FR2784174A1 - DEVICE FOR CONTROLLING THE OVERHEATING OF A HOT WATER GENERATOR WITH A DRILLED MOVABLE MEMBRANE - Google Patents

Abstract

It is a device for controlling the overheating of a hot water generator which includes a cold water inlet pipe and a hot water outlet pipe. The device comprises an enclosure divided by a deformable membrane (34) into two chambers in which the pressures existing in the cold water circuit and the hot water circuit prevail. The deformable membrane is movable under the pressure difference. The control device comprises means 45 for limiting the rise in temperature of the water contained in the cold room which consist of a passage (46) passing through the membrane.

Description

DEVICE FOR CONTROLLING THE OVERHEATING OF A GENERATOR

  The present invention relates to a device.

  to control the overheating of a hot water generator.

  The hot water generators usually encountered include a cold water inlet pipe connected to a cold water circuit and a hot water outlet pipe connected to a hot water circuit, a heat exchanger being interposed between the water circuit cold and the hot water circuit and a burner provides heat to said exchanger. After drawing hot water heated by the generator, it is necessary to lower the average temperature of the water present in the heat exchanger. For this, the hot water generator is conventionally equipped with a device for controlling the overheating of the water present in the exchanger, this device usually comprising an enclosure divided by a membrane deformable into a cold room and into a room. hot, the deformable membrane having a first face and a second face respectively turned towards the cold room and towards the hot room, the cold room being subjected to the pressure prevailing in the cold water circuit and the hot chamber 2 being subjected to the prevailing pressure in the hot water circuit, so that the deformable membrane is displaceable under the pressure difference existing between the

cold and hot rooms.

  Thus, the cold water stored in the cold room during the drawing is expelled by the movable membrane in the cold water circuit while the hot water present in the exchanger is transferred into the hot room of the enclosure. The hot water present in

  the exchanger is thus replaced by cold water.

  However, the construction of such a hot water generator leads to the installation of the overheating control device in the vicinity of the hot water circuit. Consequently, during long draws of hot water, the temperature of the cold water contained in the cold room of the control device is strongly influenced to the point of becoming hot. The water thus reinjected into the heat exchanger when the drawing off is less

  effective in combating overheating.

  The object of the present invention is to remedy the aforementioned drawbacks by proposing a control device which improves the action of the water injected into the exchanger when the drawing off stops, and this by means of

  simple, effective and inexpensive means.

  To this end, according to the invention, a control device of the aforementioned type, is essentially characterized in that the control device comprises means for limiting the rise in temperature of the water contained.

in the cold room.

  Consequently, the device according to the invention makes it possible to return to the heat exchanger, when the drawing off is stopped, water which is really cold compared to

2_ the temperature of the hot water.

  The control device according to the present invention may optionally further include one or more of the following characteristics: - the means for limiting the rise in 3C temperature of the water contained in the cold room are carried by the deformable membrane; the means for limiting the rise in temperature of the water contained in the cold room comprise at least one passage which crosses the membrane, so that the cold water contained in the cold room flows towards the hot room, renewing thus the water contained in the cold room; - The passage has two orifices opening onto the first and second faces of this membrane, the surface of the cross section of the orifices being greater than that of the cross section of the passage; - The displaceable membrane is substantially in the form of a spherical cap, the through passage being substantially radial and located at the top of the spherical cap; - The device further comprises return means of the membrane to reduce the volume of the cold room and the second face of the membrane comprises a support element of the return means, the support element being of the same axis as the passage; and - the first face of the membrane is provided with lugs

protruding towards the cold room.

  An exemplary embodiment of the invention will now be described with reference to the accompanying drawings in which: - Figure 1 is a longitudinal sectional view of a hot water generator in the off position incorporating the overheating control device according to the present invention; - Figure 2 is a view similar to that of Figure 1, the generator being in the drawing position; - Figure 3 is a cross-sectional view of the movable membrane belonging to the control device of Figures 1 and 2 and biased by a spring; and - Figure 4 is an enlarged view of part A of

  the movable membrane of FIG. 3.

