FR2742214A1 - APPARATUS FOR GENERATING DOMESTIC HOT WATER AND CENTRAL HEATING WATER - Google Patents

Abstract

It is a domestic hot water generating device implementing the combustion of a gas and comprising a closed water circuit (6) called "domestic heating" itself comprising a circulation pump (5 ), a pipe (4) associated with a gas burner (3) in a combustion chamber (2) and forming with this burner a main exchanger, and the primary of an auxiliary heat exchanger (E) and a circuit of drawing water (9) comprising a cold water inlet (7), the secondary of the auxiliary heat exchanger and a drawing outlet (8), the auxiliary heat exchanger comprising a reduced capacity tank (10) in series with a direct counter-current exchanger (14). The direct exchanger is mounted downstream with respect to the tank on the domestic heating circuit (6) and upstream with respect to the tank on the drawing circuit (9).

Description

The invention relates to domestic hot water generators

using combustion

of a gas.

  It is more particularly aimed, among these devices, at those known as "mixed", which also make it possible to supply hot water to a central heating circuit and which comprise: - a closed water circuit called "sanitary reheating" comprising itself even a circulation pump, a pipe associated with a gas burner in a combustion chamber and forming with this burner a main exchanger, and the primary of an auxiliary heat exchanger, - a water draw-off circuit comprising an inlet for cold water, the secondary of the auxiliary heat exchanger and a draw-off outlet, - and a central heating circuit mounted in parallel on the section, of the closed circuit, comprising the pump and the pipe, the connection of one end of said central heating circuit with said section being

  performed by a three-way valve.

  With such a mixed appliance, the water which circulates in the central heating circuit is also allowed to circulate in the sanitary heating circuit and it is therefore advisable that the drawing circuit is separated from this double circuit, which avoids any pollution of the water

drawn.

  In the usual embodiments of devices of the kind in question, any drawing of hot water,

  triggered by the opening of a tap connected to the outside

  downstream of the draw-off outlet, results in the following operations: excitation of the pump, ignition of the burner, heating of the water circulating in the domestic heating circuit and transfer of the calories of this water to the circuit water from the auxiliary exchanger. This process is not instantaneous so that the drawn water is not hot from the start: the user must first run a significant flow of water before

  that it doesn't get really hot.

  This drawback is important for draws requiring only a small flow of hot water: it is even common that, for such draws, the user is satisfied ultimately with cold or lukewarm water withdrawn during the first seconds of its drawdown, which reduces interest

of the installation.

  To remedy this drawback, it has already been proposed to make the auxiliary heat exchanger understand a balloon of limited capacity filled with sanitary water to be drawn, the temperature of this water being maintained at a value corresponding to the desired drawing, for example of the order of 60 degrees, said balloon being

  crossed by a section of the sanitary heating circuit

  re. Such a solution is advantageous in that the water drawn from the tank is quickly available to

  the relatively high temperature desired for it.

  However, this solution has the following drawback: the temperature of the drawn water drops sharply after distribution of the entire volume contained in the tank at the start of the drawing, so that the capacity of this tank must be relatively large, and typically higher. to 10 liters, to satisfy the

majority of said drawings.

  To remedy this drawback further, and therefore

  ability to reduce balloon capacity to lower volume

  laughing at 10 liters, it has been proposed to make the auxiliary heat exchanger understand, in addition to the balloon and in series with it, a direct exchanger comprising two

  sections belonging respectively to the heating circuit

  sanitary sanitation and the draw-off circuit, sections

  mutual thermal contact against the current.

  This improved solution is not without merit.

  rêt. However, in the embodiments which have been proposed for this, the direct exchanger was placed, - on the one hand, in the sanitary heating circuit, upstream of the tank, - and, on the other hand, in the circuit of drawing,

downstream of this balloon.

  Such a construction has a number of drawbacks, and in particular the following:

  - the section, of the direct exchanger, which appears

  relates to the domestic heating circuit, receives direct

  ment the very hot water leaving the main exchanger, which risks scaling it, especially if it is a compact construction device, - during a drawing, the sanitary water circulating in this direct exchanger after having been preheated while crossing the tank risks being overheated and therefore burning the user, - the water which reaches the tank coming from the main exchanger always starts by giving off calories in the direct exchanger , even during periods when this exchanger is not useful, know outside of the drawing periods and at the start of each drawing, - cold water from outside is

  always directly introduced into the ball without pre-

  heating, which can cause

unwanted "cold trains".

