heating tube (9) opening into the tank lower than the drawing off tube, this third tube being mounted in series with the secondary (10₂) of a heat exchanger and with a circulating pump (11) causing the water to flow in the direction of the tank (1), the upstream end of this third tube (9) being connected (at P) to the first tube (2), and a non-return member (21) being mounted on the section, of the first tube (2), comprised between the mouth of this tube in the tank (1) and the point (P) at which the uspstream end of the third tube (9) is connected to said tube, in a direction such that this section can only have flowing therethrough the water leaving the tank.
2. Hot water distribution installation according to claim 1, characterized in that the end of the third tube (9) which opens into the tank is stopped at the end and formed with lateral slits (20) whose width (l) is greater than the mutual spacing (e).

Images