  The hot water generator 1 shown in Figures 1 and 2 comprises, in a manner known per se, a cold water inlet pipe 2 connected to a cold water circuit 3, a hot water outlet pipe 4 connected to a hot water circuit 0, a heat exchanger 6 interposed between the cold water circuit 3 and the hot water circuit 5 and a burner 7 with fluid fuel which transfers heat

to the heat exchanger 6.

  For example, the fluid fuel used here is 1_ natural gas which, when a user draws hot water (Figure 2), burns by forming a flame ramp 8 whose heat is transferred to the heat exchanger 6 placed above the burner 7 to heat the circulating water

in this exchanger.

  Natural gas is supplied to the burner 7 in the direction of the arrows F via a supply 10. The gas flow rate passing through the supply 10 is regulated by a valve 11 which is connected to a device 12 for controlling the gas intake to the burner, to

  2_ passage of cold water through the cold water circuit 3.

  The valve 11 consists of a valve head 13 secured to a valve stem 14 whose movement is linked to the servo device 12. The valve head 13 is biased by a spring 15 bearing against a seat of! 0 valve 16 formed in the gas inlet pipe 10. The control device 12, known per se, consists of a reservoir 20 disposed in the cold water inlet circuit 3 downstream of which is disposed, relative to the direction of flow F1 of the water cold, a venturi 21. A movable e menen 22, placed in the reservoir 20, moves in function of the difference in oression which reigns between its two faces. The value of the pressure difference is caused by the venturi and is linked to the flow of cold water in the cold water inlet circuit 3. On the element

  displaceable 22 is mounted the rod 14 of the valve 11.

  When the hot water generator is in the off position (Figure 1), no pressure drop is caused by the venturi 21 inside the cold water inlet circuit 3. The movable element 22 is therefore inactive and the head 13 of the valve 11 rests on its seat 16. The gas supply -0 is therefore completely obstructed. The burner 7 is off. When the operator draws hot water (Figure 2), the venturi 21 creates a pressure drop in the cold water circuit 3, which induces an upward movement of the movable element 22, driving the rod 14 of the valve 11. The head 13 of the valve is detached from its seat 16, causing the passage of gas in the supply 10,

to the burner 7.

  When stopping the drawing, it is necessary not to

  not cause the heat exchanger to overheat 6.

  -5 This overheating is caused by the release of heat from the constituent parts of the hot water generator adjacent to the heat exchanger which were themselves heated during drawing. For this, it is necessary to replace the hot water present in the exchanger with a

amount of cold water.

  For this, the hot water generator is further provided with a device 30 for controlling the overheating of hot water. This control device comprises an enclosure 31 divided into a cold room 32 and a

  hot chamber 33 by a deformable membrane 34.

  The cold room 32 is connected to the cold water inlet pipe 2 by a pipe 35 while the hot room 33 is connected to the hot water outlet 4 by a pipe 36. Thus, the cold room is subjected to the pressure prevailing in the cold water inlet pipe 2 and the hot chamber 33 is subjected to the pressure prevailing in the hot water outlet pipe 5. The deformable membrane 34 is therefore displaceable under the difference of

  oression reigning between the cold and hot rooms.

  The membrane 34 is resiliently rappeeled towards the cold room 32 by a compression spring 40 which is interposed between the bottom of the room

  hot 33 and the second face 38 of this membrane.

  Furthermore, as shown more particularly in FIG. 3, the membrane 34 is substantially in the form of a spherical cap so as to match the walls of the cold rooms 32 and 33 which are themselves domed. More suitably, the membrane 34 is of approximately cylindrical shape with an axis X-X, the bottom of which is curved and the height of which is small relative to the bottom. The membrane 34 is made of a material with elastic deformation and has a thickness of small dimension compared to the diameter of the spherical cap. The sum: S of the spherical cap is of greater thickness so as to constitute a support stop 51 projecting relative to the second face 38. The compression spring 40 is in abutment on the second face 38 of the membrane by via a ring-shaped plate 52 itself

  fitted on the support stop 51 and on the second face 38.

  ? When the generator is in the off position (Figure 1) the deformable membrane 34 is biased by the compression spring 40 towards the cold room

  32 so that the volume of this chamber is very small.