  The invention aims, among other things, to remove

these latter drawbacks.

  To this end, the devices for generating domestic hot water of the type in question according to the invention also include, to ensure the heat exchange between the domestic heating circuit and the drawing circuit, a cylinder of reduced capacity in series with a

  direct countercurrent exchanger and they are essential-

  characterized in that the direct exchanger is mounted downstream relative to the tank on the domestic heating circuit and upstream relative to the tank on the

drawing circuit.

  In preferred embodiments, recourse is also had to one and / or the other of the following arrangements: - the volume of the tank is of the order of 6 liters, - the direct exchanger against the current is of a compact plate type, - the direct counter-current exchanger is embedded inside the tank, - the generating device includes a flow meter mounted on the drawing circuit, a temperature probe placed inside of the balloon and of the means subject to the crossing down of a set point by the water temperature detected by this probe so as to start the burner at its maximum speed or at a reduced speed depending on whether a threshold of setpoint is then

  whether or not exceeded by the water flow detected by the flow

be,

  - the generating device according to the preceding paragraph

  tooth includes a second temperature probe disposed on the drawing-off circuit at the outlet of the direct exchanger and associated with the above servo means so as to further use, for the start-up of the burner, the crossings towards the bottom of a second threshold

  setpoint by the water temperatures it detects.

  The invention comprises, apart from these arrangements

  main provisions, certain other provisions which are preferably used at the same time and which will be

  more explicitly question below.

  In the following, a preferred embodiment of the invention will be described with reference to

  drawing attached in a way of course not limited to

tive.

  Figure 1 of this drawing represents schematically-

  ment a mixed water heating device according to the invention usable both for drawing domestic hot water and for supplying a closed central heating circuit, as well as the associated installation

to this device.

  Figure 2 is a perspective view of a

portion of such a device.

  In a manner known per se, the heating device considered comprises, integrated inside the same casing 1: - a calorie generator itself comprising, in a combustion chamber 2, a gas burner 3 and a pipe 4 exposed to the flames and / or to the hot gases generated by the burner, pipe intended to be traversed by the water to be heated and constituting with the burner a main heat exchanger, - a circulation pump 5 connected to the pipe 4, - a section of pipe 6 forming with the

  tubing 4 and the pump 5 a closed circuit, called a heating

  sanitary fage, said section 6 constituting the primary of an auxiliary heat exchanger E, - and a drawing circuit comprising, between its cold water inlet 7 and a hot water outlet 8, a section 9 constituting the secondary of the auxiliary heat exchanger E. The invention relates essentially to the said auxiliary heat exchanger E. This exchanger E here comprises: - on the one hand, a small tank 10 capable of containing a reserve of domestic hot water of immediately reduced volume available for drawing, said tank being traversed by a loop 11 forming part of the section 6 and its interior volume, which forming part of the section 9, being connected at a low point 12 to the cold water inlet 7, and at a high point 13 from the hot water 8, - and on the other hand, a heat exchanger 14, called direct exchanger below, having a high volume heat exchange capacity, said exchanger preferably being of the plate type and cons twisted by two

  pipe portions 15 and 16 forming part respectively

  of the two sections 6 and 9 and brought into contact

mutual thermal against the current.

  The tank 10 and the direct exchanger 14 are mounted

in series as follows.

  Firstly, the two portions 11 and 15 of the section 6 of the domestic heating circuit 4, 5, 6 are crossed in this order by the water driven by the pump 5. Secondly, with regard to the section 9 of the

  drawing circuit, its two portions constituted respectively

  tively by the section 16 and by the volume inside the balloon 10 are crossed in this order by the drawing water. In other words, when the burner 3 is lit, the very hot water leaving the main exchanger 4 and circulating in the sanitary heating circuit first passes through the heating loop 11 of

  its balloon 10 before crossing the direct exchanger 14.

  As for the cold water introduced into the device, it always begins by passing through the direct exchanger

  14 before entering the ball 10.

  These traffic orders present certain

advantages explained below.

  We still see in Figure 1 several bodies or assemblies outside the envelope 1 and connected to

circuits described above.

  These are: - a pressurized cold water source 17 connected to the cold water inlet 7, - a draw-off tap 18 connected to the hot water outlet 8, - and a section of central heating circuit 19 comprising radiators 20 and mounted in parallel on the assembly constituted by the pipe 4 and by the pump 5, one of the connections of said section 19 with this assembly being produced by means of a valve three-way and two positions 21 for selectively connecting said assembly either to section 6 of domestic heating, or

  said central heating section 19.