  In the drawing position (Figure 2), the pressure difference between the cold water circuit 3 and the unaude water circuit 5 (caused by the venturi 21 and the pressure drops in the water in the circuit) the movement of the membrane 34 against the compression spring 40 in the direction of the hot chamber 33. This chamber then has a minimum volume and the cold chamber 32 is filled with cold water. When the drawing off of hot water stops, the membrane 34 expels the cold water contained in the cold room 32. This water is then transferred to the heat exchanger 6, which enables it to avoid overheating of

this exchanger.

  The control device 30 is located in the vicinity of the hot water circuit 5, which entralne during the drawing of hot water, the heating of the cold water contained in the cold room 32 (Figure 2). To avoid the rise in temperature of this water, the control device 30 has means 45 for limiting the rise in temperature of the water contained in the cold room 32

Figures 3 and 4).

  The limiting means 45 are carried by the deformable membrane 34 and consist of a passage 46 yes which passes radially through this membrane. In this example, the

oassage 46 is on the X-X axis.

  The passage 46 leads to the first face 37 by

  an orifice 47 and on the second face 38 by an orifice 48.

  These orifices are, in cross section, of good surface

greater than that of passage 46.

  As shown more particularly in Figure 3, the first face 37 of the membrane 34 is further provided with pins 50 regularly distributed and which project towards the cold room 32. These lugs avoid too strong adhesion of the membrane 34 at the bottom of the cold room 32 and facilitates the detachment of this membrane during

hot water.

  The passage 46 allows, in the position for using hot water, a flow of cold water contained in the cold room 32 towards the hot room 33. This flow is favored by the pressure prevailing in the cold room 32 which is greater than the pressure prevailing in the hot room 33. This flow causes the renewal of the cold water in the cold room 32 and prevents the rise in

temperature of this water.

  It is understood that the dimension of the passage 46 hardly affects the difference in pressure prevailing between the

  c-cold amber 32 and hot room 33.

  Furthermore, the means 45 for limiting the rise in temperature of the cold water may take a form other than a passage 46, such as for example a conduit situated outside the enclosure 30 and which communicates

  es cold room 32 and hot room 33.

Claims (7)

RESELL I CATIONS   1. Device for controlling the overheating of a hot water generator (1), the hot water generator (1) comprising an inlet pipe (2) for cold water connected to a cold water circuit (3 ) and an outlet pipe (4) for hot water connected to a hot water circuit (5), the overheating control device (30) comprising an enclosure (31) divided by a deformable membrane (34) into a chamber cold (32) and in a hot chamber (33), the deformable membrane (34) having a first face (37) and a second face (38) facing respectively the cold chamber (32) and the hot chamber (33) , the cold chamber (32) being subjected to the pressure prevailing in the cold water circuit (3) and the hot chamber (33) being subjected to the pressure prevailing in the hot water circuit (5), so that the deformable membrane ( 34) is displaceable under the pressure difference existing between the cold (32) and hot (33) chambers, characterized in that the control device (30) includes means for limiting (45) the rise in   temperature of the water contained in the cold room (32).   2. Control device according to claim 1, characterized in that the means for limiting (45) the rise in temperature of the water contained in the chamber   cold (32) are carried by the deformable membrane (34).   3. Control device according to claim 2, characterized in that the means for limiting (45) the rise in temperature of the water contained in the cold room (32) comprise at least one passage (46) which passes through the membrane (34), so that the cold water contained in the cold chamber {32) flows towards the hot chamber (33), thus renewing the water contained in the cold room (32).   4. Control device according to claim 3, characterized in that the passage (46) has two orifices (47, 48) opening onto the first (37) and second (38) faces of this membrane (34), the surface of the secticn: transverse of the orifices (47, 48) being greater than that   of the cross section of the passage (46).   J 5. Control device according to claim 3 or 4, characterized in that the displaceable membrane (34) is substantially in the form of a thermal cap, _e through passage (46) being substantially radial e: located at the sum: * S) of the spherical cap.   6. Control device according to claim 5, characterized in that it further comprises return means (40) of the membrane (34) to reduce the volume of the cold room (32) and the second face (38) of the membrane (34) comprises a support element (51) return means (40), the support element (51) being on the same axis as the passage (46).   7. Control device according to claim c-   or 6, characterized in that the first face (37) of the membrane (34) is provided with lugs (50) projecting towards the -> cold room (32)