  We also see in Figure 1 a valve

  safety 22 connected to the hot water outlet 8, a flow

  tre 23 mounted on the cold water inlet 7 and a

  temperature 24 mounted in the tank 10.

  The flow meter 23 and the probe 24 are respectively associated with means (not shown) making it possible to control the calorific power generated by the boiler 2-3-4 to the parameters (flow rates and temperatures)

that they detect.

  An advantageous mode of action of these means is as follows: crossing a given set point T downwards by the water temperature detected by the probe 24 results in the burner 3 starting up at its rate maximum or at a reduced rate (corresponding for example to a calorific power of the order of a third of the maximum power) depending on whether the water flow detected by the flow meter 23 or not exceeds a given setpoint threshold D. The operation of the installation is as follows. It is first assumed that the three-way valve 21 is arranged in the manner shown in FIG. 1, for which there is no request for

central heating.

  Initially, the draw-off valve 18 is closed,

  the burner 3 is off and the pump 5 is stopped.

  This initial state assumes that the water reserve R contained in the tank 10 is brought to a sufficient temperature, for example of the order of 60, to meet

  the needs for drawing domestic hot water.

  If, under these conditions, said temperature, detected at 24, passes below the predetermined setpoint T, this passage automatically triggers the excitation of the pump 5 and the ignition of the burner 3 at a reduced rate - corresponding for example to a gas flow of the order of a third of the maximum flow - which circulates hot water in the domestic heating circuit 4, 5, 6, until the temperature of the water reserve R has again reached the desired value, which automatically results in a new stop of the pump 5 and in a new extinction of the

burner 3.

  If a user wishes to draw hot water

  sanitary, he just has to open the tap 18.

  This opening has no consequence as long as the water temperature detected by the probe 24 remains above the set point T: the hot water coming from the reserve R is then drawn and is replaced as

  and gradually with cold water so that the temperature

  ture of this reserve gradually decreases.

  It is only when said temperature drops below the set point T that the excitation of the pump 5 is triggered, as well as an ignition of the burner 3 at a speed which depends on the draw-off rate, the calorific power generated by the burner being maximum or on the contrary reduced depending on whether the threshold D is then exceeded

or not by said flow of the drawing.

  Said ignition, as well as the circulation of hot water in the domestic heating circuit, are

  then maintained for the duration of the relevant drawdown

re.

  This is where the direct exchanger 14 comes in.

  In fact, the drawing-off water begins by passing through this exchanger before reaching the tank 10 and, given the relatively high temperature of the reheating water which passes through the portion 15 of said direct exchanger, the drawing-off water which passes through the portion 16 of said exchanger is itself heated before reaching the tank 10: its introduction into this tank therefore does not substantially cool the water in the reserve R of said tank and the temperature of the water drawn can then remain at a

  sufficient value during all heating, and even

  beyond the duration corresponding to a total distribution of the volume of reserve R. In other words, this installation has both one of the essential advantages of the installations

  equipped with large hot water tanks, find out the availability

  immediate bility of hot water from the start of each drawing, and this without the drawback of said installations due to the size and price of such a large balloon. In addition, due to the judicious order adopted for the series connections of the tank 10 and of the direct exchanger 14, the following advantages are observed: - the heating water which circulates in the primary 15 of said exchanger 14 does not penetrate in this primary only after having crossed the loop II for reheating the balloon 10 and is therefore never brought to a very high temperature, which is to be avoided because of the risks of scaling of said primary 15, - the calories intended for heating of the sanitary circuit and coming from the main exchanger 4, are, in all cases, distributed firstly to the tank 10, since the loop 11 is crossed by this water before the primary 15, which makes it possible to avoid any dispersion unnecessary calories in said primary, in

  particularly during the periods for which the exchange

  auxiliary pump 14 is not operated, as is the case outside the drawdowns or completely at the start of each drawdown, - because cold domestic water from the external network 17 enters the tank 10 only after having passed through the direct exchanger 14, the flow of this water which effectively enters the balloon is in

  already preheated, which minimizes intro

  duction of "cold trains" of water in the balloon, prejudicial

  targets of course for the temperature resistance of the water reserve R y contained therein, said location of the direct exchanger upstream of the tank on the sanitary circuit also eliminates the risks of overheating of the drawn water which could be observed when this location was combined with a direct heat exchanger assembly upstream of the tank

  on the domestic heating circuit.

  If the three-way valve 21 is put in its

  position other than that illustrated, for which the set

  ble 4-5 is connected to the central heating circuit 19, it is this circuit which is heated from the burner 3

  in any known desirable manner, provisional priorities

  res that can be automatically assigned to the service

  of the drawing circuit as required.

  The assembly of the auxiliary exchanger E, comprising in particular the tank 10 and the plate exchanger 14, can be assembled in a very small volume, for example at the base of the casing 1 of the calorie-generating device. An example of such an arrangement has been shown in FIG. 2 which has given all satisfaction, for which the balloon 10 has the general shape of a cylinder of revolution with a horizontal axis and is associated in a very small volume, not only with the direct exchanger 14, but also to the pump 5, to the valve 21 and to the various

  accessories and service pipes for the appliance.

  One of said accessories, visible at 25, is a flow safety device mounted just upstream of the pump 5, on the water intake section of this pump which receives both the water back from the circuit of heating 19 and that of the primary circuit 6 of the auxiliary exchanger E. We also see in Figure 2 the different

  pipe ends A, B, C and D which are to be connected

  der respectively: A with the outside cold water network 17, B with the taps 18,

  C with the start portion of the heating circuit

fage 19,

  D with the return portion of said circuit 19.

  These four ends A, B, C and D are aligned

  along the same horizontal line, above a location-

  intended to receive an appropriate connection strip (not shown) itself carried by the

housing 1.

  As a result of which, and whatever the embodiment adopted, there is finally a domestic hot water generator whose constitution, operation and advantages result sufficiently

of the above.

  As goes without saying, and as it already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all variants, in particular: - those where the relatively compact direct exchanger 14 would be immersed in the tank 10, - and those where the temperature probe 24 placed inside the tank 12 would be seconded by another temperature probe 26 placed on the drawing-off circuit at the outlet of the exchanger 14, in a location, of said drawing-off circuit, capable of both being continuously heated by the calories coming from the balloon and being cooled very shortly after the start of each drawing: this probe 26 is associated with the control means described above so as to trigger a reheating as soon as a second set point threshold T 'is crossed downwards by the temperature water detected by it, which makes it possible to reduce the response time of the installation due to the thermal inertia of the water reserve R contained in the tank; in such a case, it may be advantageous to slave the two setpoint thresholds T and T 'together so that the adjustment of one of the two automatically results in the correlative adjustment of

the other.

Claims (6)

  1. Domestic hot water generator of a "mixed" type using the combustion of a gas and comprising a closed water circuit (6) called "domestic heating" itself comprising a circulation pump (5), a pipe (4) associated with a gas burner (3) in a combustion chamber (2) and forming with this burner a main exchanger, and the primary of an auxiliary heat exchanger (E); a draw-off water circuit (9) comprising a cold water inlet (7), the secondary of the auxiliary heat exchanger and a draw-off outlet (8), the auxiliary heat exchanger comprising a tank of reduced capacity ( 10) in series with a direct counter-current exchanger (14); and a central heating circuit (19) mounted in parallel on the section, of the closed circuit (6), comprising the pump (5) and the pipe (4), the connection of one end of said central heating circuit with said section being effected by a three-way valve (21), characterized in that the direct exchanger (14) is mounted downstream with respect to the tank (10) on the domestic heating circuit (6) and upstream   relative to the balloon on the drawing circuit (9).   2. Apparatus according to claim 1, characterized in that the volume of the balloon (10) is of the order of 6 liters. 3. Apparatus according to any one of the preceding   claims, characterized in that the direct exchanger   against the current (14) is of a compact plate type.   4. Apparatus according to any one of the preceding   claims, characterized in that the direct exchanger   against the current (14) is embedded inside the balloon (10). 5. Apparatus according to any one of the preceding   claims, characterized in that it comprises a probe   temperature (24) disposed inside the tank (10) and means slaved to the crossing down of a set point (T) by the water temperature detected by this probe (24) so as to set on start-up the burner (3) at its maximum rate or at a reduced rate depending on whether a set point (D) is then   whether or not exceeded by the water flow detected by the flow   be. 6. Apparatus according to claim 5, characterized in that it comprises a second temperature probe (26)   arranged on the drawing circuit at the outlet of the sample   direct geur (14) and associated with the above servo means so as to further use, for the start-up of the burner (3), the crossing down of a second set point threshold (T ') by water temperatures that it detects.